Manganese content in more than 10% of alloy steel. In 1882 the first obtain the austenite of, British Hadfield in 1883 ( R.A.Hadfield ) made of patent. High manganese steel according to their different purposes can be divided into two categories:
This kind of steel containing manganese 10%~15%, carbon content is higher, is generally 0.90%~1.50%, most of the more than 1%. Its chemical composition ( % ):
Si0.30~1.0S ≤0.05P ≤ 0.10 this kind of high manganese steel was most commonly used to produce excavators, shovel teeth, cone crusher rolling wall and broken wall,, ball mill liner, bifurcated plate railway frog, plate hammer, hammer etc..
The compositions of high manganese steel cast structure is usually composed of austenite, carbide and pearlite composed, sometimes also contain a small amount of phosphorus eutectic. Carbides in large quantities, often at grain boundaries of reticular appear. Therefore, as-cast microstructure of high manganese steel is brittle, cannot use, need solid solution treatment. Commonly used methods of heat treatment is the solid solution treatment, the steel is heated to 1050~1100 ℃, thermal elimination of as-cast microstructure of austenite, single phase, and then water quenching, so that such organizations remain to room temperature. Heat treated steel strength, plasticity and toughness are increased greatly, so this kind of heat treatment method is also often called the water toughening treatment. Mechanical properties of heat treated as:σ b615~1275MPaσ 0.2340~470MPaζ 15%~85%ψ 15%~45%aKl96~294J/cm2HBl80~225
steel after solid solution treatment also have a small carbide dissolved, when its amount is less in conformity with the inspection standards, can be used.
The austenite of high manganese steel under impact load, the metal surface plastic deformation. Deformation strengthening results in deformation layer, have apparent hardening phenomenon, the surface hardness is improved greatly. Low impact load, can be achieved HB300~400, high impact load, can be achieved HB500~800. As the impact load is different, the surface hardened layer depth of up to 10~20mm. High hardness of the hardened layer can resist the impact abrasive wear. High manganese steel in impact abrasive wear conditions, with excellent anti-wear performance, it is often used in mining, building materials, thermal power and other mechanical equipment, making wear parts. In a low impact conditions, due to work hardening effect is not obvious, the high manganese steel can not play the material properties.
Chinese common high manganese steel grades and its applicable scope is: ZGMn13-1 ( C1.10%~1.50% ) for low impact, ZGMn13-2 ( C1.00%~1.40% ) for the general, ZGMn13-3 ( C0.90%~1.30% ) for complex, ZGMn13-4 ( C0.90%~1.20% ) for high impact parts. More than 4 grades of steel Mn content was 11.0%~14.0%.
In impact loading during cold deformation, the dislocation density increases in great quantities, dislocation, dislocation pile-up and delivery of dislocation and solute atoms interaction makes the steel reinforcement. This is the important reason for hardening. Another important reason is the high manganese austenitic low stacking fault energy, deformation is easy to occur when stacking fault, which is εmartensite and create the condition of deformation twins. Conventional components of high manganese steel deformation hardening layer can often see high density dislocation, dislocation and tangles. εmartensite and deformation twinning appears to make steel difficult to deformation, especially the larger role. All these factors make the high manganese steel hardened layer has high degree of intensification, hardness is improved greatly.
High manganese steel is extremely easy to work hardening, it is difficult to process, the vast majority of casting, forging processing method for a very small amount of. High manganese steel casting properties. Steel of low melting point ( approximately 14 ( ) ( )℃), the solidus temperature of liquid steel, smaller intervals, ( about 50 ℃), the thermal conductivity of steel is low, so the fluidity of molten steel is good, easy casting molding. High manganese steel line expansion coefficient of pure iron 1.5 times, 2 times for carbon steel casting, so the volume and linear shrinkage rate were larger, prone to stress and crack.
In order to improve the performance of high, a lot of micro alloying, carbon and manganese content adjustment and precipitation strengthening treatment and other aspects of the study, and in the production practice application. Metastable was Gao appear to greatly reduce carbon, manganese content in steel and the deformation strengthening speed, can be applied to the high and low impact load condition, it is the new development of high manganese steel.
This kind of steel manganese containing greater than 17% carbon content, generally below 1%, often in the motor industry for the production of retaining rings etc. This kind of steel density is 7.87~7.98g/cm3. Because the carbon, manganese content was high, the heat capacity difference steel. Thermal conductivity coefficient of 12.979W/ ( m℃), about 1/3 for carbon steel. As the steel austenitic organization, non-magnetic, its permeabilityμ1.003~1.03 ( H/m ).