JP2009220146A - Drawing die and method of drawing plated steel wire - Google Patents

Abstract

An object of the present invention is to provide a drawing die and a plated steel wire capable of smoothly producing a high-strength steel wire having a good thick plated layer by significantly reducing the amount of plating scraped, reducing the amount of plating adhesion and generating surface scratches. Provide a drawing method.
In a drawing die in which a nib 2 is fitted to a metal die case, the nib 2 sequentially forms a mouse 21, an approach 22, a bearing 23 and a back 24, and the back is a two-stage back. Ceramics whose main component is sialon with corners are used.
[Selection] Figure 2

Description

The present invention relates to a die suitable for cold drawing of a plated steel wire and a drawing method using the die.

In order to obtain a desired wire diameter and tensile strength of the rolled wire, cold drawing (cold drawing) is widely used. For this processing, a die using a cemented carbide alloy is generally used for the nib, and a sintered body of an alloy such as a WC-Co type or WC-TiC-Co type is used for the nib.

When cold drawing using such a die, a large frictional force acts on the interface between the nib and the steel wire, so a lubricant is used to reduce the frictional force and obtain a good surface. Yes. Further, in order to prevent seizure between the nib and the steel wire, an extreme pressure agent or an additive may be added to the lubricant. Furthermore, in order to improve lubrication performance, a film forming process may be performed on the steel wire surface.
In some cases, the nib is processed using a die made of ceramics whose main component is sialon.

By the way, in recent years, regarding steel wires, high strength steel wires and wire ropes are demanded from the market while maintaining good corrosion resistance. In order to meet such market demands, it is necessary to use high-strength steel wires, increase the amount of plating to improve corrosion resistance, and improve tensile strength by cold drawing.
More specifically, zinc and zinc alloy plating are used as plating in this case, both of which are plated by a hot dipping method, but the bath temperature is as high as about 450 ° C., and the steel wire passes through the plating bath. By doing so, the strength of the steel wire is reduced. Therefore, in order to obtain a desired strength of the zinc and zinc alloy plated steel wire, the steel wire after plating is cold drawn.
JP-A 62-104618 JP 2007-69230 A

  In order to obtain a high-strength steel wire while maintaining good corrosion resistance in this way, when a steel wire with a thick plating layer is cold drawn, a large frictional force is generated at the interface between the die and the plating, and the die is greatly damaged. If a heavy load is applied and the nib is a cemented carbide alloy die and the plated steel wire is cold drawn for a long time, it maintains good lubrication at the die / plating interface regardless of whether it is dry or wet. In the die entrance portion, it was unavoidable that the coating amount was insufficient and surface flaws were generated by scraping the plating, and that the wire diameter was poor and the die life was reduced due to early wear of the die.

As countermeasures, borax or the like is applied to the plated steel wire, a lubricant containing many additives such as MoS ₂ is used, or the forced lubrication method is used. The degree of instability was so poor that there was a case where almost no effect was obtained.

The object of the present invention is to eliminate the above-mentioned problems, significantly reduce the amount of plating scraping, reduce the amount of plating deposits and reduce the occurrence of surface scratches, and smoothly produce a high-strength steel wire having a good thick plating layer. An object of the present invention is to provide a drawing die that can be manufactured and a method for drawing a plated steel wire.
Another object of the present invention is to provide a drawing die and a method for drawing a plated steel wire, which can suppress the occurrence of wire diameter defects and the reduction in die life due to early wear of the die.

In order to achieve the above object, the drawing die of the present invention is a drawing die in which a nib is fitted to a metal die case, and the nib is made of a ceramic mainly composed of sialon,
The nib sequentially forms a mouse, an approach, a bearing and a back, and the back has a two-step back angle;
Die for drawing, characterized in that die case inner diameter and nib outer diameter satisfy 0.994 ≦ a / b ≦ 0.998 (where a = die case inner diameter, b = nib outer diameter) . (Claim 1)
Further, in order to achieve the above object, the method of drawing a plated steel wire according to the present invention includes a die according to claim 1 as a die in cold drawing of a steel wire plated with zinc or zinc aluminum alloy in multiple stages. It is characterized by use. (Claim 2)

The present inventors have examined in detail the circumstances and causes of the occurrence of plating scraping and scratches on the surface of the plated steel wire at the die entrance portion.
As a result, in carbide dies, zinc and alloys such as aluminum and the like are welded to the bearing portion mainly in the bearing portion, so that the lubricant does not function, that is, the lubricant film is cut off due to insufficient pull-in of the lubricant. The plating surface and the approach, and the bearing surface are directly touched, and a part of the plating layer and the nib are welded due to the temperature rise due to friction. It was judged that the main cause was that it acted as a means for ironing the surface of the steel wire and the supply of lubricant to the bearing was hindered.

Therefore, the present inventors have tested various materials suitable for nibs that are difficult to cause welding with a plating layer made of zinc or an alloy of this and other metals, and as a result, ceramics mainly composed of sialon are found in zinc alloy baths. From the knowledge that there is no reaction with zinc alloy (zero affinity), this sialon-based ceramic is composed as a nib material, and the nib is fitted into a die case to form a drawing die. Because sialon-based ceramics have no affinity with zinc alloys and do not react at all, even if the lubricant film breaks, the approach and welding between the bearing surface and the galvanized surface layer are reduced. It is possible to obtain an excellent effect that the film breakage is recovered early, the shavings of the plating layer are remarkably reduced, and stable quality can be maintained.

The nib having sialon as a main component sequentially forms a mouse, an approach, a bearing, and a back, and the back has a two-step back angle.
In the processing for obtaining a high-strength steel wire, the steel wire is pulled, and the force works strongly in the direction of expanding the diameter of the die nib. At the same time, a strong tensile force acts on the nib in the direction of travel of the steel wire, and these forces cause cracking of the nib and chipping of the back.
First, along with the drawing of the steel wire, a strong pulling force acts on the bearing and back of the die nib in the direction of travel of the steel wire. The back has an effect of facilitating the extraction of the lubricant from the bearing. However, if the difference between the bearing angle and the back angle is large, the boundary between the bearing and the back may be chipped.

In the present invention, the back has a two-stage back angle of a first back having a small angle and a second back having a large angle, and thereby, the strong acting on the bearing and the back direction of the steel wire acting on the back boundary portion. The pulling force can be relaxed, and the nib breakage due to the back defect during the drawing process can be accurately prevented.

The die case inner diameter: a and the nib outer diameter: b are in a fitting relationship satisfying 0.994 ≦ a / b ≦ 0.998.
The wire drawing to obtain a high-strength steel wire has a strong force in the direction of expanding the inner diameter of the die nib, and this force causes the nib to crack.
Therefore, the ratio of the inner diameter a of the die case to the outer diameter b of the nib is 0.994 ≦ a / b ≦ 0.998, the compression force in the inner diameter direction of the nib is increased, and the tightening margin is increased (shrink fitting). It was.
As a result, the disadvantages of ceramics that are fragile and easily chipped are improved, and the die replacement work can be reduced by greatly increasing the die life.

Hereinafter, the present invention will be described in detail with reference to examples. FIG. 1 shows a cold drawing die to which the present invention is applied, wherein 1 is a die, and a nib 2 made of ceramics mainly composed of silicon nitride-based sialon (SiAlON) is made of metal, for example It is inserted into a cylindrical case 3 made of SCM435, and is firmly fitted by shrink fitting into a fitting portion 30 having a radial protruding portion 31 at its end.

The sialon (SiAlON) is a compound of four elements of Si ₃ N ₄ —Al ₂ O ₃ —AlO—SiO ₂ , and also includes a substituted solid solution with elements such as Mg, Li, and Y. Sialon has higher oxidation resistance than silicon nitride and has no reaction with zinc or molten metal containing it.
The nib 2 is desirably a dense sialon sintered body, and in order to obtain such a dense sialon sintered body, Al ₂ O ₃ or the like is used as a sintering aid, for example, in a pressurized nitrogen gas atmosphere at 1600 ° C. For about 1 hour and 30 minutes, and then hold at 1800 ° C. for about 2 hours.
By holding in a pressurized nitrogen gas atmosphere at 1600 ° C. for about 1 hour and 30 minutes, Al ₂ O ₃ is dissolved in Si ₃ N ₄ to form a solid solution, and the structure is maintained at 1800 ° C. for about 2 hours. Dense sialon can be obtained.

As shown in FIG. 2, the nib 2 made of the sialon sintered body is composed of a mouse 21, an approach 22, a bearing 23 and a back 24 in order from the drawing direction of the steel wire. The first back 241 and the second back 242 are configured.
The back has a trumpet shape for smoothly drawing out the lubricant from the bearing, and the angle B1 of the first back 241 is preferably 15 to 60 degrees. If the angle is 15 degrees or less, the lubricant is not sufficiently pulled out. If the angle is 60 degrees or more, chipping of the bearing and the back boundary portion may occur during the drawing process. A more preferable first back angle B1 is 15 degrees to 40 degrees.

The angle B2 of the second back may be appropriately selected within the range of 60 degrees to 90 degrees, and 80 degrees is adopted in the present invention.
The angle B1 of the first back 241 and the angle B2 of the second back 242 are usually different values, for example, the angle B1 of the first back 241 is 30 degrees and the angle B2 of the second back 242 is 80 degrees. In some cases, the angles of the first back and the second back can be made the same from 15 degrees to 60 degrees.

FIG. 3 shows the die of the present invention in an exploded state, where (a) shows a die case 3 and (b) shows a nib 2 made of a sialon sintered body. The die case 3 is made of a metal SCM 435, is provided with a ring-shaped radial protruding portion 31 at an axial end portion, and a fitting portion 30 for mounting the nib 2 in the axial direction from the base thereof. In order to integrate with the case 3, the die case 3 is heated to insert the nib 2 at room temperature in a state where the inner diameter of the die case: the diameter a of the fitting portion 30 expands and expands, and shrink-fit.

Sialon sintered bodies have a lower fracture toughness value than cemented carbide, and therefore, when used for nibs, there is a risk of nibs breaking along the axial direction of the plated steel wire during drawing. Therefore, the nib 2 is strongly fitted to the die case 3 by shrink fitting, and a compressive force is applied in the circumferential direction of the nib 2.
In the present invention, the allowance for shrink fitting is increased and a large compressive force is applied to the nib. Specifically, the ratio of the die case inner diameter a and the nib outer diameter b is 0.994 ≦ a / b ≦. 0.998 is desirable. If it exceeds 0.998, tightening of the nib is weak, and cracking of the nib 2 is likely to occur due to the approach by drawing and the diameter expansion pressure of the bearing. If it is less than 0.994, even if the die case 3 is heated and expanded, the inner diameter of the die case 3 does not expand to a diameter sufficient to insert the nib 2, and it is difficult to fit the nib 2. However, the nib may be destroyed during the cooling process, so the lower limit was set to 0.994.

Cold drawing using the die 1 of the present invention is performed in a wet wire drawing machine. FIG. 4 shows an example of the wet wire drawing machine 5, in which two pairs of tapered cones 51, 51, 52, 52 are arranged at predetermined intervals in a box 50 filled with a lubricant, One at the inlet, one at the middle, one at the outlet, and the other are arranged between the upstream capstans 51 and 51 and between the downstream capstans 52 and 52, and the plated steel wire is moved at the required linear velocity. Thus, it is drawn out to a predetermined diameter, drawn to the ground raising diameter, and wound on the bobbin 6.

Next, an example of a drawing process to which the present invention is applied will be shown.
1) Sixteen dies 1 of the present invention were set in the wet wire drawing machine shown in FIG. 4, and the galvanized steel wire was cold drawn. The galvanized steel wire was plated by a hot dip galvanizing method, and a steel wire having a diameter of 1.55 mm was drawn to 0.40 mm at a wire speed of 400 m / min and wound around a bobbin 6.
2) The die 1 of the present invention comprises a die case made of a material SCM435 and a nib 2 obtained by sintering ceramics mainly composed of sialon at 1750 degrees, the die case inner diameter a is processed to 16.5 mm, and the nib outer diameter b is processed to 16.566 mm, the die case is heated at a high temperature, and the nibs are shrink-fitted to make a strong fit.

3) The nib 2 includes a mouse 21, an approach 22, a bearing 23, a first back 241 and a second back 242 as shown in FIG. The mouse 21 has a trumpet shape, the angle of the approach 22 is 12 degrees, the angle of the bearing 23 is 0 degrees, the angle of the first back 241 is 25 degrees, and the angle of the second back 242 is 80 degrees.

  Table 1 shows the results of cold drawing of a steel wire having a diameter of 1.55 mm to 0.40 mm at a wire speed of 400 m / min using the above-described sialon die of the present invention and a conventional cemented carbide die.

As is apparent from Table 1, Examples 1, 2, and 3 and Conventional Examples 1, 2, and 3 of the sairon rice of the present invention are respectively drawn by 49000 m of galvanized steel wire without the lack of approach and back interface. I was able to.
The single-stage back-type sialon die with a back angle of 80 degrees shown in Comparative Example 1 was approached in the middle of wire drawing, and chipping of the back boundary surface occurred, making wire drawing impossible. It did not occur and was able to be pulled out smoothly to the end.

  A galvanized steel wire drawn by 49000 m each with a sialon die and a cemented carbide die is wound around a bobbin 6 from a wet wire drawing machine 5. In the experiment, the body diameter of the bobbin 6 was 165 mm, and the winding diameter wound around this was 270 mm.

Explaining the evaluation method, “shaving residue” was obtained by collecting the plating shavings deposited in the box 50 of the wet wire drawing machine after 49000 m of galvanized steel wire was drawn, and measuring the amount thereof. “Plating scratches” were wound around a bobbin, and then the entire surface of the wound diameter was visually observed to count scratches on the galvanized steel wire.
Fig. 5 shows a galvanized steel wire that has been drawn and expanded 24 times to show "plating scratches". The galvanized layer was scraped to expose the iron surface, and the concave scratches pulled in the longitudinal direction. The state is exhibited.

  Explaining about “shaving residue”, the amount of shavings of Conventional Examples 1, 2, and 3 when drawn by 49000 m are 151.9 g, 208.4 g, 248, and 3 g, respectively, and on average, a large amount of 202.9 g. It becomes. The amount of shavings of Examples 1, 2, and 3 of the present invention is 4.0 g, 3.3 g, and 2.1 g, respectively, and on average, the amount is very small as 3.1 g. It is clear that this is because the nib material is a sialon that has no affinity for zinc and its alloys and has no reactivity.

  As for “scratching of plating”, scratches of the conventional examples 1, 2, and 3 are 0, 0, and 16, respectively. The scratches of Examples 1, 2, and 3 were 0, 0, and 0, respectively, clearly confirming the superiority over the conventional example.

FIG. 6 shows the internal state of the wire drawing machine according to the present invention after 49000 mm wire drawing, and FIG. 7 shows the internal state of the wire drawing machine when using a carbide die. Reference numeral 7 denotes “shaving residue”, which shows that a large amount is accumulated in the approach.
As is apparent from FIGS. 6 and 7, the present invention is in a very clean state.

(A) is a front view which shows an example of the cold drawing die | dye by this invention, (b) is AA sectional drawing of (a). It is sectional drawing which shows the detail of the nib in FIG. (A) is sectional drawing of the case of this invention, (b) is sectional drawing of a nib. It is a top view which shows the wet wire drawing machine to which this invention is applied. It is an enlarged side view showing the result (plating shaving) of a drawing process experiment. (A) is a perspective view of the die part in a wet wire drawing box after performing 49000 mm drawing using this invention die, (b) is a top view. (A) is a perspective view of the die part in a wet wire drawing box after performing 49000 mm drawing using a cemented carbide die, (b) is a top view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dice 2 Sialon nib 3 Die case 241 1st back 242 2nd back a Die case inner diameter b Nib outer diameter 5 Wet wire drawing machine

Claims (2)

It is a drawing die in which a nib is fitted to a metal die case, and the nib is made of ceramics mainly composed of sialon,
The nib sequentially forms a mouse, an approach, a bearing and a back, and the back has a two-step back angle;
Die for drawing, characterized in that die case inner diameter and nib outer diameter satisfy 0.994 ≦ a / b ≦ 0.998 (where a = die case inner diameter, b = nib outer diameter) .   A method for drawing a plated steel wire, characterized in that the steel wire according to claim 1 is used as a die when cold-drawing a steel wire plated with zinc or zinc-aluminum alloy in multiple stages.

Images