Characteristics and application of high chrome wear resistant CAST IRON
High chrome cast iron containing 12.30% chrome and 2.4-3.6% carbon can be highly alloyed and heat treated to obtain martensite or austenite or mixed matrix and special carbides of chrome. This particular carbide is a hexagonal system of Me7C3 with hardness as high as HVL200. 1600, much higher than the cementite type of carbides and common mineral abrasives hardness. In addition, the EUTECTIC structure of high chrome cast iron is different from that of Ledeburite. The ledeburite in common cast iron is the continuous network, but the EUTECTIC carbides of high chrome alloy are broken in the state of block and Strip. It is equivalent to inserting high hardness particles into the Matrix. Therefore, it not only has good wear resistance, but also weakens the embrittlement of high hardness phase, and has relatively good toughness.
The high hardness martensite Matrix in high chrome cast iron can strongly support carbide particles, avoid carbide from falling off the wear surface in the working process, and ensure the high wear resistance of the material. Therefore, high chrome cast iron as a high wear resistant material has been effectively used in crushing, grinding, Material Transportation and other mechanical and metallurgical equipment. Especially in the abrasive wear and impact wear parts (such as Crusher Drum, silo liner, blast furnace bell, hopper, coal chute liner, coal mill roller, roller, slag slurry pump parts such as the flow) is more widely used.
After casting, water toughness is the same process as quenching with water. The temperature is 1100 °c, to obtain oversaturated single phase austenite, because the austenite can exist at normal temperature, the hardness of the structure is not high, the strength is not high, However, when the surface is subjected to strong extrusion and friction, a strong work hardening occurs and the phase changes into martensite and precipitates carbides, thus obtaining high wear resistance, while the core is still a high impact austenite. The surface of the hard layer of wear exposed the heart and work hardening occurs. When the water toughens, it is no longer heat treated. Otherwise, it will become brittle when heated to 250 degrees.
This can Be understood as a solid solution treatment!
General Water ground toughening is used for ZGMn13 type high manganese steels, which are mainly used for parts subjected to impact loading, and other parts, as Lufeng put it, where the AUSTENITIC surface is subjected to impact action, resulting in strong work hardening, when the hardened layer is ground / collapsed Exposed fresh AUSTENITE, re-hardening, and so on
Because of its strong work hardening, it can not be formed by machining. In recent years, there are practices to reduce manganese content, make manganese steel, the same can be used water toughening.
In die steels, the first step in the process of double refinement (as described in an early book about 1982) is sometimes called water toughness (or oil toughness)
After forging the die steel, the steel is quenched into hot water (called water toughness) and oil (called oil toughness) at the point of ACM, in order to dissolve most of the carbides into austenite Fine and even fine granular carbides, were obtained after quenching and tempering, then normal (or slightly lower than normal austenitizing temperature) quenching, in order to improve the toughness and wear resistance of Die
Manganese steel is mainly used to withstand impact, extrusion, material wear, and other harsh conditions, the form of damage to wear and tear mainly, part of the fracture, deformation. There are three types of wear: friction wear where metal surfaces are in contact with each other and in motion; Abrasive wear where other metals or nonmetal materials strike metal surfaces; and erosion wear where flowing gas or liquid is in contact with metal. The wear resistance of wear-resistant steel depends on the material itself, but wear-resistant steel shows different wear resistance under different working conditions.
Casting wear-resistant steel and wear-resistant steel to austenitic manganese steel-based, under certain conditions after appropriate heat treatment of low-alloy steel also has a good effect, graphite steel is used for lubrication friction conditions.
2. High Manganese steel high manganese steel is typical wear resistant steel with austenite and carbide as-cast structure. 1,000. C Left and right water quenching treatment into a single structure of austenite or austenite plus a small amount of carbide, toughness, so-called water toughness treatment. The most important characteristic of high manganese steel is that under the condition of strong impact and extrusion, work hardening occurs rapidly in the surface layer, which can keep the good toughness and plasticity of austenite in the core and have good wear resistance. This is beyond the reach of other materials. But the wear resistance of high manganese steel shows its superiority only when it has enough working hardening conditions, otherwise, it is very poor.
3.Chemical composition and mechanical properties of High Manganese Steel 4. Physical Properties of High Manganese Steel 5. Due to work hardening phenomenon, high manganese steel should be avoided as far as possible. The holes and grooves in the casting are cast out as far as possible. But the processing of high manganese steel is not completely impossible. The cutting tool can be finished by one feeding. The unavoidable machining should enlarge the machining amount when designing the casting process so that the cutting amount can avoid the work hardening layer 6, HIGH MANGANESE STEEL WELDING PERFORMANCE: High Manganese Steel reheating, in the 250 ~ 800. There are embrittlement temperature intervals between C and Carbides, net carbides and casting stress in as-cast high manganese steel, so the weldability is poor. High Manganese Steel Casting, should be in water toughness after cutting riser or defects welding, welding should be rapid cooling. To eliminate or minimize heat-affected zone, apply low current, discontinuous welding, or edge welding and water cooling. Use of high manganese steel electrode or AUSTENITIC stainless steel electrode. If there is a work hardening layer, it should be removed before welding.