| The quality of Hot TIG welding is as well as manual TIG welding quality and automatic welding system brings it’s high efficiency,develop a set of corrosion resistant welding process of carbon steel and low alloy steel pipe by Hot TIG welding technology,can be used as an important technical reserve for the construction of acid gas field,but also the actual production demand of the project construction.In this Thesis,the L245 and L360 grade steel pipes were designed to meet the requirements of acidic medium service,the welding parameters were developed,the welding process was developed,the mechanical properties of the welded joints were tested and the welds were analyzed by welding with the TIG welding equipment.The corrosion resistance of the joint was studied,and the welding quality control measures and welding efficiency were analyzed.The results are showed in the following:When using V-shaped bevel,the blunt edge height and the opposite gap are the main parameters to control the root forming.Appropriate increase of the blunt edge height will help to improve the current carrying capacity of the weld root,and the gap is controlled at 2.5±0.2mm to improve the welding speed and root forming.When using U-shaped bevel without groove,the blunt edge height is the key to control the root of the weld without gap.The height of the blunt edge should be controlled at 2.5 to 3.0mm.The V-groove angle is designed to be 60°±5°,U-groove angle design 24°±5°would help to avoid stress corrosion cracking,easy to root welding operation.By useing wider bevel and multi-layer can significantly improve the impact toughness,also better than manual TIG welding + electrode arc welding,all test weld hardness to meet the acceptance requirements,Hot TIG welding the maximum filling welding line energy from 1.22 KJ/mm reduced to 0.99KJ/mm,bevel angle increased from 24°to 60 ℃,the hardness of the weld gradually reduced.The weld metal structure is F+P,the energy of the line increases and the thickness of the single weld increases.The M/A component gradually appears,and the uniformity of the tissue gradually becomes worse.Weld wire TIG weld organization than the manual TIG welding + electrode arc welding organization uniformity is better,more dense grain,non-metallic inclusions in the lower content.Hot TIG welding’s specimens meet the 90%of the actual yield strength stress conditions of hydrogen sulfide stress corrosion cracking requirements and anti-hydrogen cracking requirements.The weld self-corrosion current density is 7.1829×10-5,and the self-corrosion current density of welds with Hot TIG welding is 4.8473×10-5,and the welding wire of TIG weld is resistant to electric wire.Chemical corrosion performance is better than manual TIG welding + electrode arc welding seam.Not welded,concave is the main defects in the root of the weld,the root welding should control the distance between the tungsten and the molten pool,tungsten and the weld angle of about 45 °to 60°angle,control the reasonable slope The size of the blunt edge and the arc blowing force,to ensure that the weld at the root of a reasonable pool liquidity and penetration capacity is to solve the root defects of the main measures.Unfused is the main drawback of hot welding and filling welding.It should pay attention to the construction of weld bead,adopt multi-channel welding way,reduce the thickness of single layer welding is to avoid the main measures of non-fusion defects.U-shaped and V-shaped bevel welding efficiency of about 100%to 150%,filling the welding efficiency of about 38%to 40%.With V-bevel,the welding consumables of the Hot TIG are about 45%less than the manual welding,about 15%higher welding efficiency,about 66%less than the manual welding,and high welding efficiency when using the U-bevel About 42%. |
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