JPH04138815A - Method for de-scaling metal - Google Patents

Abstract

PURPOSE:To carry out good descaling without the generation of surface flaw, pit like corrosion and biting of foreign substance, etc., by descaling the metallic material stuck with an oxiside skin (scale) by bringing the liquid drop generated in the liquid drop streaming range constituted of the high speed water jetting stream in air of the super high pressurized water jet with the specific supplying pressure into collision with the metallic material and descaling it. CONSTITUTION:The metallic material to be worked 1 is fed from a supply stand 2 through a straightening machine 7 to a descaling device 3 and subjected to descaling. Next, it is coated with the lubricant of limestone, etc., then the 1st time drawing work is executed with the No.1 die 4, successively, it is coated with the lubricant agent, subjected to the 2nd time drawing work of No.2 die 5 and wound round the concentric circle like coil with a coiler 6. On this descaling device 3, the descaling is executed by colliding the liquid drop in the liquid drop streaming range which is generated by the super high pressurized water jet of the supplying pressure >=1,000kg/cm<2>, <=10,000kg/cm<2> against the metallic material stuck with scale.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for removing an oxide film (scale) formed on the surface of a hot-rolled or heat-treated metal before cold working. .

[Prior Art] A scale layer that adheres to a metal surface is harmful to processing in the next step, so it is necessary to completely remove it, for example, before drawing a wire rod.

Methods for removing scale are broadly divided into chemical methods and mechanical methods, with the former often using sulfuric acid or hydrochloric acid. After pickling, the metal surface has minute irregularities, so lime,
It has the function of strongly holding borax, forming a good film, and improving lubricant attraction during wire drawing, but in recent years, the issue of processing large amounts of acid waste has come under scrutiny. From the viewpoint of pollution prevention, it is necessary to have complete equipment for waste acid treatment and sludge treatment, so the latter method, which does not require these facilities, has become popular.

In addition to the reverse bending method and the shot blasting method, mechanical descaling methods include a projectile such as Alundum or Grid, which is accelerated by a nozzle using compressed air and crashes into the workpiece as a high-speed spray to grind the metal surface. Air blasting method for descaling (JP-A-50-56323)
, Japanese Unexamined Patent Publication No. 54-85125).

[Problems to be Solved by the Invention] However, each of these methods has the following drawbacks.

In the rehearsing bending method, complete descaling is difficult, and a small amount of fine scale remains, and there are limits to the steel type and wire diameter of the applicable wire.

In addition, the shot blasting method and the air blasting method have the problem that the red rust part may remain in a pattern and rust may occur, or that foreign matter may become trapped, and that the equipment is yellow and the running cost is relatively high.

[Means for Solving the Problems] The present invention provides a new method for descaling metal materials that solves the above-mentioned drawbacks. 10
This is a metal scale removal method characterized by descaling by colliding droplets in a droplet flow region generated by an ultra-high pressure water jet of 00 kg/cm2 or more and 10000 kg/cm2 or less. In the present invention, the ultrahigh-speed water jet nozzles are arranged at a constant pitch in the direction of movement of the metal material.

That is, the present invention focuses on the fact that the effective force for descaling is the impact force of the water jet, and the first
The droplets in the droplet flow region of the airborne high-speed water jet characteristics shown in the figure are
This is due to the water hammer effect caused by collision with the metal material and sudden compression, and takes advantage of the fact that the pressure increase at the impact surface is about 10 times the injection pressure.

The present invention will be described in detail below based on embodiments shown in the drawings. In FIG. 2, the workpiece 1 is transferred from the supply stand 2 via the straightener 7 to the descaling device 3 of the present invention.
is supplied to and descaled. Next, after applying a lubricant such as lime, the first drawing process is performed using the #l die 4, and then the lubricant is applied and the second drawing process is performed using the #2 die 5, and then the winding machine 6 is wound into concentric coils. Next, the descaling device 3 of the present invention will be explained in detail.

High-pressure water is sent to the injection nozzle 8 from an ultra-high-pressure pump (not shown in FIG. 3) via the water pipe IO, and the material to be metallized 1 is placed on a droplet flow tilted surface having the characteristics of a high-speed water jet in the air as shown in FIG. ,
This is a method of descaling by letting the

Here, methods for uniform descaling of the wire surface in the circumferential direction include a method of installing a plurality of nozzles in the circumferential direction, a method of making the nozzle shape an ellipse, a slit, or a notch, and a method of installing the nozzle in a header pipe surrounding the metal workpiece 1. Several methods can be considered, such as a method of rotating the header tube, a method of using a rotating eccentric nozzle, etc., but these uniform descaling methods are not limited here. Further, the straightening conditions of the straightening machine 7 also have a slight influence on descaling, but these are not limiting.

In the present invention, the water supply pressure is set to a lower limit of 10 (10 kg/
cm'' was selected by selecting the ratio of the distance from the metal to the nozzle (hereinafter referred to as nozzle distance) and the nozzle diameter that maximizes the dimensionless descaling amount for collisions in the droplet flow region shown in Figure 1. In addition, the upper limit of 10,000 kg/cm2 is the pressure that can be descaled by collision in the droplet flow region, and the ratio of nozzle distance and nozzle diameter that minimizes the amount of dimensionless descaling is selected to prevent erosion of the metal substrate. This is the limit value that leads to .

The ratio between the nozzle distance and the nozzle diameter that maximizes the descaling amount varies depending on the nozzle shape, but if the nozzle is perfectly round and the inner surface is well-finished, it will be approximately It is 400-600. This value corresponds to the droplet flow region occurring downstream of the continuous flow of the jet flow characteristics in FIG. 1, where the telescaling effect due to the water hammer described above is at work. In addition, the reason why the water jet nozzles are installed at a certain pitch in the direction of movement of the metal material is to prevent a decrease in the dimensionless descaling amount (descaling width/nozzle diameter) due to mutual interference of the water jets and to prevent variations. It is.

[Example] A wire rod coil (545G) after hot rolling was drawn using the apparatus shown in FIG. As shown in FIG. 3, the descaling device used at this time had eight nozzles with an inner diameter of 0.3 mm φ arranged in the circumferential direction of the wire, and a supply pressure of 4000 kg/cm2. Flow rate 5Ji, /win 5.5 as a wood water jet
It was made to collide with a wire rod of mmφ. The nozzle distance at this time is 1
Descaling in the droplet flow region was realized as 50IIIIII. As shown in Figure 5, the surface roughness of the wire rod after descaling is almost the same as that of the pickled surface, and the lubricant such as calcium stearate required for wire drawing is well drawn in by 15%. The surface properties of the wire drawn at the area reduction ratio of 1 were also satisfactory.

[Effects of the Invention] According to the present invention, there is no promotion of surface flaws or bit-like corrosion that occurs during pickling, and there is no foreign matter biting that occurs during mechanical descaling, resulting in good descaling. In addition, compared to conventional methods, this method is an extremely compact device and costs less, and has significant industrial effects.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of the structure of the aerial high-speed water jet of the ultra-high pressure water jet of the present invention, Fig. 2 is a wire drawing equipment equipped with the descaling device of the present invention, and Fig. 3 (a) and (b) are the main drawings. A front view and a side view of the descaling device of the invention, FIG. 4 is a diagram showing the relationship between the dimensionless descaling amount obtained by dividing the descaling width by the nozzle diameter and the water jet supply pressure, and FIG. 5 shows the relationship between the inventive method and the conventional method. Surface roughness measurements after descaling with the method.

Claims (1)

[Claims] 1. Supply pressure to the metal material to which the oxide film (scale) adheres is 1000 kg/cm^2 or more, 10000 kg/cm
A method for removing metal scale characterized by descaling by colliding droplets generated in a droplet flow region of an airborne high-speed water jet structure of an ultra-high pressure water jet of ^2 or less. 2. The method according to claim 1, wherein the ultra-high pressure water jet nozzles are arranged at a constant pitch in the direction of movement of the metal material.