JP2023087827A - Lead-free low-melting-point glass composition, coated magnesium alloy member, joint body, method for producing coated magnesium alloy member, and method for producing joint body - Google Patents

Abstract

To reduce the difference in thermal expansion coefficient between a Mg alloy member and a glass composition applied thereto, preventing the peeling of the glass composition and improving the corrosion resistance of the Mg alloy.SOLUTION: A lead-free low-melting-point glass composition comprises vanadium oxide, phosphorus oxide, iron oxide and alkali metal oxide, and satisfies the relational expressions of (1), (2) and (3) in terms of oxide: [V2O5]>[P2O5]>[Fe2O3] (1), 2[Fe2O3]≤[V2O5]≤[P2O5]+[Fe2O3] (2) and [Fe2O3]≤[R2O]≤2.5[Fe2O3] (3) (where [X] represents the content of a component X, expressed in mol%, and R represents an alkali metal).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a lead-free low-melting glass composition, a coated magnesium alloy member, a joined body, a method for producing a coated magnesium alloy member, and a method for producing a joined body.

Application of Mg alloy, which is the lightest among practical metals, is expected to reduce the weight of mobility such as automobiles, aircraft, and trains. In addition, by applying magnesium alloy members to various products such as mobile digital equipment and rotating bodies, we can expect weight reduction and high efficiency of products.

However, Mg alloys have a relatively high tendency to ionize and thus have poor corrosion resistance in wet environments. Furthermore, when the Mg alloy is combined with other members to expand its application, galvanic corrosion occurs due to the contact of the Mg alloy with dissimilar metals, and the Mg alloy is preferentially corroded.

In order to reduce the corrosion of products containing such Mg alloys, techniques such as surface treatment and painting have been studied.

In Patent Document 1, when joining an Mg alloy material containing Al and a steel material (galvanized steel sheet), eutectic melting of Mg and Zn is caused, and the oxide film, impurities, etc. are discharged from the joint interface, A method for joining dissimilar metals is disclosed in which an Al--Mg intermetallic compound or an Fe--Al intermetallic compound is produced and new surfaces of both materials are joined.

In Patent Document 2, for the purpose of obtaining a metal matrix composite material with high corrosion resistance even if the coating amount is low, aluminum or magnesium or an alloy thereof is used as a base and is coated with a transition metal oxide glass after melting. A metal matrix composite material, wherein the transition metal oxide glass contains vanadium, at least one of tellurium or phosphorus, and at least one of silver, iron, tungsten, copper, alkali metals and alkaline earth metals. is disclosed.

JP 2009-269085 A JP 2013-194285 A

By coating the Mg alloy with glass, which is an insulator, the corrosion resistance of the Mg alloy is improved, making it possible to use it for joining dissimilar materials under various environments.

In the joint of dissimilar metals described in Patent Document 1, eutectic melting is caused and the oxide film, impurities, etc. are discharged from the joint interface, but there is room for improvement in terms of corrosion resistance.

When the glass film described in Patent Document 2 is as thick as several tens of μm or more, there are problems of cracking and peeling of the glass film due to the difference in thermal expansion between the glass and the underlying metal. For this reason, it is said that a filler for controlling the thermal expansion of ceramics and metals is added to the glass paste to bring the thermal expansion of the glass film and the base metal close to each other. In other words, it is not sufficiently considered to reduce the difference in thermal expansion between the glass alone and the base metal.

An object of the present invention is to reduce the difference in thermal expansion coefficient between the Mg alloy member and the glass composition coated thereon, thereby preventing separation of the glass composition and improving the corrosion resistance of the Mg alloy. It is in.

The lead-free low-melting-point glass composition of the present invention contains vanadium oxide, phosphorus oxide, iron oxide and alkali metal oxides, and satisfies the following relational expressions (1), (2) and (3) in terms of oxides.

_{[ V2O5} ] _> [ _P2O5 ]>[ _Fe2O3 ] (1 _)
2 [ _Fe2O3 ] _≤ [ _V2O5 ]≤[ _P2O5 ]+ _{[ Fe2O3} ] ( ₂ )
[ _Fe2O3 ] _≤ [ _R2O ]≤2.5[ _Fe2O3 ] (3 ₎
(In the formula, [X] represents the content of component X, and its unit is "mol %". R is an alkali metal.)

According to the present invention, the difference in thermal expansion coefficient between the Mg alloy member and the glass composition coated thereon is reduced to prevent peeling of the glass composition and improve the corrosion resistance of the Mg alloy. can be done. As a result, weight reduction, efficiency improvement, and expansion of applications can be expected in airplanes, trains, mobility, mobile digital devices, rotating bodies, and the like.

It is a graph which shows an example of the result of the typical differential thermal analysis (DTA) of glass. FIG. 2 is a flow diagram schematically showing a method for producing a glass-coated Mg alloy member; 4 is a graph showing the temperature history when firing a glass paste in which ethyl cellulose is used as a resin binder and butyl carbitol acetate is used as a solvent. FIG. 2 is a schematic diagram showing an apparatus configuration for a saltwater immersion test for evaluating saltwater resistance of a glass-coated Mg alloy member and a glass-coated metal Al member. 4 is a graph showing the temperature history when firing a glass paste using α-terpineol as a solvent. 4 is a graph showing the temperature history when firing a glass paste using an aqueous solution of polyethylene oxide as a solvent. FIG. 2 is a flow diagram schematically showing a method of producing a joined body of an Mg alloy member and dissimilar members; FIG. 7B is a cross-sectional view showing the joined body in step (c) of FIG. 7A; FIG. 2 is a schematic diagram showing an apparatus configuration for a saltwater immersion test for evaluating the saltwater resistance of a joined body of a Mg alloy and dissimilar members. FIG. 4 is a cross-sectional view showing an example of a joined body having a fastened structure; FIG. 10 is a flowchart showing a manufacturing method of the joined body of FIG. 9;

Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the drawings. However, the invention according to the content of the present disclosure is not limited to the embodiments taken up here, and includes suitable combinations and improvements within the scope of not changing the gist of the invention.

The joined body according to the present disclosure is obtained by joining a Mg alloy member and a dissimilar member formed of a material other than the Mg alloy through a glass layer, and prevents direct contact between the Mg alloy member and the dissimilar member. is. In addition, in this specification, a magnesium alloy may be described as a "Mg alloy." Similarly, the magnesium alloy member may be referred to as "Mg alloy member".

In other words, the joined body is arranged between a magnesium alloy member made of a magnesium alloy, a dissimilar member made of a material other than the magnesium alloy and generating a potential difference when in contact with the magnesium alloy member, and the magnesium alloy member and the dissimilar member. the magnesium alloy member and the dissimilar member are separated from each other, and the glass layer contains a lead-free low-melting-point glass composition to be described later. Here, the lead-free low-melting-point glass composition according to the present disclosure is particularly effective when using aluminum, iron, etc., which have a lower ionization tendency than magnesium alloys, as the material of the dissimilar member.

First, the definition of the characteristic temperature of glass will be explained.

FIG. 1 is a graph showing an example of the results of typical differential thermal analysis (DTA) peculiar to glass.

The characteristic temperatures (transition point, yield point, softening point, etc.) of the glass were measured by differential thermal analysis (DTA). In general, DTA of glass uses glass particles with a particle size of about several tens of μm, and further uses high-purity alumina (α-Al ₂ O ₃ ) particles as a standard sample. Measured in speed.

As shown in this figure, when the glass particles are heated at the above-mentioned rate of temperature increase, heat absorption starts from the transition point _Tg and reaches the yield point _Mg corresponding to the first endothermic peak. Then, the heat absorption amount decreases once and then increases again. The temperature corresponding to the second endothermic peak is the softening point _Ts . As the material is further heated, the amount of heat generated increases sharply from the crystallization temperature _Tcry and reaches an exothermic peak. This exothermic peak is due to the crystallization of the glass, the temperature at which heat generation starts is called crystallization temperature T _cry , and the temperature at which the exothermic peak reaches its maximum value is called crystallization peak temperature T _cry-p .

In addition, each characteristic temperature is usually obtained by the tangent method. Strictly speaking, T _g , M _g and T _s are defined by the viscosity of the glass, with T _g corresponding to 10 ^13.3 poise, M _g to 10 ^11.0 poise and T _s to 10 ^7.65 poise. temperature.

The crystallization tendency of the glass is determined from the temperature difference (absolute value) between the softening point _Ts and the crystallization temperature _Tcry and the height of the exothermic peak due to crystallization, that is, the amount of heat generated. If the temperature difference (absolute value) between _the softening point _Ts and the crystallization temperature _Tcry is large, the glass can be softened and flowed in a temperature range that does not reach _Tcry even if the temperature exceeds the softening point Ts. becomes easier. That is, the closer the softening point _Ts and the crystallization temperature _Tcry are, the greater the crystallization tendency becomes and the easier the crystallization is during heating and firing. When the glass crystallizes, the softening fluidity at low temperatures becomes low.

The lower the characteristic temperatures represented by the transition point T _g , yield point M _g and softening point T _s , the higher the softening fluidity at low temperatures. On the other hand, glass with lower characteristic temperatures tends to be inferior in chemical stability such as water resistance and salt water resistance.

In addition, if the amount of heat generated during crystallization is small, when T _cry is reached by heating at a constant temperature increase rate, uncontrollable temperature rise due to heat generation is less likely to occur, so crystallization proceeds. can be suppressed. The firing temperature for bonding and coating is affected by the heating rate, atmosphere, pressure _, and other firing conditions, as well as the type, content, and particle diameter of the metal particles contained. It is often set as high as ~50°C. At this firing temperature, the glass particles are softened and flowed to perform bonding and coating.

The lead-free low melting point glass composition according to the present disclosure comprises vanadium oxide, phosphorous oxide, iron oxide and alkali metal oxides. Then, in terms of oxide, the following relational expressions (1), (2) and (3) are satisfied.

[ _{V2O5 ] >} [ _P2O5 ]>[ _Fe2O3 ] (1 _)
2 [ _{Fe2O3 ] ≤} [ _V2O5 ]≤[ _P2O5 ]+[ _Fe2O3 ] ( ₂ )
[ _Fe2O3 ] _≤ [ _R2O ]≤2.5[ _Fe2O3 ] (3 ₎
(In the formula, [X] represents the content of component X, and its unit is "mol %". R is an alkali metal. Same below.)
Furthermore, the lead-free low-melting glass composition desirably satisfies the following relational expression (4) in terms of oxide.

[ _V2O5 ] + [ _P2O5 ] + [ _Fe2O3 ] + _{[ R2O} ] _≥ 84 ( ₄ )
Also, R ₂ O is preferably K ₂ O.

The lead-free low-melting-point glass composition preferably further contains at least one of tellurium oxide, tungsten oxide and molybdenum oxide. It is desirable to satisfy the following relational expression (5) or (6) in terms of oxide.

[ _TeO2 ] + [ _WO3 ] + [ _MoO3 ] ≤ 16 (5)
[ _TeO2 ] + _{[ WO3} ] + [ _MoO3 ] ≤ [ _Fe2O3 ] (6)
The lead-free low-melting-point glass composition desirably satisfies the following relational expressions (7), (8) and (9) in terms of oxide.

27≤[ _V2O5 ]≤40 ₍ 7)
[ _V2O5 ] + [ _R2O ] ≥ 50 (8 _{)
[ R2O} ]≤2[ _Fe2O3 ] (9)
The lead-free low-melting-point glass composition preferably has a softening point of 400° C. or lower and a crystallization temperature higher than the softening point by 80° C. or higher.

The function of each element in the lead-free low-melting-point glass composition will be described.

Below, glass components are represented by oxides.

Glass has a layered structure consisting of V ₂ O ₅ , and WO ₃ , MoO ₃ and the like are thought to exist within the layers. In addition, P ₂ O ₅ , Fe ₂ O ₃ , R ₂ O, etc. exist between the layers, and P ₂ O ₅ , Fe ₂ O ₃ , R ₂ O, etc. exist between the layers, and V ₂ forms a layered structure. Presumably bound to _O5 .

V ₂ O ₅ and P ₂ O ₅ are components that vitrify, and the effect of lowering the characteristic temperature such as the softening point is V ₂ O ₅ >P ₂ O ₅ . On the other hand, when V ₂ O ₅ is too much, V ₂ O ₅ tends to dissolve in water, resulting in poor chemical stability such as water resistance and salt water resistance. Therefore, it is desirable to satisfy [V ₂ O ₅ ]≦40.

As for _{P2O5 ,} when _V2O5 > _P2O5 , _P2O5 enhances the interlayer force _{of the} glass _structure and reduces the elution _{of V2O5} . On the other hand, when P ₂ O ₅ ≧V ₂ O ₅ , the characteristic temperature increases and the thermal expansion coefficient decreases. Therefore, when P ₂ O ₅ ≧V ₂ O ₅ , there is a risk that the glass coated on the Mg alloy having a large thermal expansion coefficient will peel off.

Fe ₂ O ₃ existing between the layers of the glass layered structure strengthens the interlayer force and has the effect of suppressing elution due to moisture and the like. Therefore, chemical stability such as water resistance and salt water resistance can be greatly improved. On the other hand, when the content of Fe ₂ O ₃ is large, the characteristic temperature such as the softening point becomes high, and the difference between the characteristic temperature such as the softening point and the crystallization temperature becomes small, so crystallization is facilitated. Therefore, it is desirable to satisfy the following two expressions.

_{[ V2O5} ] _> [ _P2O5 ] > _{[ Fe2O3} ]
2 _{[ Fe2O3} ] _≤ [ _V2O5 ]≤[ _P2O5 ]+ _{[ Fe2O3 ]}
Similarly, R ₂ O present between the layers of the glass layered structure has a relatively weak interlayer force and is easily separated from the layered structure by heating or moisture. Therefore, R ₂ O is a component that lowers the glass characteristic temperature such as the softening point, and can improve the thermal expansion coefficient. On the other hand, when the content of R ₂ O is high, it is likely to dissolve in water, resulting in poor chemical stability such as resistance to water and salt water. Therefore, it is desirable to satisfy the following formula.

[ _{Fe2O3 ]} ≤[ _R2O ]≤2.5 _{[ Fe2O3} ]
Alkali metal oxides _R2O include _Li2O , _Na2O and _K2O . The smaller the ionic radius and the higher the ionization tendency, the lower the chemical stability such as resistance to salt water. Also, the larger the ionic radius, the easier it is to vitrify and the harder it is to crystallize. Therefore, _R2O is preferably _K2O .

Regarding the respective roles and effects of V ₂ O ₅ , P ₂ O ₅ , Fe ₂ O ₃ and R ₂ O, the total content thereof is preferably 84 mol % or more. Such glass has a low softening point, can be applied to Mg alloys in a safe temperature range, has a high coefficient of thermal expansion, and does not peel when coated on Mg alloys, and Due to its high corrosion resistance, it is possible to reduce corrosion of Mg alloys.

Additional components contribute to reducing the tendency to crystallize.

_TeO2 can reduce the crystallization tendency. However, if the content is large, it is reduced by Mg when it is coated on the Mg alloy, and precipitates as simple Te. Therefore, the glass structure becomes open and chemical stability such as resistance to salt water is inferior. _WO3 and _MoO3 present in the layers of the glass lamellar structure have the same effect. Therefore, it is desirable to satisfy the following formula.

[ _TeO2 ] ₊ [ _WO3 ]+[ _MoO3 ]≤[ _Fe2O3 ]
BaO, which is also present between layers of the glass layered structure, is a component that suppresses surface devitrification (crystallization) during heating of the glass. However, BaO is incompatible with Fe ₂ O ₃ and, when added at the same time, has the effect of inhibiting vitrification, and uniform glass may not be obtained.

MgO has the effect of promoting the crystallization of glass, and if the content is large, uniform glass may not be obtained.

In Example 1, the properties of a single glass composition having predetermined components, and the properties of an Mg alloy member and a metal Al member coated with the glass composition were examined.

Glass compositions shown in Tables 1 and 2 were produced and their glass properties were examined. In addition, in Tables 1 and 2, the glass properties of the compositions obtained by coating the Mg alloy and the metal Al were examined in Tables 3 and 4.

(Preparation of lead-free low-melting-point glass composition)
Lead-free low-melting-point glass compositions of Examples and Comparative Examples were produced by the following method.

150 to 200 g of raw material mixed with each oxide was placed in a platinum crucible, heated to 900 to 950° C. at a rate of 5 to 10° C./min in an electric furnace, and held for 1 hour. Stirring was carried out during holding in order to obtain a uniform glass. The platinum crucible was taken out from the electric furnace and poured onto a graphite mold preheated to about 150° C. and a stainless steel plate.

The glass poured onto the stainless steel plate solidified to become black glass cullet. By observing this state, the vitrification state was evaluated by ◯ and ×. ○ indicates the case where a uniform glass having a glass luster was obtained. On the other hand, x indicates the case where devitrification due to crystallization or phase separation was observed, and uniform glass was not obtained.

(Measurement of characteristic temperature of glass)
The characteristic temperatures (transition point, yield point, softening point, etc.) of the glass composition were measured by differential thermal analysis (DTA). In this case, the glass cullet produced by the above method was placed in an alumina mortar, manually pulverized, and further pulverized to a particle size of less than 20 μm with a grinder. Then, using the obtained glass powder, the temperature was measured at a rate of temperature increase of 5° C./min in the air.

(Evaluation of softening fluidity of glass composition)
The softening fluidity of the glass composition during heating was evaluated by a button flow test.

As a sample of the glass composition, a press molded body having a diameter of 10 mm and a thickness of 5 mm was formed by using glass powder pulverized to a particle size of 20 μm or less. This compact was placed on an alumina substrate, heated to a temperature about 40° C. higher than the softening point T _s of the glass particles at a heating rate of 5° C./min, and held for 30 minutes. By observing the state at this time, the fluidity was evaluated by ◯ and ×. ○ indicates the case where there is no surface devitrification, crystallization, phase separation, or the like, and the sample is completely melted and good fluidity is obtained. On the other hand, x indicates the case where good softening fluidity was not obtained due to crystallization, devitrification, or the like.

(Evaluation of chemical stability of glass composition)
Regarding the chemical stability of the glass composition, the water resistance and salt water resistance were evaluated as follows.

The water resistance was evaluated by immersing the glass cullet produced by the above method in 20 cm ³ of pure water and leaving it for 5 days. Similarly, the water resistance was evaluated by immersing the glass cullet in 3.5% by mass salt water and leaving it for 5 days. In any evaluation, ◯ means that no trace of corrosion was found on the surface by visual observation after immersion for 5 days, and was regarded as good. On the other hand, x indicates the case where the glass was eluted after being immersed for 5 days.

In the comprehensive evaluation of the glass, only when all the items were evaluated as ◯, it was given as good “◯”. If even one item was evaluated as x, it was determined that there was a problem as a comprehensive evaluation, and it was set as "x". In addition, when there was no X evaluation and there was a △ evaluation, it was judged that there was room for improvement as a comprehensive evaluation and was given as "△".

Glass compositions with a comprehensive evaluation of ◯ or Δ were applied to the surfaces of magnesium alloys and metal aluminum, and corrosion resistance (salt water resistance) was evaluated.

(Production of glass-coated Mg alloy member and glass-coated metal Al member)
A glass-coated Mg alloy member and a glass-coated metal Al member were produced by the following method.

The glass cullet produced by the above method was placed in an alumina mortar, manually pulverized, and further pulverized to a particle size of less than 20 μm with a grinder. A resin binder and a solvent were mixed with the pulverized powder of the glass composition, and the mixture was stirred and kneaded in an alumina mortar to prepare a glass paste.

Ethyl cellulose was used as the resin binder, and butyl carbitol acetate was used as the solvent.

FIG. 2 is a flow diagram schematically showing a method of producing a glass-coated Mg alloy member.

As shown in this figure, first, an Mg alloy member 11 (AZ31) is prepared (step (a)). The Mg alloy member 11 is a flat plate with dimensions of 1×20×20 mm. Next, the glass paste 20 prepared by the above method is applied to the surface of the Mg alloy member 11, and fixed to a pure aluminum fixing jig 31 having dimensions of 1×20×20 mm (step (b)). Then, the fixed Mg alloy member 11 is heated at 150° C. for 30 minutes to dry the glass paste 20 (step (c)). Then, it is baked to form the glass layer 21 (glass baked coating film) (step (d)).

The Mg alloy member 11 having the glass layer 21 produced in this way is called a "coated magnesium alloy member". The coated magnesium alloy member includes a base material (Mg alloy member 11) containing a magnesium alloy and a fired coating (glass fired coating film) provided on the surface of the base material, and the fired coating is the lead-free material according to the present disclosure. Contains a low-melting-point glass composition.

FIG. 3 is a graph showing the temperature history when firing a glass paste using ethyl cellulose as a resin binder and butyl carbitol acetate as a solvent.

As shown in this figure, the temperature is raised to near the yield point at a temperature increase rate of 10°C/min in the atmosphere, held for 30 minutes, and then 30 to 50°C higher than the softening point at a temperature increase rate of 10°C/min. It was heated to temperature, held at that temperature for 30 minutes, and cooled in a furnace. Thus, a glass-coated magnesium alloy member (coated magnesium alloy member) was produced.

A glass-coated metal Al member (glass-coated metal Al member) was produced in a similar manner. In this example, A6061 was used as the base material of metal Al.

(Evaluation of glass-coated Mg alloy member and glass-coated metal Al member)
The glass firing state was evaluated by ◯ and × as follows.

When glass paste was applied to a metal plate (Mg alloy or metal Al) and dried and fired, the film was relatively flat and had a glass luster. . On the other hand, when the wettability was low and a flat film could not be formed, or when the surface was devitrified due to crystallization, it was rated as x.

FIG. 4 is a schematic diagram showing the apparatus configuration for a saltwater immersion test for evaluating the saltwater resistance of a glass-coated Mg alloy member and a glass-coated metal Al member.

As shown in this figure, salt water resistance was evaluated by fixing the Mg alloy member 11 or the dissimilar member 12 having the glass layer 21 in a container 51 with a fixing jig 31, and The test was performed with the lid 52 closed.

Salt water resistance was evaluated by ◯, Δ, and × depending on the surface condition after being immersed in salt water for 5 days. When there was no change in appearance after immersion in salt water for 5 days, it was rated as ◯, when there was a trace of corrosion on the glass, it was rated as Δ, and when corrosion was observed in the Mg alloy, it was rated as x.

In addition, the overall evaluation of the glass fired coating film was evaluated by ◯, Δ, and ×.

When all of the evaluations of the glass firing state and salt water resistance were ◯, the overall evaluation was ◯. On the other hand, when even one of these evaluation items has Δ, the overall evaluation is Δ. Similarly, when even one of these evaluation items has an x, the overall evaluation is x.

Examples and comparative examples in which fabrication and evaluation were performed are summarized in a table below.

Table 1 shows compositions of glass compositions GA01 to GA50 of Examples.

Table 2 shows the vitrification state, characteristic temperature, softening fluidity and chemical stability of the glass compositions GA01 to GA50 of the examples.

As shown in Table 2, the glass compositions GA01 to GA50 of Examples have a softening point of 400° C. or lower. In addition, except for GA-43 to GA45, the crystallization temperature is higher than the softening point by 80°C or more.

Table 3 shows the compositions of glass compositions GB01 to GB44 of comparative examples.

Table 4 shows the vitrification state, characteristic temperature, softening fluidity and chemical stability of the comparative glass compositions GB01 to GB44.

Table 5 shows the glass firing state and salt water resistance when the glass compositions GA01 to GA50 of the examples are applied as coating materials to Mg alloy (AZ31) and metal Al.

Table 6 shows the glass firing state and salt water resistance when the glass composition of the comparative example, which had a good overall glass evaluation in Table 4, was applied as a coating material to Mg alloy (AZ31) and metal Al. .

Comparative Examples GB26, GB33 and GB36 in Tables 3 and 4 contained a large amount of MgO or contained both Fe ₂ O ₃ and BaO, so that they could not be vitrified uniformly. Therefore, the evaluation of the characteristic temperature and the like was not carried out.

The glass compositions of Comparative Examples GB03, GB34 and GB35 do not contain Fe ₂ O ₃ and therefore have low resistance to salt water. Moreover, the GB42 glass composition has a low saltwater resistance because the content of Fe ₂ O ₃ does not satisfy the following formula.

_{[ R2O} ]≤2.5[ _Fe2O3 ]
The glass compositions of Comparative Examples GB07, GB11, GB12 and GB18 do not contain P ₂ O ₅ and thus have low softening fluidity. Moreover, GB22, GB23, GB30, GB43 and GB44 do not satisfy the following formula, and therefore have low softening fluidity.

_{[ V2O5} ] _≧ [ _P2O5 ]> _{[ Fe2O3} ]
On the other hand, the glass compositions of Examples GA01 to GA50 satisfy all of the following formulas.

[ _V2O5 ] ₊ [ _P2O5 ]+[ _Fe2O3 ]+ _{[ R2O} ] _≧ 84
_{[ V2O5} ] _≧ [ _P2O5 ]> _{[ Fe2O3} ]
2 _{[ Fe2O3} ] _≤ [ _V2O5 ]≤[ _P2O5 ]+ _{[ Fe2O3 ]}
[ _{Fe2O3 ]} ≤[ _R2O ] _≤2.5 [ _Fe2O3 ]
[ _TeO2 ] ₊ [ _WO3 ]+[ _MoO3 ]≤[ _Fe2O3 ]
Therefore, the glass compositions of Examples GA01 to GA50 have both softening fluidity and chemical stability such as resistance to salt water.

As shown in Table 6, the glass-coated Al of the comparative example was uniformly coated, had almost the same salt water resistance as the glass alone, and hardly observed corrosion.

However, the glass-coated Mg alloy (AZ31) of the comparative example was heavily corroded and had poor resistance to salt water. The reason for this is that the glass used does not satisfy the following formula, and it is considered that Te and the like are reduced, resulting in an open glass structure and easy elution into water.

[ _TeO2 ] ₊ [ _WO3 ]+[ _MoO3 ]≤[ _Fe2O3 ]
GB38, which contains AgO ₂ which is more easily reduced than Te, has even lower saltwater resistance, and after immersion in saltwater for 5 days, all the glass-coated Mg alloy was leached into water.

Moreover, comparative examples GB03, GB34 and GB42 also had low resistance to salt water. The reason for this is thought to be that the high content of BaO is incompatible with Fe ₂ O ₃ , which improves salt water resistance, and the content of Fe ₂ O ₃ could not be increased for vitrification.

In the glass-coated Mg alloy (AZ31) shown in Table 5, GA30, GA38 and GA47 glasses were evenly coated, but some corrosion was observed. Other glasses were uniformly coated, and good salt water resistance was obtained for both glass-coated Al and AZ31.

In Example 2, the effect of the solvent used in preparing the glass paste on the properties of the glass-coated Mg alloy member was examined.

Table 7 shows that, for the glass composition with the overall glass evaluation of 0 in Tables 2 and 4, a glass-fired coated Mg alloy plate was produced by the same method as in Example 1, and the glass-fired state and salt water resistance were evaluated. The results are shown.

Here, when forming a glass fired coating film on an Mg alloy, AZ61 was used as the Mg alloy, and the ethyl cellulose solution (EC) of butyl carbitol acetate (BCA) in Example 1 was used as the solvent, as well as α-terpineol (α -T), and an aqueous solution of polyethylene oxide (PEO).

In the case of a glass paste using an EC solution of BCA as a solvent, it was dried at 150° C. for 30 minutes and fired. Here, firing was performed with the temperature history shown in FIG.

In the case of a glass paste using α-T as a solvent, it was dried at 150° C. for 30 minutes and then fired as follows.

FIG. 5 is a graph showing the temperature history when firing a glass paste using α-T as a solvent.

As shown in the figure, the temperature was raised to a temperature 30 to 50° C. higher than the softening point at a heating rate of 10° C./min in the atmosphere, held at that temperature for 30 minutes, and cooled in the furnace. Thus, a glass-coated magnesium alloy member (coated magnesium alloy member) was produced.

In the case of a glass paste using an aqueous solution of PEO as a solvent, it was fired as follows without drying.

FIG. 6 is a graph showing the temperature history when firing a glass paste using an aqueous solution of PEO as a solvent.

As shown in this figure, the temperature was raised to 190°C at a temperature increase rate of 10°C/min in the atmosphere, held for 30 minutes, and then heated at a temperature increase rate of 10°C/min to a temperature 30 to 50°C higher than the softening point. and maintained at that temperature for 30 minutes, followed by furnace cooling. Thus, a glass-coated magnesium alloy member (coated magnesium alloy member) was produced.

The glass firing state was evaluated by ◯ and ×. When the glass coating film was baked on the metal plate, ◯ indicates that the film was uniformly coated, and × indicates that the film could not be uniformly coated.

The saltwater resistance was evaluated as ◯ when there was no change in appearance after immersion in salt water for 5 days, Δ when there was a trace of corrosion on the glass, and x when it was severely corroded.

Comprehensive evaluation of the glass fired coating film was evaluated by ◯, Δ, and ×. 〇 indicates that the glass coating film is fired on the Mg alloy plate and the pure Al plate, and the glass firing state and salt water resistance are all 〇. △ indicates that even one of these evaluation items has △. was defined as the case where at least one of these evaluation items was x.

With the water-based paste, there was glass in the example that could not be uniformly coated on AZ61. These glasses were devitrified due to crystallization or the like due to the influence of moisture in the paste. The glass that could not be uniformly coated did not have sufficient adhesion to AZ61, and AZ61 was greatly corroded.

On the other hand, the organic paste showed the same result as the glass of the example shown in Table 5 without such a problem.

From this result, it was found that the solvent used for the glass paste is preferably an organic solvent rather than water. BCA and α-T were effective as organic solvents. Further, EC was effective as a resin binder for adjusting the viscosity of the paste by dissolving it in the organic solvent.

In Example 3, Al particles were mixed into the glass paste containing the glass composition examined in Example 1 to prepare a joined body of Mg alloy and Al, and the effect on salt water resistance was examined.

A glass composition and a glass paste were prepared in the same manner as in Example 1. At that time, AZ31 was used as the Mg alloy, α-T was used as the solvent, and Al metal particles were mixed into the glass paste.

FIG. 7A is a flow diagram schematically showing a method of producing a joined body of an Mg alloy member and dissimilar members.

As shown in this figure, first, an Mg alloy member 11 (AZ31) is prepared (step (a)). The Mg alloy member 11 is a flat plate with dimensions of 1×20×20 mm. Next, the glass paste 22 containing Al metal particles produced by the above method is applied to the surface of the Mg alloy member 11 (step (b)). Then, the Mg alloy member 11 is sandwiched between two plates made of pure aluminum and having dimensions of 1×15×15 mm, which are the dissimilar members 12 (step (c)). At this time, the three plates are fixed by a fixing jig.

After that, the glass paste 22 is dried by heating at 150° C. for 30 minutes while being fixed. After that, it is fired with the temperature history shown in FIG. 5 to form a glass layer (glass fired coating film).

In the coated magnesium alloy member thus produced, the fired coating contains metal particles. In this case, the metal particles are made of an aluminum alloy.

FIG. 7B is a cross-sectional view showing the joined body in step (c) of FIG. 7A.

As shown in FIG. 7B, the joined body 70 has the Mg alloy member 11 sandwiched between two dissimilar members 12 . A glass paste 22 is sandwiched between the Mg alloy member 11 and the dissimilar member 12 .

FIG. 8 is a schematic diagram showing the apparatus configuration for a saltwater immersion test for evaluating the saltwater resistance of a joined body of Mg alloy and dissimilar members.

As shown in the figure, the evaluation of salt water resistance was performed with the assembly 70 fixed in a container 51, immersed in salt water 41 having a concentration of 3.5 mass %, and covered with a lid 52 .

The salt water immersion was continued for 5 days. After that, the state of the outer surface of the joined body 70 was observed, and the resistance to salt water was evaluated as ◯, Δ, and x. When there was no change in appearance after immersion in salt water for 5 days, it was evaluated as ◯, when there was a trace of corrosion on the glass, it was evaluated as Δ, and when it was severely corroded, it was evaluated as ×.

The effective average particle size D50 of Al particles is 3 to 30 μm, and the joined body of Mg alloy and Al showed good resistance to salt water without peeling. Here, the average particle diameter D50 is a median diameter calculated from an integrated particle size distribution curve measured by a laser diffraction particle size distribution analyzer (model LA-960, manufactured by Horiba, Ltd.).

When the average particle diameter of the Al particles was less than 3 μm, the metal particles were more easily oxidized, and the stress relaxation effect was reduced. On the other hand, if the average particle size exceeds 30 μm, the metal particles may come into direct contact with the Mg alloy, which may cause corrosion. Especially when the content of Al particles is high, there is a high possibility that Al particles having a large average particle size will come into contact with the Mg alloy.

The effective content of the metal particles was 25 to 100 volume parts per 100 volume parts of the glass particles, ie, the content in the fired coating film was 20 to 50 volume %. If it is less than 25 parts by volume (20% by volume), a sufficient stress relaxation effect cannot be obtained. On the other hand, when it exceeds 100 parts by volume (50% by volume), the softening fluidity of the glass is lowered, the Mg alloy cannot be coated uniformly, the adhesion is lowered, and corrosion may occur. .

Table 8 shows the results of examining the glass compositions of Examples GA18, GA26, GA29, GA32, GA34, GA36, GA27 and GA46 and Comparative Examples GB02, GB04, GB05, GB27 and GB34 by changing the ratio of Al particles. It is a thing.

In the examples, when the Al particles are 100 parts by volume (50% by volume) with respect to 100 parts by volume of the glass particles and the average particle size of the Al particles is 20 μm, the content of the Al particles with respect to 100 parts by volume of the glass particles is 25 parts by volume ( 20% by volume) and 45% by volume (31% by volume), and when the average particle size of the Al particles is 3 μm, 20 μm, and 30 μm, the content of Al particles with respect to 100 parts by volume of glass particles is 70 parts by volume (41% by volume). It was found that when the average particle size of the Al particles was 3 μm and 20 μm, the joined bodies of the glass-coated AZ31 and Al had good resistance to salt water.

In summary, the ratio of the metal particles is desirably 25 parts by volume or more and 100 parts by volume or less with respect to 100 parts by volume of the glass particles (glass powder).

On the other hand, in the comparative examples, the content of the Al particles with respect to 100 parts by volume of the glass particles was 25 parts by volume (20% by volume), 45 parts by volume (31% by volume), 70 parts by volume (41% by volume) and 100 parts by volume ( 50% by volume) and the average particle size of the Al particles was 20 μm, the bonded body of glass-coated AZ31 and Al was immersed in salt water, and peeling occurred, and good salt water resistance could not be obtained. The reason for this is that, as shown in Table 6, in the case of the glasses of these comparative examples, the glass composition reacts with the Mg alloy when coated on the Mg alloy, or part of the glass composition is eluted into water. As a result, the glass structure becomes open and the resistance to salt water becomes low, so that the bonded body of the glass-coated AZ31 and Al delaminates.

In Example 4, in Example 3, the influence of the type of metal particles mixed on the salt water resistance of the joined body was examined for the glass of the example in which the joined body of the glass-coated Mg alloy member and Al exhibited good salt water resistance. investigated.

In the same manner as in Example 3, a joined body of a glass-coated Mg alloy member and Al was produced. Here, AZ61 was used as the Mg alloy, and Al—Mn alloy particles, Ag particles, Sn particles, Te particles and Zn particles were used as the metal particles in addition to the Al particles.

Table 9 shows the results of examination by changing the type of metal particles.

As shown in the table, Al particles (average particle size: 20 μm), A3003 alloy particles (average particle size: 30 μm), Ag particles (average particle size: 20 μm), Sn particles (average particle size: diameter of 30 μm), Te particles (average particle diameter of 30 μm), and Zn particles (average particle diameter of 7 μm) are mixed with 25 parts by volume (20% by volume) of metal particles with respect to 100 parts by volume of glass particles to form a glass. A paste was made. It was found that when Zn particles are contained, sufficient adhesion to AZ61 cannot be obtained due to crystallization of the glass, and the joined body of glass-coated AZ61 and Al separates, causing AZ61 to corrode. In the case of other metal particles, the glass was not crystallized, the glass covered the metal particles, and the adhesion with AZ61 was good, so corrosion was hardly observed. It has been found that metal Al and Al alloys are effective as metal particles to be mixed in consideration of cost in addition to salt water resistance.

In Example 5, a glass-coated Mg alloy member was produced from the glass of Example 4 in the same manner as in Examples 1 and 2, and the combustibility in the air was examined. Here, AZ31 was used as the Mg alloy, and α-T was used as the solvent.

Table 10 summarizes the results of combustibility in air.

As shown in this table, AZ31 not coated with glass as a comparative example ignited at 450 ° C. or higher, but AZ31 coated with glass in the example ignited in the ignition test at 450 ° C. to 600 ° C. I didn't. That is, it was found that the glass-coated Mg alloys of the examples are effective in improving resistance to salt water and have high fire resistance.

FIG. 9 is a cross-sectional view showing an example of a joined body having a fastened structure.

In this figure, a Mg alloy member 11 and a dissimilar member 12 are fixed by a fixing jig 13 (also referred to as "fastening member" or "fastening jig"). The fixing jig 13 includes screws, bolts/nuts, rivets, and the like. Fixing jig 13 penetrates Mg alloy member 11 and dissimilar member 12 . A glass layer 21 is provided between the Mg alloy member 11 and the dissimilar member 12, between the Mg alloy member 11 and the fixing jig 13, and between the dissimilar member 12 and the fixing jig 13. .

FIG. 10 is a flow diagram showing a manufacturing method of the joined body of FIG.

As shown in FIG. 10, in step S11, an intermediate material containing glass (a paste containing a glass composition) is applied to the surface of the Mg alloy member to which the dissimilar member is to be attached and the inner wall surface of the hole into which the fastening jig is inserted. apply. That is, step S11 is a coating step.

In this example, the process of applying the paste to the Mg alloy member is described, but the paste may be applied to different members.

Next, in step S12, the Mg alloy member and the dissimilar member are overlapped and fixed by fastening with a fastening jig. The fastening force when fixing is such that the paste remains between the Mg alloy member and the dissimilar member and between the Mg alloy member and the fastening jig, and the dissimilar metals do not come into contact with each other. to the extent that there is no That is, step S12 is a superimposition step. When the fastening jig is not used, the Mg alloy member and the dissimilar member are overlapped and fixed.

In step S13, a glass layer is formed by baking and welding the paste by heating and pressurizing. At this time, it is heated to a temperature above the softening point of the glass composition. In this case, it is desirable to maintain the temperature for 10 seconds or more. That is, step S13 is a heating step. Moreover, it is desirable to pressurize appropriately to such an extent that dissimilar metals do not come into contact with each other and voids do not remain. Furthermore, the heating temperature is desirably 20° C. or more higher than the softening point. Moreover, the heating temperature is preferably lower than the ignition temperature of the Mg alloy and lower than the melting point of the Mg alloy.

Hereinafter, a method for manufacturing a coated magnesium alloy member and a method for manufacturing a joined body according to the present disclosure will be collectively described.

A method for producing a coated magnesium alloy member includes a substrate containing a magnesium alloy, and a fired coating provided on the surface of the substrate, the fired coating containing a predetermined lead-free low-melting-point glass composition. A method for manufacturing a member, comprising a coating step of applying a glass paste containing a lead-free low-melting-point glass composition to all or part of the surface of a base material, a drying step of drying the glass paste, and firing the glass paste. and a baking step.

The coating process can be carried out by hand coating, bar coater, roll coater, screen printing, spraying or dipping.

Moreover, each of the drying process and the baking process can be performed by any one of an electric furnace, laser welding, resistance welding, friction stir welding, and induction heating.

A method for manufacturing a joined body includes: a magnesium alloy member made of a magnesium alloy; a dissimilar member made of a material other than the magnesium alloy and generating a potential difference when in contact with the magnesium alloy member; and a glass layer, wherein the magnesium alloy member and the dissimilar member are arranged in a separated state, and the glass layer contains a predetermined lead-free low-melting-point glass composition, a method for manufacturing a joined body, , a coating step of applying a glass paste containing a lead-free low-melting-point glass composition to all or part of the surface of at least one of a magnesium alloy member and a dissimilar member, and a glass paste between the magnesium alloy member and the dissimilar member The method includes a bonding step of bringing the magnesium alloy member and the dissimilar member into contact with each other so as to sandwich them, a drying step of drying the glass paste, and a firing step of firing the glass paste.

In addition, the above-described methods can be employed in the coating process, the drying process, and the baking process.

11: Mg alloy member, 12: dissimilar member, 13: fixing jig, 20, 22: glass paste, 21: glass layer, 31: fixing jig, 41: salt water, 51: container, 52: lid.

Claims (18)

including vanadium oxide, phosphorus oxide, iron oxide and alkali metal oxides,
A lead-free low-melting-point glass composition that satisfies the following relational expressions (1), (2) and (3) in terms of oxide.
_{[ V2O5} ] _> [ _P2O5 ]>[ _Fe2O3 ] (1 _)
2 [ _Fe2O3 ] _≤ [ _V2O5 ]≤[ _P2O5 ]+ _{[ Fe2O3} ] ( ₂ )
[ _Fe2O3 ] _≤ [ _R2O ]≤2.5[ _Fe2O3 ] (3 ₎
(In the formula, [X] represents the content of component X, and its unit is "mol %". R is an alkali metal. Same below.) 2. The lead-free low-melting-point glass composition according to claim 1, which satisfies the following relational expression (4) in terms of oxide.
[ _V2O5 ] + [ _P2O5 ] + [ _Fe2O3 ] + _{[ R2O} ] _≥ 84 ( ₄ ) _{2. The lead-free low melting point glass composition of claim 1, wherein said R2O} is _K2O . further comprising any one or more of tellurium oxide, tungsten oxide and molybdenum oxide;
2. The lead-free low-melting-point glass composition according to claim 1, which satisfies the following relational expression (5) in terms of oxide.
[ _TeO2 ] + [ _WO3 ] + [ _MoO3 ] ≤ 16 (5) further comprising any one or more of tellurium oxide, tungsten oxide and molybdenum oxide;
2. The lead-free low-melting-point glass composition according to claim 1, which satisfies the following relational expression (6) in terms of oxide.
[ _TeO2 ] + _{[ WO3} ] + [ _MoO3 ] ≤ [ _Fe2O3 ] (6) 2. The lead-free low-melting-point glass composition according to claim 1, which satisfies the following relational expressions (7), (8) and (9) in terms of oxide.
27≤[ _V2O5 ]≤40 ₍ 7)
[ _V2O5 ] + [ _R2O ] ≥ 50 (8 _{)
[ R2O} ]≤2[ _Fe2O3 ] (9) 2. The lead-free low-melting-point glass composition according to claim 1, which has a softening point of 400[deg.] C. or lower and a crystallization temperature higher than said softening point by 80[deg.] C. or higher. a substrate comprising a magnesium alloy;
and a baked coating provided on the surface of the base material,
A coated magnesium alloy member, wherein the fired coating comprises the lead-free low melting point glass composition according to any one of claims 1 to 7. 9. The coated magnesium alloy member according to claim 8, wherein said fired coating comprises metal particles. 10. The coated magnesium alloy member according to claim 9, wherein said metal particles are an aluminum alloy. The coated magnesium alloy member according to claim 9, wherein the metal particles have an average particle diameter (D50) of 3 to 30 µm. 10. The coated magnesium alloy member according to claim 9, wherein the content of said metal particles in said fired coating is 20% by volume or more and 50% by volume or less. a magnesium alloy member made of a magnesium alloy;
a dissimilar member that is made of a material other than the magnesium alloy and that produces a potential difference when in contact with the magnesium alloy member;
a glass layer disposed between the magnesium alloy member and the dissimilar member;
The magnesium alloy member and the dissimilar member are arranged in a separated state,
A joined body, wherein the glass layer comprises the lead-free low-melting-point glass composition according to any one of claims 1 to 7. 14. The joined body according to claim 13, wherein said material of said dissimilar member has a lower ionization tendency than said magnesium alloy. a substrate comprising a magnesium alloy;
and a baked coating provided on the surface of the base material,
A method for producing a coated magnesium alloy member, wherein the fired coating comprises the lead-free low-melting-point glass composition according to any one of claims 1 to 7,
a coating step of coating a glass paste containing the lead-free low-melting-point glass composition on all or part of the surface of the substrate;
A drying step of drying the glass paste;
and a firing step of firing the glass paste. 16. The method of manufacturing a coated magnesium alloy member according to claim 15, wherein said coating step is performed by any one of hand coating, bar coater, roll coater, screen printing, spraying and dipping. 16. The method of manufacturing a coated magnesium alloy member according to claim 15, wherein each of said drying step and said firing step is performed by any one of an electric furnace, laser welding, resistance welding, friction stir welding and induction heating. a magnesium alloy member made of a magnesium alloy;
a dissimilar member that is made of a material other than a magnesium alloy and that produces a potential difference when in contact with the magnesium alloy member;
a glass layer disposed between the magnesium alloy member and the dissimilar member;
The magnesium alloy member and the dissimilar member are arranged in a separated state,
A method for producing a bonded body, wherein the glass layer comprises the lead-free low-melting-point glass composition according to any one of claims 1 to 7,
a coating step of coating a glass paste containing the lead-free low-melting-point glass composition on all or part of the surface of at least one of the magnesium alloy member and the dissimilar member;
A sticking step of contacting the magnesium alloy member and the dissimilar member such that the glass paste is sandwiched between the magnesium alloy member and the dissimilar member;
A drying step of drying the glass paste;
and a firing step of firing the glass paste.

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