In the production process of steel welding, there will be the emergence of steel defects if the welding method is not correct. The most common defects are hot cracking, cold cracking, lamellar tearing, lack of fusion and incomplete penetration, stomata and slag.
It is produced during cooling of the weld. The major cause is the sulfur and phosphorus in steel and welding form some eutectic mixtures, the mixtures is very brittle and hard. During the cooling of the weld, the eutectic mixtures will be in tension state so that easily cracking.
It also known as delayed cracking, it is produced range from 200 ℃ to room temperature. It will be cracked after a few minutes even a few days. The reason has closely related with the structural design, welding materials, storage, application and welding processes.
When the welding temperature was cooled to minus 400 degrees, some of the plate thickness is relatively large and high impurity content,especially sulfur content, and has a strong parallel to the rolling direction along the sheet of high strength low alloy steel segregation when it is subjected to a force perpendicular to the thickness direction in the welding process, it will produce the rolling direction stepped cracks.
Lack of Fusion and Incomplete Penetration.
Both the cause is basically the same, the inappropriate of technological parameter, measures and groove dimensions, the clean not enough of groove and weld surface or poor welding technology.
The main reason of producing porosity in the weld has a connection with the choosed,stored and used of the welding material, the selection of welding process parameters, the cleaness of the groove and the protection degree of weld pool.
Type, shape and distribution of non-metallic inclusions are linked to the welding methods and the chemical composition of the welding, Flux and weld metal.
Post time: Dec-30-2019