Temperature Selection of warm forging
When selecting the warm forging temperature, the following factors should usually be considered.
(1) The effect of temperature on the flow stress and plasticity of the material
Generally, the temperature with small flow stress or higher than the temperature with large flow stress is selected. For metals with blue brittle temperature zone, warm forging temperature in this temperature range should be avoided.
(2) The problem of severe oxidation of steel
Generally, the oxidation phenomenon of steel will worsen when the temperature exceeds 800 ° C, so the warm forging temperature should be below 800 ° C. Rapid heating or coating the surface of the blank with solid lubricant can prevent the oxidation of the blank during heating.
(3) The effect of warm forging temperature on product performance
As the warm forging temperature increases, the toughness and plasticity of the product will increase, but the strength will decrease. At a certain temperature, as the degree of deformation increases, the strength of the product will increase and the plasticity will decrease. When the temperature is between 200°C and 400°C, the mechanical properties of warm extruded steel are equivalent to those of cold extruded steel with the same deformation. When the temperature is between 400°C and 800°C, the mechanical properties of warm extruded steel are 1.1 to 1.5 times those of annealed steel. [2]
Applications
(1) Stainless steels, alloy steels, bearing steels, and tool steels that are significantly hardened or have a large deformation resistance when cold forged.
(2) Materials with low plasticity and prone to cracking when cold formed, such as aluminum alloy LC4, copper alloy HPb59-1, and titanium alloys.
(3) Materials that are difficult to cold work, but oxidize significantly and absorb hydrogen when hot worked, such as titanium, molybdenum, and chromium.
(4) Parts with complex shapes that are not suitable for cold forging.
(5) Due to the large deformation or large part size, the existing equipment capacity is insufficient for cold forging.
(6) Facilitate the organization of continuous production.
Warm forging is a process of forming parts under temperature conditions where the deformation resistance of a metal material decreases and its plasticity increases after the temperature of the metal material increases, but the surface is not yet severely oxidized. The deformation temperature has an important effect on the plasticity of metals. For most metals, plasticity increases as the temperature increases, but this increase is not linear. In certain temperature ranges during the heating process, brittle areas frequently occur due to excessive phase precipitation or phase change, which reduces the plasticity of the metal. Under normal circumstances, when the temperature increases from the thermodynamic temperature of zero to the melting point, three brittle areas may appear: low-temperature brittle area, intermediate-temperature brittle area, and high-temperature brittle area.
