Low-preheating welding method for Q690-grade quenched and tempered steel medium-thickness plate for hydraulic support

Abstract

The invention provides a low-preheating welding method for a Q690-grade quenched and tempered steel medium-thickness plate for a hydraulic support. The Q690-grade quenched and tempered steel medium-thickness plate is a low-alloy high-strength steel plate which is high in carbon content and crack sensitivity index and has the thickness of 40-80 mm through the quenching and tempering technology. The low-preheating welding method comprises the steps that parts are assembled into a hydraulic support structural part assembly; the assembled hydraulic support structural part assembly is preheated at the low temperature; the preheated hydraulic support structural part assembly is subjected to manual overall backing welding; the hydraulic support structural part assembly subjected to manual overall backing welding is subjected to multi-pass filling welding through a welding robot, and the large penetration function of the welding robot is started during first-pass filling welding; and multi-pass cosmetic welding is performed on the hydraulic support structural part assembly subjected to filling welding by the aid of the welding robot. The low-preheating welding method for the Q690-grade quenched and tempered steel medium-thickness plate for the hydraulic support has the advantages that the design is scientific, only low preheating is needed, the welding quality can be guaranteed, and the production cost is low.

Description

technical field [0001] The invention relates to a welding method for a structural part for a hydraulic support, in particular to a low-preheat welding method for a Q690 grade quenched and tempered steel medium-thick plate used for a hydraulic support. Background technique [0002] As the main support equipment in fully mechanized mining equipment in coal mines, hydraulic supports have high requirements for pressure resistance and corrosion resistance due to the harsh underground service conditions. The structural parts of the hydraulic support are mainly composed of medium-thick plates. The tailor-welded parts account for more than 80% of the weight of the entire hydraulic support. The thickness of the medium-thick plates is generally 20-80mm. , Large welding volume, high material strength level, poor weldability, high welding restraint, etc. [0003] The strength grades of steel used for traditional hydraulic support structural parts are: Q355, Q460, Q550, Q690 and Q890 fr...

AI Technical Summary

Problems solved by technology

This method has the following disadvantages: (1) high-temperature preheating makes the working environment of workers worse; (2) the energy consumption is large, and the annual cost of natural gas used by the applicant for pre-welding preheating is as high as millions of yuan, and the CO produced by combustion , CO 2 It will also pollute the environment; (3) The production efficiency is low, and the structural parts need to be kept warm with the furnace for more than 3 hours before welding. If the temperature drops below 100°C during the welding process, it needs to be heated again in the furnace; (4) Production cost High, the large consumption of gas and the reduction of efficiency have all resulted in the increase of the production cost of hydraulic support structural parts

[0004] In recent years, although some preheating-free Q690-grade steel plate welding methods have been developed in succession in the industry, they are generally applied to medium and thin steel plates delivered in TMCP state with a thickness of less than 30mm. The stronger the steel plate is, and the steel plate in the quenched and tempered state is more sensitive to cracks than the steel plate in the TMCP state, the above-mentioned non-preheating welding method is applied to medium and thick plates with a thickness of 40-80mm, and defects such as cold cracks and lack of fusion are very prone to occur, resulting in failure In practical applications, due to the disadvantages of high cost, unstable performance, and poor welding stability, the above-mentioned non-preheating welding method has not been promoted in the industry, and the research on the welding process of medium and thick plates of this steel plate is even blank in the industry.

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