JPH0361348A - Steel for hardened gear - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a steel material for gears subjected to surface hardening heat treatment.

[Conventional technology]

Conventionally, the surface hardening heat treatment methods used for gears include carburizing, quenching and tempering, induction quenching and tempering, and nitriding.
SNCM420H, SCM445H, etc. specified by IS are often used.

[Problem to be solved by the invention]

According to the above conventional surface hardening heat treatment method, the carburizing, quenching and tempering method requires a long heat treatment time and is inferior in productivity.

Induction quenching and tempering reduces gear accuracy and strength. In the nitriding method, the hardened layer is thin, the fatigue strength is poor, and the processing time is long. For this reason, a pressure spray type surface hardening heat treatment method has been proposed. According to this method, the heat treatment time is short, the gear accuracy is good, the hardened layer is thick, and a gear with excellent strength can be obtained. Ideally, the hardening pattern of the tooth should be thick, with the hardened layer near the pitch circle being thick, and the hardening layer at the root of the tooth being thin. has high fatigue strength. However, steel materials with conventional chemical compositions are not suitable for obtaining gear quality by surface hardening heat treatment methods. The range recited in claim 1 indicates the basic range of steel materials suitable for obtaining the above-mentioned gear quality. An object of the present invention is to provide a steel material whose material composition can easily obtain the hardening depth at the tooth base by a pressure injection type surface hardening heat treatment method.

[Means to solve the problem]

To achieve the above objective, it is necessary to improve the hardenability of steel materials. The present researcher focused on this point and, as a result of intensive research, discovered a steel material having the material composition described below, and arrived at the present invention.

In other words, based on iron, the amount of carbon is the required surface hardness) I
In order to ensure RC50 or higher, the content is set at 0.4% by weight or more, and since too much content increases the possibility of the presence of coarse cementite, leading to a decrease in fatigue strength, the content is set at 1°3% by weight or less.

This amount is preferably 0.6% by weight or more and 1.1% by weight or less. The more silicon, manganese, nickel, chromium, and molybdenum are present, the better the hardenability will be, but if they are too much, the machinability will decrease, so upper and lower limits are set, and each is 0.05 to 1.0% by weight. , 0.30-1.5% by weight
, 0.001-2.0% by weight, 0.01-1.5% by weight
, O, OO 1 to 0.5% by weight. phosphorus, sulfur,
Too much copper will reduce fatigue strength, so the ranges are set at 0.005-0.030% by weight and 0.005-0.005% by weight, respectively.
0.030% by weight, and 1 to 0.30% by weight of O,OO. The aluminum content is 0.010 to O.1OOfE in order to refine the crystal grains and prevent a decrease in toughness, and the oxygen content is 20 ppm or less in order to ensure fatigue strength. Steel materials with the above material components have improved hardenability, and by heating them to 760° C. to 900° C., attaching them to a pressure injection hardening device, and performing heat treatment, desired gears can be manufactured.

Vanadium in the second claim increases the hardenability of steel as the hardening temperature increases when added in a large amount, but since it is an expensive element, it is limited to 0.02 to 0.30% by weight. .

Adding one or both of lead and calcium to the above ingredients improves machinability, but if too little is added, there is no free-cutting effect, and if too much, the effect is saturated and the material toughness decreases.

Therefore, lead is set at 0.03 to 0.35% by weight, and calcium is set at 0.001 to 0.010% by weight.

0.0003 to 0.00 of boron as the component of the first claim
When added in an amount of 15% by weight, hardenability is improved and silicon, manganese, nickel, chromium, and molybdenum can be reduced. If the amount of boron added is less than 0.0003% by weight, there is no effect of improving hardenability, and if it is more than 0.0015% by weight, the effect is saturated. Furthermore, the same effect can be obtained by adding a predetermined amount of boron to the components described in the second claim.

〔Example〕

Examples of the present invention will be described below. Table 1 shows the chemical compositions of comparative steels (A, B) and inventive steels (C, D) to which V is added for confirmation of improved hardenability.

As a result of the hardenability test using the sample materials shown in Table 1, as shown in Figure 1, the hardenability of the invented steels C and D improved in proportion to the heating temperature, especially for the invented steels. Significant. In addition, the hardenability is determined by the Jominy single-end hardening method, and the hardness is HRC5.
It is indicated by the distance from the quenched end where it becomes 0.

〔Effect of the invention〕

As mentioned above, hardenability is improved by defining the range of material components and adding a certain amount of vanadium, and since the hardenability is temperature dependent, even one type of steel can be used in a wider range of applications. Can be applied to parts.

[Brief explanation of drawings]

Claims (5)

[Claims] (1) In steel materials for gears that undergo surface hardening heat treatment, the material composition is basically iron and carbon is 0.40 to 1.30% by weight.
, silicon 0.05~1.0% by weight, manganese 0.30~
1.5% by weight, nickel 0.001-2.0% by weight, chromium 0.01-1.5% by weight, molybdenum 0.001-2.0% by weight
0.5% by weight, 0.005-0.030% by weight of phosphorus, 0.005-0.030% by weight of sulfur, 0.001-0.0% by weight of copper.
A quench-hardened steel material for gears, characterized in that the content thereof is 30% by weight, aluminum 0.010 to 0.100% by weight, and oxygen 20ppm or less. (2) 0.02 vanadium in the material component according to claim 1;
A quench-hardened gear steel material characterized by adding ~0.30% by weight. (3) The material component according to claim 1 contains 0.03 to 0.3 lead.
A quench-hardened steel material for gears, characterized in that at least one component selected from among 5% by weight and 0.0010 to 0.0100% by weight of calcium is added. (4) Boron 0.0003 as the material component according to claim 1
A quench-hardened gear steel material characterized by adding ~0.0015% by weight. (5) Boron 0.0003 as the material component according to claim 2
A quench-hardened gear steel material characterized by adding ~0.0015% by weight.