JP2002105600A - High hardness corrosion resistant steel having excellent workability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce low-cost steel having excellent workability, in which the production of primary eutectic carbides is evaded, having quenching and tempering hardness of >=59.0 HRC, excellent in wear resistance, rolling fatigue life and acoustic characteristics and further lower in the content of Cr though its corrosion resistance is equal to or above that of 13% Cr based steel. SOLUTION: This high hardness corrosion resistant steel having excellent workability has a composition containing, by mass, 0.35 to 0.65% C, <=2.0% Si, <=1.5% Mn, 0.050 to 0.20% N, 7.0 to 10.0% Cr and 0.3 to 0.8% Ni, also satisfying C+N<=0.70% and, if required, further containing one or more kinds selected from the three kinds of <=3% Mo, <=3% V and <=1% Nb, and the balance Fe with inevitable impurities and is used for bearings, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing, a linear motion bearing, a ball screw, a mold and the like used in an environment requiring corrosion resistance, and has excellent corrosion resistance, abrasion resistance and rolling fatigue. The present invention relates to a high-hardness martensitic corrosion-resistant steel having excellent service life.

[0002]

2. Description of the Related Art In order to secure the wear resistance and rolling fatigue life of martensitic steel used for rolling bearings, linear bearings, ball screws, dies, and the like, quenching and tempering hardness of HRC 59.0 or more is required. Need. On the other hand, martensitic corrosion-resistant steel used in rolling bearings, linear motion bearings, ball screws, dies, etc. used in environments requiring corrosion resistance should contain Cr as a steel component of 13% or more. Required corrosion resistance. For example, as such a steel type, for example, JIS SUS44 of 1% C-17% Cr which is martensitic stainless steel
0C or 0.5 to 1.3% C, 1.5% or less of Si disclosed in JP-A-7-233442.
0% or less Mn, 11 to 20% Cr, 0.06 to 0.2
There is a wear-resistant and corrosion-resistant bearing steel made of 0% N and, if necessary, adding Mo, W, V, and Nb within a specific range. But,
In JIS SUS440C, there is a problem of deterioration of rolling contact fatigue life in a rolling component due to the presence of a primary crystalline carbide, and a problem of deterioration of acoustic characteristics of a rolling component due to the presence of a primary crystalline carbide. And SU
Higher annealing hardness than general-purpose steel such as J2, cold workability and machinability (hereinafter referred to as “workability”
That. There was a problem that was not good. In addition, Japanese Patent Application Laid-Open
The steel disclosed in Japanese Patent No. 233442 has a problem in that rolling life and acoustic characteristics are superior to SUS440C but workability is not sufficient.

In order to solve these problems, the present applicant has previously filed an invention of a high hardness corrosion resistant steel having excellent workability in Japanese Patent Application No. Hei.
No. 1-94579. By the way, the present invention is a corrosion-resistant steel with low cost, excellent workability and high hardness. However, a steel having excellent corrosion resistance and excellent workability and high hardness is required.

[0004]

The present invention solves the above-mentioned problems by solving the above-mentioned problems, has excellent workability after annealing, and avoids the formation of primary eutectic carbides. It has high hardness of quenching and tempering hardness of HRC 59.0 or more, and is excellent in wear resistance, rolling fatigue life and acoustic characteristics. It is to provide a steel that has been improved.

[0005]

Means for Solving the Problems To solve the above problems, the basic idea is to set the C + N content of the steel component to a necessary minimum in order to achieve both workability improvement and quenching and tempering hardness.
In order to further improve corrosion resistance, Ni
It was found that the steel of the present invention was obtained by lowering the quenching and tempering hardness even at the same C + N amount, and ensuring the corrosion resistance by containing N while keeping the Cr content low.

[0006] That is, the means of the present invention for solving the above-mentioned problems, according to the invention of claim 1, is:
0.35 to 0.65%, Si: 2.0% or less, Mn:
1.5% or less, N: 0.050 to 0.20%, Cr:
7.0 to 10.0%, Ni: 0.3 to 0.8%, and C
High hardness corrosion resistant steel excellent in workability, characterized in that + N ≦ 0.70% and the balance is Fe and inevitable impurities.

[0007] According to the second aspect of the present invention, in mass%, C: 0.
35 to 0.65%, Si: 2.0% or less, Mn: 1.5
% Or less, N: 0.050 to 0.20%, Cr: 7.0 to
10.0%, Ni: 0.3-0.8%, and C
+ N ≦ 0.70%, Mo ≦ 3%, V ≦ 3%, N
b ≦ 1% containing at least one selected from three types, with the balance being F
This is a high hardness corrosion-resistant steel excellent in workability characterized by comprising e and unavoidable impurities.

The components contained in the steel of the present invention will be described below. Hereinafter,% is shown by mass%. C is required at least 0.35% to secure hardenability, but 0.65%
If it exceeds 0.3, the workability is reduced.
0.65%.

[0009] Si is an element added as an element mainly required for deoxidation of steel and is an element that improves hardenability, but excessive content of Si deteriorates workability and toughness. Therefore, the content is set to 2.0% or less.

Mn is inevitably contained as in the case of Si due to the deoxidizing effect of steel, but an excessive content degrades the workability.

[0011] Cr combines with C to form a hard carbide,
It is an element that improves the wear resistance and corrosion resistance. 7.0% or more is required for corrosion resistance,
At the same C + N amount, the lower the Cr, the higher the quenching and tempering hardness. Therefore, in order to obtain a quenching and tempering hardness HRC of 59.0 when the amount of C + N is 0.49% or less, it is set to 10% or less, which is lower than that of conventional steel.

Ni is an element that improves corrosion resistance.
At 3% or more, the effect of improving corrosion resistance is observed, but 0.8% or more.
%, The strike-up is large and the annealing hardness is increased, resulting in reduced workability. Therefore, the content is set to 0.3 to 0.8%.

[0013] N is generally added to refine the crystal grains, but is added in order to reduce the Cr content from the conventional 13% Cr steel and obtain a corrosion resistance superior to that of the 13% Cr steel.
%, The workability is deteriorated if the content is too large.

C + N is set to 0.70% or less in order to improve workability and avoid primary eutectic carbide.

Mo is further added to improve corrosion resistance and form carbides to improve wear resistance.
If the addition exceeds 3.0%, the effect is saturated and the hot workability is reduced.

V and Nb contribute to improvement of corrosion resistance and wear resistance similarly to Mo. Also, it is added as an element that promotes crystal grain refinement due to N content and enhances the rolling fatigue life,
If V exceeds 3% and Nb exceeds 1%, workability is impaired. Therefore, V is set to 3% or less and Nb is set to 1% or less.

[0017]

Embodiments of the present invention will be described below. C: 0.35 to 0.65%, Si: 2.0% or less,
Mn: 1.5% or less, N: 0.050 to 0.20%, C
r: 7.0 to 10.0%, Ni: 0.3 to 0.8%, and C + N ≦ 0.70%. In order to further improve the corrosion resistance as needed, Mo ≦ 3. %, V ≦ 3
%, Nb ≦ 1%
The steel consisting of the remainder Fe and inevitable impurities is melted. The obtained steel material is hot forged into a predetermined shape, kept at 870 ° C., and then gradually cooled to 650 ° C. at 10 ° C./hr for annealing. After annealing, the product is cold-worked into a product shape such as a bearing, and then kept at 1050 ° C. for 30 minutes.
Tempering at 60 ° C. for 60 minutes, quenching and tempering hardness of 59.0 or more, excellent workability after annealing, and
To obtain high hardness corrosion resistant steel with excellent wear resistance and corrosion resistance.

[0018]

EXAMPLES Table 1 shows the compositions and properties of the invention steels and comparative steels. First, test steels of the present invention and comparative steels having the steel compositions shown in Table 1 are melted. No. of test steel Nos. 1 to 6 are invention steels of the present invention. Nos. 7 to 11 are comparative steels. 10 is a 13% Cr-based steel having N of 0.05% or less.
o. 11 is SUS440C. As compared with the steel of the present invention, No. 7 has a large Ni content of 1.00%, and thus has a high annealing hardness. 8 and No. No. 9 does not contain Ni, respectively. No. 10 has a large amount of C and Cr, a small amount of N, and a large amount of C + N.
11 has more C, more Cr, less N, C +
N is large.

After forging the test steel obtained by the above-mentioned smelting into a required shape by hot forging, and holding at 870 ° C.,
Annealing was performed by gradually cooling to 650 ° C. at 0 ° C./hr. The annealing hardness is as shown in Table 1. After annealing, the test piece was processed into a pitting corrosion test specimen and a thrust type life test specimen. The test specimen was held at 1050 ° C. for 30 minutes, quenched by oil cooling, and then kept at 160 ° C. for 60 minutes to perform tempering. Pressure 540kgf / m
m ² , 1800 cpm, spindle oil # 6 as lubricating oil
With 0, performs a thrust-type life test, B ₁₀ life (1
The rolling fatigue life was evaluated in terms of (0% failure life) ratio. On the other hand, the test piece obtained by quenching and tempering was 6% NaCl + 0.5% H
_The test piece was immersed in a solution of ₂ O ₂ for 6 hours to obtain the pitting loss by the weight loss of the test piece.

[0020]

[Table 1]

In Table 1, No. 8 and No. In the comparative steel of No. 9, each component of the composition except Ni satisfies the conditions defined in the present invention. Therefore, C + N
The amount is set to the minimum necessary, and the cost is reduced by setting the Cr amount to 10% or less. It is superior to 10 13% Cr-based steel. However, according to the present invention,
1 to No. 3 shows that the corrosion resistance is further improved by further containing Ni. However, no.
Comparative steel No. 7 contains Ni more than the upper limit of the present invention, so that the corrosion resistance is equal to or higher than that of the present invention, but the annealing hardness is higher and the workability is inferior. A sample having a low C + N content of less than 0.5% has a low annealing hardness of not more than HRB 90, but a C.sub. + N content of more than 0.5%. 7, no. 10 and no. No. 11 shows that the annealing hardness is HRB94 or more and the workability is inferior. Each of the steels of the present invention has a target quenching and tempering hardness of HRC5.
9.0 is satisfied. The test steel of the present invention has a Cr content of 13% Cr-based steel or SUS440C compared to the conventional 13% Cr-based steel.
It can be seen that the pitting weight loss is equal or smaller even though the amount of r is small, and the corrosion resistance is excellent.

[0022]

As described above, the present invention sets the C + N amount to a necessary minimum to achieve both the improvement of workability and the quenching and tempering hardness, and reduces the Cr amount to the conventional 13% Cr.
While reducing the cost to 10% or less, which is lower than that of the base steel, the corrosion resistance is further improved by further containing N and further containing Ni to improve the workability without impairing the workability, and the primary eutectic carbide. Quenching and tempering hardness HRC59
It is an excellent steel which has the above and is excellent in wear resistance, rolling fatigue life and acoustic characteristics, and also excellent in corrosion resistance.

Claims (2)

[Claims] 1. mass%, C: 0.35 to 0.65%,
Si: 2.0% or less, Mn: 1.5% or less, N: 0.0
50 to 0.20%, Cr: 7.0 to 10.0%, Ni:
0.3-0.8%, C + N ≦ 0.70%, and the balance F
High hardness corrosion resistant steel excellent in workability, characterized by comprising e and unavoidable impurities. 2. Mass%, C: 0.35 to 0.65%,
Si: 2.0% or less, Mn: 1.5% or less, N: 0.0
50 to 0.20%, Cr: 7.0 to 10.0%, Ni:
0.3-0.8%, and C + N ≦ 0.70%
And high hardness corrosion resistance excellent in workability, characterized by further containing one or more selected from three types of Mo ≦ 3%, V ≦ 3%, and Nb ≦ 1%, the balance being Fe and unavoidable impurities. steel.