JPS635807A - Tube production rolling method for difficult-to-form material hollow ingot - Google Patents

Abstract

PURPOSE:To prolong the service life of tools such as a die, to prevent generation of product defects, and to improve the productivity by producing a tube by joining a thin metallic tube which easily generates scales at high temps. to the inner surface of a hollow ingot. CONSTITUTION:A metallic tube 2 such as an SGP, which easily generates scales by heating before and after tube production and the scales act as a lubricant, is joined to the inner surface of a hollow ingot 1 for tube production of a difficult-to-form material. One of the joining methods is such that the tube 2 is used as a core in casting of the ingot 1. Production of tubes using such stocks prolongs the service life of tools such as a die, prevents generation of defects such as inner surface scab, and improves the productivity and the profitability, because the ingot 1 does not directly contact with a piercing plug or die.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for rolling a pipe using a hollow lump as a raw material, such as an inclined rolling method (Mannemann-plug mill method, Mannesmann-mandrel mill method, Arasel mill method). method, Pilgamill method, etc.) and press method (Eugine-Séjournet method,
The present invention relates to a tube-making rolling method that can dramatically improve economic efficiency and productivity compared to the case where a normal hollow ingot is used in the Erhardt-Busch Bench method, etc.

[Conventional technology]

Conventionally, the materials used in the above-mentioned pipe-making rolling method are solid ingots or rolled materials, so when making pipes from difficult-to-process materials such as stainless steel and high-alloy steel using the inclined rolling method.

■ In addition to cracking at the front of the perforated plug, product defects such as internal baldness and separation occur. ■ Short life of the perforated plug. ■ Depending on the steel type, there are problems such as the impossibility of perforation, and the pipe is formed using a press method. In some cases, there were problems such as the die having a short lifespan.

In order to solve these problems, in recent years, rolling using hollow blocks as raw materials has been carried out. This has brought about effects such as a slight increase in the life of the perforated plug and improved perforation performance, but no dramatic improvement has been achieved.

Conventionally, hollow steel ingots with steel pipes made of the same material as the ingot or high-alloy steel pipes on the inner surface of the hollow steel ingots have been manufactured using the tilting-year bonding method.
Regarding the method of making pipes by the press rolling method, JP-A-58-
224044 and Japanese Unexamined Patent Publication No. 58-224 ci '49. As the inner surface of these pipes is made of the same material as the stainless steel or high-alloy steel used in ingots that are difficult to machine and difficult to drill, the effect of reducing the rolling load during the drilling process and extending the life of the drilling plug is There is not much difference from the case of using ordinary hollow blocks without steel pipes, and the expected economic and production benefits have not been obtained.

[Problem that the invention seeks to solve]

The present invention utilizes a normal hollow ingot by manufacturing a hollow ingot with a thin metal tube on its inner surface that does not have high temperature oxidation resistance, in other words, easily generates oxide scale at high temperatures. The object of the present invention is to provide a pipe-forming rolling method that dramatically improves economic efficiency and productivity compared to the previous method.

[Means for solving problems]

The present invention is directed to a method for making hollow blocks of difficult-to-process materials, as shown in FIG. The above-mentioned problems can be solved by a pipe-making rolling method characterized by joining a pipe to the inner surface of a hollow lump, oxidizing the metal pipe in a heating furnace before pipe-making, and then rolling the hollow lump to make the pipe. It is something to be solved.

The metal tube 2 does not need to be completely metallurgically bonded to the hollow lump 1, since the metal tube 2 is expanded or stretched during tube-forming rolling and is metallurgically bonded to the hollow lump 1.

A specific method for joining the metal tube 2 to the inner surface of the hollow block is to place the metal tube as a core in the center of the mold during casting of the hollow block, and to join by casting molten base material around it;
There is a method in which a metal tube that matches the inner diameter of a hollow block that has been cast is inserted, cooled, and joined, or a method in which a metal tube with an approximate outer diameter is inserted and joined to the inner diameter of a cooled hollow block.

[Effect]

In the metal tube 2, oxide scale is generated on the inner surface of the metal tube 2 due to heating and holding of the hollow lump before tube-making rolling, and this oxide scale acts as a lubricant during the subsequent drilling process. do.

Furthermore, by making the metal tube 2 of a material that has high deformability at high temperatures, such as ordinary steel, the effect of reducing the load on the perforation plug and die can be dramatically increased.

Furthermore, since there is no direct contact between the hole plug or the die and the hollow block 1, heat generation on the inner surface of the hollow block 3 is suppressed, so even hollow blocks made of difficult-to-process materials with low high-temperature strength can be prevented from peeling or lamination on the inner surface. It is possible to prevent defects from occurring. Needless to say, the life of the drilling tool is extended.

The inner metal tube 2 has a thickness of 1/10-1/1 due to high-temperature oxidation scaling, expansion, and elongation, which varies depending on the size.
30, and if reheating is performed before pipe rolling, the metal tube 2 will become even thinner due to oxidation scale removal. By determining the area reduction rate from the hollow mass to the bone formation and the amount of oxidation scale off in the heating furnace obtained empirically, the metal tube 2 is bonded to the inner surface of the hollow mass so that no metal tube 2 remains on the inner surface when the bone is formed. The wall thickness of the metal tube 2 can be determined in advance.

Even if a thin metal tube 2 remains on the inner surface at the time of bone growth, it is very thin, less than 0.2 mm thick, and can be simply removed by pickling, so there is no problem in terms of quality.

The material used for the metal pipe 2 is one that easily generates oxide scale at the heating temperatures before and after pipe making.

It is sufficient that the oxide scale generates a low melting point oxide scale that serves as a lubricant during pipe making, for example, S
It is sufficient to use carbon steel pipes such as GP, 5TPG38.5TK30, etc. Preferably, a material with a high content of Si, which is effective in promoting the formation of oxide scale and peeling, is even better.Since the high temperature deformation resistance during pipe making is low, there is no problem with the load during drilling.

〔Example〕

The following hollow steel ingots were produced by the ingot making method, and 20 pipes were made by the Mannesmann-mandrel mill method.

Size: Outer diameter: 110mm Length: 1500mm Base material: High Nt austenitic steel Al1ay 6X set
Composition: C10,025% by weight 5i70.37% by weight M n / 1.48% by weight Plo, 025% by weight S10.003% by weight A! 110.07% by weight Ni / 24.5% by weight Cr / 20.3% by weight MO / 6.25% by weight Inner metal tube: 5TPG38 Pipe diameter: 50A Wall thickness: 3.5mm It is shown in Table 1.

For comparison, the same steel type was manufactured using a sand mold core.

Outer diameter: 120mm Inner diameter: 42mm Length: 1500mm Similar pipe-making tests were conducted on hollow steel ingots.

The piercing plug used in the piercer was 0.3C-0,3S i -0,5Mn-3Cr to confirm the effectiveness of the present invention.
Table 2 shows the results after a pipe making test in which -INi steel, a material with relatively low wear resistance, was selected.

Pipe inner surface defects occurred in all the pipes (9/20 pipes) in the comparison material, whereas no defects occurred in the example. Furthermore, it is clear that the example is significantly more advantageous in terms of both the load on the plug during drilling and the life of the drilling plug, which is an index of drilling performance. This shows that the method is excellent in terms of economy and productivity.

〔Effect of the invention〕

The method of the present invention improves productivity, increases the lifespan of plugs and dies, prevents product defects, and improves quality in the pipe rolling method using hollow blocks of difficult-to-process materials. As a result, the economic efficiency of pipe-making rolling has been significantly improved.

[Brief explanation of drawings]

FIG. 1 is (a) a cross-sectional view of a hollow mass used for carrying out the present invention;
(b) It is a longitudinal cross-sectional view. 1...Hollow mass 2...Metal tube 3...Inner surface

Claims (1)

[Claims] 1. In a method for making hollow blocks of difficult-to-process materials, a metal tube that easily generates oxide scale at heating temperatures before and after pipe making, and where the oxidized scale acts as a lubricant during pipe making, is bonded to the inner surface of the hollow lump. A method for forming and rolling a hollow lump of a difficult-to-process material, which comprises oxidizing the metal tube in a heating furnace before the pipe, and then rolling the hollow lump to form a pipe.