JPH0760335A - Method for drawing steel tube - Google Patents

Abstract

PURPOSE:To prevent the production of burning flaw and increase the working capacity by setting the contact angle of a die and a blank tube in a specific range in drawing a lubricated steel tube of carbon steel or alloy steel, etc. CONSTITUTION:In drawing a lubricated blank tube 2 of carbon steel, alloy steel, a R type die that the contact angle of the blank tube 2 and the die 1 is made as <=40 deg. is used. An article of high quality can be produced by using the R type die which is a small volume of super hard part and inexpensive and preventing burning flaws producing in drawing the material to be worked of carbon steel or alloy steel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drawing a carbon steel / alloy steel pipe.

[0002]

2. Description of the Related Art Conventionally, when cold drawing a carbon steel or alloy steel pipe, seizure of a die is likely to occur, so that a low yield and a low speed drawing process are inevitable due to a flaw in the steel pipe.

Therefore, in cold drawing of carbon steel or alloy steel, it is important to reduce friction between the drawing tool and the material, reduce wear of the tool, and prevent seizure flaws. In order to achieve the above object, research has been conducted on the material and shape of the die, the lubricant, the drawing speed, the surface reduction rate, and the like.

Therefore, the applicant of the present invention is Japanese Patent Publication No. 4-48839.
Japanese Patent Laid-Open Publication proposes a lubrication method in cold drawing of carbon steel and alloy steel. Also, JP-A-62-227518
In the publication, a method for drawing stainless steel is proposed.

[0005]

However, even if the lubrication method proposed by the applicant in Japanese Patent Publication No. 4-48839 is used, the occurrence of seizure flaws cannot be completely prevented. Further, the target of the drawing method proposed in Japanese Patent Laid-Open No. 62-227518 is a taper die, and it is difficult to apply it to a die having an R shape in the drawing portion (hereinafter referred to as "R type die"). Is.

As shown in FIGS. 1 (a) and 1 (b), the larger the contact angle θ between the die 1 and the shell 2, the greater the friction.
In the conventional cold drawing method of carbon steel or alloy steel, it is carried out so that seizure does not occur under the situation where the contact angle θ between the die 1 and the raw pipe 2 has to be made small, which is inefficient. there were. Incidentally, 3 in FIG. 1 is a plug.

In view of the above-mentioned problems, an object of the present invention is to set a contact angle between a die and a raw pipe in a specific range and to bake it when drawing a lubricated carbon steel or alloy steel pipe. It is to prevent the occurrence of flaws and increase the processing amount.

[0008]

In order to achieve the above-mentioned object, the present invention has a contact angle between the work material and the die of 4 when drawing the work material of the lubricated carbon steel / alloy steel.
An R-type die having a shape of 0 ^O or less is used.

[0009]

The present inventor has examined the relationship between various drawing conditions and the occurrence of seizure by experiments, and found that seizure flaws can be prevented by setting the contact angle between the die and the processed material within a specific range and then performing the drawing. I found out.

For example, material SUJ2, outer diameter φ96.0m
After lubrication of a blank tube of m × thickness t8.8 mm, as shown in FIG.
The narrowed portion as shown in (b) uses an R-type die to change the contact angle between the R-type die and the raw pipe, and the outer diameter φ83.9 mm.
× Drawing a blank tube with a wall thickness of t 7.45 mm, and then
The contact angle between the R-type die and the base pipe and the seizure that occurred on the base pipe were measured. The measurement result is shown in FIG. The reduction rate at this time is 2
It is 5.3%.

At this time, the material of the R-type die and the plug used for the drawing process is WC-Co type cemented carbide, and in order to reduce the friction with the raw pipe, TiC and TiN are formed on the surface of the plug. It has a two-layer coating. R
The surface roughness of the die and plug is 0.8 S or less in Rmax.

From FIG. 2, when the contact angle between the R-type die and the base pipe exceeds 40 ^O , the seizure occurrence rate on the outer surface of the base pipe sharply increases, and when it is 40 ^O or less, seizure occurs on the outer surface of the base pipe. Obviously not. That is, by using the R-type die whose contact angle between the R-type die and the base pipe is 40 ^O or less, the base pipe can be drawn without causing seizure on the outer surface of the base pipe.

[0013]

EXAMPLES The following Table 1 shows the results of the drawing process after the material pipe of the material SUJ2 was lubricated by the lubrication method proposed by the applicant in Japanese Patent Publication No. 4-48839. The material of the R-type die and the plug is WC-Co type cemented carbide, and the surface of the plug is coated with two layers of TiC and TiN in order to reduce the friction with the raw pipe. The surface roughness of the R-type die and plug is 0.8 S or less in Rmax.

[0014]

[Table 1]

From Table 1, the contact angle between the R-type die and the raw pipe is 4
It is clear that the seizure on the outer surface of the blank can be prevented by setting it to 0 ^O or less.

[0016]

As described above, according to the present invention,
By using an inexpensive R-type die with a small volume of the cemented carbide part, it is possible to prevent seizure that occurs during drawing of carbon steel / alloy steel workpieces and to manufacture high-quality products with high efficiency.

[Brief description of drawings]

FIG. 1 (a) is a diagram showing a drawing process of a raw pipe with a die and a plug when a tapered die is used, and FIG. 1 (b) is a die when a die with an R-shaped narrowed portion is used. It is a figure which shows the drawing-out state of the raw pipe by a plug.

FIG. 2 is a diagram showing a relationship between a contact angle between a die and a base pipe and a seizure occurrence rate on an outer surface of the base pipe.

[Explanation of symbols]

 1 die 2 element tube 3 plug

Claims (1)

[Claims] 1. When drawing a lubricated carbon steel / alloy steel workpiece, the contact angle between the workpiece and the die is 40 ^O.
A method for drawing a steel pipe, characterized in that an R-shaped die having the following shape is used.