JPS59232641A - Hot forging method - Google Patents

Abstract

PURPOSE:To omit a normalizing stage and to decrease considerably heat energy by heating a steel material to a specific temp. then cooling quickly the steel material down to the specific depth from the surface and subjecting immediately the material to forging. CONSTITUTION:A steel material is heated to >=1,100 deg.C and is then quickly cooled down to <=1,000 deg.C in the part of 5-10mm. from the surface of said material. While the inside of the steel material is still soft right thereafter, the material is subjected to hot forging and partial machining, by which a machine part is completed. The material withstands to fatigue and wear is thus produced without normalizing.

Description

[Detailed description of the invention] This relates to the hot forging method applied to.

Conventionally, many of the main parts of mass-produced machines such as automobiles and construction machinery have been formed by hot forging and cutting, or cold forging, and then heat treated to increase the strength ('j'-'i').
and made to withstand fatigue and wear.

However, in these processes, 1200
In addition to the thermal energy consumed by heating the parts at 900° C., reheating to nearly 900° C. is required for heat treatment, which requires an enormous amount of thermal energy. On the other hand, with cold forging, the only heating process is post-forging heat treatment, but it is difficult to apply to high-strength metal parts where the tool load increases rapidly. One possible solution to these problems is to reduce thermal energy consumption by performing heat treatment using the heat generated during high-temperature heating in hot forging.

Conventionally, for high-temperature heating during hot forging, steel materials that are difficult to process at room temperature, such as high-strength steel, were used to soften the material by adding tl. The process is as shown in Figure 1. That is, Figure 1 does not show the process of the conventional hot forging method, but is a block diagram (in this figure, 1 is the preparation, 2 is the 1100℃ Heating more than
3 is hot forging, 4 is y;+'U leveling, 5 is partial cutting, and 6 mechanical parts are redundant. However, this process requires heating 2
, normalizing 4 and heating twice, and the energy consumed there is enormous.

In the present invention, instead of giving the properties required for the mechanical parts (5) in the process shown in Fig. 1 by hot forging (3) instead of normalizing (4), the purpose is to gradually improve the properties along with processing. , the gist of which is that after heating the copper phase to 110°C (1°C or higher), the portion 5 to 10mm from the surface of the steel material is heated to 1.000 U.
The following is a hot forging method characterized by rapid cooling and immediate forging.

The present invention will now be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing the steps of the hot forging method of the present invention. In the same figure, first, a steel material 1 (heating 2 to 1100°C or more is performed on it, 1 after which rapid cooling 7 to 1000°C or less is performed on a portion 9 of 5 to 10 m++ from the surface of the steel material, and immediately after that, the inside of the steel material is 1, hot forging 3 is performed while the material is sufficiently softened and partial cutting 5 is performed to complete the mechanical part 6.

Compared to the conventional method, the method of the present invention utilizes the heat generated by heating first, then performs rapid cooling 7 and f' for forging 3, and then performs the process of the conventional method shown in Fig. 1. There is a method that improves the product properties in place of step 4, which eliminates the need for reheating in step 4 of the normalizing process.
It can significantly reduce heat energy. Furthermore, since the surface temperature is lower, the shape accuracy after forging is high, and since there is no reheating after reed forging, there is less oxidation on the surface of the processed product, resulting in parts with much better surface condition.

In this case, increasing the processing temperature to 11001:
This is to austenitize the steel material, sufficiently soften it, and recrystallize it3.Furthermore, in the method of the present invention, the portion between 5 and IO from the surface of the steel material is heated to 1000°C before forging.
(By rapid cooling, the crystal grain size in the surface layer of the product is sufficiently small, and because the processing is done properly, excellent toughness is achieved.)

In this case, rapid cooling refers to instantaneous cooling of only the surface layer of the steel material, and further cooling methods include oil, water, or fountains.

The temperature limit for rapid cooling is set at 100°C (1°C).If the temperature exceeds this limit, the crystal grain size increases, so it is difficult to make the crystals of the resulting processed product finer. This temperature is set at a part 5 to 10 mm from the surface of the steel material.
If the thickness is less than mm, when the partial cutting 5 is performed, the portion imparted with toughness during processing will be cut away, and the product may be in a shape to which no toughness has been imparted. Further, if the portion exceeding 10 mm from the surface of the steel material is rapidly cooled, softening of the inside of the copper phase will be hindered.

Many automobile parts have the strength and toughness to withstand fatigue and wear1.
Cows are required, but the surface layer of the product is particularly critical. The method of the present invention involves forging the surface layer for the first time. In addition, it is designed to rapidly cool only the surface layer.
Since the central part is sufficiently heated and has one groove 1, the deformation resistance of the central part of the material, which is a controlling factor for molding load and mold filling property, is the same as in the conventional method. Therefore, even if the method of the present invention performs cooling before processing in order to improve toughness,
It can maintain the same workability as the conventional method. In the present invention, the reason for forging immediately after rapid cooling is to prevent the deformation resistance at the center of the moon from increasing after cooling.

That is, by the method of the present invention, compared to conventional hot forged materials,
Materials that are significantly more resistant to fatigue and wear can be manufactured without normalizing.

Next, Examples (hereinafter, the effects of the present invention will be described in more detail).

845C of 60 mm φX 60 mm as material
, using.

This was manufactured into a processed product having the shape shown in FIG. 3 by both the steps shown in FIG. 1 and FIG. 2. The thickness of the processed product is 1"-40 mm in Fig. 3. Heating 2 is performed in a soaking furnace,
The temperature was maintained at 1250°C for 1 hour. Steel IJ coating surface rapid cooling 7 was maintained in oil for 20 seconds. At this time, 5 mm from the steel surface
The internal position is 778℃, 10mm internal position is 9
The temperature was 90°C. Furthermore, hot forging 3 was performed immediately after cooling.

Further, normalizing 5 was held at 8:30°C for 1 hour.

The forming load during forging and the grain size number on the product surface are shown in Table 1. Although the method of the present invention cools the surface of the steel material after heating, the forming load is almost unchanged compared to the conventional method. It maintains the same workability as forging.The surface layer of the product is made finer by the method of the present invention.This effect is thought to lead to toughness of 19 grains r1J-1-ft, as shown in Figure 3. A No. 84 2mm Notch Charpy test piece was taken from the product and the impact value distribution was examined in the thickness direction.The results are shown in Figure 4. In A, the results obtained by the conventional method are shown by line B. From the same figure, the impact value of the product obtained by the conventional method is 5 K9 f・In
To a certain degree.

According to the method of the present invention, a value of 5 to 8 to 9 f-m could be secured at a depth of nearly 10 mm from the product surface. Many automobile parts require strength and toughness to withstand fatigue and wear.
In particular, the surface layer of the product is critical, and by the method of the present invention,
The ability to impart overwhelmingly higher toughness to the surface layer compared to conventional methods is a major advantage. In addition, by being able to secure an impact value of 7 to 13 K9 f·Ill with a trench close to the 5th surface, sufficient toughness can be maintained even when partial cutting is performed.

By controlling the cooling rate and temperature,
It is also useful to control the impact value distribution in the thickness direction. Furthermore, since normalizing is omitted in the present invention, as a result, the amount of heat can be reduced by nearly 30 to 40 inches.

As stated above, the present invention can reduce the heat costs involved in manufacturing mechanical parts, and at the same time improve the properties of the parts compared to the conventional ones, and has extremely large industrial benefits.

Chapter 1 Table

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the process by the conventional hot forging method, Fig. 2 is a flock diagram showing the process by the hot forging method of the present invention, and Fig. 3 is a schematic diagram showing an example of the shape of an upturned product. Figure 4 is a diagram that does not show the distribution of impact values in the town. 1... Steel material, 2... Heating 13... Hot forging, 4...
・・Normalizing, 5.・Partial cutting, 6.・Machine parts,
7...Rapid cooling. Patent Applicant Representative Patent Attorney Tomoyuki Yafuki (and 1 other person 9) Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] After heating the steel material to 1100℃ or higher,
Rapidly cool the 10mm section to below 1000℃, and immediately
A hot forging method characterized by the addition of this forging process.