JP2001226746A - Manganese alloy steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new steel provided with corrosion resistance which allows heat treatment and surface treatment such as planting treatment to be needless and moreover having characteristics excellent in wear resistance and the facial roughness of the worked surface. SOLUTION: This manganese alloy steel contains, by weight, 0.05 to 0.50% C, <=0.5% Si, 6.0 to 25% Mn, <=0.05% P, <=0.35% S, 0 to 3.0% Cu, 0 to 5.0% Ni, 5.0 to 20.0% Cr, 0 to 3.0% Mo, 0.04 to 0.30% N, <=0.10% Al, and the balance Fe with inevitable impurities, and, MnS as nonmetallic inclusions on which the ones having the shape with a width of <=3 μm and a length of <=40 μm occupy >=90% is finely dispersed into the inside.

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 more particularly, to an alloy steel suitable as a material for components inside equipment.

[0002]

2. Description of the Related Art Conventionally, steel materials or various stainless steel materials premised on plating, carbonitriding, and the like have been used as component materials for OA-related equipment, motors, automobiles, building equipment, and the like. These steel materials have been subjected to a surface treatment for realizing corrosion resistance, abrasion resistance, and high strength, or a surface treatment related thereto, depending on the use.

[0003] In addition, parts using the above-mentioned steel materials are often machined into a target shape by cutting. However, since the machined surface is roughened, a grinding process or the like may be further performed according to the demand for surface roughness. Surface treatment such as burnishing is required, and even when heat treatment or the above-described surface treatment such as carburizing / nitriding is performed, distortion and deterioration of surface roughness occur.In order to correct these, Again, it was necessary to surface-treat the part. Furthermore, when performing these surface treatments and surface treatments, it is necessary to pay close attention to preventing scratches during handling.

[0004]

In the case of a steel material or a surface treatment as described above, expensive materials such as stainless steel are problematic in terms of price, and plating is an environmental problem. In addition, heat treatments such as carburizing, quenching, nitriding, and the like have a problem in that distortion may cause a defect in shape accuracy. Further, in a machining area of an automatic lathe used for mass production of shaft members, screws, and the like, it is difficult to maintain the surface roughness of a cut surface at a certain level or less at a low peripheral speed, a low feed, and a high wall thickness. For example, when SUS303 is a work material, the cut surface is initially as good as about 3 μm Ry, but since the work material contains a large amount of 8% Ni, a Swiss-type automatic lathe having a guide bush is used. In this case, the galling phenomenon of the guide bush is always a problem, and the deterioration of the surface roughness cannot be avoided.

[0005] Even in the past, some materials have been proposed to solve the above problems. For example, JP-A-55-94464 discloses that C: 0.5 wt% or less, Si: 2.0 wt% or less, Mn: 7 to 40 wt%,
A low-carbon high-manganese steel containing 0.0005 to 0.0200% of Ca and having a specified oxide composition and good machinability has been proposed. JP-A-55-76042 discloses that C: 2.0% or less, Si: 2.0% or less, Mn:
A high carbon high manganese steel containing 7 to 40% and Ca: 0.0005 to 0.0200% and having a specified oxide composition and excellent machinability has been proposed.

However, these materials are not sufficient in terms of corrosion resistance and abrasion resistance and the like, and in terms of machinability, machinability is improved by adding Ca to control the composition of inclusions. Since the technology is aimed at carburizing and
There is a problem that heat treatment such as nitriding or surface treatment such as plating cannot be omitted.

Accordingly, the present invention has been made to solve the above-mentioned problems, and its object is to provide not only corrosion resistance which can eliminate the need for surface treatment such as heat treatment and plating treatment, but also wear resistance and processing. It is an object of the present invention to provide a new steel material having excellent surface roughness.

[0008]

Means for Solving the Problems Normally, in a manganese alloy steel, there is a case where MnS grains precipitate in the steel material. If the MnS particles are dispersed and present in the steel material, there is an effect of reducing the cutting resistance. In particular, to greatly improve the machinability, it is necessary to reduce the aspect ratio (length / width) of MnS. However, if MnS remains on the machined surface, corrosion progresses from that part. Therefore, even if the aspect ratio is small, if the particle size of the MnS agglomerate is large, the corrosion resistance decreases, The frictional resistance increases and the wear resistance deteriorates. Where MnS
As a method for reducing the particle size of, a method of controlling the oxygen concentration or the amount of oxide in the steel material is known, but it is often not easy to control the amount of oxygen by a combination of the composition ratio or the element type. Generally, in a manganese alloy steel having a composition range, the MnS particle in the steel material often has an elongated shape due to the process of forming the MnS particle, rolling or other plastic working on the steel material, or the like. Therefore, it can be considered that the characteristics of the manganese alloy steel are influenced by the elongated shape of MnS. The present invention provides:
As a result of repeating various examinations and experiments, the present invention has been achieved by focusing on the shape distribution of the elongated shape of MnS, not just the particle size or quantity of MnS.

[0009] The manganese alloy steel of the first invention has a C: 0.
05 to 0.50 wt%, Si: 0.5 wt% or less, M
n: 6.0 to 25 wt%, P: 0.05 wt% or less,
S: 0.35% by weight or less, Cu: 0 to 3.0% by weight, N
i: 0 to 5.0 wt%, Cr: 5.0 to 20.0 wt%
%, Mo: 0 to 3.0 wt%, N: 0.04 to 0.30
wt%, Al: 0.10 wt% or less, with the balance being F
e and non-metallic inclusions MnS, having a width of 3 μm or less and a length of 40 μm or less and accounting for 90% or more, are finely dispersed therein.

As a result of various studies, the present inventors have found that, in the manganese alloy steel having the above composition range, among the fine MnS particles dispersed and formed therein, the width is 3 μm or less and the length is 40 μm or less.
It has been found that if the structure occupies 90% or more in the range of not more than μm, it has sufficient corrosion resistance and abrasion resistance, and has good surface roughness of the processed surface. That is,
In the manganese alloy steel having the above composition range, the width (width in the direction orthogonal to the longitudinal direction) and the length (length in the longitudinal direction) are not less than 90% of the MnS aggregate present therein. When the size is less than each predetermined dimension, it has been found that, after securing sufficient cutting properties, the corrosion resistance and the reduction in wear resistance can be suppressed, and that the surface roughness of the processed surface can be improved, The present invention has been completed.

A second invention is directed to a manganese alloy steel having the same composition range as described above, wherein an elongated non-metallic inclusion Mn having an average width of 3 μm or less and an average aspect ratio of 4 or more.
S is finely dispersed.

The alloy having the above composition has an average width of 3 μm
In the following, since MnS in an elongated shape having an average aspect ratio (length / width) of 4 or more is finely dispersed, a steel material having extremely good surface roughness of the processed surface and excellent wear resistance is provided. it can. In general, if the MnS particle size is small and the aspect ratio is small, good characteristics can be obtained as described above. However, depending on the manufacturing conditions and composition, the MnS particle size cannot always be reduced. However, the present inventors have found that when the MnS aggregate is in an elongated shape, the average width thereof is equal to or less than a predetermined dimension and the average aspect ratio is equal to or greater than a predetermined numerical value. Even if the converted diameter is not necessarily reduced, the corrosion resistance is ensured, the surface roughness of the machined surface is significantly improved, the friction coefficient of the surface is low, and a steel material with good wear resistance can be obtained. Is found.

In each of the above inventions, the elongated M
nS is finely dispersed in a posture substantially parallel to the surface where surface roughness and abrasion resistance are required, which is considered from the viewpoint of improving the surface roughness and abrasion resistance of the processed surface. Preferred. This is particularly important for manufacturing shafts, screws, and other various parts using the steel material of the present invention.

Note that the first and second inventions do not contradict each other and satisfy the constituent features of the first invention and also satisfy the constituent features of the second invention. Is most desirable.

[0015]

Next, embodiments of the manganese alloy steel according to the present invention will be described in detail. First, the composition of the manganese alloy steel as a premise of the present invention will be described.

C (carbon): C is an element for stabilizing the austenite structure, and is contained in an amount of 0.05 wt. However, when the content exceeds 0.50 wt%, 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 wt%. Preferably 0.10 in order to adjust the hardness after processing.
０．３0.30 wt%.

Si (silicon): Si is added to molten steel as a deoxidizing agent in the refining process. Excessive addition increases non-metallic inclusions, which are deoxidizing products, and deteriorates the cleanliness of steel. Let it. 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 wt%.

Mn (manganese): Mn is an inexpensive element that stabilizes the austenite structure, and can reduce the content of Ni that stabilizes the austenite structure. As an alternative to Ni, Mn is contained in an amount of 6 wt% or more. However, if the content exceeds 25 wt%, the hot workability is significantly reduced, and the possibility of cracking during hot rolling increases, which is not preferable. Therefore, the upper limit is 25 wt%
And In these characteristics, preferably 6 to 15 w
t%, and more preferably 8 to 13 wt%.

P (phosphorus): P is a harmful element and should not be added intentionally. P tends to cause segregation and deteriorates hot workability.
wt% or less.

S (sulfur): S may not be added intentionally. If added, it has the effect of improving machinability,
When machinability is required, addition of 0.05 wt% or more is desirable. However, when the content exceeds 0.35 wt%, hot workability and corrosion resistance deteriorate. Therefore, the upper limit is set to 0.35 wt%.

Cu (copper): Cu may not be added.
If added, it has the effect of stabilizing the austenite structure during cold working. However, when the content exceeds 3 wt%, the hot workability is significantly reduced. Therefore, the content was set to 3 wt% or less.

Ni (nickel): Ni is a desired additive element, which is an effective element for stabilizing the austenite structure and improving the corrosion resistance.
If the content is more than wt%, the cost is increased, which is not preferable. In addition, it is preferable to reduce the addition amount as much as possible from the viewpoint of the influence on the environment. Therefore, considering the stability of the austenitic structure and the cost, the Ni content is set to 5.0 w.
t% or less.

Cr (chromium): Cr is a ferrite-forming element, but is an essential element for imparting corrosion resistance. In order to impart corrosion resistance, it is necessary to contain 10 wt% or more.
% Or more. However, if it exceeds 20 wt%, the stability of the austenitic structure is impaired. Therefore, the amount of Cr was set to 5 to 20 wt%. Preferably 10 to 20 wt%,
Further, the content is 13 to 17% by weight.

Mo (molybdenum): Mo may not be added. If added, it suppresses the formation of work-induced martensite during cold working, which is effective for improving cold workability. However, since Mo is a ferrite-forming element, if added in excess, the austenite structure becomes unstable. Therefore, the content was set to 3 wt% or less.

N (nitrogen): N also has an effect of improving stress corrosion cracking, and therefore, it is necessary to contain N in an amount of 0.04 wt% or more. Thereby, 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 work hardening is obtained by the nitride, thereby improving abrasion resistance. On the other hand, if N is 0.3
It is difficult to dissolve a steel material exceeding 0 wt%, and such a high N steel is not preferable because a defect due to a blowhole may occur in the steel ingot. Therefore, 0.
04-0.30 wt%.

Al (aluminum): Al is a strong deoxidizer and is added to molten steel during the refining process. However, if the addition amount exceeds 0.10 wt%, oxides which are non-metallic inclusions increase, thereby deteriorating the cleanliness of the steel. Therefore, the content is set to 0.10 wt% or less.

Shape and size of MnS: MnS is dispersed and formed in a steel material, and its particle size changes mainly depending on the oxygen concentration in molten steel. For example, generally, when the oxygen concentration decreases, Mn
The particle size of S becomes smaller and its aspect ratio also becomes smaller. The presence of the MnS particles reduces the cutting resistance and improves the machinability, but when the MnS particle size increases, the surface roughness of the processed surface deteriorates and the wear resistance decreases. Further, when large MnS exists on the processed surface, corrosion progresses from that portion, so that the corrosion resistance is reduced.

Specifically, the shape and size of MnS are such that the width (length of the short axis) is 3 μm or less and the length (length of the long axis) is 40 μm.
It is preferable that those having m or less account for 90% or more of the whole. If the MnS particle has a shape and a size within the above range, the workability and the corrosion resistance are not significantly deteriorated, and the surface roughness of the processed surface is improved, the friction coefficient is low, and the abrasion resistance is reduced. Good steel material can be constituted. Further, if the particle size within the above-mentioned size range is 90% or more, the homogeneity of the steel material is maintained, and there is no problem in workability, corrosion resistance, and wear resistance.

The MnS preferably has an average width of 3 μm or less and an average aspect ratio of 4 or more. When such elongated MnS is finely dispersed, even if the substantial particle size (for example, the diameter of a sphere having the same volume as the volume of the MnS aggregate) is not so small, the above-mentioned various properties are excellent. It is possible to realize a reduced steel material.

These manganese alloy steels can be used as general steel materials, and can be used, for example, as plates, pipes, bars, wires and the like. These applications include functional components such as shafts and screws, and structural components such as beams, frames, and support plates. In these cases, each component is preferably configured such that the elongated MnS is substantially parallel to the surface of the component that requires surface roughness and wear resistance.

Next, in the case of manufacturing a shaft member and a screw member using the steel material of the present invention, a forming method and a heat treatment method will be described. Here, examples of the “shaft member” include a carriage shaft used in a serial printer of an OA device terminal, a type wheel set used in a type wheel selection type printer, a motor shaft, and the like.
Examples of the “screw member” include a self-drilling screw, a tapping screw, a building bolt, and the like.

Generally, these members are applied with a lubricant through a process of removing scale from the material, formed into an intermediate product by cold rolling, drawing and forging (hot and cold), and then processed as they are. Or through further forming by a cutting or forging process, or a softening or hardening heat treatment (usually a softening heat treatment) is performed. The above steps and treatments are also performed on the steel material of the present invention.

In the case of shafts used in general OA equipment and shafts for automobiles, conventionally, carburizing treatment, nitriding treatment, or plating treatment was finally performed. When these steel materials are used, these final surface treatments can be omitted.

As described above, in the case of the steel material of the present invention, when there is existing equipment, especially in Japan, the above-mentioned surface treatment can be omitted, so that work costs, energy costs, distribution costs, and the like are unnecessary. In addition, since the above surface treatment can be omitted, especially when overseas investment is made, capital equipment for surface treatment is unnecessary and initial investment can be reduced.

Furthermore, in recent years, as public opinion on prevention of global warming and regulation of chemical substances has been increasing, the present invention omits carburizing treatment, nitriding treatment, or plating treatment in order to save resources and energy and minimize environmental pollution. Being able to do so is of great significance today.

[0036]

EXAMPLE The necessary elements were blended, and after performing test melting, hot rolling was performed, thereby processing into round rods and wires having a plurality of types of diameters, performing hot rolling, and then air cooling. Steel materials having the respective compositions shown in Table 1 were prepared. The wires were used as test materials for cold workability, abrasion resistance, and cutting surface evaluation tests, respectively.

The cold workability was evaluated by solution treatment conditions and wire drawing. In addition, corrosion resistance, machinability and abrasion resistance,
The test was performed and evaluated in the same manner as described below. Further, the longitudinal section of the steel material is mirror-polished, and the magnification is 40 with an optical microscope.
Observation was performed at 0x, and the shape was measured for a total of 30 large MnS inclusions in 6 visual fields in 5 visual fields.
The average was determined. Tables 1 to 3 show the results of the above tests.
Are shown together.

[0038]

[Table 1]

In Table 1, steel materials 1 to 8 are examples and steel materials 9 to 15 are comparative examples. The composition analysis value and the average shape (average width and average aspect ratio) of MnS are shown.
Shows, cutting properties, corrosion resistance, and surface roughness of the machined surface,
And the comprehensive evaluation was summarized. The evaluation of the machinability was determined based on the finished state of the cutting surface. That is, after turning the material, "○" indicates that no peeling flaws were found on the finished surface, and "Scratching flaws were recognized, but those that were judged to have no practical problem by reworking" △ ",
Those which were judged to be remarkably flawed and unsuitable for practical use were evaluated as "x", and those other than "x" were evaluated as acceptable.

As shown in Table 1, the steel materials 1-8
In the above, the composition analysis values correspond to the above composition range of the manganese alloy steel of the present invention, and the average width of MnS satisfies the condition of 3 μm or less and the average aspect ratio satisfies the condition of 4 or more. . Then, the machinability, the corrosion resistance and the surface roughness were all good, and all of them were determined to be materials that could endure practical use. On the other hand, in the comparative example, the composition analysis value is out of the above composition range, or M
The average width or average aspect ratio of the nS shape does not satisfy the above conditions. And, the comparative example is either one of poor machinability, corrosion resistance, and surface roughness, or one in which cracks occurred during rolling, and is not practical in total. Was.

[0041]

[Table 2]

[0042]

[Table 3]

Tables 2 and 3 show the results of pulling out the steel 5 of the examples and performing a turning test, a surface roughness, and a boring test. Here, SUS416 and SUS303, which are currently used in the turning test and the surface roughness, are compared with the standard S45C having the minimum necessary drilling property in mass production.
And SUS304. The cutting conditions used were Macro Alloy AF1 (trademark) as a tool (bite), the number of revolutions was 2650 rpm, the peripheral speed was 50 m / min, and the feed amount was 25 μm / RE. The processing conditions for the evaluation of the drillability shown in Table 3 were as follows: a drill having a diameter of 2.6 mm was used as a tool, the rotational speed of the drill was 500 rpm, the automatic feed amount was 70 μm / RE, and the feed depth was 10 mm. Also,
Solution treatment A shown in Table 3 was 1100 ° C. × water cooling, and B was 1
150 ° C. × water cooling, C: 1200 ° C. × water cooling, D: after drawing, 1050 ° C. × water cooling.

As shown in Table 2, the material derived from the steel material 5 has the same excellent machinability as that of the normal corrosion-resistant materials SUS416 and SUS303, and has a significantly reduced surface roughness and a large surface roughness. The dispersion is extremely small and has particularly excellent cutting characteristics. Also, as shown in Table 3, in the drilling process, the material derived from the steel material 5 has almost no inferiority to the comparative materials S45C and SUS304 or is rather excellent, and there is no problem in workability at all. I understand.

Next, after turning the test material on a lathe, # 500
A test piece finished and polished with paper
It is kept for 360 hours in an atmosphere of 90 ° C. and 90% humidity, according to JIS
"○" if the rating of the rust judgment standard of steel materials is 9 or more
Those that do not satisfy this criterion are marked with “x”. Specifically, a 6.5 mm diameter wire rod of steel 5 was ground and compared with SUS416 and SUS303. Table 4 shows the results. As shown in Table 4, it can be seen that the steel materials of the examples have good corrosion resistance and are superior to the comparative materials.

[0046]

[Table 4]

Next, a wire rod of steel 5 was drawn out, a SUM24L rod of the same size was soft-nitrided, and SUS416 and SUS303 shafts were mounted on a printer and subjected to severe repeated sliding under the same conditions. A test was performed to measure the amount of shaft wear. Table 5 shows the results. Even in a severe sliding test, it was found to have the same or better abrasion resistance as the current product.

[0048]

[Table 5]

Next, regarding the steel material 5, MnS inclusions were observed with an optical microscope, and the distribution of the width (width in a direction orthogonal to the longitudinal direction) and the length (length in the longitudinal direction) was examined. Specifically, the method was carried out in such a manner that all the inclusions observed in the visual field were measured in eight visual fields at a magnification of 400 with respect to the surface, the central part, and the part at the intermediate depth of the steel material. Tables 6 to 8 show the results. As shown in these tables, 90% or more of the MnS inclusions in any part of the steel material 5 had an elongated shape with a width of 3 μm or less and a length of 40 μm or less.
In addition, many inclusions have an aspect ratio (length / width) of 5-1.
It was concentrated in the range of 5.

[0050]

[Table 6]

[0051]

[Table 7]

[0052]

[Table 8]

On the other hand, for SUM, the distribution of the shape and size of inclusions was examined in the same manner as described above. The results are shown in Tables 9 to 11. As shown in each table, it can be seen that in the SUM, MnS inclusions exceeding 3 μm in particular, particularly in width, are distributed more in the steel material, and that the aspect ratio is more greatly varied than in the above-mentioned examples.

[0054]

[Table 9]

[0055]

[Table 10]

[0056]

[Table 11]

Finally, the shaft of steel 5 (surface roughness of 2.7 μm) and the shaft of SUS303 (surface roughness of 3.3 μm)
μm), a SUM shaft surface with Ni plating (surface roughness 1.7 μm), and a SUM shaft surface with nitriding treatment (surface roughness 2.4 μm).
With a load of 500 g applied, the coefficient of friction against copy paper (PPC paper, manufactured by KOKUYO Co., Ltd.) was measured five times each. The results (average width) are shown in Table 12 and FIG. Thus, it can be seen that in the present embodiment, the friction coefficient is significantly lower than other conventional materials. In particular, the example has a lower coefficient of friction than the SUM surface-treated product having a smaller surface roughness than the example. Therefore, it is considered that these results indicate that the coefficient of friction is determined not by the surface roughness of the material but by the wear resistance itself of the material. As a result, in the present embodiment, there is an advantage that when the paper is transported or printed (printed) on the paper, the abrasion of the contacting steel material itself is reduced and the generation of paper dust can be suppressed. It can be understood.

[0058]

[Table 12]

It should be noted that the present invention is not limited to the above-described example, and it is needless to say that various changes can be made without departing from the gist of the present invention.

[0060]

As described above, according to the present invention, it is possible to obtain a processed surface having good corrosion resistance and machinability, high abrasion resistance, high precision and small surface roughness. Manganese alloy steel can be realized, and by using this material, it is possible to omit the surface treatment such as plating, carburizing, nitriding, etc. of the component materials of OA related equipment, motors, automobiles, buildings, etc. It becomes possible.
In particular, unlike conventional manganese steels, it is possible to provide a highly versatile steel material that has many excellent properties at the same time and can be arbitrarily applied according to the needs at that time.

[Brief description of the drawings]

FIG. 1 is a graph showing a coefficient of friction between a steel material according to the present invention and a comparative product.

 ────────────────────────────────────────────────── ─── 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, Kokura-ku, Kitakyushu-shi, Fukuoka Sumitomo Metal Industries Co., Ltd. (72) Inventor Chihiro Kitazawa 3-3-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Corporation (72) Inventor Naohisa Miyashita 1-1544 Kamikawa, Suwa City, Nagano Prefecture Daito Manufacturing Co., Ltd. 72) Eijiro Muramatsu 5-13-1, Shinjuku-cho, Kawagoe-shi, Saitama

Claims (2)

[Claims] 1. C: 0.05 to 0.50 wt%, Si:
0.5 wt% or less, Mn: 6.0 to 25 wt%, P:
0.05 wt% or less, S: 0.35 wt% or less, Cu:
0 to 3.0 wt%, Ni: 0 to 5.0 wt%, Cr:
5.0 to 20.0 wt%, Mo: 0 to 3.0 wt%,
N: 0.04 to 0.30 wt%, Al: 0.10 wt%
Non-metallic inclusions MnS, which has the following composition, the balance being Fe and inevitable impurities, and having a width of 3 μm or less and a length of 40 μm or less occupying 90% or more, are finely dispersed therein. A manganese alloy steel characterized by the following. 2. C: 0.05 to 0.50 wt%, Si:
0.5 wt% or less, Mn: 6.0 to 25 wt%, P:
0.05 wt% or less, S: 0.35 wt% or less, Cu:
0 to 3.0 wt%, Ni: 0 to 5.0 wt%, Cr:
5.0 to 20.0 wt%, Mo: 0 to 3.0 wt%,
N: 0.04 to 0.30 wt%, Al: 0.10 wt%
The balance contains Fe and unavoidable impurities, and has an average width of 3 μm or less and an average aspect ratio of 4
A manganese alloy steel in which the elongated nonmetallic inclusions MnS are finely dispersed.