JPS5922769B2 - Heat treatment method for forged products - Google Patents

Description

[Detailed description of the invention] The present invention relates to a heat treatment method for forged products.

Forged products are made by heating a metal material to 1,100 to 1,300°C and plastically working it into a desired shape by intermittent impact using a metal mold. Heat treatment refines the crystal grains and improves toughness against impact. Usually, the aim is to improve mechanical properties.

The heat treatment method that has been commonly used will be explained below.

The forged product that has been forged and deburred at 1,100 to 1,300° C. is slowly cooled by leaving it at room temperature or other means to once lower it to room temperature.

The metal structure at this time has a coarse structure as shown in FIG.

This material is heated to about 900° C. in a heating furnace or the like, maintained at this state for about 2 hours, and then cooled by air cooling or the like.

By this heat treatment, the crystal grains are made fine and uniform as shown in FIG. 2, and a metal structure with excellent mechanical properties such as ensuring toughness against impact can be obtained.

The forged product heat-treated in this manner is processed into a predetermined product by machining such as cutting.

However, in the structure shown in Figure 2 obtained by the conventional heat treatment method, the crystal grains are refined, but since most alloy steels have a band-like structure, the continuity of the chips during cutting becomes excessive and the cutting edge is damaged. It has five drawbacks: it promotes wear and tear, and has extremely poor machinability, such as peeling on the machined surface.

The present invention addresses the above-mentioned drawbacks of the conventional methods and provides a heat treatment method for obtaining a metal structure with extremely good machinability.

Examples of the heat treatment method according to the present invention will be described in detail below.

Example 1 After heating, punching and deburring, the temperature was around 1000℃ (9
Approximately 100 forged products with a temperature of 50 to 1150℃)
Immerse in boiling water at ℃ for 10-20 seconds, then heat in a heating furnace at 80℃.
It is heated to 0° C., maintained at this state for 60 minutes, and cooled by air cooling.

As shown in Figure 3, the metal composition thus obtained is such that the striped or fibrous structure of the steel is destroyed, the ferrite becomes separated and independent, and the chip becomes more easily fractured during cutting. There was no tearing of the machined surface, the workability was greatly improved, and free machinability was demonstrated.

In the heat treatment process of the above example, the step of immersing the forged product at around 1000℃ after heating, stamping, and deburring in hot water is extremely important in the heat treatment of the present invention. It is thought that the forged product can be quickly and uniformly cooled on the inside and outside to break the continuity of the fiber structure, and as a result of various experiments, the temperature of the hot water in the range of about 50°C to 100°C is different from the above example. Although we were able to obtain the same preferable metal structure as y, if we tried to use hot water at a temperature below the boiling state (approximately 100°C),
It is extremely difficult to control the temperature, and the temperature of the boiling water is approximately 100%.
℃, it was possible to always keep the temperature of hot water constant without the need for troublesome temperature control.

The immersion time in hot water varies depending on the mass and shape of the forged product, but it is necessary that the immersion rapidly cools the forged product to the temperature at which it will be kept heated in the next processing step, or a temperature higher than that. The time is usually about 2 minutes at most, and usually about 10 to 15 seconds is sufficient.

The heating temperature in the heating furnace is in the range of 700℃ to 850℃, and the heating holding time is up to 10℃ depending on the mass and shape of the forged product.
In 0 minutes, usually about 30 minutes, favorable results, ie, a metallographic structure similar to that shown in FIG. 3, can be obtained.

According to the heat treatment method of the present invention as described above, heating, forging,
After immersing the deburred forged product in boiling water for a very short time7
By holding it in a heating furnace at 00 to 850°C for 100 to 30 minutes, it is possible to obtain a metal composition with extremely good machinability while ensuring the desired toughness.

Furthermore, in the present invention, since the forged product is cooled using hot water of approximately 100°C, the temperature control is extremely easy, and the cooling time using the hot water is extremely short, so that the heat treatment process can be performed easily. It has great industrial value, as it can greatly shorten the time, easily automate the heat treatment process, and the equipment is small and inexpensive.

[Brief explanation of drawings]

The attached figures are micrographs (magnification: 100) showing the metallographic structure. Figure 1 shows the metallographic structure of the forged product after heating and cooling by leaving the forged diameter in the atmosphere, and Figure 2 shows the metal structure of the forged product at 900 magnification compared to the one in Figure 1.
The metal structure after being held in a heating furnace at ℃ for 2 hours and then cooled shows the standard structure obtained by conventional heat treatment. FIG. 3 shows the metal structure of a forged product obtained by the ° heat treatment of the present invention.

Claims (1)

[Claims] 1 950-1150°C after heating, punching and deburring
The forged product is heated for about 100℃ until the temperature reaches 700-850℃.
A method for heat treatment of a forged product, which comprises immersing and cooling in hot water at a temperature of 0.degree. C., placing the product in a heating furnace at a temperature of 700 to 850.degree.