JP2001011579A - Manganese alloy steel, shaft and screw member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide steel free from the need of heat treatment such as carburizing and nitriding and plating, in which the content of Ni is the minimum including zero and excellent in cuttability. SOLUTION: This steel has a steel compsn. contg. 0.05 to 0.50% C, <=0.5% Si, 6.0 to 15.0% Mn, 0 to 5.0% Ni, 10 to 20% Cr, 0.04 to 0.30% N, <=0.10% Al, <=0.030% S, 0 to 3.0% Mo and 0 to 3.0% Cu, and the balance Fe with inevitable impurities and also satisfying the inequality of F=Ni+4.71+16.7C-0.51Si+0.088Mn+0.42Cu-0.92Cr--1.3Mo+14.6N-2.3Al>=0.5 (each element denotes weight%).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manganese alloy steel and a shaft member and a screw member using the same, and more specifically, to interior and exterior parts of OA-related equipment, motors, automobiles, construction equipment, and other products. TECHNICAL FIELD The present invention relates to a manganese alloy steel which is excellent as a steel material constituting high strength, is excellent in corrosion resistance, wear resistance, and machinability and is inexpensive, and a shaft member and a screw member using the same.

[0002]

2. Description of the Related Art Conventionally, as a component constituting material for OA-related equipment, motors, automobiles, building equipment, etc., plating processing,
Steel materials or various stainless steel materials based on carbonitriding treatment or the like are used. In other words, these steel materials have been accompanied by a surface treatment for realizing corrosion resistance, wear resistance and high strength depending on the application, or a surface treatment related thereto.

[0003] In addition, such parts are often processed into a target shape by cutting, but since the cut surface at that time is roughened, it is necessary to adjust the surface roughness required for the target part. Further, processing such as grinding and burnishing is required. Similarly, distortion also occurs in surface treatment such as carburizing and nitriding,
Since surface roughness is deteriorated, reprocessing for correcting them is necessary. Furthermore, when performing these treatments, very careful attention is required to prevent scratches during handling.

[0004]

As described above, there are the following problems in the various materials of the constituent parts and the respective processes in the prior art. For example, expensive materials such as stainless steel have problems in terms of price, plating has environmental problems, and surface treatments such as carburizing, quenching, nitriding, etc. have an accuracy of distortion. There's a problem.

Further, the machining area of an automatic lathe used for mass production of shafts, screws, etc. has a low peripheral speed, a low feed rate, a high wall thickness, and it is difficult to keep the surface roughness of a cut surface below a certain level. . For example, when SUS303 is the work material, the cutting surface is good at the initial stage of Ry around 3μ, but the work material contains 8% Ni as much as possible, so a Swiss type automatic lathe with a guide bush In this case, the galling phenomenon of the guide bush always becomes a problem, and deterioration of the surface roughness cannot be avoided.

[0006] Even in the past, some materials have been proposed to solve such problems. For example,
Japanese Unexamined Patent Publication No. 55-94464 discloses a low-melting material containing 0.5% or less of C, 2.0% or less of Si, 7 to 40% of Mn, and 0.0005 to 0.0200% of Ca, and having a good machinability with an oxide composition. Carbon high manganese steels have been proposed.

Japanese Patent Application Laid-Open No. Sho 55-76042 discloses that C:
2.0% or less, Si: 2.0% or less, Mn: 7 to 40%, Ca: 0.00
A high carbon high manganese steel containing 0.05 to 0.0200% and having a good machinability with an oxide composition specified has been proposed.

However, these materials are not sufficient in terms of corrosion resistance, wear resistance, and the like, and are also improved in machinability by controlling the inclusion composition by adding Ca with respect to machinability. Since the technique is intended for such a purpose, it is not possible to omit surface treatments such as carburizing and nitriding and to omit plating treatment, which is not sufficient for solving these problems.

[0009] Here, an object of the present invention is to provide a material having a minimum or zero Ni content without the need for surface treatment such as carburizing and nitriding, and without plating, and having high strength, corrosion resistance, and corrosion resistance. An object of the present invention is to provide a material having excellent wear and machinability.

Still another object of the present invention is to eliminate the need for surface treatment such as carburizing and nitriding, and to achieve high strength with a material having a minimum or zero Ni content without performing surface treatment such as plating. To provide a shaft and a screw having excellent corrosion resistance, wear resistance, and machinability.

[0011]

Means for Solving the Problems The inventors of the present invention have made various studies in order to achieve the above object, and since the shaft member and the screw member are first required to have improved machinability, the machinability is improved. We first focused on securing In order to improve the machinability, it is desirable that the microstructure is a single phase microstructure in terms of metallography. Therefore, in the case of the present invention, a stable single phase of an austenite phase or a ferrite phase is desired. Then, the present inventors paid attention to an austenitic structure and a metastable austenitic structure from the viewpoint of securing high strength.

Generally, to obtain a stable austenite structure at room temperature, it is necessary to add a relatively large amount of two or three of Ni, Cr and Mn in a well-balanced manner. A typical example is austenitic stainless steel such as SUS304 and SUS316. However, it is not enough to define such two or three elements.

Incidentally, a Schaeffler phase diagram is generally known as an index of the stability of the austenite structure.
However, this phase diagram uses the following equations as Nieq. And Creq., Respectively.
Since this is an index using only seven elements of Ni, Cr, C, Mn, Mo, Si, and Nb, it was insufficient for a material containing other elements.

Nieq. = Ni-30C + 0.5 Mn (%) Creq. = Cr + Mo + 1.5 Si + 0.5 Nb (%) Here, the present inventors obtain a stable austenite phase or a single phase of metastable austenite. For this reason, attention was paid to the amount of δ ferrite. Since the magnetic permeability also increases as the amount of δ ferrite increases, the present inventors manufactured steel ingots adjusted to various components, investigated the amount of δ ferrite in the steel ingot, A correlation study was performed. As a result, it was found that when the F value represented by the following formula (1) is 0.5 or more, the amount of δ ferrite in the steel ingot is remarkably reduced, that is, a stable austenite phase or a single phase of metastable austenite is obtained.

F = Ni + 4.71 + 16.7C−0.51Si + 0.088Mn + 0.42Cu−0.92Cr−1.3Mo + 14.6N−2.3Al ≧ 0.5 (Each element is% by weight) (1) The present inventors Use expensive Ni separately from the Schaeffler phase diagram
Finding the above-mentioned index that can be evaluated by balance and designing the components as shown below, unexpectedly, excellent corrosion resistance and abrasion resistance are exhibited, and as a result, surface treatment such as carburizing / nitriding It is unnecessary, and the desired characteristics can be obtained without further surface treatment such as plating.
Knowing that a steel material whose content can be reduced to a minimum or substantially zero can be obtained, the present invention has been completed.

Here, the present invention is as follows. (1) By weight%, C: 0.05 to 0.50%, Si: 0.5% or less, Mn: 6.0 to 15.0%, Ni: 0 to 5.0%, Cr: 10 to 20%, N: 0.04 to 0.30%, Al: 0.10% or less, S: 0.030% or less, Mo: 0 to 3.0%, Cu: 0 to 3.0%, the balance is steel having a composition consisting of Fe and unavoidable impurities, and having high strength that satisfies the formula (1). Manganese alloy steel with excellent corrosion resistance, wear resistance and machinability.

F = Ni + 4.71 + 16.7C−0.51Si + 0.088Mn + 0.42Cu−0.92Cr−1.3Mo + 14.6N−2.3Al ≧ 0.5 (Each element is% by weight) (1) (2) The steel When the composition further contains S: 0.030 to 0.350%, Pb:
The manganese alloy steel according to (1), containing one or more free-cutting elements selected from the group consisting of 0.04 to 0.35% and Te: 0.002 to 0.060%.

(3) The steel composition further comprises: Mo: 0.010 to 3.
The manganese alloy steel according to the above (1) or (2), containing 0%. (4) The manganese alloy steel according to any one of (1) to (3), wherein the steel composition further contains Cu: 0.10 to 3.0%.

(5) Forming or heat-treating a steel having the steel composition according to any of (1) to (4) above,
A shaft member wherein Hv ≧ 200. (6) A screw member wherein the steel having the steel composition according to any one of (1) to (4) is subjected to forming or heat treatment so that Hv ≧ 200.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, the reason why the chemical composition of the manganese alloy steel according to the present invention is defined as described above will be described. In this specification, “%” is “% by weight” unless otherwise specified.

C (carbon) C is an element that stabilizes the austenite structure,
% Or more. However, when the content exceeds 0.50%, carbides precipitate at the grain boundaries of austenite, and the cold workability and corrosion resistance deteriorate. Therefore, the upper limit is set to 0.50%.
0.10 ~ 0.30% for adjusting hardness after processing
It is.

Si (Silicon) Si is added to molten steel as a deoxidizer in the smelting process.
Excessive addition increases non-metallic inclusions, which are deoxidation products, and degrades the cleanliness of the steel. Further, since Si is a ferrite-forming element, if it is contained in a large amount, the austenite structure becomes unstable. Therefore, the upper limit was set to 0.5%.

Mn (manganese) Mn is an inexpensive element that stabilizes the austenite structure, and can reduce Ni that stabilizes the austenite structure. As an alternative to Ni, Mn is contained at 6% or more. However, when the content exceeds 15%, the hot workability is reduced, and cracks may occur during hot rolling, which is not preferable. Therefore, the upper limit was set to 15%. Preferably Mn is 8-13%
It is.

Ni (nickel) Ni is a desired additive element and is an element effective for stabilizing the austenite structure and improving corrosion resistance. However, Ni is expensive, so if Ni is contained in excess of 5%, the cost is increased. And it is preferable to reduce the amount of addition as much as possible in view of the influence on the environment.

On the other hand, since the stability of the austenite structure can be obtained by satisfying the above-mentioned formula (1), when Ni is added in the present invention, the Ni content is preferably 0.1%.
5% or more and 5.0% or less.

Cr (Chromium) Cr is a ferrite-forming element, but is an essential element for imparting corrosion resistance. 10% for imparting corrosion resistance
The above is included. However, if it exceeds 20%, the stability of the austenitic structure is impaired. Therefore in the present invention
The Cr content was 10 to 20%. Preferably it is 13 to 17%.

N (Nitrogen) N, like C, is an element that stabilizes the austenite structure and contributes to solid solution strengthening. Further, N has an effect of improving stress corrosion cracking, and for that purpose, N is contained in an amount of 0.04% or more. This stabilizes the austenitic structure,
It is also possible to avoid adding a large amount of expensive elements such as Ni for the purpose of improving corrosion resistance. In addition, N forms a nitride, and the nitride provides work hardening and improves wear resistance. On the other hand, it is extremely difficult to melt steel having an N content exceeding 0.30%, and such a high-N steel is not preferable because it may cause defects due to blowholes in the steel ingot. Therefore, the N content in the present invention is 0.04 to 0.30%
And Preferably it is 0.10 to 0.25%.

Al (aluminum) Al is a strong deoxidizer and is added to molten steel during the smelting process. However, if the addition amount exceeds 0.10%, oxides as nonmetallic inclusions increase, and the cleanliness of the steel deteriorates. Therefore
The content of Al was set to 0.10% or less.

S (Sulfur) S is usually allowed as an unavoidable impurity up to about 0.030%. Therefore, even in the present invention, when the effect of improving the machinability by adding S is not expected, S is 0.030%.
Restrict to the following.

However, since S has the effect of improving the machinability by adding S, if machinability is required, 0.030
% Or more, preferably 0.050% or more. But 0.
If the content exceeds 350%, hot workability and corrosion resistance deteriorate. Therefore, the upper limit was set to 0.350%.

When machinability cannot be obtained by addition of S or when addition of S is not preferable, one or two of Pb and Te are added, if necessary, in combination with S to improve machinability. Secure. In this case, the amount of Pb added is generally 0.
04 to 0.35%, Te: 0.002 to 0.060%. Addition beyond this is because Pb increases the precipitation of aggregated particles of lead, and Te increases the material defects due to the problem of hot cracking.

Thus, in the present invention, for improving machinability, S: 0.030 to 0.350%, Pb: 0.04 to 0.35%, and Te:
One or more selected from the group consisting of 0.002 to 0.060% are added.

Mo (Molybdenum) Mo may not be added. If added, it is effective in improving cold workability since the formation of work-induced martensite is suppressed during cold working. However, since Mo is a ferrite-forming element, when added in an excessive amount, the austenite structure becomes unstable. Therefore, when Mo is added, its content is set to 3% or less.

Cu (copper) Cu need not be added. If added, it has the effect of stabilizing the austenite structure during cold working. But 3.0
%, The hot workability is significantly reduced. Therefore, the content of Cu is set to 3.0% or less.

In the present invention, the F value defined by the equation (1) is
It is specified to be 0.5 or more, in order to secure the austenite single phase structure by making the amount of δ ferrite as small as possible in order to make it non-magnetic, that is, to zero, and the upper limit is not limited. The F value is preferably 4.5% or less in order to obtain a stable austenite single-phase structure with the minimum necessary amount of each element while ensuring the properties and high strength.

Thus, according to the present invention, a material having excellent wear resistance can be obtained, so that surface treatment such as carburizing and nitriding is not required. In addition, since the material has excellent corrosion resistance, surface treatment such as plating is not required. Furthermore, equation (1)
Is satisfied, the Ni content can be limited to 5.0% or less regardless of the austenitic single phase material.

The manganese alloy steel according to the present invention can be used as a general steel material, and can be used, for example, as a plate material, a pipe material, a bar material, a wire material, and the like. Its application may be used not only as a functional component such as a shaft material or a screw material but also as a structural material.

Next, in the case of manufacturing a shaft member and a screw member using the steel of the present invention, a forming method and a heat treatment method will be described. Here, the "shaft member" is exemplified by a carriage shaft used in a serial printer of an OA device terminal, a type wheel axle used in a type wheel selection type printer, a motor shaft, and the like. , Self-drilling screws, tapping screws, building bolts and the like.

Generally, these members are coated with a lubricant through a scale removing process from a material, formed into an intermediate product by cold rolling, drawing, and forging (hot and cold), and then processed as they are. It is used after further forming by a state or cutting, or a forging process, or a heat treatment for softening or hardening (usually a heat treatment for softening) is performed, but the same applies to the present invention.

In the case of shafts used in general OA equipment and automobile shafts, products which are finally subjected to carburizing treatment, nitriding treatment, or plating treatment through various processes using a steel material are subjected to the present invention. According to the invention, these surface treatments can be omitted.

As described above, according to the present invention, surface treatments such as carburizing, nitriding, and plating are not required in Japan, and work costs, energy costs, distribution costs, and the like are unnecessary. For overseas production, there is no need for a carburizing / nitriding furnace and plating equipment, reducing initial investment and providing the same advantages as in Japan.

In addition, in recent years, as public opinion on prevention of global warming and regulation of chemical substances has been increasing, the present invention can omit carburizing, nitriding and plating in order to save resources and energy and minimize environmental pollution. Is an invention of great significance today.

[0043]

EXAMPLE A steel having a steel composition shown in Table 1 was melted by a test, and a round bar having a diameter of 30 mm and a wire rod having a diameter of 6.5 mm were obtained by hot rolling. The round bar thus obtained was used as a test material for a machinability test and a corrosion resistance test, and the wire was used as a test material for a cold workability, abrasion resistance and a cut surface skin evaluation test, respectively. Cold workability was evaluated by solution treatment conditions and wire drawing.

The corrosion resistance, machinability and abrasion resistance were evaluated by conducting tests in the following manner. The results are summarized in Tables 1 to 3. In Table 1, steel Nos. 1 to 20 are examples of the present invention and steel Nos. 21 to 35 are comparative examples. Steel Nos. 7 to 20 and Nos. 28 to 35 are materials to which free-cutting elements are added for the purpose of improving machinability.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

Machinability: The cutting conditions are as shown in Table 2, wherein the tool is a macro alloy AF1, the rotation speed is 2650 rpm, and the peripheral speed is 50 m / mi.
n, and the feed rate was 25 μm / RE. The machinability was evaluated based on the finished state of the cutting surface. Ie 30mm
When the round bar was turned on a lathe, the finish surface showed no peeling scratches at all, and the round bar shows slight peeling defects but was judged to have no practical problem by reworking. Δ ”, those that were markedly peeled and judged to be unsuitable for practical use were evaluated as“ x ”, and those other than x were evaluated as acceptable.

Table 2 and Table 3 show the results obtained by extracting the No. 15 material and performing a turning test, a surface roughness test and a hole-boring test. The comparison materials are SUS416, which is currently used for turning and surface roughness, and standard S45C, SU, which has the minimum drilling required for mass production.
Compared to S304.

As can be seen from the results shown in Table 3, the turning property and surface roughness are superior to SUS416, and the drilling properties are slightly inferior to S45C, but have better machinability than SUS304. It was confirmed that.

In Table 3, the drilling property was evaluated. The cutting conditions at that time were as follows: a drill with a tool of 2.6 mm, a drill rotation speed of 500 rpm, an automatic feed amount of 0.07 μm / RE, and a feed depth of
It was 10 mm. In Table 3, solution treatment A was 1100 ° C. × water cooled, B was 1150 ° C. × water cooled, C was 1200 ° C. × water cooled, and D was 1050 ° C. × water cooled after drawing.

Corrosion resistance: After turning a 30 mm round bar with a lathe, # 500
The test specimen finished and polished with the paper of the temperature of 45 ℃,
The sample was held in an atmosphere of 90% humidity for 360 hours, and a rust rating of JIS steel materials of 9 or more was rated as “」 ”, and a product that did not meet the criteria was rated as“ × ”.

Further, No. 15 was drawn from a 6.5 mm wire as a representative sample, and was compared with the corrosion resistance of SUS416 currently used. The results are summarized in Table 4. As can be seen, the corrosion resistance of the steel of the present invention is good, and SUS4
Better than 16.

[0054]

[Table 4]

Cold workability: Cold workability is determined by using 6.5 mm wire.
It was evaluated by drawing wire to 6.0 mm. The evaluation method was compared between a case where solution treatment was performed before wire drawing and a case where wire drawing was performed without solution treatment. The results are summarized in Table 5. The hardness of the drawn wire without heat treatment was not much different from that of the solution-treated material, and no phase transformation was observed due to the drawn wire, confirming that the cold workability was good.

[0056]

[Table 5]

Abrasion resistance: Abrasion resistance is as follows.
It was pulled out to a mm and compared with a shaft and a SUS416 material soft-nitrided to the same size SUM24L material in a severe repeated sliding test of the printer. The results are shown in Table 6.

Under the same sliding conditions, it was confirmed that the material was equivalent to or superior to the current material. Since the sliding resistance shows good results without depending on the hardness of the material,
The hardness of the material of the present invention can be selected according to the required strength in the structure.

[0059]

[Table 6]

[0060]

According to the present invention, a high-strength manganese alloy steel having both corrosion resistance, wear resistance, machinability and galling resistance can be obtained.
It becomes possible to omit surface treatment such as plating and carbonitriding of conventional component materials of A-related equipment, motors, automobiles, buildings and the like, and use them instead.

For example, even if a steel having high strength and wear resistance and excellent corrosion resistance and machinability is required, if a component satisfying the formula (1) is adjusted, high strength and wear resistance can be obtained. Can provide a manganese alloy steel excellent in resistance, corrosion resistance and machinability.

Therefore, according to the present invention, unlike conventional manganese-based steels, a versatile steel material which has many excellent properties at the same time and can be arbitrarily provided to other fields according to the needs at that time. Can be provided.

 ──────────────────────────────────────────────────続 き Continuing from the front page (71) Applicant 591274299 Shinpokoku Iron & Steel Co., Ltd. 5-13-1 Shinjuku-cho, Kawagoe-shi, Saitama (72) Inventor Takayuki Nakamura 1 Konomi-cho, Kokurakita-ku, Kitakyushu Sumitomo Metal Industries, Ltd. Inside the Ogura Works (72) Inventor Chihiro Kitazawa 3-3-5 Yamato, Suwa-shi, Nagano Prefecture Seiko Epson Corporation (72) Inventor Naohisa Miyashita 1-1544 Kamikawa, Suwa-shi, Nagano Prefecture Daito Manufacturing Co., Ltd. (72 Inventor Eijiro Muramatsu 5-13-1, Shinjuku-cho, Kawagoe-shi, Saitama

Claims (6)

[Claims] C: 0.05 to 0.50%, Si: 0.5% or less, Mn: 6.0 to 15.0%, Ni: 0 to 5.0%, Cr: 10 to 20%, N: 0.04 to 0.30%, Al: 0.10% or less, S: 0.030% or less, Mo: 0 to 3.0%, Cu: 0 to 3.0%, the balance is composed of Fe and unavoidable impurities, and has a steel composition satisfying the formula (1). Manganese alloy steel with excellent corrosion resistance, wear resistance and machinability. F = Ni + 4.71 + 16.7C-0.51Si + 0.088Mn + 0.42Cu-0.92Cr-1.3Mo + 14.6N-2.3Al≥0.5 (Each element is% by weight) ... (1) 2. The steel composition further comprises S: 0.030 to 0.35.
The manganese alloy steel according to claim 1, containing one or more free-cutting elements selected from the group consisting of 0%, Pb: 0.04 to 0.35%, and Te: 0.002 to 0.060%. 3. The steel composition further comprises: Mo: 0.010 to 3.0.
% Manganese alloy steel according to claim 1. 4. The steel composition further comprises Cu: 0.10-3.0%
The manganese alloy steel according to any one of claims 1 to 3, further comprising: 5. A steel having the steel composition according to claim 1 which is subjected to forming or heat treatment to obtain Hv.
A shaft member characterized by ≧ 200. 6. A steel having the steel composition according to claim 1 which is subjected to forming or heat treatment to obtain Hv.
A screw member characterized by ≧ 200.