The full-length heat treatment is performed in order to achieve higher operational properties (hardness, cold resistance, corrosion resistance etc.). The transportation of plain-end pipe from the warehouse of Manufacturing Section to Heat Treatment Section is performed by truck or transfer tables/cars.
The pipe goes through the incoming inspection (1), after that pipe (lot by lot) goes to the quenching furnace where it is heated (up to 1000 °С) and hardened (2). The equipment enables us to conduct the heat normalizing, in addition, pipe goes directly to the cooling operation passing by the quenching machine.
After preheating, pipe goes to the quenching machine of a sprayer type (3). After quenching, the specimens are taken in order to check the quality of quenching (4). At the Heat Treatment Section, besides the spray quenching, there is the equipment for quenching in the bath. Quenching the pipe from two sides (inside and outside the pipe) ensures a higher through-wall uniformity of quenching and a better hardenability of thick-wall pipe.
The quenched pipe goes to the tempering furnace (5) to acquire the final mechanical properties and stress relief. The tempered and normalized pipe is straightened at the straightening machine (6) and goes to the transverse rolling table where it goes through cooling in the air up to the ambient temperature (7).
Heat-treated pipe shall be re-tested and re-accepted (hydrostatic testing, NDE, sampling for mechanical testing and chemical composition analysis) (8). At the Heat Treatment Line, the equipment of the finishing section is installed immediately after the cooling table and that enables us to eliminate the unnecessary handling operations from one section to another. After checking, the heat-treated pipe is shipped to the customer or goes through further finishing (9). Pipe that failed to meet the normative documentation requirements goes to the rejection pocket.