BORON-CONTAINING STEELS AND PROCESS FOR THEIR ANNEALING

摘要

The invention relates to boron-containing steels and a process for the annealing of steel products having boron contents of up to 200 ppm in the temperature range of between 850 and 1050.degree.C. The characterizing feature of the invention is that the products are annealed in the state of equilibrium in a non-oxidizing gaseous atmosphere with a boron potential supplied by a pulverulent boron oxide source having a value such that the products retain or adsorb their boron content. The boron source is quantitatively about 100 g of B2O3 per m3 of annealing space. In an annealing gas atmosphere mainly consisting of hydrogen the steam partial pressure can be adjusted at atmospheric pressure the presence of B2O3 to the required boron activity within the range of between 10-3 to 10-5. The products can also be simultaneously case hardened during annealing. The case hardening agent can be mixed with pulverulent boron oxide as the boron source.