Weld overlay cladding process: Weld overlay Cladding is the process of welding a layer of wear-resistant, corrosion-resistant, heat-resistant metal on the surface or edge of a workpiece.
It has significant economic benefits for improving the service life of parts, rational use of materials, improving product performance and reducing costs. Cladding work and working conditions are very complex, and the right electrode must be selected according to different requirements.
Different workpieces and cladding rods are subject to different cladding processes to achieve satisfactory cladding results.
The most common problem encountered in cladding is cracking, and the main ways to prevent cracking are.
1.Preheat before welding, control the temperature between layers, slow cooling after welding.
2. Stress relief heat treatment after welding.
3. Avoid multi-layer cladding and use low hydrogen type cladding welding rod.
4. If necessary, the overlay layer and the base material between the overlay layer and the transition layer (with low carbon equivalent, high toughness of the welding rod). There is a direct relationship between cracking and the amount of alloying elements in the weld carbon of the workpiece and the weld metal, so the preheat temperature is generally estimated based on the carbon equivalent of the weld rod used.
The carbon equivalence 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 (%) Preheating temperature Carbon equivalent (%) Preheating 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 and austenitic stainless steels, without preheating.
High alloy steel preheating temperature greater than 400°C.
The cladding effect refers to the hardness, abrasion resistance and heat resistance of the weld layer, the performance of which is related to the following factors.
1. Welding current size, arc length. The high current and long arc make the alloying element susceptible to burnout and, conversely, favor the alloying element transition.
2. Preheating temperature, slow cooling conditions determine the quality of the cladding layer.
3. Some cladding metals can be heat treated with different methods to obtain different hardness.
The hardness and chemical composition of the cladding layer refers to cladding metals that are clad in more than three layers.
