Home » Events » Industry News
Cold Crack
Sources: this site Click: Date: 2015-11-20 21:25:52
Generally cold crack refers to weld cold cracking during cooling within the temperature dropped to martensite transformation temperature range (hereinafter, 300- 200 ℃) produced, can occur immediately after welding, it can also occur in a long time after the welding, it is also known as delayed cracking. The basic conditions for its formation are three: the formation of hardened tissue welding joints; presence and concentration of hydrogen diffusion; and there is a large weld tensile stress. Its preventive measures are:
(1) Selecting the welding specifications and reasonable line can improve the state of the weld and heat affected zone organization, such as preheating before welding, control interlayer temperature, slow cooling after welding or after hot to accelerate the hydrogen molecules from escaping.
(2) The basic electrodes or flux, in order to reduce the oxygen content in the weld diffusion.
(3) Electrode and flux before use should be strictly in accordance with the requirements for drying (low hydrogen electrodes 300 ℃ ~ 3 50 ℃ incubated lh; acid electrode l 00 ℃ ~ l50 ℃ insulation lh; solder 200 ℃ ~ 250.C insulation 2h), carefully cleaning the groove and the wire, so in addition to oil, water and dirt and rust, etc., in order to reduce the source of hydrogen.
(4) Timely post-weld heat treatment. First, an annealing treatment to eliminate stress, so that quenching and tempering to improve their toughness; two: eliminate the hydrogen treatment is carried out, the hydrogen from the weld joints fully escape.
(5) Improving the quality of steel, reducing the steel layered inclusions.
(6) It can be taken to reduce welding stress of various process steps.
(1) Selecting the welding specifications and reasonable line can improve the state of the weld and heat affected zone organization, such as preheating before welding, control interlayer temperature, slow cooling after welding or after hot to accelerate the hydrogen molecules from escaping.
(2) The basic electrodes or flux, in order to reduce the oxygen content in the weld diffusion.
(3) Electrode and flux before use should be strictly in accordance with the requirements for drying (low hydrogen electrodes 300 ℃ ~ 3 50 ℃ incubated lh; acid electrode l 00 ℃ ~ l50 ℃ insulation lh; solder 200 ℃ ~ 250.C insulation 2h), carefully cleaning the groove and the wire, so in addition to oil, water and dirt and rust, etc., in order to reduce the source of hydrogen.
(4) Timely post-weld heat treatment. First, an annealing treatment to eliminate stress, so that quenching and tempering to improve their toughness; two: eliminate the hydrogen treatment is carried out, the hydrogen from the weld joints fully escape.
(5) Improving the quality of steel, reducing the steel layered inclusions.
(6) It can be taken to reduce welding stress of various process steps.
Previous: Boiler tube cleaning
Next: Boiler Pipe
