JPH02173279A - Pretreatment of drawing stainless steel wire - Google Patents

Abstract

PURPOSE:To produce a high-quality stainless steel wire free of skin roughness due to the cold drawing by scalping a stainless steel wire, then pickling the wire, bundling the wires, heating the bundle to apply solution treatment, and removing the formed oxide film by pickling. CONSTITUTION:The surface layer part on the entire periphery of a blank wire is firstly scalped to remove the surface flaw caused by the hot rolling of the wire as the pretreatment, when an austenitic stainless steel is drawn to produce the wire. The surface roughness is reduced to about 3mum by the first pickling. The wires are bundled to form a bundle having a cross section as flat as possible. The bundle is placed in a furnace contg. an oxidizing atmosphere, heated and held at about 1030 deg.C for about 5 min, then water-cooled, and subjected to solution treatment. The oxide film formed in the treatment is removed by the second pickling to obtain a wire having a uniform skin free of variance in the surface roughness. The wire is cold-drawn with a die by using a lubricant, and a high-quality stainless steel wire free of skin roughness is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pretreatment method that is carried out prior to wire drawing of a stainless steel wire using a peeling method.

[Prior art] In order to make stainless steel wire rods, especially austepite stainless steel wire rods, hot rolling, solution treatment, stretching, etc. are carried out in order (1). Since stainless steel has high deformation resistance, surface flaws are likely to occur during hot rolling.These surface flaws cause various troubles during stretching.

Therefore, in order to remove surface flaws, in order to manufacture stainless steel wire rods, conventionally, the surface layer of the wire rod is scraped all around with a cutting tool such as a cutting tool. The wire rod will be drawn.

By the way, since the surface of the shaved wire rod is extremely smooth with a surface roughness of about 3μα1, the wire rod is sometimes subjected to rj for wire drawing.
It becomes difficult for the J lubricant to adhere, and problems such as seizure are more likely to occur during expansion and contraction processing. Therefore, conventionally, as a step before wire drawing, a bundle of shaved wire rods is charged into a furnace and heated for a predetermined period of time for solution heat treatment, which removes residual stress and removes carbide and σ phase. In addition to aiming to make it a solid solution,
An oxide film is formed on the shaved surface of the wire. Furthermore, the gill with the oxide film formed thereon is buried in pickling 1a to remove the oxide film, and the wire from which the oxide film has been removed is subjected to wire drawing.

[Problems to be Solved by the Invention] However, in the above-mentioned pretreatment method, the solution heat treatment is directly applied to the shaved wire, so an oxide film is formed on the surface of the wire during the solution heat treatment. Niku (
Moreover, since the solution heat treatment is performed on the bundled wire rods, the oxide film varies depending on the portion of the wire rods. In particular, an oxide film is less likely to be formed in the overlapping portions of the wires. Therefore, even if the oxide film is removed by pickling, there is a problem that the surface texture of the wire becomes more uneven.

Figure 4 shows an external view of the area where the surface texture is uneven.

Such variations in the surface texture may cause trouble during wire drawing, which is undesirable for maintaining the high quality of the wire material after the wire drawing process.

The present invention has been made in view of the above-mentioned problems, and its purpose is to improve the problem of unevenness in the surface texture of shaved wire rods, and to improve the uniformity of the surface texture of wire rods. The object of the present invention is to provide a pretreatment method for wire drawing of steel wire rods.

[Means for Solving the Problems] The present inventor has conducted repeated research on a pretreatment method performed before wire drawing of a stainless steel wire. the result,
The present inventor has found that if the shaved surface of the wire immediately after skinning is pickled immediately after skinning and before the solution heat treatment process, even if the wire rod is solution heat treated in a bundle, It becomes easier to generate a uniform oxide film on the surface, and therefore, if the oxide film is removed by pickling1, wire drawing processing () h
It was discovered that roughening of the surface of the wire can be prevented, and if such a wire is used for wire drawing, high-quality wire can be drawn with 17 degrees of sharpness.Based on this discovery, the present invention was completed.

If you pickle the shaved surface immediately after shaving and before solution heat treatment, you can prevent the surface of the wire from becoming rough. It is assumed that this is because oxygen molecules easily penetrate into the bundled wires at this time, and a uniform oxide film can be formed on the shaved surface.

That is, the pretreatment method for wire drawing T of stainless steel IIA material according to the present invention is as shown in Table Ii! The 111th step involves shaving the part and exposing the shaving surface, and pickling the wire rod with the shaving surface, and washing the shaving surface with a sieve! A washing process, a solution heat treatment process in which an oxide film is generated on the shaved surface of the ll1l material by heating the pickled wire rods in a bundle and solution heat treatment on the wire rods, and a solution heat treatment process in which the wire rods with the oxide film formed are subjected to a solution heat treatment This method is characterized in that a second pickling step of removing the oxide film by washing is carried out in sequence.

There are many types of stainless steel wires, such as austenitic, ferritic, and martensitic stainless steels. Among them, austenitic stainless steel is representative.

By carrying out the skinning process, surface flaws on the wire rod caused by hot rolling or the like are removed. The skin shaving process uses a rotary cutting tool,
This can be carried out using an inverted die, a grinder, or the like. In the first washing process, the surface roughness of the shaved surface is usually set to 20~
In order to achieve a thickness of 30 μm, consideration was given to making the immersion time in hydrochloric acid longer than before. Solution heat treatment can be performed by charging the wire into a furnace with an oxidizing atmosphere. In addition, in the solution heat treatment step, either a continuous furnace or a batch type furnace can be employed. However, regarding the binding method before solution heat treatment, consideration is given to making the shape of the east slope as flat as possible. The heating temperature and treatment time during the solution heat treatment are appropriately selected depending on the composition of the wire, the diameter of the wire, and the like.

In the first pickling step I and the second pickling step, a method of pickling with hydrochloric acid and nitric-fluoric acid and salt bath treatment is adopted. That is, in pickling, the oxide film of the wire is usually activated with salt and a salt bath, and the oxide film is removed by pickling with nitric-fluoric acid, thereby deteriorating the surface of the wire. Concentration of hydrochloric acid and nitrofluoric acid solutions, lS! The washing time can be appropriately selected depending on the composition of the wire, the diameter of the wire, and the like.

[Example 1] Hereinafter, the method of the present invention was applied to austenitic stainless steel N4.
An example will be described in which the present invention is applied to a manufactured wire rod.

First, in the skinning process, an austenitic stainless steel wire rod (J) that has been hot-rolled to a diameter of 5.5 mm and then subjected to strain removal treatment is used. The diameter of the wire rod is set to 5.0 mm, thereby removing surface flaws generated during hot rolling and exposing the shaved surface of the wire rod. The wire rod with a shaved surface has a shiny appearance. Figure 1 shows the surface roughness profile of the surface layer of a wire rod with a shaved surface. As shown in FIG. 1, the surface roughness of the machined surface was 2.5 μm. The surface roughness was measured using a stylus type roughness meter.

Note that the austenitic stainless steel wire rod used in this example is an ASTM wire rod that is highly affected by surface texture variations.
It is 205.

Immediately after the above-mentioned skin shaving process, step 1i! Perform I-washing for 1 culm. In the first pickling culm, the cut surface is pickled along the line I. Salt M immersion in the first pickling process) 21 hours only, conventionally about 5
Process for about 10 minutes. The wire rod subjected to the first pickling process has a grayish-white appearance. Figure 2 shows the surface roughness profile of the surface layer of the wire that was subjected to the first pickling process after being skinned. As shown in FIG. 2, the surface roughness of the wire rod subjected to the first pickling step was 3 μm.

After the first pickling step ①, the culms are subjected to solution heat treatment. In the solution heat treatment process, the wire rods that have been subjected to the first pickling process are bundled so that they have a bundle cross-sectional shape and are as flat as possible, and then charged into a furnace with an oxidizing atmosphere. 103 wire rods
The wire is heated and maintained at a temperature of about 0° C. for about 5 minutes, and then the wire is cooled with water and subjected to solution heat treatment. In the solution heat treatment step, a substantially uniform oxide film is generated over the entire shaved surface of the wire.

After carrying out the solution heat treatment step, a second pickling process is carried out. In this second pickling culm, hydrochloric acid? One crushing time is carried out in the conventional manner, thereby removing the oxide film on the wire.

1. Appearance of the wire with the oxide film removed! As far as I can tell, the surface texture is uniform with no variation in surface texture. Figure 3 shows the surface roughness profile of the surface layer of the wire. As shown in FIG. 3, the surface roughness was 25 μm. Moreover, the diameter of the wire rod was also excessively small (it never became).

Using the wire produced as described above, the wire was drawn and expanded using a drawing die in a cold state using lubricant to obtain a wire with a diameter of 2.7 mm.The wire was drawn successfully without any trouble. It was possible to perform high-quality wire drawing (q).

As a comparative example, using the same type of wire rod, #1 was applied after the skin shaving process. The surface roughness profile of the surface layer of a conventional wire rod was subjected to solution heat treatment (1030°C for 5 minutes) without a washing process, and the oxide film was immediately removed by the 4M pickling treatment. Shown in the figure. As shown in FIG. 5, in the conventional wire rod, the pickling process produces a pickled area A1 with a rough surface roughness of about 24 μm, but the surface roughness is 4 μmPi! It can be seen that the scraped surface A2 remains as it is.

[Effects of the Invention] According to the present invention, the problem of unevenness in the surface texture of shaved wire rods is improved, and the expansion and contraction processing of stainless steel wire rods is effective for obtaining uniform surface texture over the entire length of the wire rod. A pretreatment method can be provided. Therefore, if wire drawing is performed using a stainless steel wire pretreated according to the present invention, a good wire drawing process 1 can be performed, and high quality wire drawing can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the profile of the surface roughness of the surface layer of the wire after the skinning process has been carried out. Figure 2 shows the skin shaving process and #1! It is a figure which shows the profile of the surface roughness of the surface layer part of the wire in the state which carried out the washing process. Figure 3 shows solution heat 51! A diagram showing the profile of the surface roughness of the surface layer of the wire after the second pickling process was carried out after the first pickling process. FIG. 4 is a side view showing the appearance of the rough surface of a conventional wire at a magnification of 7 times, and FIG. 5 is a diagram showing the surface roughness of the surface layer. Patent applicant Aichi Steel Co., Ltd.

Claims (1)

[Claims] (1) A shaving step of shaving the surface layer of a stainless steel wire to expose the shaving surface, and a first pickling process in which the wire having the shaving surface is pickled and the shaving surface is washed with acid. a solution heat treatment step of generating an oxide film on the shaved surface of the wire by heating the pickled wire in a bundle and subjecting the wire to solution heat treatment; and generating the oxide film. A pretreatment method for wire drawing of a stainless steel wire rod, characterized in that a second pickling step is performed in order to remove the oxide film by pickling the wire rod.