JP2859287B2 - High hardness corrosion-resistant wear-resistant stainless steel for induction hardening - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is suitable for induction hardening necessary for manufacturing stainless steel shafts mainly used for IC manufacturing equipment, precision measuring machines, automobile parts and the like. The present invention also relates to a stainless steel having high hardness and high corrosion and wear resistance.

[Conventional technology]

Martensitic stainless steel has been widely used in many industrial fields including bearing applications since it has high hardness and excellent corrosion resistance and wear resistance. Among martensitic stainless steels, the mainly used steel type is a high carbon-17Cr type represented by JIS SUS440C. This steel is usually used after being heated and quenched in a gas heating furnace or an electric heating furnace, and then tempered. However, recently, a method of induction hardening has been studied from a conventional quenching method due to a demand for cost reduction. In induction hardening, good hardenability is an absolute condition, but SUS440C is not satisfactory in terms of hardness. In particular, in the case of shaft applications where the surface is hardened, the hardness obtained by induction hardening SUS440C is at most about HRC53, so that it cannot be used at all.

HRC5 hardness after quenching and tempering by induction hardening
Known martensitic stainless steels exhibiting 8 or more include, for example, JP-A-48-88014 (C: 0.75
0.95%, Si: 0.1-0.5%, Mn: 0.1-2.0, Cr: 11.0-14.
0%, Mo: 0.1-1.5%, V: 0.1-1.0%, Fe: Bal)
No. 57-45821 (C: 1.1 to 1.5%, Si: ≤ 2.0%, Mn: ≤ 1.0
%, Cr: 7.0-11.0%, Mo: 0.5-4.0%, V: 0.1-1.0%, F
e: Bal), JP-B-62-56226 (C: 1.2-1.6%, Si: 0.8-
1.6%, Mn: 1.0-1.5%, Cr: 9-12%, Mo: 0.3-0.6%,
V: 0.1-0.8%, Fe: Bal) and JP-A-60-243249 (C:
0.5 to 0.7%, Si: 1 to 2%, Mn: ≤ 1.0%, Cr: 9 to 15%, M
o: 1-3%, Fe: Bal).

That is, the amount of carbon for adding Mn and Mo for improving the hardenability and for improving the hardness is limited in relation to the carbide forming element (wear resistance).

[Problems to be solved by the invention]

The above-mentioned known examples including SUS440C are not suitable for use as shaft materials having high hardness, high corrosion resistance and high wear resistance because they are easily heat-treated by induction hardening due to the following disadvantages. In other words, in SUS440C, the ratio of Cr / C is large,
Hardness in quenching decreases. In addition, an increase in retained austenite also contributes to lack of hardness. In the component system disclosed in JP-A-48-88014, the amount of C in the matrix is insufficient and no hardness is obtained. In JP-A-57-45821 and JP-A-62-56226, the amount of Cr is smaller than the amount of C, the corrosion resistance is poor, and there is a problem in use. JP-A-60-243249 also discloses that the amount of retained austenite is smaller than that of SUS440C but the hardness is low. In these known examples, a hardness of HRC60 or more required as a shaft material is not achieved, and at present, the requirements for corrosion resistance are not sufficiently satisfied.

An object of the present invention is to provide a stainless steel which solves the above-mentioned drawbacks, has a sufficient surface hardness of at least HRC60 or more even by induction hardening, and has high corrosion and wear resistance.

[Means for solving the problem]

The present invention, by weight ratio, C: 0.96 to 1.10%, Si: 0.80 to 1.2
0%, Mn: 1.0% or less, Cr: 12.00-15.00%, Mo: 0.30-0.7
0%, V: 0.10 ~ 0.30%, balance Fe and inevitable impurities, high hardness hardening corrosion resistant wear resistant stainless steel for induction hardening, Cr / C ratio is controlled from 11 to 14, High hardness corrosion-resistant wear-resistant stainless steel for induction hardening used for shafts.

 The reasons for limiting the components in the present invention are described below.

C is an element necessary for increasing the hardness of the base,
Form carbides to improve wear resistance. If C is less than 0.96%, a surface hardness of HRC 60 or more cannot be obtained during induction hardening. If C is added in excess of 1.10%, the corrosion resistance deteriorates with the Cr content of the present invention, so the range of C is set to 0.96 to 1.10.
%.

Si is added as a deoxidizing agent, but has the effect of increasing tempering softening resistance. The effect is small when it is less than 0.80%, and even if it exceeds 1.20%, the effect corresponding to the added amount cannot be obtained. Therefore, the Si component range is 0.80 to 1.20
%.

Mn is added as a deoxidizing agent and a hardenability improving element,
Even if added over 1.0%, the effect is small, so the upper limit was made 1.0%.

Cr improves corrosion resistance and forms carbides to increase wear resistance. If it is less than 12.00%, sufficient corrosion resistance cannot be obtained with the amount of C of the present invention, and even if it exceeds 15.00%, the improvement of corrosion resistance cannot be obtained in proportion to the added amount, and the ratio of Cr / C becomes large. In case of induction hardening, hardness of HRC60 or more cannot be obtained. Therefore, the Cr component range is set to 12.00 to 15.00%.

Mo is added to improve hardenability, refine crystal grains and improve toughness. Mo also improves the corrosion resistance, but less than 0.30% has less of these effects, and 0.7%
Even if it is added in excess of the above, an effect corresponding to the added amount cannot be obtained. Therefore, the component range of Mo is set to 0.30 to 0.70%.

V forms VC carbides, has the effect of refining crystal grains and increasing toughness. In the present invention, C in the base is used as a carbide.
Was fixed so as not to dissolve as much as possible during quenching. That is, it is added to reduce C in the matrix and reduce the amount of retained austenite as much as possible. If it is less than 0.10%, the effect is small, and if it exceeds 0.30%, a giant carbide is formed and the toughness is deteriorated, and the C content of the matrix is lowered and the hardness is lowered. Therefore, the component range of V is set to 0.10 to 0.30%.

〔Example〕

 Hereinafter, examples of the present invention will be described.

Table 1 shows the measured values of the components (% by weight) and the hardness of the alloy used in this example.

A steel bar having a diameter of 8 mm was manufactured by hot rolling and cold working from a steel ingot having the components shown in Table 1 above, and an induction hardening test was performed.

The induction hardening condition is 1100 ° C and the coil moving speed is 12.5
mm / sec, after quenching with water cooling, tempering 180 ° C x 1
After holding for a while, air cooling was performed.

Among the conventional alloys, Sample Nos. 6 to 9 are representative alloys described in the above-mentioned Patent Publication. Table 1 shows that
The evaluation about SUS440C is also described.

The hardness was evaluated by measuring Vickers hardness at a depth of 1 mm from the most required outermost surface of the shafts.

All conventional alloys have an HRC equivalent of less than HRC 60 or less and have insufficient hardness, but the alloys of the present invention all show an HV of 700 or more (HRC equivalent of 60.1 or more), and the target hardness can be obtained. Was.

Fig. 1 shows the hardness distribution in the depth direction for sample Nos. 1 and 2 and SUS440C.
700 or more ((HRC equivalent 60.1 or more), SUS440C
It can be seen that the target hardness has been achieved as compared with. FIG. 2 shows the results of the corrosion resistance test in the salt spray test, and it can be seen that the alloy of the present invention shows equal or higher corrosion resistance than 440C.

〔The invention's effect〕

As described above, according to the present invention, since at least the surface portion has a hardness of HRC60 or more by induction hardening, which is a simple quenching method, a shaft material having high hardness, high corrosion resistance and wear resistance, Can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing the hardness distribution of the alloy of the present invention and SUS440C after induction hardening and tempering, and FIG. 2 is a metallographic photograph showing the results of a corrosion resistance test of the alloy of the present invention and SUS440C in a salt spray test.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-57-23049 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00-38/60

Claims (3)

(57) [Claims] 1. A weight ratio of C: 0.96 to 1.10%, Si: 0.80 to 1.2
0%, Mn: 1.0% or less, Cr: 12.00-15.00%, Mo: 0.30-0.7
0%, V: 0.10 ~ 0.30%, balance Fe and unavoidable impurities, high hardness corrosion resistant wear resistant stainless steel for induction hardening. 2. The high hardness corrosion-resistant wear-resistant stainless steel for induction hardening according to claim 1, wherein the Cr / C ratio is controlled from 11 to 14. 3. The high-hardness, corrosion-resistant, wear-resistant stainless steel for induction hardening according to claim 1, which is used for a shaft.