JP2827592B2 - Manufacturing method of steel parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface hardening machine structure.
Table consisting of carbon steel and low-alloy steel for machine structural use for surface hardening
Parts with improved wear resistance and fatigue strength by subjecting a surface hardening process on the surface hardened steel material, for example, various types of gears such, various shaft acids, to produce a machine structural parts for so various retainer such by plastic working The present invention relates to a method for producing a steel part used for the above.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned components for various mechanical structures are
It was often manufactured by cutting steel materials, but in recent years it has also been often manufactured by plastic working such as forging or rolling, and it is a working heat treatment that combines plastic working and heat treatment. Many laws have been adopted.

[0003] Such a thermomechanical heat treatment method includes the following (1) a thermomechanical heat treatment method involving a process before transformation,
(2) a thermomechanical method involving processing during transformation, and (3) a thermomechanical method involving processing after transformation. Forging and quenching, in which plastic working is performed at an austenite temperature, and ausforming, in which plastic working is performed at a metastable austenite temperature, followed by rapid cooling. Alternatively, there are isoforming in which plastic working is performed during the bainite transformation and quenching is performed, and sub-zero processing in which plastic working is performed during the martensitic transformation is performed. There are patenting in which plastic working is performed later, and malform in which martensite is subjected to plastic working.

Among these, the thermomechanical heat treatment method before transformation of (1) is useful as a processing technique for greatly improving the strength and toughness of steel by improving hardenability, refining crystal grains and precipitates, and the like. It has become something.

However, in such a thermomechanical method,
Since there is a limit in improving the wear resistance and fatigue strength of the surface, a surface hardening treatment is also performed.

FIGS. 1 (C) and 5 illustrate a manufacturing process of a steel part in which a surface hardening treatment and a working heat treatment before transformation are combined. For example, carburizing is performed, followed by plastic working such as forging (for example, tooth forging), and quenching after holding for a required time to produce a steel part having excellent wear resistance and fatigue strength by plastic working. It is something to do.

[0007]

However, in such a conventional method of manufacturing a steel part, forging (for example, tooth shape forging) is performed while maintaining the heating temperature in the carburizing step. Because the material is in a high temperature state throughout the entire process, it is not possible to form a forging die lubrication film on the surface of the steel material, and therefore the load on the forging die increases. And the life of the forging die is reduced, and the dimensional accuracy of the steel part may be varied.

It is not surprising that the lubricant is directly sprayed on the forging die inside the forging machine. However, the sprayed lubricant may accumulate in the forging die, thereby lowering the processing accuracy. There is also a problem that there is a possibility, and it has been a problem to solve the above problem.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has an advantage in that the lubrication of a plastic working mold can be sufficiently improved to prevent the occurrence of uneven wear, thereby extending the life of the mold. It is an object of the present invention to provide a method of manufacturing a steel part which can reduce the variation in dimensions due to the occurrence of uneven wear and improve the quality of the steel part.

[0010]

Means for Solving the Problems The method of the present invention relating to steel parts, carbon steel and surface hardening for machine structural use surface hardening
After performing a surface hardening treatment on a surface hardening steel material such as a low alloy steel for machine structural use , a hot plastic working type lubricating film is applied to the surface of the steel material at a temperature lower than the surface hardening temperature. It is characterized in that it is configured to be formed at a temperature higher than the quenching temperature and then subjected to hot plastic working before transformation by a hot plastic working mold and then quenched. The configuration of the invention relating to the manufacturing method is used as means for solving the above-mentioned conventional problems.

[0011] In the manufacturing method of steel parts according to the present invention, the for surface hardened steel material, and mechanical structural carbon steel Ru Tei enacted as JIS SC material, JIS SCr
Wood, SCM material, SNC material, SNCM material, SMn material is or for machine structural low-alloy steel Ru Tei established as such, they to or adjust the appropriate component amount, and those may be added components used.

When performing a surface hardening treatment on such a steel material, carburizing or carbonitriding treatment is employed, but the present invention is not limited to these.

Next, a hot plastic working type lubricating film is formed on the steel material after the surface hardening treatment. At this time, if the temperature of the steel material is too high, it is difficult to form the lubricating film. For example, when a graphite film is to be used as a lubricating film, the temperature of the steel material is set to 150 to 200 ° C.
And then perform graphite coating.

In this case, when the carburizing treatment is performed as the surface hardening treatment, the steel material is once cooled to normal temperature or near normal temperature after the carburizing treatment, and then cooled to 150 to 20%.
After reheating to 0 ° C., it may be coated with graphite, or after carburizing, the steel material may be coated with 150 to 20%.
After cooling to 0 ° C., graphite coating may be performed.

The hot forging die lubricating film is not limited to graphite, and other W-based or Mo-based solid lubricants may be used.

In this way, after forming a hot plastic working type lubricating film on the surface of the steel material subjected to the surface hardening treatment, the temperature is raised to a temperature higher than the quenching temperature, and then to a predetermined shape by the hot plastic working die. by hot plastic working before transformation (hot forging <br/> granulation process, hot rolling, hot upsetting, etc.) after quenching was performed (to transform into martensite and the like), high Manufacture steel parts with excellent wear and fatigue strength by plastic working.

FIG. 1A and FIG. 2 show an embodiment of the present invention.
After carburizing at about 050 ° C, the steel is cooled once to room temperature and then subjected to primary heating to reduce the steel material by 150 to 20.
Graphite coating is performed at a temperature of about 0 ° C., followed by secondary heating to bring the steel material to a temperature of about 900 to 1050 ° C., followed by hot forging and then 800 to 9
After holding at about 00 ° C. for an appropriate time, quenching is performed, and if necessary, tempering is performed to obtain a steel part.

FIG. 1B and FIG. 3 show another embodiment of the present invention.
After carburizing at about 1050 ° C, 150-200
After cooling to a temperature of about 100 ° C. and performing graphite coating, subsequently heating the steel material to a temperature of about 900 to 1050 ° C., performing hot forging, and holding the steel material at about 800 to 900 ° C. for an appropriate time. It is quenched and tempered if necessary to make steel parts.

[0019]

According to the method of manufacturing a steel part according to the present invention, the steel part having the above-described structure can be obtained, which is excellent in abrasion resistance and fatigue strength, and can be lubricated to a hot plastic working die. The action is sufficiently good, and the prevention of uneven wear of the hot plastic working type and the extension of the life are realized, and the product quality is also improved.

[0020]

FIG. 4 shows an embodiment of the present invention, in which a gear is manufactured by the steps shown in FIGS. 1B and 3 as an example.

In this embodiment, the steel material is JIS S
It is made of Cr420 steel, as shown in FIG.
The steel material 1 was charged into the carburizing furnace 2 and subjected to a carburizing treatment at 950 ° C. for 5 hours, and then cooled in the cooling furnace 3, and then cooled in the graphite water tank 4.
A graphite lubrication coating at a temperature of 180 ° C. to form a lubricating film made of graphite on the surface of the steel material 1, and then feed it into a heating furnace 5 and heat it to 950 ° C., and then form a forging process in a forging machine 6. Is carried out, and after being made into a gear-shaped component material 7, it is put into a temperature holding tank 8, and 850.
After the temperature was maintained at ℃, and then put into a quenching tank 9 for quenching, the steel was tempered at 170 ℃ to obtain a steel part consisting of gears.

The steel parts (gears) thus obtained are:
Since the steel material subjected to the surface hardening treatment is used, it is excellent in wear resistance and fatigue strength, and the lubricating action between the forging die of the forging machine 6 and the forging die is sufficiently good. No troubles such as abrasion are caused, and the dimensions are stable and the precision is high. In the conventional case, the variation in quality is about 3σ ± 0.1,
The quality could be improved within the range of σ ± 0.05, and at the same time, the mold life could be extended from about 2000 times to about 6000 times.

[0023]

According to the method for manufacturing a steel part according to the present invention, the carbon steel for machine structure for surface hardening and the machine structure for surface hardening are provided.
After performing a surface hardening treatment on a surface hardening steel material such as a low alloy steel for forming a hot plastic working type lubricating film on the surface of the steel material at a temperature lower than the surface hardening treatment temperature, The configuration is such that the temperature is higher than the quenching temperature , hot plastic working before transformation is performed by the hot plastic working mold, and then quenching is performed.Therefore, wear resistance and fatigue strength are achieved by using a surface-hardened steel material. It is possible to manufacture steel parts excellent in heat resistance, and it is possible to extend the life of the mold by preventing the occurrence of uneven wear by sufficiently lubricating the hot plastic working mold and preventing the occurrence of uneven wear. In addition, there is an excellent effect that the dimensional variation due to the occurrence of uneven wear is extremely small, and it is possible to further improve the quality of the steel part.

[Brief description of the drawings]

FIG. 1 is a process explanatory view illustrating a method for manufacturing a steel part by carburizing forging and quenching according to the present invention (FIGS. 1A and 1B) and the conventional method (FIG. 1C).

FIG. 2 is an explanatory view showing an embodiment of a method for manufacturing a steel part according to the present invention.

FIG. 3 is an explanatory view showing another embodiment of the method for producing a steel part according to the present invention.

FIG. 4 is a schematic explanatory view of a manufacturing facility used for carrying out a method of manufacturing a steel part according to the present invention.

FIG. 5 is an explanatory view showing a conventional method for manufacturing a steel part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel material 2 Carburizing furnace 3 Cooling furnace 4 Graphite water tank 5 Heating furnace 6 Forging machine 7 Parts material 8 Temperature holding tank 9 Quenching tank

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI C23C 30/00 C23C 30/00 C (58) Fields investigated (Int.Cl. ⁶ , DB name) B21J 3/00 B21J 1 / 00 B21K 1/00

Claims (1)

(57) [Claims] Claims: 1. Carbon steel for machine structural use for surface hardening and surface hardening
After performing a surface hardening treatment on a surface hardening steel material such as a low alloy steel for machine structural use , a hot plastic working type lubricating film is applied to the surface of the steel material at a temperature lower than the surface hardening temperature. A method for producing a steel part, comprising: forming, heating at a temperature higher than a quenching temperature, performing hot plastic working before transformation by a hot plastic working mold, and then quenching.