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Pretreatment method for preventing cold bending cracking of austenitic stainless steel and improving corrosion resistance

An austenitic stainless steel, cold-bending and cracking technology, used in heat treatment furnaces, heat treatment equipment, ion implantation and plating, etc., can solve the problems of safety hazards of rail transit equipment, corrosion and perforation damage of stainless steel, and accelerated anode dissolution. Follow-up cleaning, elimination of internal stress, and good surface smoothness

Active Publication Date: 2015-10-28
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Moreover, the work hardening index of the existing stainless steel cold-rolled strips used for cold-bending is high, so surface cracking often occurs due to stress concentration during the cold-bending process
[0005] Stainless steel has excellent corrosion resistance, but it is prone to pitting corrosion under the attack of solutions containing chloride ions, etc.
After cold bending, the stainless steel plate forms a large cathode-small anode structure geometrically, and the anode dissolution rate of pitting corrosion is accelerated; at the same time, due to the characteristics of automatic acceleration in the development of pitting corrosion, it will soon lead to the corrosion corrosion perforation damage
This poses a serious hazard to the safety of rail transit equipment

Method used

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  • Pretreatment method for preventing cold bending cracking of austenitic stainless steel and improving corrosion resistance
  • Pretreatment method for preventing cold bending cracking of austenitic stainless steel and improving corrosion resistance
  • Pretreatment method for preventing cold bending cracking of austenitic stainless steel and improving corrosion resistance

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] 1. The cross-section shape of 301L stainless steel plate cold-formed is as follows figure 1 As shown, calculate the horizontal distance from the bending point to the symmetry center of the stainless steel plate, and arrange the distribution position of the heating pipes according to the obtained data. Send the stainless steel plate into the designated position of the heating furnace, so that the heating tubes are distributed above the cold bending area of ​​the stainless steel plate. Heat up the temperature to 300°C with electricity, and keep it warm for 2h.

[0026] 2. After heating and keeping warm, send the stainless steel plate to a temperature of 20°C. The composition is NaOH 60g / L, NaOH 2 SiO 3 10g / L, Na 2 CO 3 Soak in 20g / L cleaning solution 1 for 5 minutes. Then feed 65%NaOH and 20%NaNO at a temperature of 350°C 3 , 7%Na 2 SO 4 , 8%Na 2 CO 3 (wt%) in cleaning solution 2 for 15 minutes. Then the surface passes through 25% HNO at a flow rate of 10cm / s...

Embodiment 2

[0036] 1. The cross-section shape of 301L stainless steel plate cold-formed is as follows figure 2 As shown, calculate the horizontal distance from the bending point to the symmetry center of the stainless steel plate, and arrange the distribution position of the heating pipes according to the obtained data. Send the stainless steel plate into the designated position of the heating furnace, so that the heating tubes are distributed above the cold bending area of ​​the stainless steel plate. Heat up the temperature to 400°C with electricity, and keep the temperature for 2.5h.

[0037] 2. After heating and keeping warm, put the stainless steel plate into the temperature 25℃, the composition is NaOH 65g / L, NaOH 2 SiO 315g / L, Na 2 CO 3 Soak in 25g / L cleaning solution 1 for 8 minutes. Then feed 70%NaOH and 25%NaNO at a temperature of 400°C 3 , 2%Na 2 SO 4 , 3%Na 2 CO 3 (wt%) in cleaning solution 2 for 20 minutes. Then the surface passes through 20% HNO at a flow rate o...

Embodiment 3

[0047] 1. The cross-section shape of 301L stainless steel plate cold-formed is as follows image 3 As shown, calculate the horizontal distance from the bending point to the symmetry center of the stainless steel plate, and arrange the distribution position of the heating pipes according to the obtained data. Send the stainless steel plate into the designated position of the heating furnace, so that the heating tubes are distributed above the cold bending area of ​​the stainless steel plate. Heat up the temperature to 350° C. and keep it warm for 3 hours.

[0048] 2. After heating and keeping warm, send the stainless steel plate to a temperature of 30°C, the composition is NaOH 70g / L, NaOH 2 SiO 3 20g / L, Na 2 CO 3 Soak in 30g / L cleaning solution 1 for 10 minutes. Then feed 67%NaOH and 23%NaNO at a temperature of 450°C 3 , 4%Na 2 SO 4 , 6%Na 2 CO 3 (wt%) in cleaning solution 2 for 25 minutes. Then the surface passes through 15% HNO at a flow rate of 20cm / s and a tem...

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Abstract

The invention relates to a pretreatment method for preventing cold-bending cracking of austenitic stainless steel and improving corrosion resistance, and belongs to the field of cold-bending forming of stainless steel for rail transit equipment. According to the pretreatment method, a cold-bending zone of the stainless steel is subjected to heat preservation treatment at the temperature of 300-400 DEG C for 2-3 hours, surface cleaning and plasma treatment before cold-bending forming of the stainless steel so as to realize the beneficial effects of preventing cold-bending cracking and improving corrosion resistance. The cold-bending zone is subjected to heat preservation treatment so as to eliminate internal stress, improve the plasticity of a bending part of a corrosion resistant plate and prevent cracking caused by stress concentration in a cold-bending process of the corrosion resistant plate. Oxide skin and impurities on the surface of the stainless steel are removed through surface cleanness, and finally the corrosion resistance is improved by utilizing plasma surface treatment.

Description

technical field [0001] The invention relates to a pretreatment method for preventing cold-bending cracking of austenitic stainless steel and improving corrosion resistance, and belongs to the field of stainless steel cold-bending forming for rail transit equipment. Background technique [0002] Rail transit is a green transportation mode with large capacity, low consumption and low pollution. The development of urban rail transit and high-speed railways is a common trend in the development of railways in the world today. In recent years, with the urgent demand for lightweight, high-precision, and complex cross-section profiles for rail transit equipment, stainless steel cold-formed profiles have become the main material to replace ordinary steel materials for rail transit equipment. [0003] Cold roll forming is a process technology that continuously bends metal strips transversely through sequentially configured multi-pass forming rolls to produce specific cross-section pr...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23F17/00C21D9/00C23G1/19C23G1/08C23C14/38
Inventor 姚正军林玉划张平则魏东博罗西希陈煜杨红勤吴小凤张泽磊徐尚君
Owner NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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