Influence of Heat Treatment on the Mechanical Properties of Rebar Products

The purpose. Investigation of the effect of heat treatment on the mechanical properties of low-carbon and low-alloy reinforcing steels.

Methods. Three batches of samples of reinforcing steels of the following grades were selected as objects of research: low-carbon steel St5, low-alloy steel 25G2S and 30XG2S. The first batch of samples with a length of 250 mm was subjected to furnace heating (muffle furnace), quenching and furnace tempering at various temperatures. The second batch of samples – rods with a length of 1300 mm were subjected to furnace heating (tube furnace), and then quenched and cut into samples with a length of 250 mm. One part of the samples was subjected to furnace tempering, the otherto electric start-up. The third batch of samples was made from rods with a length of 2000 mm. After furnace heating (tube furnace), they were quenched and electro-fired, and then cut into samples with a length of 250 mm. After furnace heating, samples with a length of 250 mm were quenched in water from temperatures of 850, 880, 900, 910, 930 and 950°С.

Results. Mechanical tests were carried out. The regularities of changes in the characteristics of mechanical properties are revealed: time resistance, yield strength, true elongation stress of the initial working length. It is established that the optimal tempering temperature of the reinforcing bar for all tested steels is 900 ±20°С.  It is shown that the electric start-up provides better mechanical properties, in comparison with furnace tempering in the temperature range of 250400°С. It is revealed that the 30XG2S, 25G2S and St5 rod fittings, strengthened by drawing during heat treatment, as well as high-strength steel wire can be subjected to electric heating at 400 ℃ without significant influence on the strength of the steel.

Conclusion. The results obtained can be used to determine the behavior patterns of different types of ingot, powder, and composite materials with high dispersion in the phase and structural components under different conditions and states.

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