JPS5948710B2 - Seizouhouhou - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing metal-plated steel pipes from metal-plated steel strips, which is free from cracking at welded joints and has excellent weld strength. .

To manufacture steel pipes from steel strips, a steel strip that is wider than the outer circumference of the steel pipe is sheared into multiple strips with a width suitable for the steel pipe to be manufactured, and the steel strips are sequentially processed into a cylindrical shape using multiple forming rolls. A commonly used method is to weld the joint of both edges processed into a cylindrical shape using high-frequency resistance welding or high-frequency induction welding. In this case, the metal-plated steel strip is formed of a structure consisting of a plating layer 1, an alloy layer 2 of plated metal and steel, and a steel layer 3, as shown in the photograph of the cross-sectional structure of the metal-plated steel strip in Fig. 1. Therefore, when a metal-plated steel strip having such a structure is sheared, the edges of the sheared metal-plated steel strip are similar to the aluminum-plated steel strip in Figure 2 and the photograph showing the state of aluminum adhesion in the sheared cross section, and in Figure 3. The shape is as shown in the explanatory drawing, and although it is not observed on the fracture surface 7, the adhesive plated metal 4 is observed on the sheared surface 5.

Conventionally, when manufacturing metal-plated steel pipes using such metal-plated steel strips, in order to prevent scratches from forming on the surface of the forming roll due to burrs 8 when processing it into a cylindrical shape with a forming roll, As shown in FIG. 4b, the burr 8 is placed on the inner surface of the metal-plated steel pipe, and the sheared surface 5 to which the adhesive plated metal 4 is adhered is placed on the outside of the metal-plated steel pipe. It was molded as shown in Figure 4a.

However, pipe production is carried out under such conditions. Then, as shown in the photograph of the cross-sectional structure of the joint by the conventional manufacturing method of metal-plated steel pipes in Figure 5 and the enlarged photograph of the same in Figure 8, entrainment 6 of the plated metal occurs near the outer surface of the weld joint. do.
For this reason, cracks were observed in the welded joints when flattening tests and push expansion tests were carried out, and the welding strength was reduced by the curling 6. In order to eliminate such defects, it is conceivable to make the squeeze force larger than usual in order to squeeze out the molten plated metal from the joint during welding, but in this case, the inner bead 9 will become larger. However, it is not suitable for practical use due to the following problems.

(1) When used as a metal-plated steel pipe for assembly, it is inconvenient for fitting.

(2) When used as a conduit, the cable gets caught.

(3) When used in various types of piping, flow path loss may occur;
It becomes a starting point for corrosion and foreign matter accumulates.

In addition, in order to prevent a decrease in welding strength due to entrainment 6,
There is a method in which the adhesive plated metal 4 on the sheared surface 5 on which the adhesive plated metal 4 is adhered is continuously removed using a cutting tool before pipe making. The cutting allowance is not constant because it meanderes during cutting.

2. The life of the cutting tool is short, so cutting may become insufficient, so extreme care must always be taken.

3. Removing the cut chips is time-consuming and requires extra personnel.

There are drawbacks such as.

The present inventors have conducted various experiments in order to eliminate the drawback that the welding strength is reduced due to the winding 6, and as a result, the forming roll is a hard roll to prevent the forming roll from being scratched, Money. The burr 8 caused by shearing the metal-plated steel strip is made to be on the outside surface of the metal-plated steel pipe, contrary to the conventional method, and the sheared surface 5 on which the adhesively plated metal 4 is adhered is made to be on the inside surface of the metal-plated steel pipe. and mold it into
By welding, there is no cracking and it is excellent. They established a method for manufacturing metal-plated steel pipes with welding strength.

That is, the present invention provides a metal-plated steel pipe for forming a wide metal-plated steel strip when a metal-plated steel pipe is made from a metal-plated steel strip by high-frequency resistance welding or high-frequency induction welding. 'The burrs that occur when shearing to a width suitable for the steel pipe are formed into a cylindrical shape so that the burrs that occur when the pipe is sheared are on the outer surface of the metal-plated steel pipe, and the sheared surface where the adhesive plating metal is adhered is on the inner surface of the metal-plated steel pipe. The present invention provides a method for manufacturing metal-plated steel pipes, which is characterized by welding the joints. below,
DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for manufacturing metal-plated steel pipes according to the present invention will be explained in detail with reference to the drawings.

FIGS. 6a and 6b are explanatory diagrams of the method for manufacturing metal-plated steel pipes according to the present invention, and FIG. 7 is a photograph of the cross-sectional structure of the joint of aluminum-plated steel pipes by the method for manufacturing metal-plated steel pipes according to the present invention.

In the drawing, 1 is the plating layer, 3 is the steel layer, 4 is the adhesive plating metal that adheres to the sheared surface 5 when the metal-plated steel strip is sheared to a width suitable for the metal-plated steel pipe, and 7 is the metal-plated steel. The fractured surface when the strip was sheared, 8 is a burr produced at the end of the fractured surface 7, and 9 is the inner bead in the metal-plated steel pipe produced when welding the joint.

As shown in FIG. 6b, the method of the present invention is such that the burr 8 formed by shearing the metal-plated steel strip is placed on the outer surface of the metal-plated steel pipe to be pipe-formed, and the sheared surface on which the adhesive-plated metal 4 is adhered. 5 is formed into a cylindrical shape using forming rolls so that it becomes the inner surface of the metal-plated steel pipe, and the joint is welded after being formed as shown in FIG. 6a.

That is, when the joint in the state shown in FIG. 6a is welded by high-frequency resistance welding or high-frequency induction welding, it adheres to the fracture surface 7, shear surface 5, and shear surface 5 due to the heating during welding. Since the adhesive plated metal 4 is melted and the adhesive plated metal 4 is on the inner surface side, the molten adhesive plated metal 4 is pressed down on the inner surface of the metal plated steel pipe by the melted molten steel at the fracture surface 7 on the outer surface side. The inner surface bead 9 is formed and extruded from the joint, resulting in a joint having no rolled-up portions as shown in FIG. In the conventional method, as shown in Fig. 4a, the joint is welded so that the adhesive plated metal 4 is on the outer surface of the metal plated steel pipe. However, in the method of the present invention, the adhesive plated metal 4 becomes the inner surface of the metal plated steel pipe. Since the joint is welded in this way, the adhesive plated metal 4 is pushed out from the joint during welding, and there is no rolled up part at all at the joint, so there is no cracking in the flattening test or push-spread test. There is no occurrence of welding, and welding strength can be significantly improved. As described in detail above, the method for producing a metal-plated steel pipe according to the present invention involves removing burrs that occur when shearing the metal-plated steel strip to the outer surface of the metal-plated steel pipe when manufacturing a metal-plated steel pipe using a metal-plated steel strip. , To obtain a welded joint with no curling part by forming the sheared surface on which the plated metal is adhered into a cylindrical shape so that it becomes the inner surface of the metal-plated steel pipe, and then welding the joint. It has excellent advantages such as no cracking in the welded joint and improved welding strength, and there is no need to cut the sheared surface during forming, making it easier to weld. It has various excellent advantages such as no need to increase the size of the squeeze force, and is particularly effective in making aluminum plated pipes, and has great industrial value.

Hereinafter, the method of the present invention will be further explained with reference to Examples.

Exception: In order to make an aluminum-plated $ steel pipe with a diameter of 42.7 mm and a thickness of 1.2 mm, an aluminum-plated steel strip was sheared,
The method of the present invention is used to form and weld the sheared burrs on the outer surface and the sheared surfaces on the inner surface. Separately, the conventional method is used to form and weld the burrs caused by shearing on the inner surface and the sheared surfaces on the outer surface. The pipe was formed so as to be on the side and welded to produce a class 2 aluminum plated steel pipe.

Furthermore, as a comparative example, after cutting the sheared surface with a cutting tool, welded the pipes with the sheared surface facing the inner surface and the pipes with the sheared surface facing the outside to form aluminum-plated steel pipes. Manufactured. The results of the flattening test and push expansion test of each aluminum plated steel pipe obtained,
The height of color check and inner heat were as shown in the table below.

As shown in the table, the method of the present invention shows no abnormality in the flattening test and the pushing spread test even if the squeeze force is lower than normal, and the strength test is good, but the conventional method
Those with a high squeezing force are good in the strength test, but those with an average or low squeezing force show cracking and low welding strength. In addition, when the sheared surface is cut, the strength test is good whether the sheared surface is on the inner side or the outer side, and there is no difference between the two, but cutting the sheared surface requires considerable effort. It could not be carried out as efficiently as the method of the present invention.

[Brief explanation of the drawing]

Figure 1 is a photograph of the cross-sectional structure of a metal-plated steel strip, Figure 2 is a photograph showing the state of aluminum adhesion in a sheared cross-section of an aluminum-plated steel strip, Figure 3 is an explanatory diagram of the same, and Figures 4 a and b.
5 is an explanatory diagram of a conventional method for manufacturing metal-plated steel pipes, FIG. 5 is a photograph of a cross-sectional structure of a joint of aluminum-plated steel pipes produced by a conventional method for manufacturing metal-plated steel pipes, and FIGS. 6 a and b are diagrams showing metal-plated steel pipes according to the present invention. Explanatory diagram of the manufacturing method of steel pipes, No. 7
The figure is a photograph of the cross-sectional structure of the joint of aluminum-plated steel pipes produced by the method for manufacturing metal-plated steel pipes according to the present invention, and FIG. 8 is an enlarged photograph of the cross-sectional structure of the joint of aluminum-plated steel pipes produced by the conventional method of producing metal-plated steel pipes. be. 1... Plating layer, 2... Alloy layer, 3
... Steel layer, 4 ... Adhesive plating metal, 5
...Shear plane, 6...Involvement, 7...
...Fracture surface, 8...Burr, 9...
Inner bead.

Claims (1)

[Claims] 1. When manufacturing metal-plated steel pipes from metal-plated steel strips using high-frequency resistance welding or high-frequency induction welding,
The burr side that occurs when a wide metal-plated steel strip is sheared to a width suitable for the metal-plated steel pipe to be manufactured is used as the outer surface of the metal-plated steel pipe, and the sheared surface side where adhesive plating metal has adhered is metal-plated. Form it into a cylindrical shape so that it is on the inner side of the steel pipe,
A method for manufacturing metal-plated steel pipes, characterized by welding joints.