JPH0470086B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for manufacturing high-strength stainless steel wire for processing. <Conventional technology> Conventionally, high-strength stainless steel wire for processing was drawn with Ni plating on the surface of the stainless steel wire in order to improve lubricity during wire drawing and during subsequent processing. Wire materials have been used. <Problems to be Solved by the Invention> However, although such wire materials are superior in various respects to conventional surface-coated wire materials, the recent demand for even higher performance wire materials has increased. Considering the current situation, stainless steel wire has poor heat conductivity, toughness, and severe work hardening, making it inferior to carbon steel in wire drawability and workability in the next process. There were disadvantages such as insufficient flexibility, insufficient processing speed in the next step, and variations in the shape of the resulting product. <Means for Solving the Problems> As a result of studies to eliminate the drawbacks of the conventional high-strength stainless steel wires for processing described above, the present inventors have found that:
This is what led to the manufacturing method of this invention. The details of this invention will be explained below using as an example a stainless steel wire for a spring, which is the most difficult to process. That is, the present invention applies, for example, to the production of 18Cr-8Ni-Fe stainless steel wire, in which Ni is removed before the final wire drawing.
After plating, the upper layer is fluorine and/or
Alternatively, a film made of synthetic resin containing chlorine is formed, and then the steel wire is 50% coated using a wire drawing lubricant.
This method is characterized by drawing the wire at the above reduction rate. High-strength stainless steel wire is a material with extremely high hardness, and when drawn with a high area reduction of 50% or more, it becomes difficult to lubricate the final die. When the manufacturing method of the present invention is carried out, a coating consisting of Ni plating and a synthetic resin containing fluorine and/or chlorine on the upper layer forms a two-layer structure, which exhibits a lubricating effect and is also suitable for steel wire drawing. Depending on the powder lubricant used and the wire drawing process with a high degree of processing,
When intertwined with the two-layer structure film, the three types of substances intertwine to form a complex film at the processing stage where the area reduction rate is 50% or more, which has a special effect on die lubrication. The lubricity is maintained even after wire drawing, making it easier to form a spiral when forming a coil spring, suppressing chatter vibration, and preventing defects such as irregular pitch and radius of the spiral. It can be prevented. In addition, the surface roughness (unevenness) of the steel wire after final wire drawing
is coarser than 0.8S (0.6~0.9μ) and 12S (9~15μ)
It is preferable to make it even finer, and for that purpose, it is also necessary to control the wire surface and plating conditions (liquid composition, pH, temperature, current, stirring, etc.). In particular, when using a Watts bath as the plating bath, the current density should be 10A/dm ² ~
It is best to perform this within the range of 100A/ ^dm2 ; outside this range, the roughness of the Ni-plated surface is inappropriate and the surface roughness mentioned above after final wire drawing cannot be secured, resulting in poor lubricity during spiral processing. result. <Function> By performing the manufacturing method of the present invention as described above, since the frictional resistance between the die and the wire is reduced, the wire drawing speed can be increased. The lubricant enters the recesses on the wire surface and increases lubrication performance, reducing seizure during wire drawing and extending die life. Because the frictional resistance between the bending die and the wire is reduced, and because the lubricant enters the recesses on the wire surface to improve lubrication performance, the coiling speed of the spring can be increased and variations in the shape of the spring can be reduced. Since the pieces and wires slide more easily, the speed of rotation and straightening can be increased. Many features such as these can be obtained. Incidentally, rotational straightening is one of the methods of straightening a curled wire, and involves twisting the wire to remove the curl and make it straight. Since the pieces are tightened and twisted in order to give twist, good slipping and lubrication properties are required, as in this invention, to prevent the wire surface from seizing the pieces and causing scratches. Stainless steel is particularly prone to seizing, so careful coating is required. As mentioned above, according to the method of this invention, 50%
By drawing the wire at the above-mentioned area reduction ratio, the obtained wire can be suitably subjected to subsequent rotational straightening and coiling into a spring. In this invention, fluorine and/or
Alternatively, as the synthetic resin containing chlorine, a tetrafluoroethylene resin, a trifluorochloride ethylene resin, etc. may be used, and the coating film thickness may be about 2 to 10 microns. <Example> The manufacturing method of the present invention having the above-mentioned advantages will be described below with reference to Examples. First, as a stainless steel wire, C 0.075%,
Si 0.61%, Mn 1.25%, Cr 18.72%, Ni 8.34%
18Cr-8Ni stainless steel (SUS 304) with a chemical composition of (1) Sample material for wire drawing test As sample material for wire drawing test, 2.3 mmφ sample material was prepared with various treatments as shown in Table 1. The plating conditions for applying Ni plating to 18Cr-8Ni stainless steel are as follows: a Watt bath is used as the plating bath, and the current density is 10 A/dm ² to 100 A/dm ² . In addition, as a synthetic resin, 4 with a particle size of 0.1 to 0.3 μm is used.
Ethylene fluoride resin, chlorinated ethylene trifluoride resin, and chlorinated polypropylene resin are dispersed and mixed in a methylene chloride solution containing a surfactant and an adhesive, and the coating is applied with a thickness of 2 to 3 μm after application and drying. It was hot.

【table】

[Table] In the case of comparative product D, the surface roughness was reduced by electrolytic polishing after Ni plating, whereas comparative product E
The current density during Ni plating was set at 200 A/dm ² to increase the productivity of the plating process. (2) Wire drawing test 1.0mmφ of 2.3mmφ test wire created in Table 1
All wire drawings were carried out using a straight-type continuous wire drawing machine using alloy dies and a calcium stearate-based wire drawing lubricant. The life of the final die at a drawing speed of 400 m/min and the surface roughness after drawing are shown in Table 2.

[Table] From the above table, it was confirmed that wire drawing according to the method of the present invention had a much better die life than the conventional single-coated wire. In addition, wire drawing D with very fine surface roughness (comparison product)
The wire drawing lubricant did not adhere well to the wires, and seizures were likely to occur, resulting in extremely short service life. Furthermore, the surface after wire drawing is wire drawing E (comparison product).
However, the surface roughness was severe, and it was aesthetically unsuitable for use as a high-grade stainless steel material. Next, since all of the drawn wire materials listed in the above table except the comparative product E can be used as springs, a coiling test was conducted below. (3) Coiling test For wire drawing A to D and F to H in Table 2, wire diameter: 1.0 mmφ, coil center diameter: 10.0 mm
A spring with the specifications of φ total number of turns 8.5, effective number of turns 7.5, and free length 40.0 mm was coiled, and the coiling characteristics were evaluated based on the variation in free length. That is, using a precision automatic coiling machine at a feed rate of 50 cm/sec, 300 springs were manufactured from each wire, and the average and standard deviation of their free lengths were calculated using the third method.
Shown in the table.

[Table] From Table 3 above, it was clearly recognized that the wire produced by the method of the present invention had little variation. Furthermore, when looking at these wire rods in terms of defective rate, as shown in Table 4, ±0.1% (free length ratio) for precision springs and ±0.05% (free length ratio) for ultra-precision springs are as shown in the table below. The method was found to be better.

[Table] <Effects> As detailed above, wire rods manufactured using the manufacturing method of the present invention not only have a die life more than double that of conventional products during wire drawing, but also significantly improve the defect rate during spring coiling. It was also recognized that In addition to the above-mentioned spring wires, the wire manufactured by the manufacturing method of the present invention is particularly useful for hard straight wires (limited to those manufactured by rotating and straightening), inner wires, and the like.

Claims (1)

[Claims] 1 18Cr-8Ni stainless steel wire is heated to a current density of 10 A/dm 2 to 10 A/dm ² using a Watt bath before final wire drawing.
After Ni plating is applied under the condition of 100A/ ^dm2 , a fluorine-based and/or chlorine-based synthetic resin coating film is further formed on top of the Ni plating, and then the steel wire is heated by 50% using a wire drawing lubricant. A method for manufacturing a high-strength stainless steel wire for processing, which comprises performing wire drawing at the above area reduction rate and adjusting the surface roughness of the stainless steel wire after drawing to a range of 0.8S to 12S.