A post-weld heat treatment method for improving the low-temperature impact toughness of welded joints of 690mpa low-c, medium-mn, high-strength and tough medium-thick plates
A technology of low-temperature impact toughness and post-weld heat treatment, which is applied in heat treatment furnaces, heat treatment equipment, welding equipment, etc., can solve the problem of less research work on weldability, and achieve excellent performance, eliminate hydrogen embrittlement, and uniform organization.
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Embodiment 1
[0034] Traditional post-heating process (200 ° C for 120 minutes, air cooling to room temperature), the process steps are as follows:
[0035] (1) Welding process
[0036] The 20mm-thick low-C, medium-Mn, high-strength and tough medium-thick plate is processed into a symmetrical double V-shaped groove, with a single-side groove of 30°, a blunt edge of 2mm, and a gap of 1.5mm. Grind the surface of the plate to be welded on both sides of the groove, remove iron oxide scale and iron filings, fix the plate to be welded around with bolts, and then carry out Ar+CO 2 Mixed gas shielded tack welding.
[0037] After the tack welding is completed, use a flame gun to preheat the weld seam and the surrounding 200mm range, and the preheating temperature is 150-200°C. After preheating, weld medium-manganese medium-thick plates with a welding current of 200A, a welding voltage of 25V, a gas flow of 15L / min, a welding speed of 5mm / s, and a welding line energy of 10KJ / cm. During the welding...
Embodiment 2
[0042] Post-weld heat treatment process (650 ° C for 15 minutes, air cooling to room temperature), the process steps are as follows:
[0043] (1) Welding process
[0044] The welding process is the same as in Example 1, and the welding process and welding parameters are the same as in Example 1.
[0045] (2) Post-weld heat treatment process
[0046]Put the welded plate after filling welding into a 650°C resistance furnace and keep it warm for 15 minutes (it takes 35 minutes to heat the welded steel plate to 650°C) to eliminate the thermal stress generated by welding and eliminate the hydrogen embrittlement generated by the weld during the welding process. Uniform weld and heat-affected zone structure, refine the grains of weld and heat-affected zone, reduce the degree of hardening of welded joints, and make the weld metal and the base metal better fused. Then it was air-cooled to room temperature, and the tensile properties, impact properties and hardness values of the wel...
Embodiment 3
[0049] Post-weld heat treatment process (630 ° C for 30 minutes, air cooling to room temperature), the process steps are as follows:
[0050] (1) Welding process
[0051] The 30mm thick low-C, medium-Mn, high-strength and tough medium-thick plate is processed into a symmetrical double V-shaped groove, with a single-side groove of 30°, a blunt edge of 2mm, and a gap of 2mm. Grind the surface of the plate to be welded on both sides of the groove, remove iron oxide scale and iron filings, fix the plate to be welded around with bolts, and then carry out Ar+CO 2 Mixed gas shielded tack welding.
[0052] After the tack welding is completed, use a flame gun to preheat the weld seam and the surrounding 200mm range, and the preheating temperature is 150-200°C. After preheating, the medium-manganese plate is welded, the welding current is 250A, the welding voltage is 30V, the gas flow rate is 20L / min, the welding speed is 5mm / s, and the welding line energy is 15KJ / cm. During the weld...
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