Basic Information on Weldability and Technological Advice

introduction of technological recommendations for welding of cast iron

Basic information on weldability and technological advice.

Welding heating and subsequent cooling so alter the structure and properties of iron in the zone of fusion and heat affected zone, which is a defect-free welds with the required level of properties is very difficult. In this regard, iron refers to materials having a bad technology weldability. However, welding of cast iron has a very wide distribution as a means to fix the marriage of cast iron castings, cast iron repair products and sometimes in the manufacture of structures. High-grade weld should at least have the necessary level of mechanical properties, density (impermeability) and satisfactory workability (handled cutting tool). Depending on the conditions of the compound may be brought to him and other requirements (eg, one-color, heat resistance, etc.).

Reasons for the difficulty in obtaining high-quality welds, the following.

1. Cooling rate of weld metal and heat affected zone corresponding to the thermal cycle of welding, lead to bleaching of iron, ie, the appearance of areas with secretions cementite one form or another in varying amounts. The high hardness of bleached areas of practice makes it impossible to handle cast iron cutting tool.

2. Due to the uneven heating of the local metal welding stresses arise, which are due to the very low ductility of cast iron lead to the formation of cracks in the weld and heat affected zone. The presence of bleached areas with high density (7,4-7,7 g/cm3) than gray cast iron (6,9-7,3 g/cm3), creates additional structural stresses that contribute to cracking.

3. Intensive gas evolution from the weld pool, which continues at the stage of crystallization may lead to the formation of pores in the weld metal.

4. Increased fluidity of cast iron makes it difficult to hold the molten metal from leaking and forming a seam.

5. The presence of silicon, and sometimes other elements in the metal promotes the formation of the weld pool on the surface of refractory oxides, leading to the formation of fusions.

See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color