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Welding repair method of defects after precision processing of large-scale carbon steel casting

A post-finishing, welding repair technology, applied in welding medium, welding equipment, welding equipment and other directions, can solve the problem of difficulty in ensuring dimensional accuracy, surface flatness and smoothness, welding seam and base metal can not achieve metallurgical fusion, special repair equipment. The problem of low repair efficiency, etc., can reduce the generation of hardened structure of the weld, reduce the cooling rate, and increase the temperature between the passes.

Active Publication Date: 2015-01-28
KOCEL STEEL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

If the hardness is too high after welding, it will cause the phenomenon of cutting and hitting during finishing and repairing, and it is difficult to guarantee the dimensional accuracy, surface flatness and smoothness after processing.
At present, there are some special equipment for repairing defects after finishing workpieces, but there are certain disadvantages: the repair efficiency of special repair equipment is extremely low, and after repair, the weld seam and the base metal cannot achieve complete metallurgical fusion. After the inspection, the defect shows that it is serious, and it cannot meet the requirements for use
Since the castings after welding can no longer undergo post-weld heat treatment, the hardness of higher-strength castings after welding is higher. The maximum hardness after argon arc welding can be greater than 500HB, which seriously affects the subsequent processing quality control; this problem has not been solved yet. way

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0011] Embodiment 1: Base material ASTM A148 90-60 material. Use oxyacetylene flame to preheat, preheat to 150-200°C, and ensure that the preheating requirements are met within 50mm around the defect. The diameter of the welding wire is 2.4mm, the welding current is 220-300A, the voltage is 16-25V, and the welding speed is 3-8cm / min. During the whole welding process, the interlayer temperature of the weld is kept between 400-500°C. The thickness of each layer of weld is controlled at 3-5mm, so that the next layer of weld bead can temper the previous layer of weld bead. The weld reinforcement is 7-8mm. After the welding is completed, use an arc to bake the weld reinforcement for 2-3 minutes, and then slowly cool the weld. After the weld cools, grind and remove the weld reinforcement.

[0012] After the weld seam is polished, the magnetic particle inspection and penetration inspection are carried out, and the results are qualified; the hardness inspection of the weld seam is c...

Embodiment 2

[0013] Embodiment 2: Base material ASTM A27 70-40 material. Use oxyacetylene flame to preheat, preheat to 100-200°C, and ensure that the preheating requirements are met within 50mm around the defect. The diameter of the welding wire is 2.4mm, the welding current is 200-250A, the voltage is 20-30V, and the welding speed is 5-8cm / min. During the whole welding process, the interlayer temperature of the weld is kept between 300-500°C. The thickness of each layer of weld is controlled to 2-5mm, so that the next layer of weld bead can temper the previous layer of weld bead. The weld reinforcement height is 5-8mm. After the welding is completed, use an arc to bake the reinforcement weld seam for 2-3 minutes, and then slowly cool the weld seam. After the weld is cooled, the weld reinforcement is removed by grinding.

[0014] After the weld seam is polished, the magnetic particle inspection and penetration inspection are carried out, and the results are qualified; the hardness inspe...

Embodiment 3

[0015] Embodiment three: base material J03006 90-60 material. The size of the leakage defect after the finishing of the casting after grinding: the maximum diameter is 20mm, and the maximum depth is 10mm. Use oxyacetylene flame to preheat, preheat to 100-200°C, and ensure that the preheating requirements are met within 50mm around the defect. The diameter of the welding wire is 2.4mm, the welding current is 220-280A, the voltage is 16-25V, and the welding speed is 3-8cm / min. During the whole welding process, the interlayer temperature of the weld is kept between 400-500°C. The thickness of each layer of weld is controlled at 3-5mm, so that the next layer of weld bead can temper the previous layer of weld bead. The weld reinforcement is 7-8mm. After the welding is completed, use an arc to bake the weld reinforcement for 2-3 minutes, and then slowly cool the weld. After the weld cools, grind and remove the weld reinforcement.

[0016] After the weld seam is polished, the magn...

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Abstract

The invention relates to a welding method, in particular to a welding repair method of defects after precision processing of a large-scale carbon steel casting. The method comprises the following steps: preheating by adopting oxygen acetylene flame, welding by adopting a grade-AWSA5.28ER7S-6 carbon steel argon arc welding wire, keeping the temperature among weld layers between 300-500 DEG C in the welding process, controlling the thickness of each layer of welds within 2-5 mm, enabling a next layer of weld passes to play a role in tempering an upper layer of weld passes, ensuring that the weld reinforcement is 5-8 mm, baking the reinforcement welds for 2-3 minutes by utilizing electric arc after the completion of welding, slowly cooling the welds, and polishing and removing the weld reinforcement after the welds are cooled. The welding repair method has the beneficial effects that the process method is special, a weld part can be ensured to meet the requirements of parent metal magnetic powder detection or penetrant testing without postweld heat treatment, the maximum hardness of the weld part is smaller than 220HB, and the maximum hardness of a weld heat affected zone part is smaller than 250HB to meet the processing requirements.

Description

technical field [0001] The invention relates to a welding method, in particular to a welding repair method for defects after finishing of large carbon steel castings. Background technique [0002] At present, after finishing large-scale steel castings, casting defects will be exposed, which will affect the use of castings, and the defects of external leakage must be polished, transitioned or welded to repair. The microstructure of medium and low carbon steel castings consists of bainite, martensite or pearlite plus a small amount of ferrite. After welding, most of the weld microstructure is bainite and martensite, and the hardness is relatively high. If the hardness is too high after welding, it will cause the phenomenon of cutting and hitting during finishing and repairing, and it is difficult to guarantee the requirements of dimensional accuracy, surface flatness and smoothness after processing. At present, there are some special equipment for repairing defects after fin...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B23K9/04B23K9/16B23K9/095B23K35/22
Inventor 曹鹏杨爱宁唐钟雪付龙张宏凯罗永建
Owner KOCEL STEEL