In the use of welding tools to carry out welding operations, in the process of steel welding, there are still steel cold cracking phenomenon. There are many reasons for this situation, which are generally related to the chemical composition, steel degree, preheating temperature and cooling conditions of steel. In order to appear the phenomenon of the maximum limit underground steel cold crack, we must pay attention to the following technical points:
First of all, for steel welding, attention should be paid to the moisture in welding materials, rust, oil stain at the groove of welding parts, and environmental humidity. In general, the amount of hydrogen in the base metal and welding wire is very small, but the moisture in the electrode coating and the moisture in the air can not be ignored and become the main source of hydrogen enrichment.
The solubility of hydrogen in austenite is much higher than that in ferrite. Therefore, the solubility of hydrogen decreases suddenly when the austenite changes to ferrite during welding. At the same time, the diffusion rate of hydrogen is just opposite, and increases suddenly when it changes from austenite to ferrite.
Finally, a large amount of hydrogen will be dissolved in the molten pool under the action of high temperature during welding. In the subsequent cooling and condensation process, due to the sharp decrease of solubility, hydrogen is trying to escape. However, due to the rapid cooling, hydrogen is retained in the weld metal to form diffusion hydrogen.
This article comes from the manual welding equipment of water tankhttp://www.cl-onsale.com
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