JPH075934B2 - Composite member having excellent wear resistance, seizure resistance, and rough skin resistance, and method for manufacturing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite member having a laminated structure of a metal base material and a sintered alloy layer, and a method for producing the same.

[Conventional technology]

The surface of the body of the roll for hot rolling or cold rolling is less worn, less likely to have rough skin (cracks, unevenness, chipping, etc.), and less likely to cause seizure with the material to be rolled. is necessary. Conventionally, as a hot rolling roll, a cast iron roll having a body made of cast iron, as a cold rolling roll, a forging cylinder roll having a body made of forged steel is used, and its resistance In order to increase the wear resistance, cast iron rolls are highly alloyed in the body to increase the hardness by crystallizing cementite, double carbides and other special carbides, while forged steel rolls are highly alloyed in the body. By the heat treatment such as quenching and tempering, martensite transformation, bennatoite transformation, secondary hardening, etc. are caused to achieve a high hardness diagram. In addition to the above, as the cold rolling roll, alloy powder (C: 1.3 to 3%, C
It has also been proposed to use a sintered product using r: 15 to 21% and W + 2Mo: 8% or less) as a sintering material (Japanese Patent Laid-Open No. 58-213856).
issue).

[Problems to be solved by the invention]

For both cast iron rolls and forged steel rolls,
It is made from cast products. These cast products generally have a coarse structure, and the carbide exhibits a coarse net-like crystallization morphology. The body of the cast iron roll has this coarse cast structure almost as it is, while in the case of the forged steel roll, it passes through the structure change due to processing and heat treatment, but its structure is affected by the original cast structure, so its structure is It is relatively coarse. Therefore, these rolls have relatively good wear resistance, but have a problem that they have poor mechanical properties such as toughness and ductility. On the other hand, the sintered material of the alloy powder has a fine and fine structure and has good mechanical properties as well as wear resistance and surface roughening resistance superior to those of cast iron rolls and forged steel rolls,
There is a drawback that seizure easily occurs between the material to be rolled.

In view of the above, the present invention is to provide a composite member having surface characteristics such as wear resistance, surface roughening resistance, and seizure resistance, and good mechanical properties, particularly toughness, and a method for manufacturing the same. is there.

[Means and Actions for Solving Problems]

The composite member of the present invention comprises a metal base material and a sintered alloy layer formed on the surface of the metal base material, and the sintered alloy layer has a C: 2 to
3.5%, Si: 0.4% or less, Mn: 0.4% or less, Cr: 3-6%, V: 6
.About.12%, W: 5 to 14%, Co: 7 to 14%, Mo: 3 to 9%, and the balance being substantially Fe.

Hereinafter, the present invention will be described first for the reason of limiting the components of the sintered alloy layer. All percentages are weight percentages.

C: 2 to 3.5% C forms a solid solution in the matrix, and partly combines with V or W to form a carbide, thereby increasing the hardness of the sintered alloy. If the lower limit of the amount of C is set to 2%, if it is less than that, the balance of the amount of C necessary for forming V and W carbides is poor, and the effect of highly alloying the sintered alloy is sufficiently obtained. On the other hand, if it exceeds 3.5%, the toughness decreases due to coarsening of V and W carbides. Therefore, it is set to 2 to 3.5%.

Si: 0.4% or less Si enhances the hardenability of the sintered alloy, but it has little effect on the secondary hardening due to the tempering treatment, so the effect of improving high temperature hardness is small, so addition up to 0.4% is sufficient. is there.

Mn: 0.4% or less Mn is an element that improves the hardenability of sintered alloys, but secondary hardening due to tempering cannot be expected, so the effect of improving high-temperature hardness is small, so addition up to 0.4% is sufficient. Is.

Cr: 3 to 6% Cr is an element that forms a solid solution in the matrix of the sintered alloy to greatly enhance the hardenability and also exhibits resistance to temper softening. To obtain this effect, addition of 3% or more is required. But,
Increasing the amount of Cr causes a decrease in the seizure resistance of the sintered alloy, and particularly in applications such as hot rolling rolls, when it exceeds 6%, a problem of practical seizure occurs. Therefore, the Cr amount is 3 to 6
%.

V: 6-12% V is one of the most important elements that characterize the composition of the sintered alloy of the present invention. That is, V forms a solid solution in the matrix of a sintered alloy and precipitates as fine MC type carbides by the tempering treatment after quenching to cause a remarkable secondary hardening phenomenon, and also exhibits tempering softening resistance. . In addition, it contributes to the refinement of the sintered alloy structure and the improvement of mechanical properties such as toughness. Even if the addition amount is less than 6%, the effect of improving the mechanical properties can be obtained by the refinement of the structure, but by tempering treatment a sufficient amount of MC type carbides are precipitated and high hardness and high hardness are obtained. At least 6 for wear resistance
% Addition is required. The effect increases as the amount of addition increases, but if it exceeds 12%, precipitated carbides become coarse, mechanical properties such as toughness deteriorate, and machinability and the like deteriorate. Therefore, the V amount is set to 6 to 12%.

W: 5 to 14% W is an important element along with V. That is, W is a strong carbide-forming element, which forms a solid solution in the matrix and finely precipitates as an MC-type carbide by tempering treatment to cause remarkable secondary hardening. It also exhibits tempering softening resistance.
The lower limit of the amount added is 5%,
This is because the amount of MC type carbides deposited is insufficient and sufficient secondary hardening cannot be achieved. The effect increases as the added amount increases, but if it exceeds 14%, coarsening of precipitated carbides causes
See deterioration of mechanical properties such as toughness. Therefore, it is specified to be 5 to 14%.

Co: 7 to 14% Co promotes the precipitation of carbides by the tempering treatment and the strengthening of the sintered alloy by the conversion of the matrix to secondary martensite, and is effective in improving the high temperature hardness. To obtain this effect, it is necessary to add at least 7%, but above 14%, the effect is almost saturated. Therefore, it is set to 7 to 14%.

Mo: 3 to 9% Mo enhances hardenability and forms fine carbides by tempering treatment to cause remarkable secondary hardening, which is effective in maintaining high temperature hardness. If the added amount is less than 3%, the effect is not sufficient, while if it exceeds 9%, the effect is almost saturated. Therefore, it is set to 3 to 9%.

The sintered alloy layer that covers the surface of the metal base material of the composite member of the present invention has an increased composition of carbides in the sintered alloy layer due to the composition of components containing a relatively large amount of carbide-forming elements.
It exhibits excellent material properties such as abrasion resistance, seizure resistance, and surface roughness. The effect of improving the hardness and wear resistance is due to the effect of precipitation of carbides, and the effect of improving seizure resistance is due to the enrichment of carbides (increasing the area ratio of carbides in the sintered alloy increases , The contact area between the metal phases on the contact surface with the mating material becomes relatively small), which is considered to be due to the suppression and relaxation of the diffusion fusion phenomenon between the metal phases due to the frictional heat at the contact interface. .

The composite member of the present invention uses a metal powder having the above-mentioned composition as a sintering material, preferably by a hot isostatic pressing method to form a sintered alloy layer on the surface of the metal base material, and then firing the sintered alloy layer. It is manufactured by performing quenching and tempering treatments for refining the bonded gold layer.

The formation of the sintered alloy layer on the surface of the metal base material may be performed according to a known process. That is, on the surface of the metal substrate,
Forming a packed layer of a metal powder that is a sintering material using an appropriate encapsulant, degassing the powder packed layer, then sealed, subjected to hot isostatic pressing, for example 900 ~ 1200 ° C x 5
A sintered alloy layer is formed under the condition of 00 to 1500 kgf / cm ² . When the metal powder used has a relatively large amount of oxide film, a reducing gas may be introduced under heating to reduce the oxide film before deaeration / sealing of the powder packed layer. . After sintering is complete, machining is applied to remove the encapsulant and make any necessary shape modifications. The material of the metal base material is arbitrarily selected according to the intended use and use conditions of the composite member, and requires strength and toughness, such as a rolling roll. In this case, various tough steels such as SCM steel and SMCM steel are preferably used.

The quenching temperature for quenching the sintered alloy layer is 1050 to 12
The temperature is 50 ° C., preferably 1100 to 1200 ° C., and cooling from that temperature is performed by gas cooling using a gas of approximately normal pressure as a refrigerant, or pressurized gas (for example, 3 to prevent cracking and deformation).
It is preferably carried out by forced gas cooling using a refrigerant of about 7 kgf / cm ² ). The tempering process that follows the above quenching process is
After heating and holding at 500 to 600 ° C., more preferably 520 to 580 ° C., gradual cooling is performed once or plural times (for example, 2 to 4 times).
It is preferably achieved by repeating this process. By this tempering treatment, the sintered alloy layer undergoes a phase transformation from austenite of its matrix to martensite or bentonite, and secondary hardening due to fine precipitation of MC type carbides.

The composite member of the present invention has a dense and fine structure of a sintered alloy layer formed by hot isostatic pressing, a combination of the alloy component composition and the heat treatment effect of quenching and tempering,
Since it has a high degree of wear resistance, surface roughening resistance, and seizure resistance, and has a composite structure with a metal member, for example, a machine with sufficient strength and toughness when it is used as a body member of a rolling roll. When combined with other members such as arbor, it can be assembled into a desired structural member by a simple operation such as shrink fitting.

〔Example〕

Example 1 As shown in FIG. 4, a cylindrical metal encapsulant (C) was fitted into a ring-shaped metal base material (10) and weld-bonded to the inside of the capsule member (C). The metal powder (20), which is a sintering material, is filled, deaerated at room temperature, sealed, and then subjected to hot isostatic pressing. After sintering, capsule material (C)
Is removed by machining, and rough machining is performed leaving a margin of 1 mm. Next, quenching and tempering treatments for refining the sintered alloy layer are performed, and after the heat treatment, the metal substrate (10)
Finishing is applied to the inner diameter surface of. Through the above steps, an annular composite member having a concentric two-layer laminated structure of an outer layer which is a sintered alloy layer and an inner layer which is a metal base material was obtained. Outer diameter: 364m
m, inner diameter: 220 mm, length: 100 mm, sintered alloy layer layer thickness: 7 mm.

[I] Metal substrate Material: SCM440 steel (0.4% C-0.35% Si-0.75% Mn-1% Cr
-0.2% Mo) Size: Inner diameter (D ₁ ) 200 mm, outer diameter (D ₂ ) 350 mm, capsule material outer diameter (D ₃ ) 410 mm, width (W): 120 l (mm) [II] Sintered material (metal powder) ) Gas atomized powder (100 mesh under) Component composition (wt%): C: 2.2, Si0.3, Mn0.3, Cr4.4, V6.2, W7.1, Co10.8, Mo7.2, FeB
al. Oxygen concentration 150ppm.

[III] Sintering conditions 1150 ℃ × 1000kgf / cm ² × 3Hr [IV] Heat treatment of the sintered alloy layer (1) Quenching treatment After holding at 1200 ℃ for 1 hour in a vacuum quenching chamber, gas (normal temperature and normal pressure Ar gas ) Is introduced and quenching is performed by gas cooling.

(2) Tempering treatment The treatment of heating and holding at 540 ° C for 5 hours and allowing to cool is repeated three times.

[V] Material of sintered alloy layer (1) Surface hardness The surface hardness of the sintered alloy layer is as high as Hs92 to 94 over the entire surface in the axial and circumferential directions, and the variation is within ± 1Hs. is there. The amount of carbide in the sintered alloy is about 22% (area). Further, it was confirmed by ultrasonic flaw detection that the interface between the sintered alloy layer and the metal base material was completely fusion-bonded over the entire circumference.

(2) Seizure resistance test Fig. 1 shows the results of measuring the seizure resistance of the sintered alloy layer by the flex type seizure test (load: 150 kg). FIG. 2 and FIG. 3 are comparative examples, and FIG. 2 shows chilled cast iron which is a conventional typical material for the body of a casting roll, and FIG.
The figure shows C2.8 as the sintering material, instead of the metal powder.
%, Si0.4%, Mn0.4%, Ni1.2%, Cr20%, Mo1%, Fe B
The measurement results are shown for the sintered alloy layer formed through the same sintering conditions and quenching and tempering treatment as those described above except that the metal powder of al was used. The carbide amount in the comparative sintered alloy is about 22% (area), and the surface hardness is Hs.
It is about 80. In each figure, the curve (a) is the load (kg) of the mating material (material: SUS304) on the surface of the test piece, and the curve (b).
Is the rotational torque (kg · cm). The vertical scale showing load (kg) is 50 kg, the vertical scale showing torque (kg · cm) is 10 kg · cm, and the horizontal axis is time (1 scale 10 seconds).

For chilled cast iron (Fig. 2), the torque is not stable, and about 40kg ・
The fluctuation range of cm (the fluctuation range is 160 to 200 kg · cm) is shown. The vertical fluctuation of the torque indicates that seizure occurs at the contact interface with the mating material. In the comparative sintered alloy (Fig. 3), the vertical fluctuation of the torque is extremely large (the maximum torque is about 260 kg · cm), and significant seizure occurs on the contact surface with the mating material. On the other hand, the torque of the sintered alloy of the invention example (Fig. 1) has a peak (about 180 kg · cm).
, The fluctuation range of about 10 kgcm (the fluctuation range is 14
It is stable within the range of 0 to 150 kg · cm), and it can be seen that a stable interface state without seizure with the mating material is stably maintained.

(3) Test using actual machine An arbor was fitted into the hollow hole of the composite member of the present example by shrink fitting, and after performing necessary finishing work as a rolling roll, it was used as a roll for finishing rolling round steel in actual use. As a result, compared with the conventional high-hardness ductile cast iron roll (surface hardness Hs: 65), which is a typical casting roll, the wear rate is about 1/6, and the surface roughness is extremely slight, There was no seizure.

Example 2 As shown in FIG. 5, a metal cylinder as an encapsulant (C) is externally fitted to a cylindrical metal substrate (10) and fixed by welding, and the inside of the encapsulant (C) is closed. The metal powder (20), which is a sintering material, is filled in the container. While vacuum degassing this
After heating to 800 ° C., the inside of the metal powder layer is vacuum degassed and replaced with a reducing gas (H ₂ gas) to reduce the metal powder in the capsule, and then vacuum degassing is performed again and sealing is performed. Then, hot isostatic pressing is performed, and after the completion of sintering, the encapsulant (C)
Is removed by machining, and rough machining is applied leaving a margin of 1 mm. Then, the sintered alloy layer is subjected to quenching and tempering treatment, and after the heat treatment, the inner surface of the metal base material (10) is finished. Through the above steps, a hollow cylindrical composite member having a concentric two-layer laminated structure of an outer layer which is a sintered alloy layer and an inner layer which is a metal substrate was obtained. Outer diameter: 430 mm, inner diameter: 2
50mm, length: 410mm, layer thickness of sintered alloy layer: 15mm.

[I] Metal substrate Material: S45C steel (0.45% C-0.7% Mn) Size: Inner diameter (D ₁ ) 200mm, outer diameter (D ₂ ) 400mm, capsule material outer diameter (D ₃ ) 490mm, length (L ) 420mm [II] Sintered material (metal powder) Water atomized powder (150 mesh under) Component composition (wt%): C2.7, Si0.2, Mn0.3, Cr4.0, V9.2, W9.5 , Mo3.6, Co9.3, Fe Ba
l Oxygen concentration 950PPm.

[III] Sintering conditions 1100 ℃ × 1200kgf / cm ² × 3Hr [IV] Heat treatment of sintered alloy layer (1) Quenching treatment After heating and holding at 1200 ℃ for 1 hour in a vacuum quenching chamber, Ar of 5kgf / cm ² Gas (normal temperature) is introduced as a refrigerant, and quenching is performed by forced gas cooling.

(2) Tempering treatment A tempering treatment of heating and holding at 520 ° C. for 6 hours and then allowing to cool is repeated three times.

[V] Material of sintered alloy layer (1) Surface hardness The surface hardness of the sintered alloy layer of the obtained composite member is as high as Hs91 to 94 over the entire surface in the axial direction and the circumferential direction, and varies. Is within ± 1.5Hs. The amount of carbide in the sintered alloy is about 2
It is 5% (area). Further, it was confirmed by ultrasonic flaw detection that the interface between the sintered alloy layer and the metal substrate was completely fusion-bonded over the entire circumference.

(2) Seizure resistance test The seizure resistance of the sintered alloy layer was measured by a Falex seizure tester, and was substantially the same as the measurement result (FIG. 1) of the sintered alloy layer of Example 1. The measurement result was obtained. The maximum torque is about 190 kgcm, and the fluctuation range in the stable area after the peak is about 10 kgcm (the fluctuation range is 140 to 150 kgcm.
Range).

(3) Test on actual equipment The arbor was fitted and fixed in the hollow hole of the obtained composite member by shrink fitting, and after performing necessary finishing processing as a rolling roll, it was used as an actual equipment as a roll for flat finishing rolling. As a result, compared with the conventional chilled cast iron roll, which is a typical casting roll, the wear rate is about 1/7, the surface roughness is extremely slight, and there is no seizure with the material to be rolled. It was

〔The invention's effect〕

The composite member of the present invention has excellent surface abrasion resistance, surface roughening resistance, and seizure resistance, has the toughness necessary as a structural member, and is easy to assemble with other members. By using the composite member of the present invention in combination with, for example, an arbor or the like as a body material of a rolling roll, the service life of the rolling roll is improved, and the surface state of the body is stable. Also effective in improving the quality of rolled materials. The composite member of the present invention is also useful as a structural member such as a bearing and a cylinder.

[Brief description of drawings]

1 to 3 are graphs showing torque and load change measurement results by the Falex seizure test, and FIGS. 4 and 5 are sintered materials (metal powders) filled on the outer peripheral surface of the metal base material. It is a radial direction partial sectional view which shows an example. 10: Metal substrate, 20: Sintered material, C: Capsule material.

Claims (2)

[Claims] 1. A metal substrate, and C: 2 to 3.5%, Si: 0.4% or less, Mn: 0.4% or less, Cr: 3 to, formed on the surface of the metal substrate.
6%, V: 6-12%, W: 5-14%, Co: 7-14%, Mo: 3-9
%, And the balance being a sintered alloy layer which is substantially Fe. 2. C: 2 to 3.5%, Si: 0.4% on the surface of the metal substrate.
Below, Mn: 0.4% or less, Cr: 3-6%, V: 6-12%, W: 5-14
%, Co: 7 to 14%, Mo: 3 to 9%, the balance being substantially Fe as a sintering material, a sintered alloy layer is formed by a hot isostatic pressing method, and then 1050 Quenching from ~ 1250 ℃,
And a tempering treatment at 500 to 600 ° C., and a method for producing a composite member comprising a metal base material and a sintered alloy layer having the above component composition.