Surfacing is welding the surface or edge of the workpiece with a layer of wear-resistant, corrosion-resistant, heat-resistant and other properties of the metal layer welding process.
To improve the service life of parts, the rational use of materials, improve product performance, reduce costs have significant economic benefits. Surfacing work and working conditions are very complex, surfacing must be based on the different requirements of the appropriate selection of electrodes.
Different workpieces and welding electrodes to use a different surfacing process, in order to obtain satisfactory surfacing effect.
The most common problem encountered in welding is cracking, the main method to prevent cracking is:
1. preheating before welding, controlling the temperature between layers, slow cooling after welding.
2. after welding stress relief heat treatment. This article by Jiangxi Jinyang Steel Co., Ltd. (New Steel cold and hot roll distribution center) to provide.
3. to avoid multi-layer surfacing, the use of low-hydrogen surfacing electrode.
4. if necessary, surfacing layer surfacing between the surfacing layer and the base metal (low carbon equivalent, high toughness of the electrode). Cracking and welding of weld metal and weld metal is directly related to the amount of alloying elements, so the preheat temperature is generally based on the electrode used to estimate the carbon equivalent.
Carbon equivalent formula is as follows:
Ceq = C + 1 / 6Mn + 1 / 24Si + 1 / 5Cr + 1 / 4Mo + 1 / 15Ni
This estimation formula is suitable for low, medium and high carbon steel and low alloy steel materials.
|Carbon equivalent (%)||Preheat temperature||Carbon equivalent (%)||Preheat temperature|
|≤0.40||above 100 ℃||≤0.70||above 250 ℃|
|≤0.50||above 150 ℃||≤0.80||above 300 ℃|
|≤0.60||above 200 ℃||≤0.90||above 350 ℃|
High manganese steel and austenitic stainless steel, without preheating.
High alloy steel preheating temperature is greater than 400 ℃.
Surfacing effect refers to the hardness of the weld layer, wear and heat and other properties, the performance level of the following factors:
1. Welding current size, Short arc length. Large current, Long arc, Easy to burn alloying elements, On the contrary, Beneficial alloying element transition.
2. Preheat temperature, Slow cooling conditions determine the quality of surfacing.
3. Some of the surfacing metal with different heat treatment methods can get different hardness.
Surfacing layer hardness and chemical composition refers to surfacing over three layers of surfacing metal.