Weld seam heat treatment method of steel for 700 MPa-grade automobile torsion beam

A heat treatment method and torsion beam technology, applied in heat treatment furnaces, heat treatment equipment, process efficiency improvement, etc., can solve the problems of easy cracking of automobile torsion beams and low fatigue life of finished automobile torsion beams

Active Publication Date: 2020-08-14
SHOUGANG CORPORATION +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Aiming at the deficiencies of the above-mentioned prior art, the present invention provides a heat treatment method for steel weld seams of 700MPa grade automobile torsion beams, to solve the problem that after adopting integral high-temperature tempering to eliminate tissue stress, the manufactured automobile torsion beams are easy to crack, resulting in torsion of finished automobiles. The problem of low fatigue life of beams

Method used

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  • Weld seam heat treatment method of steel for 700 MPa-grade automobile torsion beam
  • Weld seam heat treatment method of steel for 700 MPa-grade automobile torsion beam
  • Weld seam heat treatment method of steel for 700 MPa-grade automobile torsion beam

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Experimental program
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Effect test

Embodiment 1

[0060] Embodiment 1 provides a kind of heat treatment method of 700MPa class automobile torsion beam steel weld seam, welded steel pipe is 700MPa class high-frequency welded pipe, steel pipe wall thickness is 2mm, weld seam width is 2mm, steel pipe chemical composition is as shown in Table 1, all the other are Fe and unavoidable impurities. Using intermediate frequency induction heating, the temperature is raised to 800°C in an area with a distance of 8mm from the weld seam, with the weld seam as the axis of symmetry, the first heat preservation is 20s, the cooling rate is controlled at 15°C / s, the air is cooled to 580°C, and the second heat preservation is 25s. Air cool to room temperature.

[0061] Observation before heat treatment, the weld center fusion line structure is ferrite + lath bainite structure; weld heat affected zone is martensite + lath bainite structure; base metal structure is granular bainite structure . Weld structure such as figure 1 As shown, the base ...

Embodiment 2

[0065] Embodiment 2 provides a kind of heat treatment method of 700MPa grade automobile torsion beam steel weld seam, welded steel pipe is 700MPa grade high-frequency welded pipe, steel pipe wall thickness is 3mm, weld seam width is 1.5mm, steel pipe chemical composition is as shown in Table 1, the rest For Fe and unavoidable impurities. Using intermediate frequency induction heating, the temperature is raised to 820°C in an area with a distance of 6 mm from the weld seam, with the weld seam as the axis of symmetry, the first heat preservation is 27s, the cooling rate is controlled at 18°C / s, the air is cooled to 560°C, and the second heat preservation is 30s. Air cool to room temperature.

[0066] Observation before heat treatment, the weld center fusion line structure is ferrite + lath bainite structure; weld heat affected zone is martensite + lath bainite structure; base metal structure is granular bainite structure .

[0067] Observation after heat treatment: the fusion ...

Embodiment 3

[0070] Embodiment 3 provides a kind of heat treatment method of 700MPa grade automobile torsion beam steel weld seam, welded steel pipe is 700MPa grade high-frequency welded pipe, steel pipe wall thickness is 4mm, weld seam width is 2mm, steel pipe chemical composition is as shown in Table 1, all the other are Fe and unavoidable impurities. Medium frequency induction heating is used to heat up to 810°C in an area with a distance of 8mm from the weld seam, with the weld seam as the axis of symmetry. The first heat preservation is 17s, the cooling rate is controlled at 13°C / s, the air cooling is to 560°C, and the second heat preservation is 35s. , after air cooling to 254°C for 1min, water cooling to 25°C at a water cooling rate of 30°C / s.

[0071] Observation before heat treatment, the weld center fusion line structure is ferrite + lath bainite structure; weld heat affected zone is martensite + lath bainite structure; base metal structure is granular bainite structure .

[00...

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Abstract

The invention discloses a weld seam heat treatment method of steel for a 700 MPa-grade automobile torsion beam. The weld seam heat treatment method comprises the steps of welding a steel plate into asteel tube with a weld seam; and conducting heat treatment on regions having a distance d away from the weld seam on the steel tube with the weld seam as the symmetry axis, wherein the heat treatmentprocess comprises the steps of primary heating, primary heat preservation, primary cooling, secondary heat preservation and secondary cooling; primary cooling belongs to air-cooling, the air-cooling rate is 10-20 DEG C / s, and the air-cooling ending temperature is 480-600 DEG C; d is 3-5 times higher than the width of the weld seam, and the width of the weld seam is 1-2 mm. Through the weld seam heat treatment method, local heat treatment is carried out on the weld seam of the steel tube and the regions nearby the weld seam, and the formability of the steel tube with the weld seam is improved.The problem of cracking of the weld seam is solved. Accordingly, the fatigue performance of the torsion beam is improved.

Description

technical field [0001] The invention belongs to the technical field of metal heat treatment, and in particular relates to a heat treatment method for steel weld seams of 700MPa grade automobile torsion beams. Background technique [0002] The production of automobile torsion beam needs to weld the plate first and make the tube. During the rapid heating of high-frequency induction welding and the rapid cooling after welding, a temperature gradient is generated at the position of the tube at different distances from the weld. After cooling to room temperature , the welding residual stress is generated inside the pipe; after the weld is cooled to room temperature, the central fusion line is very easy to form a coarse Widmansite structure, and the heat-affected zone of the weld is easy to form non-equilibrium structures such as martensite, resulting in structural stress. [0003] At present, most of the welded pipes for automobile torsion beams adopt the method of overall high-t...

Claims

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Application Information

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IPC IPC(8): C21D9/50C21D1/10C21D1/78C21D6/00C22C38/02C22C38/04C22C38/06C22C38/12C22C38/14
CPCC21D9/505C21D1/10C21D1/78C21D6/005C21D6/008C22C38/02C22C38/04C22C38/002C22C38/12C22C38/14C22C38/06C21D2211/002C21D2211/001C21D2211/005C21D2211/004Y02P10/25
Inventor 李秋寒郭子峰郭佳张衍冯军陈斌李玉鹏吕宝锋赵青尼兴范然然杨业周娜徐伟张嘉琪宋春华陈波
Owner SHOUGANG CORPORATION
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