JPS63111121A - Production of slag for cold forging - Google Patents

Abstract

PURPOSE:To permit production of hollow and solid slug having uniform structure by using circular conical or circular truncated cone-shaped dies to upset the hollow slug having the spheroidized structure of a high-C hard-to-work steel at the time of producing said hollow slug by upsetting. CONSTITUTION:After a carbon steel bar or low alloy steel bar for machine structural purposes is cut to a prescribed length, the material is upset at >=40% in the axial direction by a pair of the upper and lower circular conical or circular truncated cone-shaped dies having 120-176 deg. tip angle in the (Ac1-60 deg.C)-(Ac3-40 deg.C) temp. region of said material. The material is further held for 1-3hr in the (Ac1-60 deg.C)-(Ac3-40 deg.C) temp. region in succession thereof after or without boring and is then subjected to air cooling or slow cooling or cooling at <=50 deg.C/h cooling rate from the above-mentioned holding temp. down to 650 deg.C to form the spheroidized structure. The material is thereafter subjected to a descaling and lubricating treatment. The respective parts of the upset product are nonuniformly strained and the spheroidization is dispersed if the tip angle of the above-mentioned dies is off the above-mentioned range.

Description

[Detailed description of the invention] Industrial field of application This invention is a material for cold plastic working (slag) used as a material for parts such as gears of automobiles, industrial machines, etc.
The present invention relates to a low-cost and efficient manufacturing method of hollow slag or solid slag having a spheroidized structure.

Background Art As a slag for cold forging, NK high-precision hollow slag (manufactured by Nippon Kokan Co., Ltd.) is known. This is manufactured through the following process: steel bar → cutting → cold press forming → drilling → spheroidizing annealing → descaling → Bonde-Honda Lube lubrication treatment → hollow slag. However, mechanically manufactured carbon steel up to 340C and low alloy steel up to about 20C are only manufactured.

The reason for this is thought to be that difficult-to-process materials such as 545C and 5CH435 are difficult to cold press form as they are rolled, and require spheroidizing annealing during forming, resulting in high costs. The spheroidizing process performed before cold press forming is an essential process for difficult-to-work materials $31 to improve the deformability of the material and reduce the forging load, but this ashtray has 16
It takes a lot of time and a lot of energy. Also, the spheroidizing process after press forming also takes a lot of time and energy.For these reasons, hollow slag, which is a difficult-to-process material, It has not been previously manufactured.Also, since it is cold press formed, the deformation resistance is high, and in order to manufacture a hollow slug with a large diameter, a press with a large capacity is required, resulting in high equipment costs.

Problems to be Solved by the Invention In view of the current situation, the applicant previously proposed a method for manufacturing a hollow slag having a spheroidized structure of high C, difficult-to-work steel (Japanese Patent Application No. 56-189941). . This method takes advantage of the high deformability, low deformation stress, and microstructure improvement ability of warm I25 forging, and warmly forges highly processed hollow molded products without spheroidization treatment before forming, and then heat-retains them as is. This is a method to form a spheroidal structure, followed by descaling and lubrication treatment to form a hollow slag. However, in the case of this method, there is a problem in that simply upsetting the molded product results in variations in the degree of processing of the molded product, making it difficult to obtain a hollow slag with a uniform structure.

Purpose of the Invention The present invention was made to solve the above-mentioned conventional problems, and by devising the upsetting method using a mold, it is possible to produce hollow slag and solid slag having uniform spheroidization and spheroidization. It is necessary to propose a method that can be manufactured at low cost.

Means for Solving the Problems The present invention solves the problems of the method of the above-mentioned Japanese Patent Application No. 189941/1982 by using a conical or truncated conical mold for upsetting, thereby achieving uniform spherical formation. This paper proposes a method for producing hollow slag and solid slag with texture.

In other words, the present invention provides for cutting a carbon steel bar or a low alloy steel bar for machine 11R production into a predetermined length, and then cutting the material (AC+-6
Point angle 120~ in the temperature range from 0℃ to (AC3-40℃)
1*, in which upsetting of 40% or more in the axial direction was performed using a pair of upper and lower molds in the shape of a 176° cone or truncated cone, followed by (
AC, ~60℃) ~ (AC3-40℃) 1~3
After holding for a period of time, air cooling or slow cooling, or cooling from the holding temperature to 650°C at a cooling rate of 50'0.4 or less to form a spheroidized structure, followed by descaling and lubrication treatment. The present invention is characterized by producing a solid slag having a spheroidized structure by omitting the drilling process in the method.

Here, the steel materials used are those normally used for cold forging, but since we are specifically targeting 545C-355C, 5C) 1435, etc., which are difficult-to-work materials, the steel materials used are was carbon steel or low alloy steel for mechanical structures.

The heating temperature of the material cut into a predetermined length is determined by the (Ac
1-60°C) to (AC3-40°C) is because in the temperature range outside this range, the spheroidization rate of the slag after forging, heat retention, or slow cooling is poor, and the hardness is also high, making it difficult to This is because it is not suitable for forging.

In the upsetting process, a conical or truncated conical mold with a tip angle of 120 to 176° is used. The process becomes incomplete. On the other hand, if the upsetting amount is less than 120° C., the strain at each part will be non-uniform and the spheroidization will vary, but variations in the upper and lower end surfaces are particularly problematic. This variation in distortion is thought to be caused by the friction between the forged product and the die. The upsetting rate using this mold was 40% or more in the axial direction.
If it is less than this, the processing strain will be small and the spheroidization due to heat retention or slow cooling after forging will be insufficient, making it unsuitable for cold forging.

The heat retention temperature after forging is (8C+ -60℃) ~ (AC3
-40°C) because the forged product becomes spherical and softens in this temperature range. In addition, the holding time at this temperature was set at 1 to 3 hours because, although spheroidization progresses to some extent even if the heat is held for less than 1 hour, more than 1 hour is required to achieve sufficient spheroidization, and on the other hand, it exceeds 3 hours. Heat retention for a long time is not economical and increases costs, so it is not preferable.

As a cooling method, Kube C1-60℃) ~ (AC3-40
The reason why we decided to perform air cooling or slow cooling from a temperature range of This is necessary because air cooling or gradual cooling is desirable for cooling.

Further, since a sufficient spheroidized structure cannot be obtained at a cooling rate exceeding 50°C/h, the cooling rate in slow cooling was limited to 50°C/h or less. Further, since a sufficiently spheroidized structure can be obtained by slowly cooling to 650''C, it is preferable from an economic point of view to air-cool from a temperature as high as possible, so it was decided to slowly cool to 650''C.

Disclosure Based on Drawings of the Invention FIG. 1 is a block diagram showing an example of the manufacturing process of the invention, and FIG.
The figure is a schematic vertical cross-sectional view showing the upsetting die mold to be drilled in the same manner as above.
Figure 3 is a schematic diagram showing the drilling process in the same as above, @l r
It is a JfT surface view.

In other words, this invention involves cutting a steel bar made of carbon steel for structural use or low alloy steel into a predetermined length, descaling the cut material, and then applying a carbon lubricant for lubrication during warm forging. do. After that, in a high frequency heating furnace (Acl-60
℃) to (AC3-40℃) and immediately
Perform upsetting of 40% or more in the axial direction using the upsetting die shown in the figure. In Figure 2, (1) is the die, (2) is the pressure receiving plate, (3) is the centering ring, (4X5)
(6) indicates an upper mold and a lower mold, each having a tip angle θ of 120 to 176°, and (6) an upholstered product.

Note that (7) is a spring for raising the centering ring (3) for centering.

In other words, when performing upsetting, the centering ring (3) is raised by the spring (7), and the cut steel bar is installed in a pair of upper and lower molds (4 x 5) with a processing degree of 40% or more. It's crowded. As the upsetting progresses, the centering ring (3) descends, resulting in a complete upsetting product (6). Subsequently, in the drilling process shown in FIG. 3, the center is punched using a punch (8) to form a hollow slug (9). At this time, hit the punch (
8) is more efficient if the end face is straightened. In addition, when producing solid slag, only the end face correction is performed after upsetting.

After the above processing, the product is immediately charged into a heat retention furnace or slow cooling furnace, and kept at a temperature of (Acl-60℃) to (AC3-40℃) for 1 to 3 hours, then air cooled or slowly cooled. Alternatively, a spheroidized structure is formed by cooling from the above temperature to 650°C at a cooling rate of 50°C4. Thereafter, it is cooled, descaled, and subjected to a lubrication process to form hollow or solid slag.

By employing such a method, slag having a spheroidal structure, which is a difficult-to-process material, can be obtained at low cost. That is, warm forging does not cause upsetting cracks and can be carried out under low loads, and the plastic strain introduced by warm forging makes it easy to form a spheroidal structure by subsequent short-term heat retention or slow cooling.

Examples of this invention are shown below.

Example Hot-rolled steel material with the components shown in Table 1 (size 40 mmφ
A hollow slag was manufactured using a slag (60 myyn long) as a raw material according to the first manufacturing process shown in FIG. 1, and the processing temperature, mold tip shape, processing degree, and post-processing cooling method shown in Table 2 were investigated.

In each test, cutting was performed by shear cutting, descaling by shot blasting, carbon lubrication by Saiguchi, or Delta Forge 14.
4 (manufactured by Acheson Co., Ltd.) was used.

A high frequency heating furnace was used for heating, and a 500 TON press was used for upsetting. In addition, an electric furnace was placed close to the press machine so that heat retention or slow cooling could be carried out immediately after forging. Lubrication after one scale was performed using Bonde-Honda Lube treatment.

The properties of the obtained hollow slag are as shown in Figure 4. A tensile test piece (11) and a compression test piece (12) were taken from the hollow slag (10), and the tensile strength, area of area, and critical compressibility were determined respectively. I asked for The critical compressibility was determined by the method of measuring the critical compressibility of steel by the Japan Society for Plasticity.

The average spheroidization rate was determined by cutting micro test pieces at five locations from the hollow slag and comparing them with a standard photograph of the spheroidization rate using a microscopic microscope.

In this example, in test No. 1, the processing degree was 60%.

Using a conical mold with a tip angle of 170", after forging, test forest A was heated to 700°C; test forest B was heated to 720°C.
The processing was carried out under various conditions of heat retention for 2 hours and at various processing temperatures. The results are shown in Table 3.

From the results shown in Table 3, (Act-60℃) ~ (AC3
At a processing temperature in the range of -40°C), cementite 1 undergoes good spheroidization, has a high critical compressibility, and has a low tensile strength.

Trial AANc, 2, machining degree 60%, 700 after forging
The relationship between the mold tip angle and each characteristic when the processing temperature was 700°C was investigated under heat retention conditions of 2 hours at ℃. The results are shown in Table 4.

From Table 4, it can be seen that each characteristic is better when upsetting with a punch with a tip angle of 160' or 170', which is within the range of the present invention, than with a smooth punch with a tip angle of 180°.

In test N0.3, the forging temperature was 700°C, and the temperature was 700°C after forging.
Using a cylindrical die with a tip angle of 170° under heat retention conditions of X2 hours, changes in each characteristic were investigated when the degree of processing was changed. The results are shown in Table 5.

From Table 5, it can be seen that when the working degree is 40% or more, the spheroidization rate becomes good and it can be used for cold forging.

In test No. 4, a Nissin die with a forging temperature of 700° C. and a tip angle of 170° was used, and the changes in each characteristic were investigated when the cooling conditions after processing were changed under the conditions of a tool depth of 60%. The results are shown in Table 6. The heat retention temperature and cooling start temperature were each 700°C.

For comparison, Table 6 shows spheroidizing annealing as a conventional method →
The characteristics of the NK type medium slag produced through the process of cold upsetting, drilling and annealing are also shown.

From Table 6, it was found that according to the cooling and holding conditions of the present invention, almost the same characteristics as the conventional example were exhibited.

As explained in detail, the method of this invention makes use of the high formability, low deformation stress, and ability to improve the microstructure of warm forging to form highly processed hollow slag by forging without prior spheroidization treatment. When retaining heat to form a spheroidal structure, it is possible to produce hollow slag with a uniform spheroidal structure at low cost without any variation in the degree of processing by upsetting the slag using a conical mold. This is highly effective in producing high-quality steel slag.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of the manufacturing process of this invention, Figure 2 is a block diagram showing an example of the manufacturing process of this invention.
The figure is a schematic vertical cross-sectional view showing the upsetting die mold in the same as above.
FIG. 3 is a schematic longitudinal cross-sectional view showing the drilling process, and FIG. 4 is an explanatory diagram showing a method for collecting tensile test pieces and compression test pieces in an example of the present invention. 1...Die, 2...Pressure plate, 3...Center alignment ring, 4...Upper mold, 5...Lower mold, 6...
・Upgraded product, 8...Dashing method punch, 9,10...Hollow slug.

Claims (2)

[Claims] (1) After cutting carbon steel rods or low alloy steel rods for machine structures into specified lengths, cut the material into (AC_1-60°C)
After performing upsetting of 40% or more in the axial direction using a pair of upper and lower conical or truncated conical molds with a tip angle of 120 to 176 degrees in the temperature range of 3-40℃, and then drilling. , Subsequently, after holding at a temperature of (AC_1-60℃) to (AC_3-40℃) for 1 to 3 hours, air cooling or gradual cooling, or cooling from the holding temperature to 650℃ at a rate of 50℃/Hr or less A method for producing slag for cold forging, characterized by cooling it at a high speed to form a spheroidal structure, followed by descaling and lubrication treatment. (2) The method for producing a cold forging slag according to claim 1, characterized in that the drilling process after the upsetting process is omitted.