JPS62187537A - Cold forging bar steel wire and its manufacture - Google Patents

Abstract

PURPOSE:To improve the cold forging lubricity by providing a Cu concentration layer of a limited sticking quantity, on an interface between a lubricating film of the surface of a bar steel wire which has been brought to wire drawing, and a ground iron surface. CONSTITUTION:A rolling material which has executed hot rolling to a bar steel wire 1 is pickled, and thereafter, Cu plating is executed by a plating process, and a Cu concentration layer 2 of >=0.2g/m<2> is formed. Subsequently, by a lubricating ground treating stage, a zinc phosphate calcium film is formed, and next, by a lubricating treating stage, a lubricating treatment is performed by a lubricant composed mainly of sodium stearate. By this treatment, a reaction film 3-2 is formed on a zinc phosphate calcium film 3-1, and also, on said film, a molten metal soap film 3-3 is formed. Also, wire drawing is executed to a prescribed size, and a cold forging bar steel wire is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a steel bar wire rod for cold forging with excellent cold forging properties (cold forging lubricity) and a method for manufacturing the same.

Prior art and its problems Steel bar wire rods for cold forging are hot-rolled, descaled, lubricated, cold-drawn, and then processed into final products. Conventionally, general rimmed steel, general low-to-medium grade raw steel, and alloy steel have been used as bar wire rods for cold forging that are subjected to such processing. The lubricating film used was a zinc phosphate film that had problems with heat resistance and adhesion, and had problems with cold forgeability (cold forging lubricity).

In other words, in recent cold forging, extreme cold forging has become more difficult due to an increase in the degree of processing, the complexity of the machined shape, and an increase in the processing speed. Wire rods can no longer be subjected to the forging process described above.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned conventional situation, and its object is to propose a steel wire rod with excellent cold forgeability and a method for manufacturing the same.

Structure of the Invention The steel bar wire rod for cold forging according to the present invention has a lubricating film consisting of a zinc calcium phosphate film, a reaction layer film, and a molten soap film on the surface after wire drawing, and the lubricating film and the base metal 0.2 at the interface with the surface! It is characterized by having a Cu-enriched layer of /- or more, and its manufacturing method includes descaling a hot-rolled material of cold forging steel and then applying Cu plating to 0.2 g.
/m2 or more, followed by lubrication treatment with zinc calcium phosphate and lubrication treatment with a lubricant mainly consisting of sodium stearate, followed by wire drawing. It is.

Figure 1 shows the coating structure of the steel bar wire rod for cold forging of the present invention, where (1) is the base steel, (2) is the Cu enriched layer, and (3)
(3-1) is a zinc phosphate calcium film, (3-2) is a reaction layer film, and (3-3) is a molten soap film.

That is, in this invention, a zinc phosphate calcium film is used as the phosphate film in place of the conventional zinc phosphate film. The reason for this is that the zinc-calcium phosphate film has much better heat resistance than the conventional zinc phosphate film, and as a result, the film has excellent adhesion. Therefore, in normal cold forging processing, conventional zinc phosphate coating requires a deposition amount of 7 y/- or more, whereas zinc calcium phosphate coating requires a deposition amount of about 5 f/d. The amount of adhesion is enough. The fact that cold working is possible even with a small amount of phosphate film is advantageous in terms of the size of the cold worked product because there is less mold clogging due to falling off of the lubricating film.

A reaction layer film (3-2) and a molten soap film (3-3) formed on the zinc calcium phosphate film (3-1).
) is formed with a lubricant (reactive type surface coating) mainly composed of sodium stearate, and the reaction layer film (
If the adhesion amount of 3-2) is 1y/- or more, and the adhesion amount of the molten soap film (3-3) is 2 g/m2 or more, cold forging will not occur.

In this invention, in addition to the above-mentioned lubricating film (3), the base metal (1)
) is characterized by forming a Cu-enriched layer (2) on the surface of the steel plate.The reason for forming this Cu-enriched layer (2) is to further improve cold forging lubricity. However, this C
The adhesion amount of the u-concentrated layer (2) needs to be 0.2 y/d or more, and if it is less than this, there is no effect.

The material steel is not particularly limited, but it is desirable that the tensile strength of the steel wire rod is 90 kg/- or less, and its composition is C0.50% or less, Si0.
35% or less, Mn 0.20-2.0%, P 0.03
0% or less, 80.035% or less, 5olAJ? 0.0
20-0.090%, N 100 ppm or less alone,
Or CrO, 7-1.3%, Mo 0.06-0
．． 45%, BO, 0005~0.005%, Ti0
．． 01 to 0.05% can be used.

Next, the method of this invention will be explained.

FIG. 2 is a block diagram showing the manufacturing process of this complete cold forging steel bar wire rod.

That is, after a hot-rolled steel wire rod is pickled in a descaling process, it is plated with Cu in a Cu plating process to form a Cu-enriched layer of 0.2y or more. Cu
Examples of plating methods include immersion plating, electroplating, and plasto plating. Next, in the lubrication base treatment step, a zinc calcium phosphate treatment is performed to form a zinc calcium phosphate film, and then in the lubrication treatment step, a lubricant ζ trowel lubrication treatment is performed using a lubricant mainly containing sodium stearate. Through this lubrication treatment, a reaction layer film (zinc stearate film) is formed on the zinc calcium phosphate film, and a molten soap film is further formed thereon. After the lubrication treatment, the wire is drawn to a predetermined size and used as a steel bar wire rod for cold forging.

Example Using a test material (22 fll) having the components shown in Table 1, Cu plating treatment after descaling by pickling (immersion plating: cuso4.5 H, 010f/Il or less + H, S
0°70 f/l
/Zn ratio of 0.4) and lubrication treatment (sodium stearate treatment: concentration 2 points, treatment temperature 80°C, treatment time 3 minutes), and wire drawing (area reduction rate of 17.4%). Bounden test, cold forging process (
The results of cold forward extrusion are shown in Table 2, FIG. 3, and FIG. 4 in comparison with the case without the Cu-enriched layer. In addition, the amount of lubricant coating is 7.
49/d, reaction layer coating 1.31/rd.

Molten soap film 2.0? /rd.

As is clear from Table 2, Figures 3 and 4, Cu
The test material with the Cu enriched layer has extremely superior cold forging lubricity compared to the material without the Cu enriched layer. That is, the second
From the table, the number of sliding times when μ=0.2 in the Bounden test is Cu concentration #0.2? It can be seen that the effect is observed at Ad or more, and in particular, it is greatly improved at 0.5 y/- or more. Furthermore, from FIG. 3, it can be seen that in the forward extrusion test, the extrusion stress is reduced in the case of the Cu-concentrated layer. Furthermore, from Figure 4, seizure occurred at 81% of the forward extrusion area reduction rate in the specimen without a Cu-enriched layer, whereas no seizure was observed in the sample material with a Cu-enriched layer. It can be seen that the adhesion of the lubricating film is good.

Table 1 Sample material composition (%) Table 2 Bounden test results Test steel ball diameter: 2N- Test load: 3000 gr Test temperature: normal temperature As described in detail of the invention, the steel bar wire rod for cold forging according to the present invention has a zinc-calcium phosphate film with excellent heat resistance and adhesion on the surface after wire drawing, as well as a Cu-enriched layer at the interface of the steel base, so it has extremely good cold forging lubricity and increases the degree of workability. , it has an effect that can sufficiently withstand the complexity of the processed shape, the increase in the processing speed, etc., and can be used for a variety of applications more than ever before. In addition, the method of the present invention is that after descaling the rolled material, Cu plating is performed to form a Cu-enriched layer on the surface of the steel base, and then a lubricating base treatment is performed with zinc calcium phosphate and stearic acid is used as the main component. By applying the lubrication treatment, it is possible to obtain a drawn wire material with excellent cold forging lubricity, which can greatly contribute to expanding the uses of wire products.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a longitudinal cross-sectional view showing the coating structure of the steel bar wire rod for cold forging according to the present invention, Fig. 2 is a block diagram showing the manufacturing process of the steel bar wire rod as above, and Fig. 3 is the same as above. A diagram showing the cold forging lubricity in Example 1, and FIG. 4 are diagrams showing the adhesion of the zinc calcium phosphate film in the same Example. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Cu concentrated layer, 3... Lubricating film, 3-1... Zinc calcium phosphate film, 3-2...
- Reaction layer film, 3-3... Molten soap film. (?V6.) qτ] Kōtai γsuν cloth pick・■Z硼Y6

Claims (1)

[Claims] 1. A lubricating film consisting of a zinc calcium phosphate film, a reaction layer film, and a molten soap film is provided on the surface after wire drawing, and 0.2 g/l is provided at the interface between the lubricating film and the surface of the base steel. A steel bar wire rod for cold forging characterized by having a Cu enriched layer of m^2 or more. 2 After descaling the hot rolled material of cold forging steel, Cu plating is applied to form a Cu concentrated layer of 0.2 g/m^2 or more, followed by lubrication base treatment with zinc calcium phosphate, and A method for manufacturing a steel bar wire rod for cold forging, which comprises drawing the wire rod after lubrication treatment with a lubricant mainly containing sodium stearate.