Harness, structure, residual stress and tensile strength at high temperature were tested of preheated or post-heated weld metals using four kinds of martensitic and two kinds of austenitic hard facing electrodes. And abrasion resistance and crack sensitivity were also examined of merchant bar roll caliber welded with these electrodes.
The following are the results obtained:-
1. It seems that the wear resistance of hot roll caliber has mainly a correlation with hot tensile strength of the material, and as to the wear resistance the austenitic steel is the best, and of the martensitic steel the higher the carbon content is, the better.
2. For martensitic steel the residual stress can fairly be decreased by preheating at 300°C and post-heated at 500°C. And insufficient annealing may result in cracks or break of rolls. For austenitic steel, preheating and post-heating have small effects, and there is a danger of embrittling rolls by carbide precipitation during annealing.
3. Hardness and wear resistance of martensitic steel is influenced to no small degrees by preheating temperature, while it is easy to get uniform hardness for austenitic steel.
4. Austenitic steel is liable to cause severe heat checking cracks.
5. Expected saving of rolling cost cannot be attained by manual arc welding due to the high labor cost, and for this purpose mechanical welding is preferred for economy.
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