METHOD OF THE THERMAL TREATMENT OF THE CONNECTING ELEMENTS OF THE PIPELINES MADE OUT OF THE LOW-ALLOY STEEL Russian patent published in 2007 - IPC C21D9/50 

FIELD: ferrous metallurgy; methods of the thermal treatment of the connecting elements of the pipelines made out of the low-alloy steel.

SUBSTANCE: the invention is pertaining to the field of ferrous metallurgy, in particular, to the engineering process of the thermal treatment of the pipes made out of the low-alloy constructional steel and may be used at manufacture of the welded connecting elements and the assemblies of the main pipelines and the field pipelines of the large diameter (up to 1420 mm) of the facilities of the petroleum industry and the natural gas industry transporting the non-aggressive petroleum, the oil products and the gas. For improvement of reliability of the connecting elements at simultaneous reduction of the power inputs conduct simultaneously normalization and hardening with heating in the austenitic area up to_{Ас3+80-100°С (940-960°С), aging at this temperature within 1 hour and cooling in the water with application of the water bubbling by the compressed air, the backing of the connecting elements within the interval of the temperatures of 300±10°С, their aging at this temperature within 1 hour with the further cooling in the open air. The connecting elements of the pipelines have the mechanical properties corresponding to the К60 strength class and the heightened impact elasticity at the negative temperatures (-60°C).}

EFFECT: the invention ensures the improved reliability of the connecting elements at simultaneous reduction of the power inputs.

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