Cast iron

Cast iron production in addition to the proper choice of ingredients to be gifted to the organization, the heat treatment is further adjust and improve the matrix structure to enhance the performance of a cast iron important ways. Iron and steel heat treatment of the heat being buried in common, but also different. Cast iron heat treatment in general can not improve the original graphite in the shape and distribution. The grey cast iron, because flake graphite caused by the effects of stress concentration of iron play a leading role in the storm, the gray iron impose the enhanced effect of heat treatment are far less ductile iron and steel as significant. Guyou iron main heat treatment process for annealing, normalizing, and so on. For ductile iron, as a spherical graphite, the base of the fragmented role greatly reduced, through heat treatment will be based organizations to fully play its role, which can significantly improve the mechanical properties of the ball. Therefore, ductile iron like steel, its heat treatment process are annealed, normalizing, conditioning, multi-quenching, induction heating and hardening the surface, such as chemical heat treatment.

The cast iron heat treatment process:

1. Annealing elimination of stress due to uneven casting thickness, heating, cooling and phase transition process will produce stress and stress. Also in large parts of its processed within easy residual stress, all of which are necessary to eliminate stress. Annealing is usually to stress the heating temperature of 500 ~ 550 ?鏍╫lding time for 2 ~ 8 h, and then furnace cold (gray iron) or air-cooled (ductile iron). Using this technology can eliminate the stress of casting 90 to 95 percent, but the cast iron organization does not change. If the temperature exceeds 550 ?鏍痳 holding time is too long, it will cause graphite, to reduce the casting strength and hardness.

2. Elimination of the high-temperature casting white graphite annealing casting cooling, surface and thin cross sections, often produce white. White hard and brittle organizations, poor processing performance, easily peeling off. Annealing to be used (or normalizing) approach to the fight against white organizations. Annealing Process: heated to 550-950 ?鏍﹏sulation 2 ~ 5 h, then cold to furnace 500-550 ?鏍磑air-cooled. In high-temperature insulation, high outbound cementite and eutectic cementite divided into graphite and A, in the subsequent cooling process for the second cementite and eutectoid cementite also decomposition, in the process of graphite. As cementite of decomposition, resulting in hardness decline, thereby enhancing the cutting of.

3. Ductile iron is the iron fireballs normalizing the purpose is to be pearlite matrix organization, and refined grains, uniform organizations, to enhance the mechanical properties of casting. Sometimes the ball is normalizing iron surface hardening in the organization of preparation, normalizing at low temperature and high temperature normalizing normalizing. High-temperature normalizing temperature generally no more than 950 ~ 980 ?娆爈ow-temperature heat to a total of normalizing the general presentation of the temperature range 820 ~ 860 ?娈燗fter normalizing for the general need to deal with four to eliminate at normalizing the stress.

4. Ductile iron quenching and tempering in order to improve the mechanical properties of ductile iron, heated to Afc1 general casting more than 30 ~ 50 ?鏍ˋfc1 heating A representative of the end of a temperature), the insulation after quenching oil, be martensite . In order to appropriately lower after quenching the residual stress, the general should be quenched tempered, low-tempered organizations to increase tempering Markov for residual bainite with spherical graphite. This wear-resistance organizations, and demand for high wear resistance, high-strength parts. Tempering temperature in the temperature of 350-500 ?鏍ter tempering tempering troostite organizations to increase spherical graphite, applicable to the requirements of good wear resistance, a certain validity of the stability and flexibility in thick pieces. High-temperature tempering temperature of 500-60 D ?娆燼fter tempering tempering Soxhlet for organizations to increase spherical graphite, a good combination of strength and toughness of the comprehensive performance, wide application in production.

5. Ball and the use of multi-quenching ductile iron, such as the temperature can be quenched high-intensity, and both plastic and good toughness. Multi-quenching heating temperature of the main consideration so that the original choice of organizations of all A, non-residual F, but also to avoid A grain growth. The general Afc1 heating temperature above 30 ~ 50 ?娆爏uch as temperature temperature of 0 ~ 350 ?鏍磑 ensure access to a comprehensive mechanical properties of the bainite organizations. Mg-Al-iron, and other rare earth temperature quenched ?覡b = 1200 ~ 1400MPa, ??k = 3 ~ 3.6J/cm2, HRC = 47 ~ 51. It should be noted, such as temperature quenched with a tempering process.

6. Hardening the surface of certain items in order to improve the surface hardness, wear resistance and fatigue strength, the surface can be quenched. Ductile iron and gray iron castings to the surface can be quenched. The general high (in) frequency induction heating and hardening the surface, hardening the surface contact.

7. Chemical heat treatment requirements for wear-resistant surface or anti-oxidation, corrosion resistance of the castings, steel can be used similar to the chemical heat treatment process, such as soft chloride gas, chloride, boronizing, seepage, such as sulfur treatment.