Structural Transformations in the Heat Affected Zone during Welding of Cast Iron

gives a graphical scheme to see the thermal effect on the weld, the temperature distribution

Structural Transformations in the Heat Affected Zone during Welding of Cast Iron

To assess the influence of the thermal cycle of welding on the structure and properties of different zones of welded joints consider the state diagram of the pseudobinary Fe - C - Si, linking it with the distribution of temperature in the weld and heat affected zone (Fig.). The seam is a metal was completely melted. Depending on the cooling rate structure it will be a white or gray cast iron with different amounts of structural and free carbon.

Section 1 (incomplete fusion) is characterized by the presence in it of both liquid and solid phases. The solid phase is austenite with maximum carbon content (up to 2.14%). After rapid cooling of the liquid phase forms a white iron in austenite areas, the formation of martensite.

Section 2 is limited to the eutectic and eutectoid temperatures. Its structure is largely dependent on the initial structure of cast iron and can consist of austenite and cementite or austenite and graphite (depending on the cooling rate and composition of pig iron) With the rapid cooling of the metal base structure becomes hardened.

Section 3 (incomplete recrystallization) due to rapid heating and short duration of stay of the metal in the temperature range of ferrite - the basis of the structural components of cast iron at room temperature - do not have time to completely dissolve. After cooling in this area may experience some grain refinement. With the rapid cooling of the metal base may become partially hardened.

Section 4 is the part of the heat-affected zone, which was heated to 500 ° C to a temperature of c 1 . At long stay in this temperature range may occur due to partial graphitization of the cementite decomposition and spheroidization of carbides. However, in the heat of welding in the area marked structural changes are observed.

Section 5 is characterized by the initial structure of welded iron.

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