The cold winter has arrived, and higher requirements have been placed on welding preheating.
Preheating temperature is usually measured before welding, and maintaining this minimum temperature during welding is often overlooked. In winter, the weld joints are cooled quickly. If the minimum temperature control during the welding process is ignored, it will bring serious quality risks to the welding quality. Plasma ARC Welding Torch Manufacturer shares with you.
Cold cracks are the most harmful and most harmful in winter welding defects. The three main factors for cold crack formation are: hardened material (base metal), hydrogen, restraint. For conventional structural steel, the reason for the hardening of the material is that the cooling rate is too fast, so increasing the preheating temperature and maintaining this temperature can solve this problem well.
For general construction in winter, the preheating temperature is 20°-50°C higher than the normal temperature. Pay particular attention to the preheating of the tack welding of thick plates, which is slightly higher than that of the formal weld. Higher welding methods can be the same as conventional preheating temperatures.
For long components (generally greater than 10m), it is not recommended to evacuate the heating equipment (heating tube or electric heating sheet) during welding to prevent the situation of "one end is hot and the other is cold".
For outdoor work, heat preservation and slow cooling measures should be performed on the weld area after welding.
It is recommended to use low hydrogen welding materials in winter. According to AWS, EN and other standards, the preheating temperature of low hydrogen welding materials can be lower than ordinary welding materials. Pay attention to the formulation of the welding sequence. A reasonable welding sequence can greatly reduce the degree of welding restraint. At the same time, as a welding project, it is also a responsibility and obligation to review the welded joints that may cause large restraints in the drawings, and coordinate with the designer to change the joint form.
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