JPS59129752A - Induction hardenable material - Google Patents

Abstract

PURPOSE:To obtain an inexpensive induction hardenable material having a long life for roller bearing parts by properly regulating the amounts of C, Mn and Cr in a steel composition, and making use of an element having a small affinity for C. CONSTITUTION:This induction hardenable material for parts of a roller bearing, a ball screw, etc. consists of, by weight, 0.5-0.7% C, 1.0-1.5% Mn, 0.6- 1.0% Cr and the balance Fe. Mn in the composition contributes largely to the improvement of the hardenability and has a small affinity for C. Cr contributes to the improvement of the hardenability and prolongs the rolling life. By the composition the hardenable material has a long rolling life after induction hardening without using any expensive alloying element.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an induction hardening process for parts of rolling bearings and ball screws which are induction hardened and used as materials for rolling pins.

←) Prior art Recently, from the viewpoint of cost reduction, the use of induction hardened bearing parts has been increasing. 't'llll The material used as the receiving part has a surface hardness HRojJ after heat treatment.
? It is essential to have a high hardness of ~ty, and in order to have a hardness of HROj (f' or higher) by induction hardening, the carbon content must be at least O,g%. ,
For example, J Engineering S. According to the standard, S R j? 0XS300.8
330, Sj♂0, SOMgudaj, SN0Mgu5/2.
5trp/3.5UP7, SUJ/, 5UJ-, etc. However, the rolling life of bearing parts made of such materials and subjected to frequency hardening is 1, compared to that of conventional bearings made of copper oxide.
At present, it cannot be said that this is sufficient compared to bearing parts that use carburizing. This is because in the heat treatment process of copper, the more alloying elements there are, the better the hardenability is and the harder the hardening depth can be obtained, but it takes time for the carbon to become a solid solution, and the cylindrical periphery is hardened. This is because it is difficult to obtain a sieve value with such short-time heating. For this reason, alloy steels such as S (IM Data J) require pretreatment such as S negative and semi-hardening.It is also necessary to thoroughly heat the steel, which prevents the coarsening of the assembled tin. arise.

Therefore, increasing the amount of alloying elements in high frequency furnace materials has a negative effect on obtaining high hardness. In addition to the hardness of the product, it has recently been found that the cooling rate during one quenching is an important factor in determining the rolling life of bearing parts. That is, by reducing the cooling rate, the crack sensitivity of the marten site is reduced, and the rolling life is improved. In other words, taking the time to harden a steel that is easy to work with will lead to a long life.

Considering the above points, the reason for the short life of induction hardened bearing parts is that due to short-time heating called high frequency heating, the alloying elements do not diffuse sufficiently, and therefore the cooling rate is increased. This is thought to be due to the fact that high hardness cannot be obtained otherwise.

Considering the short lifespan of induction hardening materials mentioned above, the invention contributes to hardenability and has an affinity for carbon (ability to easily combine with carbon to form carbide). By utilizing small elements, we aim to provide long-life and inexpensive induction firing materials for rolling bearing parts.

2) Structure of the Invention This invention has a carbon content of 0.0% by weight. j −0.2%−
The gist is an induction hardened material for parts such as roller bearings and ball screws containing manganese/, 0~/, j%, chromium θ, Δ~/, 0%, and the balance iron.

(e) Example The reason why the chemical composition of the induction hardened material for parts such as rolling bearings and pole screws of the present invention is limited to the above range is as follows.

Since induction hardening requires heating for a short time, the alloying elements existing as carbides must be separated from the carbon by heating and diffused into the matrix (austenite phase) to contribute to hardenability. Therefore, if we compare the same content, Mn has the highest hardenability among common alloying elements such as manganese (MQ), molybdenum (MP), chromium (Or), silicon (Sl), and nickel (N1). The contribution rate is high, and the contribution rate decreases in the following order: Mo, Or, Si, and Ni.

In addition, the affinity with carbon is Mo, Or, Mn, N1
, Sl. Mn is a component that increases the amount of retained austenite and is effective against special transfer orders.
Therefore, it is better to have more Mn. However, if it is too large, the amount of carbon and carbide formed increases, and the amount of carbon dissolved in austenite decreases at the same heating temperature, which is not preferable. MO is unsuitable because it has a large affinity for carbon and is the most expensive of these alloying elements. Also, O
r has the same function as Mn, but lJn contributes to hardenability and increases residual austenite.
It is inferior to Mnj, and its affinity with carbon is also large, so it cannot be said to be preferable.

Next, it is considered that the effectiveness of Mn on rolling life is greater than on induction hardened materials. That is, since induction hardening is performed by heating for a short time and cooling with water, high alloy fi% is not suitable due to insufficient penetration of carbon during heating and uncontrolled cooling. Alloying elements in steel combine with carbon to form carbides at room temperature, but at point A1 (223°0
) By heating above, the sifunirite phase transforms into the austenite phase, at which time the carbides are decomposed and carbon and alloying elements are dissolved in the austenite.

Upon quenching (cooling), austenite undergoes martensitic transformation (if cooling is fast enough) or troostite transformation (if cooling is slow), but alloying elements dissolved in austenite suppress troostite transformation, that is, troostite transformation. In addition, carbon dissolved in austenite increases the hardness of martensite. Therefore, if there is an element that has a high affinity for carbon, the carbide will be difficult to decompose even when heated, so the hardenability will be low, and it will not have the hardness of martensite. Product component, for example, 0.5% to obtain HRcIzO or higher
The above is required. On the other hand, if the cinnabar content is 0.2% or more, the amount of carbon that melts into the austenite cannot be adjusted when using a short-time heating process such as induction hardening and 7JC cooling.
(As the heating temperature increases, the amount of carbon in the austenite increases.) If 0.2% or more of carbon is injected into the austenite, there is a high risk of burnout.

(f) ゛Table of effects of the invention-/A table of 5joa and A1817750, which are typical induction firing materials for bearing parts with a carbon content of about O1J%-/A pivot support! The data for the 1.2 type (B U'T -, 2) parts are also added, but compared to this, the rolling life of induction hardened steel products is more than 1g times θ, which is sufficient. I can't say that. Therefore, we created 0,5%0 carbon steel with Mn increased to /1.2% and the or amount changed from o, o7% to o,z 7%, and the rolling contact fatigue strength after induction hardening was The results of the investigation are shown in Table 2.

- Below margin - Table 1 Co. Rolling life of induction hardened products (O,,S%0 carbon #) According to the above experimental results, it was found that as or'& t increases, the rolling life increases and becomes stable. In order to obtain a long life t-, an amount of Or of 09 g% or more is required.

On the other hand, from the experiments so far, as shown in Table 3, 017
% or more, the rolling life decreases for the reasons mentioned above. Therefore, the appropriate range of the amount of Or is θ, Δ~/, 0%. Similarly, if the amount of Mn is large, it becomes difficult for carbon to melt in during heating, so a range of 7.0 to 5% is appropriate.

- Below margin - As explained above, this invention obtains an induction hardened material for parts such as roller bearings and ball screws that has a long life and is inexpensive by appropriately selecting the amounts of carbon, manganese, and chromium. It is something.

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Claims (1)

[Claims] (1) Carbon Q, j~02%, manganese/by weight. High frequency furnace personnel containing 0~7.5%, chromium Q1g~/, 0% and the balance iron.