Dongguan Rongteng Mold Steel Business Department

-Plate -Bar -Round ball graphite cast iron is referred to as ductile iron. It is obtained by adding a certain amount of nodularizing agent and inking agent to the molten iron before casting to promote the crystallization of spheroidal graphite. Compared with steel, except for slightly lower plasticity and toughness, it has almost all other properties. It is an excellent material that combines the advantages of steel and cast iron. It is widely used in mechanical engineering. Special performance cast iron. This is a cast iron with certain characteristics. It can be used according to different uses. Divided into wear-resistant cast iron, heat-resistant cast iron, corrosion-resistant cast iron, etc. Most of them belong to alloy cast iron and are widely used in machinery manufacturing
Cast iron - heat treatment process
. Stress relief annealing. Due to the uneven wall thickness of the casting, effective stress and structural stress will be generated during the heating, cooling and phase transformation processes. In addition, large parts are prone to residual stress after machining. All these internal stresses must be eliminated. The usual heating temperature for stress relief annealing is ~°C and the holding time is ~~ and then furnace cooling (gray iron) or air cooling (ductile iron). Using this process can eliminate ~% of the internal stress of the casting without changing the cast iron structure. If the temperature exceeds ℃ or the holding time is too long, it will cause graphitization and reduce the strength and hardness of the casting.
.High-temperature graphitization annealing to eliminate cast iron white spots
When castings are cooled, white spots often occur on the surface layer and thin sections. The white structure is hard and brittle, has poor processing performance and is easy to peel off. Therefore, annealing (or normalizing) must be used to eliminate the white structure. The annealing process is: heating to -℃, keeping warm, then cooling the furnace to -℃ and then leaving the furnace for air cooling. During the high-temperature holding period, high-temperature cementite and eutectic cementite decompose into graphite, and during the subsequent cooling process, secondary cementite and eutectoid cementite also decompose and graphitize. Due to the decomposition of cementite, the hardness decreases and the machinability is improved.
.Normalizing of ductile iron
The purpose of normalizing ductile iron is to obtain the pearlite matrix structure and refine the uniform grain structure to improve the mechanical properties of the casting. Sometimes normalizing is also the structural preparation for surface quenching of ductile iron. Normalizing is divided into high-temperature normalizing and low-temperature normalizing. The high-temperature normalizing temperature generally does not exceed ~℃. The low-temperature normalizing temperature is generally heated to the co-folding temperature range ~℃. After normalizing, four people are generally required to handle it to eliminate the internal stress generated during normalizing.
The above information is provided by Dongguan Rongteng Mold Steel Co., Ltd. If you need to order, please call us for consultation and negotiation!