Method for improving wall-thickness uniformity during large-sized thick-wall pipe vertical hot extrusion process

A technology of vertical extrusion and thick-walled pipes, which is applied in the direction of metal extrusion, metal extrusion control equipment, metal processing equipment, etc., can solve the problem of uneven wall thickness of large-diameter thick-walled pipes, and improve the uniformity of wall thickness , prolong the service life and save the cost of raw materials

Active Publication Date: 2016-12-14
CENT IRON & STEEL RES INST
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0013] The purpose of the present invention is to provide a method for improving the uniformity of wall thickness in the vertical hot extrusion process of large-diameter thick-walled pipes, and to solve the problem of uneven wall thickness of large-diameter thick-

Method used

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  • Method for improving wall-thickness uniformity during large-sized thick-wall pipe vertical hot extrusion process
  • Method for improving wall-thickness uniformity during large-sized thick-wall pipe vertical hot extrusion process
  • Method for improving wall-thickness uniformity during large-sized thick-wall pipe vertical hot extrusion process

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Embodiment 1

[0044] The main components of the nickel-based heat-resistant alloy in the embodiment of the present invention are as follows: C: 0.03%; Cr: 24.1%; Co: 19.8%; Si: 0.05%; Mn: 0.07%; Al: 1.45%; Ti: 1.38%; Nb: 1.2%; B: 0.002%; Zr: 0.08%; P: 0.001%; ​​S: 0.0005%; Ni is the balance and unavoidable impurity element. The product specification is a large-diameter thick-walled heat-resistant alloy pipe with an outer diameter of Φ460mm and a wall thickness of 80mm.

[0045] According to the above composition, the invention produces a tube blank with an outer diameter of Φ945mm x wall thickness of 320mm x 1000mm through VIM smelting + VAR self-consumption of a furnace of 7 tons of nickel-based heat-resistant alloy.

[0046] The special process of the present invention is as follows: the tube blank is hollow cylindrical, and the extrusion front end is processed into a specific shape matching the extrusion die, see Figure 4 . The mold preheating temperature is 390°C. The furnace temper...

Embodiment 2

[0049] Example 9 of the present invention: Cr-3W-3Co series martensitic heat-resistant steel (ferritic system) The weight percentage of the main components is: C: 0.080%; Cr: 8.99%; Si: 0.30%; Mn: 0.50%; Co: 3.01 %; W: 2.81%; V: 0.21%; Nb: 0.53%; N: 0.008%; B: 0.014%; Cu: 0.8%; impurity elements. The product specification is a large-diameter thick-wall heat-resistant steel pipe with an outer diameter of Φ590mm×a wall thickness of 90mm.

[0050] The present invention smelts 40 tons of molten steel according to the above-mentioned composition EAF+LF+VD process, casts 3 steel ingots, selects two for comparison hot extrusion, and makes tube blanks with outer diameter Φ1080mm×wall thickness 330mm×length 1400mm respectively. One is implemented according to the existing technology; the other is implemented according to the process of the present invention, that is, the tube blank extrusion front end is processed into a specific shape, the lower limit extrusion temperature is control...

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Abstract

The invention relates to a method for improving the wall-thickness uniformity during a large-sized thick-wall pipe vertical hot extrusion process. The method for improving the wall-thickness uniformity during the large-sized thick-wall pipe vertical hot extrusion process belongs to the technical field of large-sized thick-wall pipe hot extrusion forming, and comprises the process steps and control technical parameters as below: one end of a pipe blank to be extruded is processed to a specific shape; mold preheating temperature is set: for a heat-resisting steel material, the mold preheating temperature is 400 to 450 DEG C, and for a heat-resisting alloy material, the mold preheating temperature is 350 to 400 DEG C; the pipe blank extrusion minimum limit temperature is controlled: for the heat-resisting steel material, the extrusion minimum limit temperature is 1,000 to 1,010 DEG C, and for the heat-resisting alloy material, the extrusion minimum limit temperature is 1,030 to 1,040 DEG C; and reasonable glass lubricant type and granularity are selected according to extrusion characteristics of different positions. The method for improving the wall-thickness uniformity during the large-sized thick-wall pipe vertical hot extrusion process has the advantages that the metal uniformity flow of the pipe blank during a stable extrusion process is greatly improved, the wall-thickness uniformity during the large-sized thick-wall pipe hot extrusion process is remarkably improved, meanwhile, the cost of raw materials is saved by 20 percent, the service life of a mold is prolonged by 20 percent, the labor productivity during the extrusion process is improved by 15 percent, and about 70 percent of workload of follow-up cutting processing is reduced.

Description

technical field [0001] The invention belongs to the technical field of large-diameter thick-walled pipe hot extrusion forming, and in particular provides a method for improving the wall thickness uniformity of the large-diameter thick-walled pipe in the vertical hot extrusion process, which is suitable for the preparation of large-diameter thick-walled pipes. Background technique [0002] At present, the specifications of large-diameter thick-walled seamless pipes for ultra-supercritical power plant boilers are Φ273mm-1066mm in outer diameter and 20mm-130mm in wall thickness. The production of large-diameter thick-walled heat-resistant steel pipes and heat-resistant alloy pipes in China mainly adopts the vertical hot extrusion method. Compared with the traditional method, this method has obvious advantages. See patent CN 101706019 B for details. my country has several large-scale vertical extrusion machines with a force of more than 30,000 tons. It has broken the technologic...

Claims

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Application Information

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IPC IPC(8): B21C23/01B21C23/08B21C31/00B21C23/32B21C29/04
CPCB21C23/01B21C23/085B21C23/32B21C29/04B21C31/00
Inventor 刘正东陈正宗包汉生干勇杨钢
Owner CENT IRON & STEEL RES INST
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