JPS62197237A - Manufacture of seamless steel pipe - Google Patents

Abstract

PURPOSE:To reduce a production cost by forming a hollow blank pipe from a solid blank material through a punching press, then, inserting a mandrel to the blank pipe and forging. CONSTITUTION:The hollow blank pipe is formed from the solid blank material by utilizing the punching press, then to deal with a generated thickness eccentricity, a rolling with a small rolling reduction or a blank rolling without a plug is performed to correct the thickness eccentricity. Furthermore, a mandrel is inserted in the hollow part of the hollow blank pipe to product a seamless steel pipe by forging. Moreover, the steel pipe is left as it is or cold worked by a pilger mill to obtain the product with a required dimension. In this way, because the product is obtained from a hardly workable material by utilizing a part of existing equipments efficiently, the production cost is largely reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing seamless steel pipes from difficult-to-work materials.

(Prior Art) In general, seamless steel pipes are manufactured using the so-called Mannesmann drilling method, in which the process includes a Mannesmann drilling machine, a plug mill, and a sizing mill.
As disclosed in Japanese Patent Publication No. 5B-4321,
For example, indentation drilling machines, inclined roll rolling machines, plug mills,
It is broadly divided into methods using rolling, such as the indentation perforation method, where the process consists of a sizing mill, and methods using hot extrusion.

Which of these two seamless steel pipe manufacturing methods to use depends on the production volume, but in general, when using difficult-to-process materials as the raw material, the hot extrusion method is used, and when using other materials as the raw material, the hot extrusion method is used. , a rolling method is adopted.

On the other hand, as a special manufacturing method for seamless steel pipes, a process is also known in which a material is machined into a hollow member and the hollow member is forged into a seamless steel pipe.

Seamless steel pipes are manufactured using a process that takes into consideration production volume, quality, and cost, and is tailored to the purpose.

Although each of these seamless steel pipe manufacturing methods has its own advantages, there are problems in that they lack versatility and that they are not necessarily satisfactory in terms of cost.

That is, the so-called Mannesmann drilling method is not suitable as a manufacturing method because of its severe drilling conditions, as it causes defects when attempting to manufacture seamless steel pipes from difficult-to-process materials, such as high-alloy steel.

In the push drilling method, the push drilling process itself is effective even for difficult-to-process materials, but in the subsequent inclined roll rolling process, the same deformation method as in the Mannesmann drilling machine is adopted, so the material There are limits to the production of seamless steel pipes from difficult-to-process materials using this process, as the products are exposed to severe deformation and cracks occur.

On the other hand, with the forging method, the method of deforming the material can be freely selected, so if the appropriate conditions are found, it is possible to sufficiently process even difficult-to-work materials. must be machined into a hollow member.

For example, drilling holes in a round billet by machining imposes a large cost burden.

(Problems to be Solved by the Invention) The present invention aims to provide a significantly lower cost process by rationally utilizing existing processes in obtaining seamless pipes from difficult-to-process materials. It was done.

(Means for Solving the Problems) The feature of this invention is that after a solid material is made into a hollow shell by an indentation piercing rolling machine, a mandrel is installed in the hollow part of the hollow shell, and in this state. A method of manufacturing a seamless steel pipe is characterized in that the pipe is processed into a pipe by forging.

The present invention will be explained in detail below.

As a result of research on the process for obtaining seamless pipes from difficult-to-process materials, the inventors found that by combining the elements of the existing processes mentioned above in the most rational way, they could make seamless pipes from conventional difficult-to-process materials. Compared to the process used to obtain seamless pipes, it is a much lower cost and higher quality process.
For example, it has been found that the manufacturing process of high-alloy steel seamless pipes can be configured.

In other words, in the seamless steel pipe manufacturing process using the indentation perforation method, even difficult-to-process materials can be perforated and rolled without directly causing quality problems such as scratches and cracks. Focusing on what can be done, we eliminated the high cost factor in the forging method.

When manufacturing seamless steel pipes by the process of this invention, so-called uneven wall thickness (non-uniform wall thickness in the circumferential direction of the pipe) may occur during the perforation process using the indentation perforation rolling machine, as in the case of other rolling methods. However, in such a case, it is possible to reduce the unevenness without causing problems such as cracks and flaws by performing light reduction rolling using an inclined roll rolling mill that uses a forced perforation process, or by performing empty rolling without using plugs. Meat can be corrected.

A hollow material that is difficult to process is heated using a push-punch machine, and a mandrel is fitted into the hollow part to perform forging.

The tube (product) after forging is formed as it is or is further formed by cold working using a pilger mill or the like to be finished into a product with the desired cross-sectional size.

(Example) Cross section 215mm x 215m+a 18% Cr -8
%Ni Stainless steel square material was injected into a hollow tube with a diameter of 256mm and a wall thickness of 85m+i using a piercing rolling machine.After reheating this, a hollow tube with a diameter of 120μm was created in the hollow part of the hollow tube.
A mandrel was fitted and forging was performed in this state to obtain a product with an outer diameter of 280 m11 and a wall thickness of 20 mm.

18XCr-8$ with no defects such as cracks or scratches on the surface or inner surface.
Ni stainless steel seamless tubing could be manufactured at a fraction of the cost by conventional processes.

(Effects of the Invention) Since the present invention is configured and operated as described above, seamless steel pipes can be manufactured at low cost from difficult-to-process materials by effectively utilizing a part of existing processes. The industrial effect is great.

Claims (1)

[Claims] After turning the solid material into a hollow tube using a punching and rolling machine,
A method for manufacturing a seamless steel pipe, characterized in that a mandrel is fitted into the hollow part of the hollow raw pipe, and in this state, the pipe is processed by forging.