Augmenter la dureté des coudes pressés à chaud

Quenching is a heat treatment process where the hot-pressed elbow is heated above its critical temperature, held at that temperature for a specific period, and then rapidly cooled by immersing it in a quenching medium to achieve a sudden temperature drop. This rapid cooling, at a rate exceeding the critical cooling rate, results in an unbalanced microstructure primarily composed of martensite. Quenching enhances the strength and hardness of steel but reduces its plasticity. Common quenching media include water, oil, alkaline water, and salt solutions.

Normalizing is a heat treatment process in which the hot-pressed elbow is heated above its critical temperature to transform it entirely into homogeneous austenite, followed by natural cooling in air. This process eliminates the network cementite in hypereutectoid hot-pressed elbows and refines the grain structure in hypoeutectoid elbows, improving their overall mechanical properties. Normalizing is a cost-effective alternative to annealing for components with less stringent requirements.

Tempering involves reheating a previously quenched hot-pressed elbow to a specific temperature and then cooling it using a controlled method. The purpose of tempering is to relieve internal stresses induced by quenching, reduce hardness and brittleness, and achieve the desired mechanical properties. Tempering is classified into high-temperature, medium-temperature, and low-temperature tempering. It is often used in conjunction with quenching and normalizing.

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The heat treatment process combining quenching followed by high-temperature tempering is known as quenching and tempering. High-temperature tempering is performed within the range of 500-650°C. This treatment significantly adjusts the steel's properties, resulting in a good balance of strength, plasticity, and toughness, along with excellent comprehensive mechanical performance.

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To prevent dimensional and shape changes in precision measuring tools, molds, or components during prolonged use, aging treatment is often employed. After low-temperature tempering (at 150-250°C) and before finishing, the workpiece is reheated to 100-150°C and held for 5-20 hours. This treatment, aimed at stabilizing the quality of precision parts, is called aging. Aging treatment is particularly crucial for steel components operating under low-temperature or dynamic load conditions to eliminate residual stresses and stabilize the microstructure and dimensions of hot-pressed elbows.

Annealing is a heat treatment process where the hot-pressed elbow is heated to a specific temperature, held at that temperature for a period, and then slowly cooled. This involves heating the steel to a temperature where phase transformation occurs or partially occurs, followed by slow cooling after holding. The purpose of annealing is to eliminate microstructural defects, homogenize the composition, refine the grain structure, improve mechanical properties, and reduce residual stresses. It also lowers hardness, enhances plasticity and toughness, and improves machinability. Annealing serves to eliminate and improve microstructural defects and internal stresses from previous processes while preparing the component for subsequent operations. Thus, annealing is classified as a semi-finished product heat treatment, also known as preliminary heat treatment.