1. Different leather texture and color, welding spots
Cause 1 : The material of the welding area is different from the original material.
Corresponding measures: Use welding wire that is consistent with the base material, preferably special welding wire used in steel mills; secondly, saw the material from the base material; or use universal welding wire.
Cause 2 : The heat treatment of the welding area is different from that of the original area, and the structure changes.
Corresponding measures: Tempering treatment is carried out after welding to make the grain structure consistent; important parts are strictly operated according to the steel plant’s welding process.
2. Cracks and deformation
Cause: When the parts are subjected to argon arc welding, they are locally overheated, resulting in different temperatures in different areas of the parts and generating thermal internal stress; after welding, the area adjacent to the welding area actually undergoes quenching, and this area is very hard and prone to cracking.
Note:
1. The larger the welding area, the greater the internal stress generated.
2 The higher the carbon and alloying element content, the worse the weldability . If it exceeds 0.4%, preheating and post-heating are required.
3. The higher the hardness of a part, the greater its original internal stress and the easier it is to crack.
4. The sharper the shape, the easier it is for the part to crack.
Corresponding measures: Preheat the whole and perform tempering after welding.
Note:
For large inserts, in order to avoid stress caused by preheating (even if the whole part is preheated, the temperature of the part is from the outside to the inside, which may still cause internal stress) , When preheating, keep it warm at the intermediate temperature for a while before heating it up again.
3. Sand holes and pores
Cause 1 : Welder technical problems, gaps in weld point accumulation.
Corresponding measures: Use welding rods as much as possible ; Be careful and meticulous when welding.
Cause 2 : When nitrided parts are welded, nitrogen molecules vaporize and form pores due to heating.
Corresponding measures: welding before nitriding ; Grind off the nitride layer.
Cause 3 : There are impurities on the welding surface and the welding rod is not dried as required, resulting in gas generation during melting.
Corresponding measures: Before welding, the grease , coating , processing lubricant and oxide film on the surface of the weldment must be removed ; the welding rods must be dried as required.
4. Hardness reduction and local annealing
Cause: The change in temperature during welding causes heat treatment on the parts, resulting in changes in the material of the parts.
Corresponding measures: Follow the welding process provided by the steel supplier.
5. Other Suggestions
Basic knowledge of steel heat treatment: 1. When steel is subjected to heat treatment such as nitriding or overall preheating welding, be careful that the temperature must not exceed the tempering temperature of the steel before leaving the factory, otherwise the hardness of the steel will be reduced and deformation of the parts will be caused.
P20 overall preheating recommended general heat treatment process: preheat to 350-450 degrees and then weld, temper at around 550 degrees (for welding of important molds, the heat treatment process needs to be strictly controlled according to the manufacturer’s recommendations).
In order to prevent repeated sand holes during polishing after welding, a welding flaw detector can be used to check first after welding. The problematic areas can be dug up and then welded to avoid repeated sand holes.
Welding of beryllium copper: Beryllium copper is particularly susceptible to oxidation. It must be welded immediately after the oxide film is removed with a sharp brush or sandblasting. The hardness of the welded area and its surrounding areas will decrease. If the hardness decrease is unacceptable, re-heat treatment is required.
Post time: Jun-08-2025
