Preventive Measures for Crack Defects of High Speed Tool Steel

High-speed tool steel is a high-end…
High-speed tool steel is a high-end tool steel with good wear resistance and toughness. However, if you do not pay attention to it in production, defects such as cracks will easily occur, resulting in scrap. This is mainly because:

1. Low plasticity. High-speed steel has many alloying elements, especially S, Ph, Sn and other impurity elements, which tend to weaken the inter-grain bonding force and reduce the plasticity.

2. Large deformation resistance. The alloy composition of high-speed steel is complex, the recrystallization speed is slow, the temperature is high, and it has high deformation resistance at the deformation temperature.

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3. Narrow forging temperature range. High-speed steel heating temperature is too high, it is easy to overheat, over-burn, stop forging temperature is too low, it will produce coarse-grain phenomenon, theoretically high-speed steel forging temperature range is very narrow, generally 200-280 ℃.

4. Poor thermal conductivity. The thermal conductivity of high-speed steel is much lower than that of carbon steel. It needs to be heated slowly at 600-900℃, otherwise it will cause temperature stress and cause metal brittleness.

The relevant preventive measures are:

1. Strictly control the metal content of high-speed steel raw materials. For example, the tin content must be strictly controlled below 0.08%.

2. It is stipulated that the ingot must be peeled or cleaned by the grinding wheel before heating forging to improve the performance of high-speed steel processing.

3. Control the heating temperature, holding time and deformation temperature of high-speed steel, and adopt multi-fire forging.

4. When the slab is drawn, lightly tap it at the beginning, and increase the amount of deformation after the as-cast structure is properly broken and the plasticity is improved. When free forging is long, the deformation of each fire is controlled within 2-4 times, and it should be sent from the head to the tail.

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5. When forging high-speed steel, reduce the number of continuous rotation deformations in the same part of the raw material, and specify less than 8 times.