In 1882 Robert Abbot Hadfield invented the high-manganese steel. This steel under high shock loads and high compressive stress, so that the workpiece surface to work hardening, microhardness about HV250 to HV750, while the workpiece remains within the excellent toughness, even if the parts are thin, the withstand large impact load without fracture, wear resistance and HRC50 martensite quite. It is widely used in the metallurgy, mining machinery, construction machinery, tractor crawler board wearing parts.
High manganese steel work hardening mechanism of accumulation of dislocation and deformation induced variable two theories. More recent studies support the dislocations piled theory. That thefriction under highly amplified because of the formation of a large number of dislocations and deformation twinning, the chainlet embedded defects and massive organizational refinement. The dislocation density reaches the limit value, the slip is practically impossible, which is the form of the main deformation twins become.
However, in the low-impact load or under low stress, since it is impossible to achieve as high a degree of hardening, when the wear resistance of the high manganese than other wear-resistant steel is good. Such as with theof the nozzle of the shot-blasting machine, their life and the general carbon steels. Ball mill liner with ZGMn13 doing generally six to eight months, more than a year, the service life is not as good as of T8 steel and other low alloy wear-resistant steel.
In addition, even under a high impact load, if the crushed ore is relatively soft, its wear resistance is also poor. Hammer crusher hammer crusher softer ore containing sediment, the hammerhead surface work hardening only 240-300HB, hammerhead life up to 18 hours. Fully visible, high manganese steel is not any case of wear-resistant, show a higher abrasion resistance, only high impact and high stresses quick hardening, the formation of the wear-resistant surface layer.
Although a lot of new material in recent years, in part to replace the high-manganese steel, but it is also all aspects of high-manganese steel to improve and achieved a great deal. There are three main ways, high manganese steel re-alloying, change the high manganese steel, Mn / C ratio and the third is the improvement of the production process. Are as follows:
1, high manganese steel re-alloying
In order to improve the wear resistance of high manganese steel and the yield strength and other properties, widely used inside and outside alloyed or micro-alloying Qi is to strengthen the solid solution, reduce carbide precipitation, change the carbide morphology and distribution, improve the austenitic hardening performance. mo>Cr,V, Mo, Cr, and the elongation and impact toughness decreased.”>Alloying elements to improve the yield strength and tensile strength of the magnitude of order of V> mo> Cr, V, Mo, Cr, are the elongation and impact toughness down. Wherein, V the elongation and impact value of the largest decline, MO, Cr followed.
Adding 2% of Cr, the i.e. Mn13Cr2, can increase the yield strength, improve abrasion resistance in the Mn13. But because of the grain boundary carbide precipitation tends to increase, so that the ductility of the steel and a 30-40% reduction ratio of Mn13.
Add up to 1% – 2% of Mo can yield strength increases, and to increase 980 when the high-temperature strength and ductility, thereby reducing the tendency to hot cracking. Molybdenum can also prevent the continuous cooling or isothermal dwell austenite decomposition. The molybdenum can be fitted with the lower austenitizing temperature, form dispersion promulgated carbides, and can inhibit the formation of pearlite and acicular carbides Heavy manganese steel pieces cooling. Tungsten also have a similar effect, but the effect is not as good as molybdenum.
Adding 2-3% Ni in the manufacture of non-magnetic workpiece. If 0.2-0.4% Bi, can improve the performance of high-manganese steel processing. Micro-alloying (about 0.05% – 0.14%), high manganese steel modification used production method, production process is simple, low cost, low technical difficulty, the effect is obvious.
Add 0.1-0.5% Ti, have a reduced tendency for forming a grain boundary carbide films, can be refined organization and improved abrasion resistance. However, the amount of Ti should not be too high, too high to promote carbide and nitride deposition, the adverse effect on toughness. Ti added after the abrasion resistance can be increased 25-50%.
Vanadium titanium modification of the high manganese steel, grain refinement, elimination of columnar crystals to improve the yield strength, reduce plastic toughness conditions. Generally added to the package in the steel, the steel before the aluminum deoxidation. Plus vanadium and titanium of high manganese steel, the lower the amount of deformation (15%), it can obtain a high hardness value. Mn13 To the amount of deformation of 25% in order to achieve the same hardness value. Ti, or V, TI’s while adding about 0.2% of a rare earth, and also very effective. Mn13 in the addition of 0.7-0.8% Mo ,0.3-0 .4%, Vey 0.2-0.4% Ti, and 600 for 6 hours and then heated to 1000 Solid content processing, 4M3 Shovel scraping teeth life increased by 70-170%.
The domestic high manganese Add about 0.05% N and about 1.5% of Cr, and its properties are shown in Table 1.
|Program||Steel grades||σkg/mm²||δkg/mm²||σ%||Ψ%||αk||Hardness||Amount of wear|
|5||More than a raise||32||48||12||5||48||25||54|
As can be seen from Table 1, the nitrogen is added chromium better overall performance of the high manganese steel. Installed comparative test results show that the high manganese steel mill Mn13NCr resistance increased by 35% than the standard high-manganese steel.
Japan was added in the high manganese 1.0-3.5% Cu, <0.6% of Mo and 0.01-0.03% of B, to improve the work hardening performance, and for joining the elements of V, Nb, W, N, etc., wear resistance than Mn13 increased by 50% for the crusher and ball mill liner wear parts.
Rich rare earth resources in China, metamorphic high manganese steel with rare earth processing, grain refinement to improve the distribution of the morphology of carbides and non-metallic inclusions, help to improve the toughness and resistance to thermal cracking tendency. Rare earth ferrosilicon in Mn13 0.1-0.3% for the crusher hammer than Mn13 life improve by 16.1%, for the shovel teeth 1.6-16%, 20-30% astooth plate, and good toughness, impact resistance, and can not afford to teeth, no fracture wear uniform, as a ball mill liner life can be increased by 25%.
2, changing the manganese carbon than reduce the high manganese steel austenite stability, improve the wear resistance.
(1) low-carbon and high manganese steel. C ,0.3-0 .9%, Mn 11-14%, suitably added such as Ni Mo in order to ensure the mechanical performance. Cast under high-carbon low-manganese carbides, cast higher impact value, can produce complex-shaped castings, heat resistance of this steel is also better suited to the occasion a certain temperature.
(2) high. C1.2%, Mn content of 6-7%, and containing 0.5-1.0% of Mo, since Mn is low, the low stability of the Austrian low under low stress can also be hardening. Toughness of high fell more than Mn13, toughness and wear resistance are shown in Table 2.
Table 2 modified high manganese steel manganese steel toughness and wear resistance.
|Material||The impact of power(ft*i)||Heat treated specimens
Wear weight loss(mg)
1.15C – 12Mn
1.15C -12Mn – 0.5Mo
1.15C -12Mn – 1.0Mo
1.4C – 12Mn
1.4C – 12Mn – 0.5Mo
1.4C – 6.5Mn – 1.0Mo
1.2C – 6.5Mn – 0.5Mo
1.2C – 6.5Mn – 1.0Mo
Note: The pin on disc wear testing machine, abrasive 150 mesh red garnet.
High carbon manganese steel used for ball mill liners, life expectancy has increased by 18-20%. For fan mill strike plate life than Mn13 increased by more than 30%. This manganese steel, can be used in various mines and mining sector crusher hammer,, grinding balls, tailgate, the main liner construction sector in various forms of the loader and dredger bucket teeth, drill , chisel, and bulldozers scraper.
(3) carbon (0.6-0.9%), manganese referral metastable. Adding an appropriate amount of Cr, Mo, V, Ti, rare earth, etc., and after solution and aging, since the Mn content is lower, Albright Hugh beads stability is poor, can be processed in a low impact force stress hardening, and due to the lower carbon content, the precipitation of carbides tend to be higher carbon manganese steel small and therefore also better toughness, can be used in the occasion of the strong impact load, the abrasion resistance of the obtained.
(4) high manganese steel. Of carbon and manganese Mn13 in an appropriate increase the upcoming carbon increased to 1.5%, manganese up to about 18%, found better than the high-manganese steel hardening capacity. 1.53% C; 0.55% Si; 18.2% Mn; 2.65% Cr; 0.22% Ti; 0.35% Re; <= 0.06P; <0.05% S ultra-high manganese steel impact plate making fan grinding life than Mn13 raise nearly doubled. Tests proved the improvement of carbon will help improve the wear resistance of the steel; increased manganese content yesterday on improving the impact toughness.
If the carbon content is maintained at 1.0-1.2% to about 18% in Mn, you can improve and reduce the tendency of carbide precipitation, wear parts can be used to produce large cross-section, such as a sledgehammer first class, use effect is quite good. In addition, ultra-high manganese steel can also be used at low temperatures has great significance to the characteristics of the winter cold of northern China.
Recently abroad a patent invention Containing a Mn25% ultra-high manganese steel, its performance: The patent of this steel work hardening fast run of 25 units in the four countries, life expectancy increased by about 30%. This will be another direction of development of ultra-high manganese steel.
3, high manganese steel production process improvements
(1) was suspended casting is advantageous for the improvement of abrasion resistance. Suspension casting improved wear resistance. The suspension casting alloy powder (such as WC, VC powder) in the molten steel is cast into a mold cavity, to achieve chilling, increased nuclear and dense, thereby improving the wear resistance of the castings.
(2) argon blowing. Can reduce the hydrogen, oxygen and inclusions in the steel, the uniform temperature of the molten steel and to improve the fluidity of the liquid steel, which can reduce the pouring temperature to refine the primary grain to improve the mechanical properties, and ultimately improve the wear resistance. In addition, considering the economic benefits, but also can blow nitrogen treatment, the effect is also very good.
(3) surface hardening technology. I.e. of the high manganese steel by mechanical methods to produce a pre-hardened, in order to achieve the purpose of improving wear resistance. More than the explosion hardening.