JP3488395B2 - High hardness corrosion resistant steel with excellent workability - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rolling bearing, a shaft, a linear motion bearing, which is used in an environment requiring corrosion resistance.
Excellent corrosion resistance for use in ball screws, molds, etc.
In addition, the present invention relates to a high hardness martensitic corrosion resistant steel excellent in wear resistance and rolling fatigue life.

[0002]

2. Description of the Related Art In order to ensure wear resistance and rolling fatigue life of martensitic steel used for rolling bearings, shafts, linear motion bearings, ball screws, dies, etc., HRC
Quenching and tempering hardness of 59.0 or higher is required. On the other hand, in martensitic corrosion-resistant steel used for rolling bearings, linear motion bearings, ball screws, dies, etc. used in environments requiring corrosion resistance, contain 13% or more of Cr as a steel component. Has obtained the required corrosion resistance. For example, as such a steel type, for example, JIS of 1% C-17% Cr, which is martensitic stainless steel, is used.
SUS440C or 0.5 to 1.3% C, 1.5% or less Si, 2.0% or less Mn, 11 to 20% Cr, 0.0 disclosed in JP-A-7-233442.
6 to 0.20% N, and if necessary Mo, W,
There is a wear and corrosion resistant bearing steel in which V and Nb are added within a specific range. However, in JIS SUS440C, there are problems of deterioration of rolling contact fatigue life of rolling parts due to the presence of primary crystal carbides, and deterioration of acoustic characteristics of rolling parts due to the presence of primary crystal carbides. Compared with general-purpose steels such as carbon steel and SUJ2, there is a problem that the annealing hardness is higher and the cold workability and machinability (hereinafter, these two characteristics are collectively referred to as “workability”) are not good. Further, the steel disclosed in JP-A-7-233442 is superior to SUS440C in rolling life and acoustic characteristics, but has a problem that workability is not sufficient.

[0003]

The problem to be solved by the present invention is to solve the above-mentioned problems of the prior art, is excellent in workability, and avoids the formation of primary eutectic carbides. However, it has a quenching and tempering hardness of HRC 59.0 or more, is excellent in wear resistance, rolling fatigue life and acoustic characteristics, and has corrosion resistance of 13% Cr series steel or more, but contains Cr in a lower amount. To get steel.

[0004]

[Means for Solving the Problems] In order to solve the above problems, as a basic idea, in order to improve workability and quench hardening and tempering hardness at the same time, the C + N content of the steel component is set to a necessary minimum, and Cr is set. It was found that even if the C content is C + N, the quenching and tempering hardness can be further enhanced, and the corrosion resistance can be secured by the N content while keeping the Cr content, and the steel of the present invention was obtained.

That is, the means of the present invention for solving the above-mentioned problems is, in the invention of claim 1, mass%,
C: 0.35 to 0.65%, Si: 0.27 to 2.0
% , Mn: 1.5% or less, N: 0.050 to 0.20
%, Cr: 7.0 to 10.0%, and C + N ≦
It is a high hardness corrosion resistant steel excellent in workability, characterized in that it is 0.482 % and the balance is Fe and unavoidable impurities.

In the invention of claim 2, in mass%,
C: 0.35 to 0.65%, Si: 0.27 to 2.0
% , Mn: 1.5% or less, N: 0.050 to 0.20
%, Cr: 7.0 to 10.0%, and C + N ≦
0.482 %, Mo ≦ 3%, V ≦ 3%, Nb
1% or more selected from 3 kinds of ≦ 1%, the balance Fe
And workability characterized by consisting of unavoidable impurities
It is an excellent high hardness corrosion resistant steel.

The components contained in the steel of the present invention will be described below. Hereinafter,% is shown by mass%. C is required to be at least 0.35% in order to secure quenching and tempering hardness,
If it exceeds 0.65%, the workability decreases, so
It is set to 0.35 to 0.65%.

Si is an element mainly added as an element necessary for deoxidation of steel and is an element for improving hardenability, but excessive inclusion of Si deteriorates workability and toughness. Therefore, it is 2.0% or less.

Like Mn, Mn is inevitably contained due to the deoxidizing effect of steel, but excessive Mn deteriorates workability, so Mn is made 1.5% or less.

Cr combines with C to form a hard carbide,
It is an element that improves wear resistance and corrosion resistance. 7.0% or more is required for corrosion resistance,
As can be seen from FIG. 2, with the same C + N amount, the lower the Cr, the higher the quenching and tempering hardness. Therefore, the C + N amount is 0.
In order to obtain a quenching and tempering hardness HRC of 59.0 at 49% or less, the level is 10% or less, which is lower than that of conventional steel.

N is added in order to improve the corrosion resistance, and is added in an amount of 0.05% or more in order to reduce the amount of Cr as compared with the conventional 13% Cr steel and to obtain the corrosion resistance superior to that of the 13% Cr steel.
If it is too large, bubbles may be generated in the atmospheric pressure ingot, so the content is made 0.20% or less.

C + N is 0.482% or less in order to improve workability and to avoid primary eutectic carbides.

Mo is added to improve the corrosion resistance and the formation of carbides and wear resistance.
If it is added in excess, the effect will be saturated and the hot workability will be deteriorated, so it is made 3.0% or less.

Similar to Mo, V and Nb form carbides and contribute to wear resistance. V exceeds 3% and Nb is 1%
If added in excess of 10%, the workability is impaired, so V is 3% or less and Nb is 1% or less.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. C: 0.35 to 0.65%, Si: 0.27 to 2.
0% , Mn: 1.5% or less, N: 0.050 to 0.20
%, Cr: 7.0 to 10.0%, and C + N ≦
0.482% , and if necessary, Mo ≦ 3
%, V ≦ 3%, Nb ≦ 1%, and one or more kinds selected from the three kinds, and the balance Fe and unavoidable impurities are melted. After hot forging into a predetermined shape and holding at 870 ° C., annealing is performed by gradually cooling to 650 ° C. at 10 ° C./hr. After annealing, cold work into product shape, then hold at 1050 ° C for 30 minutes, quench with oil cooling, hold at 160 ° C for 60 minutes for tempering, and quenching and tempering hardness HRC 59.0 or more. To obtain a high hardness corrosion resistant steel which is excellent in workability after annealing and is also excellent in wear resistance and corrosion resistance.

[0016]

EXAMPLE A sample steel having the steel composition shown in Table 1 is melted. No. of test steel Nos. 1 to 4 are the invention steels of the present invention. 5-12
Is a comparative steel, especially No. 11 is 13% Cr-based steel and N
Is 0.05% or less, and No. 12 is SUS4
It is 40C. Compared to the steel of the present invention, No. 5
Has less Cr, and No. No. 6 has a small N content, and No. 7, N
o. 8 and No. No. 9 has a large amount of Cr, and No. 9 No. 10 has a large amount of C, a little more Cr and a small amount of N, 11
Is high in C and Cr, low in N, and No. 12 has a large amount of C and Cr, has a small amount of N, and further has No. 7-No.
In 12, C + N is large.

The test steel obtained by the above melting is hot forged into a desired shape, and then held at 870 ° C.
And annealed 650 ℃ or in gradually cooled and at 10 ℃ / hr. The annealing hardness is as shown in Table 1. After annealing, it is processed into a pitting test piece or a thrust type life test piece,
Hold at 30 ℃ for 30 minutes, cool with oil and quench, then 160 ℃
And hold for 60 minutes to perform tempering, and the surface pressure is 540 kgf / m.
m ² , 1800 cpm, using spindle oil # 60 as a lubricating oil, a thrust type life test was conducted, and B ₁₀ life (10%
The rolling fatigue life was evaluated by the ratio of (damage life). As a result, the test steels of the present invention are all excellent in rolling contact fatigue life because the formation of primary eutectic carbides is avoided. On the other hand, the test piece obtained by quenching and tempering was immersed in a solution of 6% NaCl + 0.5% H ₂ O ₂ for 6 hours to obtain the pitting corrosion weight loss by the weight reduction amount of the test piece, and the pitting corrosion weight loss The corrosion resistance was evaluated. The results are shown in Table 1 and further shown in FIGS. In addition, Table 1
"QT" of the QT hardness in "" represents "quenching and tempering".

[0018]

[Table 1]

FIG. 1 shows the C + N content (%) and the annealing hardness (HR).
The relationship of B) is shown as a graph. From this graph, it can be seen that in order to improve the workability of the annealed material, the lower the C + N content is, the more advantageous it is.

FIG. 2 is a graph showing the relationship between the amount of C + N (%) and the quenching and tempering hardness (HRC). From this graph, low C
It can be seen that as r, the quenching and tempering hardness is higher for the same C + N amount. And it turns out that all of the steels of the present invention satisfy the target quenching and tempering hardness HRC59.0.

FIG. 3 shows the Cr content (%) and the pitting corrosion loss (g / m).
The relationship of m ² · h) is shown in a graph. The test steel of the present invention has a conventional Cr content of 13% Cr steel or SUS440C.
It can be seen that the amount of pitting corrosion is equal to or smaller than that of Cr, and the corrosion resistance is excellent, although the amount of Cr is small.

[0022]

As described above, according to the present invention, the C + N amount is set to a necessary minimum and the Cr amount is set to the conventional 13% Cr in order to improve workability and quench and temper hardness at the same time.
Corrosion resistance is ensured by adding N while reducing the cost to 10% or less, which is less than that of the system steel.
Steel with excellent workability, avoiding the formation of primary eutectic carbides, as a result, having a quenching and tempering hardness of HRC59 or higher, excellent wear resistance, rolling fatigue life, acoustic characteristics, and corrosion resistance. Is.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of C + N (%) and the annealing hardness (HRB). The numbers in the figure indicate the No. of the test steel.

FIG. 2 is a graph showing the relationship between the amount of C + N (%) and the quenching and tempering hardness (HRC). The numbers in the figure indicate the No. of the test steel.

FIG. 3 is a graph showing the relationship between the Cr content (%) and the pitting corrosion loss (g / mm ² · h). The numbers in the figure indicate the No. of the test steel.

Claims (2)

(57) [Claims] 1. C: 0.35 to 0.65 in mass%
%, Si: 0.27 to 2.0% , Mn: 1.5% or less,
N: 0.050 to 0.20%, Cr: 7.0 to 10.0
% Containing, and at C + N ≦ 0.482%, high hardness corrosion resistant steel having excellent workability, characterized in that the balance Fe and unavoidable impurities. 2. Mass%, C: 0.35 to 0.65
%, Si: 0.27 to 2.0% , Mn: 1.5% or less,
N: 0.050 to 0.20%, Cr: 7.0 to 10.0
%, And C + N ≦ 0.482 %, M
1 selected from 3 kinds of o ≦ 3%, V ≦ 3%, and Nb ≦ 1%
A high-hardness corrosion-resistant steel excellent in workability, characterized in that it contains at least one kind and the balance is Fe and unavoidable impurities.