High hardness ductile brittle ductile good ductile iron rod imports

Ductile iron is obtained by ball and spherical graphite inoculation, effectively improve the mechanical properties of cast iron, especially to improve the ductility and toughness, resulting in higher strength than carbon steel. Ductile iron is the 1950s developed a high-strength cast iron materials, its overall performance is close to steel, is based on its excellent performance, has been successfully used to cast a number of complex stress, strength, toughness, wear require a higher part. Ductile iron has quickly become second only to gray cast iron, cast iron material is widely used. The so-called "iron and steel", mainly referring to ductile iron. Pig iron is a carbon content greater than 2% of the iron-carbon alloys, the carbon content of pig iron industry in general 2.5% --4% and containing C, SI, Mn, S, P and other elements, with iron ore by blast furnace products. According to the different forms of pig iron in the presence of carbon, can be divided into steel-making pig iron, cast iron and ductile iron and so are several. Precipitated spherical graphite cast iron. Spheroidal graphite split the role of the metal substrate is smaller than the flake graphite cast iron the strength of 70 to 90% of the matrix organizational strength, tensile strength of up to 120kgf / mm2, and with good toughness. Ductile iron outer chemical composition is generally as follows: carbon content of 3.6 to 3.8% silicon content of 2.0 to 3.0% manganese, phosphorus, sulfur total does not exceed 1.5% and the amount of rare earths, magnesium nodulizer 1 Press the fracture color component (1) gray cast iron in this most or all of the carbon in the form of flake graphite in a free state, the fracture was dark gray, have certain mechanical properties and good to be cutting, universal application in the industry (2) white cast iron white cast iron is no organization or almost complete absence of an iron-carbon alloy graphite, the fracture was bright white, hard and brittle, can not be cutting, few in the industry directly used to produce mechanical parts. That it has a high surface hardness and wear resistance, also known as chilled cast iron or chilled cast iron (3) Ma Ma cast iron cast iron is between a white cast iron and gray cast iron between the fracture was Ma dotted gray and white, poor performance, and very few applications 2. Chemical composition score (1) refers to an ordinary iron without any alloying elements iron, such as gray cast iron, malleable iron, ductile iron, etc. (2) iron alloy is adding some alloying elements in the ordinary cast iron, a high-iron to improve the performance of some special formulated. Such as various corrosion and heat resistance properties of cast iron 3. special production methods and organizational performance score (1) ordinary gray cast iron See "gray cast iron" (2) bred gray cast iron which is based on the use of " Modification "is made of cast iron, also known as metamorphism. Its strength, ductility and toughness is much better than the general gray cast iron, organizations are more uniform. Mainly used in higher manufacturing mechanical performance requirements, and changes in the larger cross-sectional size of large castings - (3) malleable iron malleable iron by annealing white cast iron components made certain graphitized than gray cast iron with high toughness, and He said ductile cast iron. It can not be forged, used to manufacture castings to withstand impact loads (4) ductile iron ball short. It is by adding a certain amount of liquid iron casting went nodulizer and Mexican agents to promote crystallization of spherical graphite obtained. It compared to steel, in addition to ductility, toughness slightly lower, other properties are near, the advantages of both steel and cast iron excellent material, is widely used in mechanical engineering (5) which is a special properties of cast iron have certain characteristics cast iron, depending on the application can be divided into cast iron, heat-resistant cast iron, cast iron corrosion. Most belong to the alloy cast iron, stress relief annealing wider application 1. Since casting uneven thickness in heating, cooling and phase change process, will produce the equivalent stress and the stress on the machinery. In addition, after the machining of large parts of its interior is also easy residual stress, all of which stress must be eliminated. Stress relief annealing heating temperature is usually 500 ~ 550 ℃ holding time of 2 ~ 8h, then furnace cooling (gray iron) or air (ductile iron). Using this process can eliminate 90% to 95% within casting stress, but cast iron does not occur. If the temperature exceeds 550 ℃ or the holding time is too long, it will lead to graphite, the casting strength and hardness decreased. 2. Elimination of white high-temperature graphite cast iron castings annealing cooling, surface and thin section was often produce white. White tissue hard and brittle, poor processing performance, easy to peel. It must be annealed (or normalized) method to eliminate white tissue. Annealing process: heating to 550-950 ℃ heat 2 ~ 5h, followed by furnace cooling to 500-550 ℃ and then cooled baked. During high temperature insulation, high travel and eutectic cementite cementite decomposed into graphite and A, in the subsequent cooling process in nursing and secondary cementite eutectoid cementite decomposition also occurs graphitization. Due to the decomposition of cementite, resulting in decrease in hardness, resulting in improved machinability. N fireball iron normalizing Ductile Iron 3. The purpose is to obtain pearlite matrix structure and grain refinement, uniform structure, in order to improve the mechanical properties of the casting. Sometimes normalizing surface hardening ductile iron also in the organization of preparation, sub-high-temperature normalizing normalizing normalizing and low temperature. High temperature normalizing temperature is generally not more than 950 ~ 980 ℃, low-temperature normalizing generally heated to a temperature range of co-fold 820 ~ 860 ℃. After normalizing the need to carry out four general treatment to eliminate the internal stress generated when normalizing. The ductile iron quenching and tempering in order to improve the mechanical properties of ductile iron, cast generally heated to Afc1 over 30 ~ 50 ℃ (when Afc1 A representative of the formation of the end of the heating temperature), after holding quenched into oil, to be martensite . In order to appropriately reduce the residual stress after quenching, tempering should be carried out after the general quenching and tempering is tempered martensitic as plus plus residual bainite spheroidal graphite. This organizational good wear resistance for applications requiring high wear resistance, high strength parts. Tempering temperature of 350-500 ℃ after tempering is tempered troostite plus spherical graphite, for applications that require abrasion resistance, a certain effect stability and flexibility of thick pieces. Kennedy Proton - related personnel are more concentrated in the steel network of excellence. Tempering temperature of 500-60D ℃, tempered tempered sorbite organization for added spheroidal graphite, with a good combination of toughness and strength of 500-60D ℃, after tempering is tempered as a plus spherical graphite Soxhlet with toughness and strength combined with good overall performance, it is widely used in production. 5. Multi-temperature hardening ductile iron ductile iron can be obtained by Austempering high intensity, with both good ductility and toughness. Multi-temperature quenching temperature selection make major consideration of the original organization of all A, no residue F, but also to avoid A grain growth. The heating temperature generally use Afc1 over 30 ~ 50 ℃, isothermal treatment temperature is 0 ~ 350 ℃ in order to guarantee access to lower bainite has comprehensive mechanical properties. Rare earth magnesium aluminum ductile iron Austempering σb = 1200 ~ 1400MPa, αk = 3 ~ 3.6J / cm2, HRC = 47 ~ 51. It should be noted Austempering plus a tempering step 6. After surface hardening to improve the surface hardness, wear resistance and fatigue strength of certain castings, can be surface hardening. Gray iron and ductile iron castings can be carried out surface hardening. Usually high (in) frequency induction heating surface hardening and electrical contact surface hardening. 7. chemical treatment requirements for surface wear or anti-oxidation, corrosion-resistant castings, steel can be used similar chemical heat treatment process, such as a gas soft chloride, ferric chloride, boriding and sulfur treatment.