Recommendations on Alleviating the Saturation of Slab Metal by Hydrogen Based on the Results of Physical Modeling

Resumo

This article discusses reducing the hydrogen content of low-alloy steels for oil and gas line pipe and shipbuilding and improving these steel’s ductility. In addition to the saturation of the liquid steel with hydrogen, it is also possible for the steel’s hydrogen content to increase after it has solidified. For example, this could occur when slabs are heated in furnaces that are fired with certain types of fuel and have different atmospheres. When a furnace is fired with coke-oven gas and the internal pressure in the furnace is positive, the high hydrogen content of this gas helps saturate the steel with hydrogen. That in turn increases the steel’s contents of discontinuities and nonmetallic inclusions, which leads to the formation of structural stress concentrators and a decrease in ductility. Results are presented from physical modeling of the saturation of pipe steel with hydrogen during the heating of slabs made of the above-indicated types of steel. Aspects of the steel’s saturation in different furnaces atmospheres are examined, the degree of contamination of the steel by hydrogen is determined, and the formation of its structure and hydrogenation are studied. It is definitively established that an increase in the moisture content of the furnace atmosphere increases the degree of saturation of the steel by hydrogen. Recommendations are given on alleviating the hydrogen saturation of steel. It is noted in particular that it is necessary to replace coke-oven gas by natural gas for the slab-heating operation, shorten the heating time to an acceptable extent, and establish the correct values for gas pressure and the gas/air ratio in the furnace.