Effect of heat treatment on the strength of wear-resistant plates

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Effect of heat treatment on the strength of wear-resistant plates
Wear-resistant plate is a very important metal material with high strength, good ductility and good welding performance. The strength of traditional wear-resistant plates is mainly related to its carbon content and alloy element content. It is known that precipitation strengthening and grain refinement are also important means to improve the strength of metal materials, but so far few people have studied its role in wear-resistant plates. The role of alloying elements Nb, V, and Ti in grain refinement and precipitation strengthening in high-strength steels makes them widely used. In alloys containing Nb, V, and Ti elements, the precipitation of carbonitrides under controlled rolling conditions can not only prevent the recrystallization growth of austenite grains, but also effectively prevent the growth of large deformation austenite grains. The dispersion strengthening function of the carbonitride precipitated phase greatly improves the strength and toughness of the wear-resistant plate. The reason why Ti is selected as the added element is because the precipitation phase of Ti has the greatest precipitation strengthening effect under the same precipitation amount and the same precipitation size. The magnitude of the strengthening effect is controlled by the number, distribution and size of TiC particles. The purpose is to obtain as much 1 to 5nm TiC precipitate phase as possible through controlled rolling, controlled cooling and later heat treatment, on the one hand to provide higher precipitation strengthening On the other hand, it plays the role of refining the grains and produces a fine-grain strengthening effect, which not only improves the strength, but also helps to improve the toughness. Based on this design idea, the structure of the Ti microalloyed wear-resistant plate was characterized. By analyzing the contribution of each component to the strength, the main strengthening mechanism of the experimental steel and the strengthening effect of the microalloying element Ti were clarified.

The chemical composition of the experimental wear-resistant plate is 0.2C1.5Mn0.16Ti30×10-6N. The experimental steel was cast into a mold after vacuum smelting. The ingot was kept at 1250°C for 2 hours and then forged at 1200-850°C into a 30 mm × 200 mm × 100 mm forging billet. The forged billet was then kept at 1250°C for 2 hours in a muffle furnace. After soaking, it was finally rolled into a 7mm thick plate through 4 passes of deformation on a reversible rolling mill in the laboratory, with a total reduction of 76%. The final rolling temperature is 850~880℃, and quenching cooling method is used after rolling. The quenched steel plate after rolling was then placed in a furnace at 550°C for 3 hours to study the effect of the tempering heat treatment process on Ti precipitation in the steel. After tempering treatment, the wear-resistant plate is placed in a furnace at 880°C for 5 minutes and then quenched to room temperature so that the steel obtains a martensitic structure.

After Ti is added, the strength of the wear-resistant plate is improved due to the precipitation strengthening effect provided by the formation of TiC. The tempering and reheating process can promote the formation of finer TiC precipitates of 1 to 10 nm and refine the grains to 8 μm. The combination of precipitation strengthening and grain refinement further improves the yield strength of the wear-resistant plate. The fine TiC precipitates in the sample after reheating can provide a strength increase of 188MPa, which is greater than the 80MPa provided by fine-grain strengthening.