JPH06238488A - Production of coiled steel pipe and pipe stock for coiled steel pipe - Google Patents

Abstract

PURPOSE:To provide a manufacture for the coiled steel pipe which prevents the inside surface fold flaws of the coiled steel pipe and gas excellent cold workability by managing the bead height on the inside surface of an electric resistance welded tube to a certain specific range at the time of producing the coiled steel pipe 14 by hot stretch reducing. CONSTITUTION:The coiled steel pipe 14 is manufactured by cutting and/or grinding the inside surface beads of the electric resistance welded tube 11 to reduce the bead height from -200mum to +200mum, subjecting the tube to hot stretch reducing and coiling the tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a coiled steel pipe from an electric resistance welded steel pipe and a coiled steel pipe.

[0002]

2. Description of the Related Art Coil-shaped steel pipe is manufactured by squeezing a forged welded steel pipe, an electric resistance welded steel pipe, a seamless steel pipe or the like as a raw pipe by a hot stretch reducer and then winding it into a coil. Conventionally, low-priced electric resistance welded steel pipe has been used as a raw pipe for coiled steel pipe. However, the bead on the inner surface of the electric resistance welded steel pipe is removed by cutting or the like, but the bead cutting portion on the inner surface has a cutting condition of −300 μm to +30 with respect to the inner surface of the electric resistance welded steel pipe.
Cutting was performed in the range of 0 μm. The coiled steel pipe is subjected to secondary processing such as drawing, cold forging, rolling, and thread cutting, and is used for various pipes, machine parts and the like.

On the other hand, for automobile materials, industrial machine parts, etc., which require a high degree of cold workability, materials whose surface flaw depth is strictly controlled are generally used. Therefore, when cold forging or rolling is performed using a conventional coiled steel pipe, work cracks occur, which hinders productivity.

[0004]

[Problems to be Solved by the Invention] When a coiled steel pipe manufactured from a raw material for coiled steel pipe in which the inner bead of the inner surface of the electric resistance welded steel pipe is removed by a conventional method is subjected to severe cold working, There was a crack. The inventors have conducted numerous experiments and evaluations, and the cause of the work crack is due to the wrinkle flaw depth near the inner surface welded portion of the coiled steel pipe, and the work crack does not occur when the wrinkle flaw depth is +20 μm or less. Found.

In order to prevent cracking during cold working due to inner wrinkles formed in the inner bead portion of the coiled steel pipe, the present invention provides a method for producing a coiled steel pipe blank tube,
The purpose is to manage the bead height on the inner surface of the electric resistance welded steel pipe in a specific region to prevent wrinkles and flaws near the inner surface welded portion of the coiled steel pipe, and to improve the cold workability.

[0006]

DISCLOSURE OF THE INVENTION In order to prevent the formation of wrinkles in the vicinity of the inner surface welded portion of a coiled steel pipe obtained by hot drawing and rolling, the present invention provides an inner surface bead height of an electric resistance welded steel pipe. The present invention provides a method for producing a coiled steel pipe having excellent cold workability, which is characterized in that a specific region is provided, and the coiled steel pipe. The gist of the point is that, when a coil-shaped steel pipe is manufactured by hot drawing and rolling using an electric resistance welded steel pipe, the bead height is obtained by cutting or / and grinding the inner bead portion of the electric resistance welded steel pipe. Is -200 μm to +20 μm,
Then, it is a method of producing a coiled steel tube by winding it into a coil by hot drawing and rolling.

The height of the bead on the inner surface of the electric resistance welded steel pipe is-
It is a coil-shaped steel pipe base pipe having a diameter of 200 μm to +20 μm.

[0008]

The following will describe the method for manufacturing a coiled steel pipe and the coiled steel pipe of the present invention. The method for manufacturing a coiled steel pipe and the coiled steel pipe of the present invention are, as shown in FIG. Then, the electric resistance welded steel pipe 12 whose inner surface beads have been cut is heated in the heating furnace 5, and the electric resistance welded steel pipe is hot-squeeze rolled. Subsequently, the rolled pipe 13 is wound into a coil by the winder 8 to manufacture the coiled steel pipe 14.

As the electric resistance welded steel pipe 11, a steel pipe manufactured by an electric resistance welded mill and made of carbon steel, low alloy steel or stainless steel can be used. Heating furnace for heating ERW welded steel pipe 5
Can use a barrel furnace, a walking beam furnace, an induction heating furnace, or the like.

The stretch reducer 6 is a rolling mill in which roll housings of 2 rolls or 3 rolls are continuously arranged in an array of 10 to 30 stands, and the steel pipe 12 has an outer diameter sequentially rolled and a peripheral speed between adjacent stands. Rolled tube 1 stretched in the axial direction due to the difference to have a desired outer diameter and wall thickness
3 is guided by a pinch roller 7 and wound by a winder 8 to form a coiled steel pipe 14.

The reason why the inner bead height of the electric resistance welded steel pipe is limited to -200 μm or more and +20 μm or less when the coil-shaped steel pipe is manufactured by hot drawing rolling using the electric resistance welded steel pipe is as follows. On the street. The steel to be tested is S30C, and an electric resistance welded steel pipe with an outer diameter of 89.1 mm and a wall thickness of 4.8 mm is made. Immediately after the pipe making, the inner bead removal method is two-step cutting and two-step cutting + The inner surface bead height was adjusted in the range of +120 μm to −240 μm by rotary grinding, the heating temperature was 1000 ° C. to 1040 ° C., the biting temperature was 980 ° C. to 1020 ° C., and the hot drawing rolling end temperature was 73.
After producing a coiled steel pipe having an outer diameter of 25.4 mm and a wall thickness of 4.8 mm in the range of 5 ° C to 755 ° C, the inner surface wrinkles of the coiled steel pipe were measured with an optical microscope.

As a result, as shown in FIG. 1, when the inner surface bead height is less than -200 μm, inner surface wrinkles are generated in the vicinity of the inner surface welded portion in the hot drawing rolling process. Further, if the inner bead height exceeds +20 μm, inner wrinkles are generated at the boundary between the inner surface of the steel pipe and the inner bead during the hot-drawing process. The inner surface wrinkles are the starting points of work cracks during cold forging and rolling. For the above reason, the inner bead height of the electric resistance welded steel pipe is limited to -200 μm or more and 20 μm or less.

The inner bead height of the electric resistance welded steel pipe is set to -20.
As a method of controlling from 0 μm to 20 μm or less, for example, multi-step cutting (two to four steps) cutting, rotary grindstone grinding or the like may be performed. That is, after roughly cutting with a one- or two-step cutting tool, finish cutting with a three-step or four-step cutting tool. Alternatively, after roughly cutting with a single-stage or double-stage cutting tool, finish grinding is performed with a rotary grindstone. The cutting surface or the grinding surface should always follow the inner surface of the electric resistance welded steel pipe by attaching a control roll to the tip of the spilling shaft on the opposite side and both sides of the cutting bite and the rotary grindstone grinding device. The cutting amount from the inner surface of the steel pipe was controlled.

[0014]

The effects of the embodiments of the present invention will be described below. Using carbon steel and stainless steel, quality characteristics of the coiled steel pipe manufactured by hot drawing rolling by changing the inner surface beat height of the welded portion of the electric resistance welded steel pipe, that is, inner surface wrinkle depth near the inner surface welded portion, Table 1 shows the results of evaluation of cold workability.
Shown in.

[Table 1] Since the coiled steel pipe manufactured by the manufacturing method of the present invention has no internal wrinkles that are harmful to cold workability, the critical compression rate of the coiled steel pipe is high and the coiled steel pipe is colder than the conventional coiled steel pipe. The inter-workability is greatly improved.

[0015]

The method for producing a coiled steel pipe according to the present invention is such that, when a coiled steel pipe is produced by hot drawing and rolling, by using an electric resistance welded steel pipe whose inner bead height is controlled in a specific region, It is possible to prevent the generation of wrinkles on the inner surface in the vicinity of the inner surface welded portion during the drawing and rolling process. Furthermore, the coiled steel pipe manufactured according to the present invention is intended to prevent the generation of inner surface wrinkles in the vicinity of the inner surface welded portion, and has dramatically improved cold workability as compared with the conventional coiled steel pipe. Yes, the industrial value is enormous.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the inner surface beat height of a coiled steel pipe and the inner surface wrinkle depth of the coiled steel pipe.

FIG. 2 is a diagram showing an example of a method for manufacturing a coiled steel pipe of the present invention.

[Explanation of symbols]

 1 ERW Welding Mill 2 Induction Coil 3 Squeeze Roll 4 Inner Cutting Device 5 Heating Furnace 6 Stretch Reducer 7 Pinch Roll 8 Winder 11 ERW Welded Pipe 12 ERW Welded Pipe with Inner Bead Height Control 13 Rolled Pipe 14 Coil Steel pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B23K 31/00 7920-4E

Claims (2)

[Claims] 1. When producing a coiled steel pipe by hot drawing and rolling using an electric resistance welded steel pipe, an inner surface bead portion of the electric resistance welded steel pipe is cut or / and ground to reduce a bead height. 200
A method for producing a coiled steel pipe, which comprises producing a coiled steel pipe having a thickness of μm to +20 μm, followed by hot drawing and rolling into a coil. 2. The inner bead height of the electric resistance welded steel pipe is -200.
A coiled steel pipe blank for a steel pipe, characterized in that the diameter is from μm to +20 μm.