Coating process: heat treatment process of cast iron for machine tool bed

Core tip: heat treatment generally does not change the shape of the workpiece, but gives or improves the performance of the workpiece by changing the internal microstructure of the workpiece, or changing the chemical composition of the cast iron platform and the surface of the machine tool The following describes the heat treatment process of cast iron for machine tool bed First, the multi temperature quenching of nodular iron can obtain high strength and good plasticity and toughness The selection of heating temperature for multi temperature quenching is mainly to make the original structure all a-turn, without residual F, and at the same time to avoid grain growth of A The heating temperature is generally 30 ~ 50 ℃ above Afc1, and the isothermal treatment temperature is 0 Paint knowledge how about Akzo Nobel Powder Coating Recommended introduction: powder coating is a kind of coating with different form from general coating, which is in powder form It is a new type of coating, because of its own advantages and more and more known by people Let's introduce Akzo Nobel Powder coating Akzo Nobel Powder coating is a cost-effective coating solution, which can be applied to different kinds of products After the treatment of static electricity and fire baking, a tough and durable coating surface will be formed, with the least impact on the environment Since the introduction of this technology, powder coating has been able to continue to maintain the Coating House News: heat treatment generally does not change the shape of the workpiece, but gives or improves the performance of the workpiece by changing the internal microstructure of the workpiece, or changing the chemical composition of the cast iron platform and the surface of the machine tool The following describes the heat treatment process of cast iron for machine tool bed First, the multi temperature quenching of nodular iron can obtain high strength and good plasticity and toughness The selection of heating temperature for multi temperature quenching is mainly to make the original structure all a-turn, without residual F, and at the same time to avoid grain growth of A The heating temperature is generally 30 ~ 50 ℃ above Afc1, and the isothermal treatment temperature is 0 ~ 350 ℃ to ensure that the lower bainite with comprehensive mechanical properties can be obtained After austempering, σ B = 1200 ~ 1400MPa, α k = 3 ~ 3.6j/cm2, HRC = 47 ~ 51 However, it should be noted that an additional tempering process should be added after isothermal quenching Second, stress relief annealing, because of the uneven wall thickness of the casting, will produce effect force and structure stress in the process of heating, cooling and transformation In addition, the internal stress of large parts is easy to remain after machining, and all these internal stresses must be eliminated The general heating temperature of stress relief annealing is 500-550 ℃, holding time is 2-8h, then furnace cooling (gray iron) or air cooling (nodular iron) This process can eliminate 90-95% of the internal stress of the casting, but the structure of the cast iron does not change If the temperature exceeds 550 ℃ or the holding time is too long, it will lead to graphitization and reduce the strength and hardness of castings Thirdly, high temperature graphitization annealing is used to eliminate the white hole in the casting When the casting is cooled, white hole often appears in the surface layer and thin section White mouth structure is hard and brittle, processing performance is poor, easy to peel off Therefore, annealing (or normalizing) must be used to eliminate the white structure The annealing process is: heating to 550-950 ℃ for 2-5h, followed by furnace cooling to 500-550 ℃ and then air cooling During the high temperature holding period, the free high cementite and eutectic cementite decompose into graphite and a, and the secondary cementite and eutectoid cementite decompose and graphitization takes place in the subsequent cooling process Due to the decomposition of cementite, the hardness of cementite decreases, which improves the machinability The purpose of normalizing is to obtain the pearlite matrix structure, refine the grain and even the structure, so as to improve the mechanical properties of the casting Sometimes normalizing is also the preparation of surface quenching on the structure of nodular iron, and normalizing includes high temperature normalizing and low temperature normalizing The high temperature normalizing temperature is generally no more than 950 ~ 980 ℃, and the low temperature normalizing temperature is generally heated to 820 ~ 860 ℃ After normalizing, generally four people are needed to deal with it to eliminate the internal stress produced during normalizing Fifthly, the quenching and tempering of nodular iron; in order to improve the mechanical properties of nodular iron, generally, the casting is heated to 30 ~ 50 ℃ above Afc1 (Afc1 represents the end temperature of a formation during heating), and after heat preservation, it is quenched into oil to obtain martensitic structure In order to reduce the residual stress after quenching, tempering should be carried out after quenching The structure of low temperature tempering is tempering martensite plus residual bainite plus spheroidal graphite This kind of structure has good wear resistance and is used for parts requiring high wear resistance and high strength After tempering at 350-500 ℃, the microstructure is tempered troostite and spheroidal graphite, which is suitable for thick parts with good wear resistance, stability and elasticity The high temperature tempering temperature is 500-60d ℃, and the microstructure after tempering is tempered Soxhlet plus spheroidal graphite, which has a good combination of toughness and strength, so it is widely used in production Sixth, chemical heat treatment: for castings requiring wear-resistant, oxidation-resistant and corrosion-resistant surface, chemical heat treatment process similar to steel can be adopted, such as gas soft chlorination, chlorination, boronizing, sulfurizing and other treatment This process is related to the use effect and efficiency of machine tools, so we should pay more attention to it Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,