Mutsuo Nakanishi

The development of normalized and tempered A1-B treated 1 1/4Cr-1/2Mo steel plate

Strength and toughness of normalized and tempered 1 1/4Cr-1/2Mo steel plate decrease to a certain extent after stress relief annealing during fabrication. The addition of Al and small amounts of B increases the hardenability of 1 1/4Cr-1/2Mo steel for normalizing treatments and improves the strength and toughness so that enlargement of stress relief annealing condition up to 720°C × 50 h (temper parameter 21.5 × 103) is possible for plate thicknesses of 200 mm. The increase of hardenability during normalizing by a very slight amount of total boron is due to the redistribution of boron atoms during slow cooling. Such behavior of boron atoms is explained by the Gibbs absorption equation.

Cold cracking susceptibility of girth welding for arctic grade line pipe

High strength line pipe steels require not only good low temperature toughness but also excellent weldability. The use of cellulose welding electrodes has introduced the possibility of cold cracking due to the introduction of hydrogen. This report deals with the cracking susceptibility of line pipe steels. Test results make it possible to establish a diagram to predict and determine the welding conditions for crackfree girth welds. This diagram contains an emperical parameter, Pw, which includes the alloying composition of the steel, the effective hydrogen concentration at the root of the weld, and the restraining stress. When Pw is plotted against the cooling time (the time to cool from the weld condition to 100 °C), a distinct separation is seen between cracked and crack-free weld joints. Thus, the Pw parameter has utility.It is found that crackfree girth welds can be made in line pipe steels if the equivalent carbon parameter is sufficiently low. References are given to pertinent literature from the International Institute of Welding (ILW).