JPH02307686A - Production of stainless electric welded steel tube - Google Patents

Abstract

PURPOSE:To improve the product quality by suppressing an appearance failure by bringing edge parts of both side end parts of a stainless steel plate to rolling reduction to a tapered shape before roll forming, at the time of manufacturing a stainless electric welded steel tube. CONSTITUTION:At the time of feeding a stainless steel plate 1 in the direction as indicated with an arrow, while performing the flattening by plural stages of belt guide rolls 2, 2..., simultaneously, by plural edge forming rolls 4, 4... provided between the belt guide rolls 2, 2..., edge parts of both its side end parts are brought to rolling reduction a tapered shape. As for a V-shape groove angle alpha formed by both side edge parts 5, 6 of the stainless steel plate 1 in this case, 30 - 85 deg. is desirable, by which an appearance failure caused by a molten bead at the time of welding is suppressed and the quality of a product is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a stainless resistance welded steel pipe with no appearance defects.

<Conventional technology> ERW steel pipes have traditionally been manufactured by forming strip-shaped skelps into a tubular shape using forming rolls, heating the edges of the skelps formed into the tubular shape using high-frequency waves, and then welding them with an 8-touch welding process. It is common that

Welding of this electric U steel pipe usually requires 180 to 400 kllz.
High frequency heating is used. A feature of high-frequency heating is that it mainly heats only the edges of the skeleton, which is the part to be welded, formed into a tubular body, due to the proximity effect and the skin effect. However, temperature unevenness inevitably occurs in the thickness direction, and the highest temperature occurs at the corners of the inner and outer surfaces.

Normally, there is an appropriate range of heating temperature during ERW welding, the upper limit is determined by melt drop or the generation of venetrator, and the lower limit is determined by the occurrence of cold welding. The appropriate range is determined by the frequency of the power source used, welding conditions, etc.

By the way, as the wall thickness increases, the heating temperature at the edge part becomes more uneven in the wall thickness direction, and if it exceeds the above upper limit, it may melt, scatter, and adhere to the tube surface, damaging the appearance. There's a problem.

As a means for improving the temperature unevenness in the thickness direction of such a tubular squelp edge part, for example, Japanese Patent Application Laid-Open No. 57-31485
As disclosed in the publication, when forming the edge part with a fin bath roll of a plurality of forming rolls, the forming was performed so that the X-shaped opening angle α was 5 to 20 degrees, and the edge part was heated with high frequency. After that, the meckle flow angle θ of the welded part is 50°
An X-shaped groove welding method has been proposed in which welding is performed by adjusting the squeeze amount of the welding roll as follows.

<Problems to be Solved by the Invention> However, in the above-mentioned Japanese Patent Application Laid-Open No. 57-31485, it is possible to improve the temperature unevenness in the thickness direction in the case of materials such as ordinary steel; When attempting to apply this X-shaped groove welding method to the production of physically hard stainless steel resistance welded steel pipes, the following problems arise. That is, ■ Stainless steel plates made of materials such as SO3304 and SO3409 have a greater springback than ordinary steel plates such as carbon steel, and therefore have a greater unloading recovery strain.
If a forming load that is large enough to deform the edges during fin bath forming is applied, fin bath roll defects are likely to occur.

■ If a lubricant is used or its amount is increased in order to prevent the above-mentioned fin bath roll flaws, welding quality will deteriorate.

An object of the present invention is to provide a method for manufacturing a stainless steel electric resistance welded pipe that solves the above-mentioned problems.

<Means for Solving the Problems> The present invention is a method for manufacturing a stainless steel resistance welded steel pipe in which a belt-shaped stainless steel plate is roll-formed into a tubular shape, and then both ends of the stainless steel plate are brought together and resistance welded. This is a method for producing a stainless steel resistance welded steel pipe, which is characterized in that the ridges at both ends of the stainless steel plate are first rolled down into a tapered shape.

<Function> According to the present invention, in manufacturing a stainless steel resistance welded steel pipe, before roll forming a stainless steel plate, V-shaped bevel processing is performed on both ends of the stainless steel plate to make the so-called corners obtuse. Therefore, it is possible to reduce the temperature unevenness at the corner, and thereby it is possible to suppress the occurrence of venetrator.

<Examples> Examples of the present invention will be described in detail below with reference to FIGS. 1 to 3.

FIG. 1 is a side view schematically showing an embodiment of the stainless steel resistance welded pipe manufacturing apparatus according to the present invention, FIG. 2 is a front view showing an enlarged edge forming roll, and FIG. It is a sectional view showing the state of shape beveling processing.

As shown in the figure, stainless steel plate 1 is fed in the direction of the arrow.
is flattened by a plurality of stages of band guide rolls 2, 2, etc., and then formed by a plurality of forming rolls 3, 3, such as breakdown rolls. At the same time, the MF guide rolls 2, 2... A plurality of edge forming rolls 4° 4 provided between the edges of the edges on both sides are rolled down into a tapered shape.

As shown in detail in FIG. 2, the edge forming roll 4 has W
It has a width in the center thereof, and has a ■-shaped groove vertically symmetrical to the roll width direction center line C at an angle of θ, and its outer diameter is DI and its inner diameter is D2. As shown in FIG.
An angle in the range of 30 to 85 degrees is desirable.

In reality, there are some limitations depending on the thickness t of the stainless steel plate 1 to be formed, the diameter of the pipe to be formed, the speed of pipe production, welding conditions, etc., but this is why we set the upper limit of the angle θ to 85°. If it is less than 30', the effect of creating a shaped bevel is weak, and
This is because if the temperature is less than 1, the temperature at the center becomes too high, while the temperature at both ends becomes low, making it impossible to obtain a good welding result.

Also, the reason for providing a flat part f in the center of both side ends 1a of the stainless steel plate 1 is to suppress local overheating at the corners by making the seven corners as obtuse as possible without forming a beveling. The size of the flat portion f is preferably 20 to 80% of the plate thickness t. The reason for the lower limit is to prevent local overheating of the flat portion f, and the reason for the upper limit is that if the upper limit is exceeded, the effect of forming the ■-shaped groove becomes weaker.

Material is SO3410L, plate thickness: 1.5 body x plate width, 13
Using 4.0 wholesale stainless steel plate, outer diameter 42.7 mm
The method of the present invention was applied to manufacturing a φ automobile exhaust pipe by electric resistance welding.

The material of the edge forming roll used here is 5K.
II 11 (cold die steel), the width W is 65 mm, the outer diameter is 120 mmφ, and the inner diameter is 60 mmφ■
Those having shaped grooves (V-shaped angle θ-45°) were arranged in two stages.

When the edge of the stainless steel plate was rolled down in a tapered shape to a distance of 0.5 mm from the edge using this edge forming roll, the thickness distribution was reduced at a larger slope than in the conventional example, as shown in the wall thickness distribution in Figure 4. I could have meat.

Then, when performing electric resistance welding, the temperature of the welded part was measured from the outside at a position 40 mm downstream from the squeeze point with the welding roll, and the temperature was 1310°C ± 20°C, which was previously 1320°C ± 31°C. Then? Temperature variations due to the bead were significantly reduced, and welding was significantly improved.

In addition, the appearance defect rate of stainless steel pipes due to flash encroachment was reduced from 3.0% to 0.4%.

<Effects of the Invention> As explained above, according to the present invention, since the ridges at both ends of the stainless steel plate are not tapered in advance, poor appearance due to scattering of molten beads can be suppressed. This contributes to improving product quality.

[Brief explanation of drawings]

FIG. 1 is a side view schematically showing an embodiment of the stainless steel resistance welded pipe manufacturing apparatus according to the present invention, FIG. 2 is a front view showing an enlarged edge forming roll, and FIG. 3 is a ■-shaped FIG. 4, which is a sectional view showing the state of bevel processing, is a characteristic diagram showing the wall thickness distribution at the end of the stainless steel plate. l...Stainless steel plate. 2...Obi guide roll. 3...Molding 1 call. 4...Edge forming roll. 5.6...Side end. Patent applicant: Kawasaki Steel Corporation Figure 1 Figure 3 Figure 4 Distance from the side edge of Figure 2 (mm)

Claims (1)

[Claims] A method for manufacturing a stainless steel electric resistance welded steel pipe in which a band-shaped stainless steel plate is roll-formed into a tubular shape, and then both ends are brought together and electric resistance welded, and the ridges at both ends of the stainless steel plate are tapered before roll forming. A method for manufacturing a stainless steel ERW steel pipe, which is characterized by rolling down the pipe into a shape.