JPS604251B2 - Partial quenching method for steel parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for partially quenching annular steel parts, in particular, after uniformly heating to a predetermined quenching temperature, quenching is performed with a folding surface that is not desired to compete.
The diameter surface is cooled separately, and the hardness of the mysterious surface that you do not want to enter at dawn is reduced to H.
Hardened to RC30-50, and the hardness of the face is HRC6
This relates to a method of increasing the number to 0 or more.

In general, annular steel parts, such as bearing races, are generally hardened throughout, but in some cases, such as mast roller bearings, the outer surface of the outer ring is directly connected to the mast material (relatively low hardness). , since they are used in contact with each other, when considering the wear of the mast material, it is desirable that only the outer diameter surface of the bearing raceway has low hardness.

Therefore, bearing manufacturers must respond to these demands by applying carburizing after applying carburizing prevention treatment to the outer diameter surface using carburized steel, or applying high-frequency competition only to the raceway surface by using carbon steel. I'm doing it. However, the anti-carburizing process takes a long time and requires a lot of energy, resulting in high costs, and induction hardening requires expensive high-frequency equipment. The present invention was developed in view of the drawbacks of the above-mentioned conventional examples, and the structure of the present invention will be described below with reference to the accompanying drawings.

Fig. 1 shows a partial hardening device for mast roller bearings according to the present invention, in which numeral 1 indicates an outer ring of a mast roller bearing;
2, 2 is a protection ring to prevent the coolant from splashing on other parts, 3 is the injection port on the inner diameter side, and 4 is the mist generating nozzle. In other words, the bearing steel (for example, SUJ-2) is shown in Figure 2. As such, it has a heat transformation nose at a temperature of around 650 qo, and is in a state where it is susceptible to troustite transformation.

Therefore, first, a mist of coolant (air and coolant are mixed and the cooling rate is considerably slower than cooling in oil) is injected to the extent of about 1 ounce of sand only on the outer wall side. At this time, the temperature on the outer side is near the isothermal transformation nose, making it quite easy to undergo isothermal transformation. On the other hand, at that time, although the temperature on the inner side is still slightly lower, it is in a state where it will be sufficiently dawn hardened (HRC 60 or higher) if rapidly cooled. Therefore, at the same time as the outer diameter mist injection ends, a liquid coolant is injected from the inner diameter side (at a cooling rate that is approximately the same as or higher than that of oil cooling) to quench and harden only the raceway surface. Further details regarding the above are as follows.

SUJ-2 mast roller bearing (SXO9
After uniformly heating the outer ring 1 of the 54L) in an electric furnace at 840 pm for about 30 minutes, as shown in Fig. A mist coolant was injected only on the radial side for one inkstone interval.

Immediately after this outer diameter injection is completed, apply liquid coolant to the inner diameter side only.
The sand was sprayed between. At this time, the temperature of outer ring 1 is approximately 180~2
0000, so after removing the defense ring 2, I air-cooled it to room temperature and completed the dawn entry. As a result, as shown in Figure 3, the raceway surface side had an HRC of 64 to 65 up to a depth of about 4 yen.
It is completely quench hardened, and at deeper depths, the amount of troustite precipitated increases as it approaches the outer flea side, resulting in low hardness. It exhibits almost the same hardness (HRC38) from about 8 skin depth to the outer flea surface. In the examples, a water-soluble coolant (polyvinyl alcohol + polyacrylic acid league aqueous solution) was used as the coolant, but ordinary tap water may also be used. As explained above,
This invention involves uniformly heating an annular workpiece such as a bearing raceway to a dawning temperature in the austenite region above the transformation point, and then subjecting the inner and outer radial surfaces, which do not want to be wetted, to constant temperature transformation at a slow rate. Cool to the temperature near the nose, and after slow cooling, rapidly cool the other ridge where you want to insert ants, and cause troustite transformation on the radial surface where you do not want ants to enter, and make the radial surface HRC30~
50, and the other quenched, radial surface undergoes martensitic transformation to make the ridge surface HRC 60 or higher,
Extremely easily, reliably, and inexpensively, the radial surface where you do not want to add phosphorus can be made to a low hardness HRC of 30 to 50, and the flea surface where you want to add phosphorus can be made to a high hardness HRC.
It can be 60 or more.

Furthermore, by changing the mist injection time on the outer diameter side and the injection pressure on the inner diameter side, the hardening depth can be controlled extremely easily.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a coolant injection device using the method according to the present invention, Fig. 2 is a temperature transformation diagram of SUJ-2, and Fig. 3 is a cross-sectional hardness of a workpiece quenched by the method according to the present invention. It is a distribution map. 1... Ring-shaped steel part, 2, 2... Defense ring, 3...
...Inner diameter injection port, 4...Mist generation nozzle. Figure 2 Figure 1 Figure 3

Claims (1)

[Claims] 1 After uniformly heating an annular workpiece such as a bearing raceway to a quenching temperature in the austenite region above the A_1 transformation point, heat the radial surface, which is not desired to be quenched, among the inner and outer surfaces, at a slow speed to a temperature near the isothermal transformation nose. After cooling and slow cooling, the other radial surface to be quenched is continuously rapidly cooled to cause troostite transformation on the radial surface that is not to be quenched to make the radial surface HRC 30 to 50, and the other radial surface to be quenched is A method for partially quenching an annular steel part, characterized by causing martensitic transformation to occur in the radial surface to make the radial surface have an HRC of 60 or more.