CN113278883A

CN113278883A - Rare earth wear-resistant ultrahigh manganese steel for toothed plate of double-toothed roller screening coal crusher and manufacturing method thereof

Info

Publication number: CN113278883A
Application number: CN202110467940.1A
Authority: CN
Inventors: 张选; 韩晓东; 许先义; 李智; 张礼; 冯跃华; 马鹏飞; 黄晶亮; 谭清泉; 李冬取; 王凯; 朱正芳
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-04-28
Filing date: 2021-04-28
Publication date: 2021-08-20

Abstract

The invention relates to the field of super-grade manganese steel, in particular to ultrahigh manganese steel for a toothed plate of a double-toothed roller screening coal crusher and a manufacturing method of the ultrahigh manganese steel. The material characteristics of the crushing toothed plate made of the ultrahigh manganese steel material provided by the invention are that the work hardening capacity is obviously improved compared with that of the common high manganese steel, and very high work hardening capacity is generated under the condition of small deformation. The surface structure of the toothed plate is strengthened by the ultrafine carbide particles precipitated by work hardening. Not only has high abrasion resistance, but also has enough strength and toughness.

Description

Rare earth wear-resistant ultrahigh manganese steel for toothed plate of double-toothed roller screening coal crusher and manufacturing method thereof

Technical Field

The invention relates to the field of super-grade manganese steel, in particular to ultrahigh manganese steel for a toothed plate of a double-toothed roller screening coal crusher and a manufacturing method of the ultrahigh manganese steel.

Background

The 2 DG 1177/17.4-II type circulating fluidized bed boiler (CBF) fuel system matched with the 2 x 330MW unit of the Shenhua quasi-energy coal gangue power plant is responsible for the tasks of conveying, supplying and the like of fire coal, and the system mainly comprises a raw coal conveying system and a fire coal preparation part. The conveying system is used for conveying and supplying raw coal, the conventional CBF boiler requires that the particle size of the coal supplied to the raw coal bin is 8 mm-10 mm, and the screening and crushing equipment is arranged in the fuel conveying system. In order to improve the crushing efficiency of the coal crusher and save electric energy, incoming coal is screened before crushing, coal with small particle size directly falls to a downstream belt, and large coal enters the coal crusher to be crushed.

At present, a coal crusher configured in a fuel system of a CBF coal-fired power plant has a ring hammer type and a tooth roller crusher because the coal crusher has the characteristics of high crushing efficiency, high coal type adaptability, reliable operation and moderate maintenance and economy. The 2 MMD 625-series double-toothed-roller screening coal crusher put into operation in the fuel system of our factory mainly comprises a machine body, toothed rollers (comprising a main shaft, a rotor body, a bow-shaped toothed plate and the like), a dredging toothed plate, a side wear-resistant plate, an end wear-resistant plate, a speed reducer, a hydraulic coupler, a stall sensor and the like. In operation, the crusher may receive material from any direction. The oversize material is sheared and crushed by the gear teeth on the two rotating gear roller shafts and is forcibly discharged from the lower part of the machine. In feeding, the coal gangue with qualified granularity is discharged quickly after entering the double-geared roller crusher and is not further crushed; the materials with the granularity larger than the qualified granularity level are clamped by the two toothed rollers after entering the crusher, and the weak and fragile parts of the materials generate stress concentration under the action of shearing force and pulling force, so that the materials are crushed. The material is discharged from the space between two teeth and the space between two side teeth, so the granularity of the product can be accurately controlled. The crusher has the main advantages of simple structure, small volume, light weight, simple maintenance, capability of automatically removing impurities and iron, low noise, micro negative pressure at the feeding port, micro positive pressure at the discharging port, small air supply amount, capability of forming internal circulation air, small dust and the like, and is suitable for crushing coal, coal gangue, coke, shale and other materials with the surface moisture of less than 15%. The rotor body of the double-tooth roller screening coal crusher is provided with bow-shaped 5-tooth 3-row toothed plates, and when the double-tooth roller rotates, firstly, the coal is impacted to be crushed; the coal after being impacted obtains kinetic energy from the tooth head of the toothed plate, so that impact force, shearing force, extrusion force and grinding force are generated between the tooth head and the double-tooth roller coal crushing toothed plate and between the coal and the toothed plate, and the impact force, the shearing force, the extrusion force and the grinding force are greater than or exceed the inherent impact resistance, compression resistance and tensile strength limits of the coal before being cracked, so that the coal blocks are crushed.

The toothed roller of the double-toothed roller screening coal crusher rotates at a high speed in a working state, and is subjected to strong impact after violent impact with materials to form abrasive wear, so that fatigue stripping of a working part of the toothed plate and formation of plow groove abrasion are caused, and the toothed roller screening coal crusher fails.

The wearing parts mainly comprise a toothed plate, a thinning plate and a side end plate, and then a crushing shaft and a double-row centripetal spherical roller bearing, if purchased accessories are qualified in quality, basically the wearing and the erosion damage occur, if the toothed plate is unqualified in material, the breakage occurs easily, and the crusher wearing parts are stopped due to the fact that the side end wear-resisting plate, the crushing thinning plate and the rotor strike and break, so that the crusher wearing parts fail early.

The coal breaker toothed plate can be purchased from Mining Machinery Development Co., Ltd, the type of the coal breaker is an MMD625 series double-toothed roller screening crusher, the rated output is 800t/h, the particle size of a fed material is less than or equal to 300mm, the particle size of a discharged material is less than or equal to 10mm, and the rotating speed of a motor is 1480 r/min.

The model is that the coal breaker vulnerable part tup of MMD625, dredge the pinion rack, the wear-resisting plate board of side, end, fence etc. are the import piece, and not only the expense is high, the purchase cycle is long, and the cost of overhaul is high. The toothed plates imported from England and the like are mostly made of medium carbon alloy structural steel or common ZGMn13 ordinary ultra-high manganese steel which is not subjected to modification treatment, so the hardenability in the water toughening treatment process is not ideal, and the working condition wear mechanism mainly comprises furrow abrasive wear and fragmentation. In the market economy environment, coal-fired power plants are of primary concern for safety and economy of production. Failure of mechanical products is mainly in three forms, namely fracture (including transient deformation), corrosion and wear. Statistically, one third to one half of the energy is lost due to wear and friction, with wear accounting for more than 80% of failures of mechanical parts. The economic loss of the U.S. is about more than 1000 billion dollars due to abrasion every year, and at present, the metal abrasion-resistant material is consumed by China every year due to abrasion and has more than 500 million tons and more than 400 billion yuan. Wherein the wear-resistant metal parts are consumed by the power industry every year due to wear and corrosion, and the consumption is about 120 ten thousand tons. Therefore, in order to ensure safe, economic, environment-friendly and efficient production of coal-fired power plants, analyze and research the metal wear, corrosion and fracture failure mechanisms of power generation equipment, ensure the reliable performance of the equipment in safe production under various working condition environments, and research, develop and popularize wear-resistant and corrosion-resistant materials of novel power generation equipment are important tasks faced by technologists in the field of new energy resources at present.

The factors influencing the service life of the toothed plate of the double-toothed roller screening crusher at least comprise the following two factors: 1. the toothed plate is poor in wear resistance due to unreasonable material, manufacturing process and alloy element proportion components, and is broken in the using process due to air holes, cracks and the like in manufacturing. 2. The screening efficiency that sets up the sieve coal machine before the coal breaker descends, and a large amount of fine grain coal get into the coal breaker after, also can increase the wearing and tearing of pinion rack, reduce the life of pinion rack.

At present, the material that the pinion rack generally adopted is medium, high carbon alloy high manganese steel, and the manufacturing process of high manganese steel is stable and after applying to the pinion rack, can satisfy actual work demand to a certain extent. High manganese steel is the wear resistant steel with the longest history, which was invented in 1882 by Hadfield in the uk and has been used for over one hundred years. The high manganese steel has austenite structure in the use state, and has good toughness and work hardening capacity. That is, under a strong impact load or a pressing load, the stressed surface is work hardened, the hardness can be improved from original HB200 or so to HB500 or more, and the core still maintains good toughness. Therefore, the steel is still widely manufactured into wear-resistant parts resisting impact load. The chemical composition of the high manganese steel used in the market at present is roughly as follows: c, carbon C: 0.9 to 1.5%, manganese Mn: 10 to 15%, silicon Si: 0.3% to 1.0%, S: less than or equal to 0.05 percent, phosphorus P: less than or equal to 0.10 percent.

In recent years, many studies have been made on the property improvement of the ultra high manganese steel in order to obtain the ultra high manganese steel having excellent wear resistance, excellent mechanical properties, and a long service life. Numerous studies have shown that: alloying and dispersion treatment (such as rare earth modification) are two effective ways to improve the wear resistance of the ultra-high manganese steel. For example, the inventor's shui paper of houwinxia's Master 'the influence of rare earth on the structure and performance of wear-resistant cast steel' records the influence of rare earth on the performance of the ultra-high manganese steel, in the experimental part of the paper, experiments are carried out by adopting different proportions of 0.035%, 0.0445% and 0.052% of rare earth, and the result shows that the grain size of 0.052% is relatively uniform, however, the mechanical indexes of the ultra-high manganese steel provided in the paper, such as hardness value, yield strength, elongation after breakage, tensile strength and the like, still can not meet the application requirements of the toothed roller of the double-toothed roller screening coal pulverizer, and need to be improved. Wherein the weight percentage of carbon C is between 0.20 and 0.35 percent, and the weight percentage of manganese Mn is between 1.3 and 1.6 percent, however, the carbon content and the manganese content of the ultra-high manganese steel are too low. In addition, although the application of rare earth RE is mentioned in the technical scheme, the specific content of rare earth in the components of the ultra-high manganese steel is not specifically pointed out, and the ultra-high manganese steel obtained by the technical scheme disclosed in the application is still difficult to meet the requirements and needs to be improved. The Chinese patent application with the application number of CN20061005169 discloses a novel rare earth chromium manganese nitrogen series high manganese steel, which introduces a plurality of alloys including copper, nickel and nitrogen elements into the components of the ultra-high manganese steel, and the technical proposal obviously leads the manufacturing process to be complicated and the contents of carbon and rare earth in the components are lower. The application number is CN200610134360.6, Chinese invention patent application discloses an ultra-high performance wear-resistant ultra-high manganese steel and a production method, the components of the application have complex proportion, a plurality of alloys, including Ti, V, Mg, B, N and other elements, need to be additionally added in a production process, the processing process makes the processing difficulty too complex and the production cost higher, in addition, the weight percentage of RE in the application is 0.08-0.4%, the weight percentage range of RE is too large, so that the stability of the product performance of the finished product obtained according to the process is greatly reduced, the weight percentage range of RE is necessarily reduced, thereby achieving the optimized technical scheme and improving the product stability of the ultra-high manganese steel.

In summary, the alloying ingredient design scheme has various problems, such as complex process, unstable product properties, high production cost and insufficient improvement effect of the finished product performance. In comparison, the method for carrying out dispersion treatment on the ultrahigh manganese steel by utilizing rare earth doping is more direct, simple, convenient and effective. However, as mentioned above, although the technology of improving the ultra-high manganese steel by using rare earth has been developed according to the description of the prior art, in order to further control the component ratio of the ultra-high manganese steel to obtain a better ultra-high manganese steel in a more preferable component range for manufacturing a toothed plate for a coal pulverizer with high performance, the technical scheme of the component manufacturing technology and the component ratio of the rare earth ultra-high manganese steel still needs to be further optimized.

Disclosure of Invention

In view of the above, the invention provides an ultra-high manganese steel for a toothed plate of a double-toothed roller screening coal crusher and a manufacturing method of the ultra-high manganese steel. Specifically, a composite modifier containing rare earth RE is added in the manufacturing method of the ultrahigh manganese steel, the weight of each element in the components of the ultrahigh manganese steel is controlled within a preset proportion range, and the precipitation strengthening heat treatment process parameters adopted by the ultrahigh manganese steel are controlled within a preset control range.

The invention provides ultrahigh manganese steel for a toothed plate of a double-toothed roller screening coal crusher, which comprises the following components in percentage by mass:

the invention also provides application of the ultrahigh manganese steel in preparation of a toothed plate of a double-tooth roller screening coal breaker.

The invention also provides application of the ultrahigh manganese steel in preparation of a double-geared roller screening coal crusher.

The invention also provides a preparation method of the ultrahigh manganese steel, which comprises a smelting process and a heat treatment process.

In some embodiments of the invention, the smelting process comprises 4 key steps of a melting period, a refining period, molten steel alloying and component adjustment, and final deoxidation tapping;

step 1, melting period: taking furnace charge required by smelting, and carrying out low-temperature desulfurization and dephosphorization at 1350-1500 ℃; when the molten steel is exposed in the air, CaO-CaFe slag is used for covering, so that the oxidation is reduced; when the temperature of the molten steel is raised to 1540 ℃, firstly adding Mn accounting for 0.2 percent of the mass of the molten steel, then adding Si accounting for 0.1 percent of the mass of the molten steel for pre-deoxidation, and purifying the molten steel;

step 2, refining period: deoxidizing and heating to 1360-1580 ℃;

step 3, alloying and component adjustment of molten steel: when the temperature of the molten steel is increased to 1580-1600 ℃, alloying is carried out, wherein the alloying temperature is lower than the tapping temperature by 40 ℃; the addition of the alloy elements is as follows in principle: mn, Si, Ni, Cr, C, V, Nb, Al, Ti, B, Mo; after the alloy elements are added, stirring the molten steel, and tightly covering the metal liquid surface with a covering agent to prevent air oxidation and stabilize the molten steel;

step 4, final deoxidation tapping: the tapping temperature is adjusted according to the casting temperature requirement of steel, a casting ladle is baked to 400-420 ℃ before the molten steel is taken out of a furnace, molten slag on the surface of the molten steel is taken out 2-3min before tapping, Si-Fe alloy is added, the mixture is stirred uniformly, and the temperature is rapidly increased to 1630 +/-10 ℃ for tapping. Immediately reducing the power after the aluminum insertion, for example, reducing the furnace of 500kg to below 100kW to organize and tap steel; during the tapping period, one or more trace elements of V-Fe, Ti-Fe and Re are used for modification treatment to refine grains; re is added after aluminum addition and final deoxidation; pouring, and opening the box after keeping the temperature for 8 hours to obtain a casting.

In some embodiments of the invention, the deoxygenation in step 2 comprises pre-deoxygenation, final deoxygenation, complex deoxygenation, enhanced deoxygenation, and diffusion deoxygenation; pure aluminum is adopted for the pre-deoxidation, the final deoxidation and the composite deoxidation, and rare earth is adopted for the enhanced deoxidation; the diffusion deoxidation adopts one or more of ferrosilicon powder, calcium silicoferrite powder, aluminum lime or carbon powder; the time for diffusion deoxidation is 15-20 min;

in some embodiments of the invention, in step 3, pure aluminum in an amount of 0.2% of the molten steel is added to the furnace for final deoxidation before tapping.

In some embodiments of the present invention, aluminum supplement is required during the tapping period in the step 4, and the amount of aluminum supplement is 0.05-0.08% of the weight of the residual molten steel; for thick-wall castings, the residual aluminum content in the molten steel is 0.035-0.045%;

in the step 4, Re is added in a form of a rare earth composite modifier according to a proportion of 0.02-0.03% by adopting a ladle, the rare earth composite modifier is obtained by modifying one or more elements in Re + B, V, Ti in a ladle, the grain size of the added rare earth composite modifier is 0.5-3 mm, the mixture is used after being dried, stirred and subjected to slag skimming after being added into molten steel, and then the mixture is subjected to covering and cutting and is subjected to sedation; when the temperature of the molten steel is reduced to 1480 ℃, pouring is started, the temperature of the poured molten steel is not lower than 1450 ℃, and the initial pouring temperature is not lower than 1550 ℃.

In some embodiments of the invention, the heat treatment process comprises: heating the casting from room temperature to 650-670 ℃ at a temperature of 80-100 ℃/h, preserving heat for 5 hours, heating to 1080-1100 ℃ at a temperature of 110-150 ℃/h, preserving heat for 4 hours, and carrying out water toughening treatment; and then the ultrahigh manganese steel is prepared by tempering treatment.

In some embodiments of the invention, the time from opening the furnace door to the water entering the casting is controlled to be completed within 30 seconds, so as to ensure that the water entering temperature of the casting is above 1080 ℃; the temperature of the circulating cooling water is kept below 30 ℃, and the highest temperature of the circulating cooling water after water toughening is not more than 50 ℃; the cooling speed of the casting is 30 ℃/second;

the tempering treatment is heating from room temperature to 250 ℃, keeping the temperature for 4 hours, and then air cooling.

The beneficial effects of the invention include but are not limited to:

the ultra-high manganese steel subjected to rare earth modification treatment has uniform austenite structure, fine spherical carbide is dispersed and precipitated in grains, and the ultra-high manganese steel is excellent in mechanical property. Because the content of Mn and C of the ultrahigh manganese steel ZGMn18Cr2Re is higher, and alloy elements and alterant are added, and the increase of the content of Mn further enlarges the austenite region, more carbon and alloy elements can be dissolved, the work hardening capacity is improved, the surface hardness of the toothed plate is favorably improved, and the pit drilling and abrasive wear are reduced. Meanwhile, the impact toughness of the material is increased, the generation and the propagation of cracks in a wear surface layer are inhibited, and the fatigue peeling wear is reduced. Especially has very good performance in the low-temperature and high-cold working condition environment. In actual production, the contents of carbon and alloy elements of the ultrahigh manganese steel can be properly adjusted according to various working condition environments and conditions, and the heat treatment process is designed and controlled, so that the austenite structure of the ultrahigh manganese steel is uniform and stable, high work hardening capacity and excellent mechanical property can be generated in a small deformation environment, and the method is suitable for safe, economic, environment-friendly and efficient operation of crushing equipment under various working conditions. The patent has popularization value.

This technological improvement is based on the idea of respecting the original design, does not make transformation by a wide margin to double-toothed roller screening breaker, only has made the adjustment to broken pinion rack structural morphology, arrangement parameter and novel wear-resisting material chemical composition and thermal treatment process for control gangue fuel income stove granularity and efficiency. The production operation results show that: the 5-tooth 3-row olecranon arc toothed plate of the double-tooth roller screening crusher made of the ultrahigh manganese steel ZGMn18Cr2Re has the advantages that the tooth tip structure is designed in an arc manner, the discharge gaps between the teeth are uniform along with the rotation of the tooth rollers in any direction, the granularity of gangue coal is small, the uniformity is good, the noise is low, secondary rolling is avoided, and the preset screening crushing granularity requirement and the production capacity are achieved. The novel crushing toothed plate has the advantages of good toughness, high strength, high hardness and wear resistance, is suitable for screening and crushing small and medium particles in gangue coal, and practical application data prove that: the improved double-toothed roller screening crusher has uniform particles, the discharged particles are less than or equal to 10mm under the working condition that the particle size of the fed materials is less than or equal to 50mm, the over-crushing rate is less than or equal to 10%, and the production capacity is over 400t/h, so that the service life is prolonged by over 5 times compared with that of the original toothed plate.

The crushing toothed plate made of the ultrahigh manganese steel material independently developed by the applicant is characterized in that the material has higher work hardening capacity than common high manganese steel, and the high work hardening capacity is generated under the condition of small deformation. The surface structure of the toothed plate is strengthened by the ultrafine carbide particles precipitated by work hardening. Not only has high abrasion resistance, but also has enough strength and toughness. Practice proves that: the novel ultra-high manganese steel crushing toothed plate has no crack or brittle fracture phenomenon in the working condition environment of severe cold and low temperature (-26 ℃), and simultaneously has good cutting, welding and forging process performances, for example, the mutual welding, the surfacing welding or the mutual welding of dissimilar materials of the ultra-high manganese steel are solved relatively mature, and the field remanufacturing technology can be implemented, so that the service life of the novel ultra-high manganese steel crushing toothed plate is prolonged, the purpose of overhauling equipment taking reliability as the center is achieved with the lowest cost investment, and the overhauling period and the overhauling cost are greatly reduced.

After the transformation is successful, 75.9 ten thousand yuan of electricity charge of the ring hammer type fine crushing and high-frequency amplitude sieve and 155 ten thousand yuan of maintenance main and auxiliary material charge can be saved every year. The comprehensive statistics can save 230.9 ten thousand yuan per year, and obvious economic benefit is obtained.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 shows a process flow diagram of a process for casting an ultra-high manganese steel toothed plate;

FIG. 2 illustrates a precipitation strengthening heat treatment process;

FIG. 3 shows the microstructure (200X) of ZGMn18Cr2Re after precipitation strengthening heat treatment.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

It should be noted that, in the case of no conflict, the features in the following embodiments and examples may be combined with each other; moreover, all other embodiments that can be derived by one of ordinary skill in the art from the embodiments disclosed herein without making any creative effort fall within the scope of the present disclosure.

It is noted that various aspects of the embodiments are described below within the scope of the appended claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the disclosure, one skilled in the art should appreciate that one aspect described herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented and/or a method practiced using any number of the aspects set forth herein. Additionally, such an apparatus may be implemented and/or such a method may be practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.

1. Design of chemical composition of ultra-high manganese steel toothed plate

The series high manganese steel as an excellent wear-resistant material is widely applied to material crushing equipment. But fracture failure is generated due to insufficient toughness of a workpiece with high load working condition and a large section; the cold fracture phenomenon often occurs under the working condition of low-temperature environment, and the using effect of the conventional high manganese steel is poor particularly under the working condition of low-impact abrasive wear, so that the material is worn, corroded, deformed and cracked, and finally the fracture is failed, so that the maintenance cost of equipment is increased. Therefore, in recent years, many researchers have made a lot of work in research and development of alloying, component design, smelting process, heat treatment process and the like of the modified high manganese steel to find ways to improve toughness and wear resistance.The ultra-high manganese steel is a new wear-resistant material developed on the basis of conventional ZGMn13, and the contents of carbon and manganese in the steel are further increased High, obviously enhances the work hardening capacity of the steel, thereby obtaining higher wear resistance. The ultrahigh manganese steel belongs to the high alloy steel category, which is Further improves the mechanical property and the processing property, and other alloy elements are often added into the steel for alloying. Alloyed with The purpose is as follows: firstly, refining an as-cast crystal structure. Strengthening matrix, reducing grain boundary carbide, preventing dislocation movement, and increasing superhigh speed Strength and wear resistance of manganese steel. Secondly, the mechanical property of the steel is improved. Most alloy elements are uniformly refined in the austenite of the ultra-high manganese steel Solid solution improves the strength of the steel. Improving the technological performance. The ultrahigh manganese steel forms single austenite in a matrix after precipitation strengthening heat treatment The first carbide with the structure of the solid and the fine uniform dispersionTwo-phase particles, which can improve the impact toughness of the ultra-high manganese steel material And abrasive wear ability are very advantageous.

In order to improve the efficiency of a coal gangue double-geared roller crusher, ensure the safety, economy, environmental protection and high-efficiency power generation of a coal-fired power plant and realize the economic targets of energy conservation and consumption reduction, aiming at the problems of the material of a toothed plate of the gangue crusher, an alloyed ultra-high manganese steel ZGMn18Cr2Re crusher toothed plate material is developed through more than two years of experimental research on the basis of extensive research and production practices of our factory, so that the novel toothed plate has enough toughness, is not broken and is safe to use, high in hardness and long in wear resistance and service life. Practice proves that: the novel toothed plate runs for more than one year under the very severe cold low-temperature working condition environment, and no crack and fracture phenomenon of the toothed plate are found.

The ultrahigh manganese steel belongs to steel grades with high carbon content, the carbon content is 0.90-1.50%, and the carbon acts in the ultrahigh manganese steel: firstly, a single austenite structure is promoted to be formed; and secondly, solid solution strengthening is carried out to ensure the mechanical property of the steel and improve the strength and the wear resistance of the steel. Research shows that under the condition of non-strong impact working condition, when the carbon content in the high manganese steel exceeds 1%, the wear resistance can be improved by 5-10% every time 0.1% of carbon is added. However, if the carbon content is too high, the carbide is likely to be crystallized and precipitated during the processing of the material, resulting in intergranular corrosion. Under low temperature, high impact conditions, it is often desirable to reduce the carbon content appropriately to ensure material toughness. When the carbon pair is reduced to 0.90-1.05%, the manganese content is unchanged, and the carbon pair is tempered after water toughening precipitation strengthening, has better plastic toughness and is easy to strengthen in the deformation process. Through the proportion control and optimization of the components, the result shows that the carbon content in the ultrahigh manganese steel component used for the coal breaker toothed plate is preferably in the range of 0.9-1.35%.

Manganese Mn is a main alloying element in ultra-high manganese steel and is also an element that promotes the formation of austenite. An austenite structure can be obtained, and when the content of manganese Mn is gradually decreased, the stability of austenite is also decreased, and the work hardening ability can be enhanced. However, too high manganese Mn is easy to generate segregation in the alloy solidification process, so that the alloy structure and the performance are not uniform, and the physical properties and the technological properties of the steel are influenced. Such as the primary crystal structure of the steel, the tendency of the casting to crack, etc. The ratio of manganese and carbon elements determines the structure and performance of austenite, and the manganese Mn content in the ultrahigh manganese steel component for the coal breaker toothed plate is preferably within the range of 17-19% in comprehensive consideration of formation of matrix structure carbide and work hardening.

Silicon Si can be dissolved in austenite in the ultrahigh manganese steel and plays a role in solid solution strengthening. Silicon can change the solubility of carbon in austenite. The content of silicon Si is high, and the cast carbide is more, so that the performance of the steel is poor at a high temperature state, the steel becomes brittle at a low temperature state, the deformation strengthening capability is reduced, and the tendency of cracking of a casting is increased. Excessive silicon in the composition may reduce the toughness of the ultra-high manganese steel. By controlling and optimizing the proportion of the components, the content of silicon and Si in the components of the ultrahigh manganese steel used for the toothed plate of the coal breaker is preferably in the range of 0.30-0.90%.

Research and practice results show that: the ultrahigh manganese steel with multi-component alloying has the greatest characteristic of obviously improving the strength and work hardening. The yield strength and work hardening of the ultrahigh manganese steel can be effectively improved by Ti, V, Mo, Cr, Ni and Re. Therefore, the addition of few and trace alloy elements is beneficial to improving the physical and mechanical properties of the ultrahigh manganese steel.

Cr and Mn are weak carbide-forming elements, and Cr and C have affinity better than that of Mn and are more likely to form carbides than Mn. After the ultra-high manganese steel is added with chromium, the stability of austenite is improved due to the diffusion characteristic of chromium and the influence on the diffusion process of carbon, and chromium is added into the ultra-high manganese steel to form chromium alloy cementite (Fe, Cr)₃C, in comparison with cementite Fe₃C is more stable. The alloy is distributed in steel, so that dispersed carbide hard particles are distributed in an austenite matrix, chromium atoms are easy to gather to block dislocation movement, the hardening effect is improved, the wear resistance is enhanced, and the content of Cr in the ultrahigh manganese steel used for the toothed plate of the coal breaker is preferably within the range of 1.50-2.50%.

Ni can improve the low-temperature toughness of the ultra-high manganese steel, and the Ni is dissolved in the ultra-high manganese steel in a solid mode and has an important effect on the stability of austenite. The method can inhibit acicular carbonization precipitation at 300-500 ℃, improve the embrittlement temperature of the ultrahigh manganese steel, and particularly avoid gamma → alpha transformation under the low-temperature working condition (-196 ℃), so that austenite is very stable, and the low-temperature working condition toughness of the ultrahigh manganese steel can be improved. The Ni content of the components of the ultra-high manganese steel used for the toothed plate of the crusher is within the control range of 2.5 to 4.0 percent.

The Ti and C have strong binding capacity, TiN and TiC are formed in alloy steel, the structure of the TiN and TiC is very stable and is not easy to decompose, the TiN and TiC can be slowly dissolved in austenite at the temperature of more than 1000 ℃ to form high-hardness TiC, and the abrasion resistance of the abrasion-resistant material can be improved. The components of the ultrahigh manganese steel for the toothed plate of the crusher comprise 0.08 to 0.15 percent of Ti.

V and C can combine to form stable V₄C₃And insoluble carbides such as VC. The V in the composition of the ultra-high manganese steel used for the toothed plate of the crusher is 0.20 to 0.30 percent.

Mo can form special carbide MoC, Mo₂C，(FeMo)₂₃C₆，(FeMo)₆C, and the like; but also other carbides can be dissolved in solid solution and are difficult to dissolve. The composition of the ultra-high manganese steel for the toothed plate of the crusher comprises 0.70 to 0.90 percent of Mo. Ti, V, Mo, Ni and Cr are added from alloy pig iron.

Phosphorus P and sulfur S are harmful elements and are as low as possible, and the lower the content of the components in the components of the ultrahigh manganese steel, the more the performance of the ultrahigh manganese steel can be improved. In smelting, the influence of phosphorus segregation is generally reduced by appropriately reducing the carbonaceous fraction. Embodiments of the present invention provide for controlling the phosphorus P to be in the range of less than 0.04%. The sulfur S is controlled within the range of less than 0.04 percent, an alkaline furnace is adopted for smelting, high-quality raw materials are strictly selected, effective technological measures are adopted in the smelting process, and the phosphorus and the sulfur can be controlled below 0.0035 percent.

The rare earth elements are very active and can capture MnS and other metal sulfides in the molten steel, and the distribution of MnO in a crystal boundary is eliminated. The rare earth is added into the steel to play the roles of deoxidation, desulfurization, deterioration and nucleation. The rare earth is added into steel to purify molten steel, refine crystal grains, inhibit precipitation of carbide, reduce as-cast carbide, change carbide nonuniformity and change the quantity, form distribution and the like of non-metallic inclusions. The inclusion in the grain boundary is obviously reduced, and the low-temperature toughness is improved. The addition of the rare earth can reduce the stacking fault energy of austenite, lead to the formation of a large amount of twin crystals, increase the dislocation density and promote the work hardening of the ultrahigh manganese steel. During solution treatment, the rare earth elements are enriched in the grain boundary, so that the diffusion of atoms is hindered, and the growth of austenite is hindered. Therefore, the addition of rare earth obviously refines austenite grains, and improves the strength and low-temperature toughness of the ultrahigh manganese steel. The results of controlling and optimizing the proportion of the components show that Ce, La, Pr and Nd are contained in the light rare earth. The Nd-containing ultra-high manganese steel can increase the wear resistance of the austenitic manganese steel no matter under the high stress working condition or the medium and low stress working conditions. The strengthening effect of La is best, and the comprehensive performance of the Ce-based light rare earth is improved and optimized. The rare earth Re in the components of the ultra-high manganese steel for the toothed plate of the coal breaker is preferably within the range of 0.08 to 0.20 percent.

The design chemical composition of the ultra-high manganese steel toothed plate is shown in table 1.

TABLE 1 ZGMn18Cr2Re ultra high manganese steel toothed plate design chemistry W (%)

ZGMn18Cr2Re ultra-high manganese steel toothed plate metallographic structure: fine spherulite carbide is dispersed and separated out in austenite structure and intragranular.

Process control of casting technology of ZGMn18Cr2Re superhigh manganese wear-resistant steel toothed plate

The production process of the ultrahigh manganese steel mainly comprises the following steps: preparing a casting process, manufacturing a die, smelting and pouring, performing heat treatment, performing a detection test and the like. After the chemical composition of the material is determined, the metallurgical quality influencing the material performance mainly has the following aspects: controlling the operation processes of smelting equipment, smelting raw materials, smelting process and heat treatment process.

The method comprises the control of a precise casting process of a toothed plate of the ultrahigh manganese steel crusher (shown in figure 1).

The smelting production equipment and the production process conditions are as follows:

adopting 500kg alkaline medium frequency induction furnace non-oxidation smelting process to produce 5 teeth 3 rows toothed plate of MMD625 double-tooth roller crusher, the material ZGMn18Cr2Re super high manganese steel, casting single piece with weight of 58kg and main wall thickness of 46mm,the key is to adopt high-quality alkalinity Magnesite clinkerThe furnace lining, the ladle lining and the molding material are beneficial to deoxidation, sulfur and phosphorus. Is suitable for the alkaline property of the ultrahigh manganese steel and ensures the high quality of smelting Molten steel. The slag-making material is prepared from fluorite which is prepared from crushed lime 2: 1. It is crushed into pieces of 25mm or less before use, and kept dry. The metal scrap steel material is low-carbon scrap steel, such as scrap steel, plates and the like. No high manganese steel return material. Alloy furnace charge: the block sizes of vanadium-titanium pig iron, ferromolybdenum, high-carbon ferrochromium, high-carbon ferromanganese, medium-carbon ferromanganese and 65 ferrosilicon are preferably 50-80 mm. The final deoxidizer and the alterant adopt pure aluminum and rare earth alloy (the granularity is 0.5 mm-3 mm), and are poured by subpackage by small ladles. And making slag and smelting steel.

Control of the process of the three-step smelting process

The process of the super-high manganese steel smelting production technology comprises the following steps: 4 process control points including melting period, refining period, molten steel alloying and component adjustment and final deoxidizing and tapping.The key is the control of furnace temperature and time, and the key points are low-temperature deoxidation, sulfur, phosphorus, And hydrogen, slagging, covering and oxidation prevention, impurity reduction and molten steel purification.

Melting period: the main task is to melt the furnace charge quickly, require reasonable charging, produce bottom slag and reduce heat loss. Calculating method according to super-high manganese steel batchingAccurately calculating various furnace charges required by smelting, and preparing manganese, nickel, chromium, vanadium and titanium according to the middle limit.Before charging, metallurgical lime, low-carbon steel scrap, pig iron and the like with the lumpiness less than or equal to 20mm and accounting for 2 percent of the weight of the furnace burden are firstly put into the furnace bottom,by removing bottom slag Phosphorus is charged in a dense, solid and smooth manner and melted at the maximum power. After the furnace charge is melted, the dephosphorization operation in the low-temperature stage is noticed, and the furnace is in the melting period The temperature is 1350-1500 ℃ to facilitate P, S removal;during smelting, S and Mn form MnS to float upwards and enter slag, and S reacts with lime to generate CaS and CaP which enter bottom slag to be removed. The viscosity of the steel slag is adjusted by fluorite.Found in the whole smelting and slagging process The molten steel is exposed in the air and is immediately covered by CaO-CaFe slag to reduce oxidation. After the furnace burden is completely melted, taking a furnace front molten steel sample, melting and cleaning the furnace burden, heating and making 1% of new slag. The slag proportion is CaO: SiO is 3:2, and belongs to weakly alkaline slag.When the temperature of the molten steel is raised to 1540 ℃, can be added after 0.2 percent of (Mn) is added(Si) 0.1% pre-deoxidizer, which is pressed to the deep part of the furnace to reduce the content of deoxidizer The total amount of impurities in the steel is reduced, and the purpose of purifying molten steel is achieved.After pre-deoxidation, a sample can be taken, a small amount of aluminum powder is added into a sample mold to stir molten steel, the furnace bottom is explored, and after the material is confirmed to be completely molten and clear, the sample is taken and sent for analysis. Adding alloy elements along with the scrap steel and transferring the scrap steel into a refining period.

② refining period: the main tasks are deoxidation and molten steel temperature rise, and the temperature in the refining period is 1540-1580 ℃. Super-superHigh manganese steel The cast steel is not only easy to cold crack but also easy to hot crack. The hot cracking and deoxidation prevention is the key.The pre-deoxidation, the final deoxidation and the composite deoxidation adopt pure aluminum, rare earth is utilized to strengthen the deoxidation, simultaneously, the deoxidation product is easy to float upwards after the composite modification treatment of the molten steel, and a secondary deoxidation product is generated when the molten steel is solidified, thereby ensuring the smelting quality of the ultra-high manganese steel. In the refining period, deoxidation, dehydrogenation and denitrification are generally carried out on slag, the slag with low melting point and good fluidity is produced, and ferrosilicon powder, silicocalcium powder, aluminum lime, carbon powder and the like are added into the slag to carry out diffusion deoxidation on molten steel. The slag components are adjusted by the fragments of the high-alumina bricks, the melting point of the slag is reduced, and the fluidity of the slag is improved. The induction furnace slag is cold slag (slag is heated by molten steel), and the improvement of the fluidity of the slag is difficult. But the addition of a proper amount of silica sand reduces the melting point of the slag and increases the fluidity. In fact, only a layer of slag with good fluidity is arranged in contact with molten steel, the slag in contact with air is generally in a crusting state,if the slag can turn white, the slag (FeO) is reduced to below 2 percent, the residual oxygen in the molten steel is not high, and the residual oxygen diffuses The deoxidation effect is good.The diffusion deoxidation time is determined by the furnace capacity, and is generally 15-20 min for a 500kg furnace.

Thirdly, alloying and component adjustment of molten steel:

1) in the later stage of smelting or after refining (maintaining refining slag),when the temperature of the molten steel is increased to 1580-1600 ℃, the alloy can be combined The temperature is generally lower than tapping to 40 ℃ during alloying.Because the molten steel is subjected to pre-deoxidation and diffusion pendulum deoxidation in the refining period, the oxygen in the molten steel is low, and the alloy elements cannot be seriously oxidized after being added.

2) The order of addition of the alloying elements. The addition of the alloy elements is as follows in principle: mn, Si, Ni, Cr, C, V, Nb, Al, Ti, B and Mo are added respectively to play a role of one-step deoxidation, and because of low price, the yield of the post-added elements can be ensured.

Final component adjustment:after the alloy elements are added, the molten steel is immediately stirred, and the metal liquid surface is tightly covered by covering agent to prevent Oxidizing in air and stabilizing molten steel.Sampling and analyzing, and adjusting the final components according to the analysis result. All alloys of the adjusted composition must be added within 8min before tapping. If the temperature of the molten steel reaches the tapping temperature, the input power of the furnace must be reduced, and the temperature is adjusted to tap after the addition of the alloy elements is finished.

Fourthly, final deoxidation tapping

1) Tapping temperature adjustment tapping temperature is adjusted according to the casting temperature requirement of steel, which is particularly important for ladle casting. Because: and (3) tapping in a converter, wherein no thick slag layer is formed on the surface of molten steel for heat preservation, the cooling speed of the molten steel after the molten steel is placed into the converter is different, the cooling speed of the surface of the molten steel is high, and the cooling speed of the middle part and the lower part is low. If the tapping temperature is too high, the steel is cooled in the ladle, the surface of the molten steel is cooled to the casting temperature requirement, but the lower temperature is higher, so that the casting temperature is higher. If the tapping temperature is too low, the surface temperature of molten steel (ladle opening) is reduced too fast, and crusting is formed and pouring cannot be carried out.

2) After the final deoxidation alloy element is adjusted, the temperature of the molten steel reaches the steel temperature, and the slag can be removed and the final deoxidation can be carried out. The final deoxidation of the steel making and the aluminum adding of the induction furnace is an important operation environment, a large amount of oxygen in the molten steel is removed by slagging, but the slagging can not be completely deoxidized, and FeO and MnO in the molten steel are removed for the high manganese steel. MnO is a non-metal inclusion seriously harmful to the ultrahigh manganese steel, once the MnO is partially aggregated in a crystal boundary, the heat crack, toughness and wear resistance of the material can be reduced, the ultrahigh manganese steel is easy to oxidize, the deoxidation task of molten steel is very heavy to control in the smelting process, and the deoxidation and aluminum addition amount in the smelting process of the ultrahigh manganese steel is higher than that of other steel types. The final deoxidation and the aluminum addition are insufficient, subcutaneous air holes appear on the casting, excessive aluminum addition appears, and pinholes or intrusive air holes appear. Dry type ultrahigh manganese steel castingBefore tapping Pure aluminum in an amount of 0.2% of the molten steel is added into the furnace for final deoxidation. Al is added as a final deoxidizer or as an alloy element to obtain Tapping, otherwise burning loss is serious.

3)It is important to bake the ladle to a temperature of 400 ℃ or above before tapping molten steelAnd the steel is hung in front of the furnace to be tapped after the steel is completely roasted.Removing molten steel surface slag 2-3min before tapping, adding Si-Fe alloy, stirring, rapidly heating to 1630 + -10 deg.C, and taking out And (3) steel. Immediately after the aluminum insertion, the power is reduced (the furnace with 500kg is reduced to below 100 kW) and the steel is tapped.Tapping is carried out by large flow. If tapping is carried out in several packs, attention is paid to: a. for the heat preservation of molten steel, the 40% power is the heat preservation power of the molten steel (full furnace), and the power is gradually reduced along with the reduction of the molten steel in the furnace. b. The time of the deoxidized aluminum is 10min, and aluminum is supplemented in the furnace 7min after final deoxidation and aluminum addition.In the furnace discharging During the period, V-Fe, Ti-Fe, Re and other trace elements are used as key measures for modifying and refining grains, and it has very high rigidity to superhigh manganese The impact of energy is crucial.Aluminum is supplemented in the furnace, the aluminum supplementing amount is determined according to the molten steel in the furnace, and the aluminum supplementing amount is generally 0.05-0.08 percent of the residual molten steel amount. For thick-wall castings, particularly large thick-wall castings, the residual aluminum content in the molten steel is ensured to be 0.035-0.045%. Because the molten steel of the thick-wall casting is solidified slowly, the thick-wall casting can be attacked by oxidation and water vapor, residual aluminum is required to resist oxidation, and the metallurgical quality is ensured.

The affinity of the rare earth Re and oxygen is strong, and the rare earth element must be added after Al is added for final deoxidation. After Re is added into molten steel Will decline for 10min, so the rare earth composite modifier is added by pouring into a bag according to the proportion of 0.02 percent to 0.03 percent and is put into the bag And (4) carrying out element modification treatment such as Re + B, V, Ti and the like, (the grain size is 0.5-3 mm after package filling, and the obtained product is used after drying). After rushing into molten steel Stirring rapidly, removing slag, covering, cutting, and tranquilizing. When the temperature of the molten steel is reduced to 1480 ℃, pouring is started，The temperature of the casting molten steel is not lower than 1450 deg.C (initial pouring temperature should not be lower than 1550 deg.C),the casting ladle must not have residual molten steel before the next ladle.

4)PouringIn the pouring process, the vertical distance between the ladle nozzle and the pouring gate is kept between 50mm and 100mm, and the pouring of single-box casting is finished within 15 seconds to 20 seconds. Firstly, care should be taken to conduct the manipulations, and the pouring with small ends and large middle part is adoptedPouring for 2-3 times after the pouring is full; secondly, the slag is stopped, and any impurities are not allowed to enter the mold; and thirdly, air is introduced and exhausted. Good pouring quality control is a reliable guarantee for good castings. Molten steel is poured into the cavity to achieve accurate drainage, stable injection flow and slow flow collection. The phenomena of flow interruption and turbulence can not occur during pouring, and overflow and splashing can not be generated.After casting, the casting is insulated for 8 hours and then opened,and sand removal, polishing, defect elimination and inspection are carried out to the heat treatment process.

And 5 material samples are respectively cast with the product in the same furnace to form standard Y-shaped Kerr test blocks. The chemical composition of the samples is shown in table 2.

TABLE 25 chemical composition W (%)

Controlling the heat treatment process:

the heat treatment was carried out in a high temperature box furnace model RT 2-3-11.

The purpose of the heat treatment is to obtain an ideal metallographic structure and achieve the best matching of hardness and toughness.

The ultra-high manganese steel adopts a precipitation strengthening heat treatment process, and the purpose of the precipitation strengthening treatment is to be suitable in the smelting process When the alloy is added in proper amount, a certain amount and size are obtained in the ultra-high manganese steel matrix by a heat treatment method Second phase particles of the carbide distributed in a dispersed manner; such a texture is very advantageous for improving the ability of the material to withstand abrasive wear In (1).

The principle of precipitation strengthening heat treatment is that the solution treatment is firstly carried out, and the main purposes are as follows: elimination of carbonization in as-cast structure Article (A)Various carbides (such as grain boundary network carbide and block-shaped carbide) in the cast structureCarbides, needle-like carbides, etc.) and eutectoid tissues are all dissolved,becoming a single solid solution of austenite; subsequent cooling of the austenite from high temperature due to the austenite The desolventizing of the medium carbon can separate out carbide containing alloy elements, the strength and the toughness of the ultrahigh manganese steel are improved,the application range is expanded.

FIG. 2 isThe process specification of the precipitation strengthening heat treatment method of the ultra-high manganese steel. The heat treatment method is to make the casting state super high The manganese steel toothed plate casting is heated to 650-670 ℃ from room temperature at the rate of 80-100 ℃/h, is kept warm for 5 hours, and then is heated to 110-150 ℃/h Heating to 1080-1100 deg.c and maintaining for 4 hr for toughening ultrahigh manganese steel with homogeneous crystal grains and no carbide inside crystal And a small amount of undissolved carbides exist on the grain boundaries.The control of the specific cooling process: the time from opening the furnace door to pouring the casting into the water is controlled to be finished within 30 seconds,ensuring the water inlet temperature of the casting to be above 1080 ℃,otherwise, the carbide is re-precipitated before water quenching; the temperature of the circulating cooling water is kept below 30 ℃, the highest temperature of the circulating cooling water after water toughening is not more than 50 ℃, and the mechanical property of the ultra-high manganese steel is remarkably reduced when the water temperature is higher; the water quantity needs to be more than 8 times of the weight of the casting and the hanging basket, and a circulating water and automatic water replenishing system with clean water quality is adopted; meanwhile, the hanging basket swings the casting up and down, left and right, and front and back, so that the cooling of the casting is accelerated, and the cooling speed of the casting is ensured to reach 30 ℃/second. Finally, a tempering procedure is carried out:the purpose of the tempering treatment is to bring the austenite matrix into the heat treatment And a second-phase strong matrix which is dispersed and distributed is separated out, so that the abrasive wear resistance of the material is improved.The hardening capacity of the ultrahigh manganese steel is improved compared with that of ZGMn13 and ZGMn18, and the ultrahigh manganese steel is mainly a cross twin crystal of dislocation quantity. The resistance of twin boundary formation to dislocation motion is significantly increased, resulting in a higher degree of strengthening of the steel.The casting is heated to 250 ℃ from room temperature in a heat treatment furnace, kept warm for 4 hours and then cooled in air. Go through and return The fire treated ultra-high manganese steel ZGMn18Cr2Re can be seen from the metallurgical structure after tempering in figure 3: separate out particles for carbonization The material is fine and evenly dispersed and distributed, and the improvement of the carbonization shape is beneficial to the improvement of the mechanical property.The mechanical property detection: the appearance of the impact fracture is dimple-shaped, fine and uniformAnd fiber morphology. Under the process condition, the ultra-high manganese steel has the best impact toughness. The transmission flaw detection and electron diffraction detection results of the ultra-high manganese steel film sample are as follows:the ZGMn18Cr2Re super-high manganese steel has austenite and carbonization structures ₂₃ ₆The material MC (see figure 3 in detail), which is dispersed on the substrate to increase its wear resistance.

This heat treatment is similar to conventional water toughening, but the time for low temperature incubation is extended. In this stage the austenite of the as-cast structure continues to precipitate carbides and eutectoid decomposition occurs. During the subsequent temperature increase, recrystallization of the austenite occurs, with partial dissolution of the carbides and graining thereof. The improvement of the carbide form improves the mechanical property of the ultrahigh manganese steel, so that the obdurability, the wear resistance and the service life of the toothed plate of the crusher are improved.

Effect case mechanical property test and organization structure analysis

The samples (Kill test blocks) were processed into Charpy U-notch impact specimens of 10 mm. times.10 mm. times.55 mm and compression specimens of 10 mm. times.20 mm as defined in GB229 standard. The impact test was carried out on a JB-300B impact tester. Hardness was measured using a Brookfield hardness tester model HBRU-187.5 (see Table 3 for results). The compression test was carried out in a WE-30 compression universal material tester, and the Brinell hardness was measured by a hardness meter for compression deformation. Indenter D5 mm, F/D²30, 750kgf, 15% deformation.

TABLE 35 mechanical properties of the heat-treated high-manganese steel sample materials with different compositions

Grouping	Sample materialMaterial	Rm/Mpa	Rp/Mpa	As％	A_k(J/cm²)	HB
							Comparative example 1	ZGMn13	712.3	374	37.20	93.8	182
Comparative example 2	ZGMn18	884.50	430.90	53.00	260	218
							Example 1	ZGMn18Cr2Re-1	996.82	436.12	56.86	263.62	229
Example 2	ZGMn18Cr2Re-2	935.40	426.34	56.05	260.96	225
							Example 3	ZGMn18Cr2Re-3	880.40	418.73	54.74	240.52	229

The ZGMn18Cr2Re-1 ultra-high manganese steel (C: 1.08%, Mn: 18.2%, Cr1.86%, Ni: 3.26%, Mo: 0.76%, Re: 0.20%) with a low carbon content had most of the carbon dissolved in austenite, and thus, it was not possible to form network carbides at grain boundaries, and only bulk carbides were present in the grains. As the rare earth Re-Ti is added, the crystal grains are obviously refined, and the massive carbides become tiny. The ultrahigh manganese steel toothed plate ZGMn18Cr2Re-1 adopting the precipitation strengthening heat treatment process has the best tensile strength and yield strength, and reaches Rm: 996.82MPa, Rp: 436.12MPa, and the impact toughness also reaches 263.6J/cm²。

The compression deformation test considers that the working condition operation condition of the toothed plate of the ultrahigh manganese steel ZGMn18Cr2Re crusher does not allow large plastic deformation, and the work hardening capacity under the condition of small deformation has more guiding significance for actual production and use. Therefore, the maximum compressive strain amount is about 15%. And (3) test results:ultrahigh manganese steel ZGMn18Cr2Re-1 precipitation strengthening heat added with rare earth elements After treatment, the initial hardness HB229 has a deformation hardness HB397 under the condition that the deformation amount under pressure is 15 percent(ii) a The super-high manganese steel ZGMn18 without rare earth elements has the deformation hardness HB342 under the condition that the hardness HB218 is 15 percent of the pressure deformation after water toughening treatment, and the test results are shown in Table 4.

TABLE 4 deformation (15%) and hardness HB of high manganese steels

The ultra-high manganese steel after modification treatment is subjected to precipitation strengthening treatment after being toughened at 1100 ℃, the austenite structure is uniform, and fine spherical composite carbides of Mn, Ni, V, Ti, Cr, Mo and Re are dispersed and separated out in grains. Therefore, the wear resistance is good, and the comprehensive mechanical property is excellent. The development of the performance of the ultrahigh manganese steel is suitable for the working condition of stronger impact. Due to the addition of elements such as Ni, Cr, Mo, Re and the like, the carbon content is properly adjusted, so that the method is also suitable for large-section workpieces, and has wide application prospect.

The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The ultrahigh manganese steel for the toothed plate of the double-toothed roller screening coal crusher is characterized by comprising the following components in percentage by mass:

2. the application of the ultra-high manganese steel as claimed in claim 1 in preparing toothed plates of double-tooth roller screening coal pulverizer.

3. The use of the ultra-high manganese steel according to claim 1 in the preparation of double-geared roller screening coal pulverizer.

4. The method for preparing the ultra-high manganese steel according to claim 1, comprising a smelting process and a heat treatment process.

5. The method for preparing the ultrahigh manganese steel according to claim 4, wherein the smelting process comprises 4 key steps of melting period, refining period, molten steel alloying and component adjustment, and final deoxidation tapping;

step 2, refining period: deoxidizing, dehydrogenating and denitrifying to ensure the smelting quality of the ultra-high manganese steel and heating to 1560-1580 ℃;

6. The method of claim 5, wherein the deoxidation in step 2 comprises pre-deoxidation, final deoxidation, complex deoxidation, enhanced deoxidation and diffusion deoxidation; pure aluminum is adopted for the pre-deoxidation, the final deoxidation and the composite deoxidation, and rare earth is adopted for the enhanced deoxidation; the diffusion deoxidation adopts one or more of ferrosilicon powder, calcium silicoferrite powder, aluminum lime or carbon powder; the time for diffusion deoxidation is 15-20 min.

7. The method of claim 5, wherein pure aluminum in an amount of 0.2% of the molten steel is added to the furnace before tapping for final deoxidation in step 3.

8. The preparation method of claim 5, wherein aluminum supplement is required during the tapping in the step 4, and the amount of the aluminum supplement is 0.05-0.08% of the weight of the residual molten steel; for thick-wall castings, the residual aluminum content in the molten steel is 0.035-0.045%;

in the step 4, Re is added in a form of a rare earth composite modifier according to a proportion of 0.02-0.03% by adopting a ladle, the rare earth composite modifier is obtained by modifying one or more elements in Re + B, V, Ti in a ladle, the grain size of the added rare earth composite modifier is 0.5-3 mm, the mixture is used after being dried, stirred and subjected to slag skimming after being added into molten steel, and then the mixture is subjected to covering and cutting and is subjected to sedation; when the temperature of the molten steel is reduced to 1480 ℃, pouring is started, the temperature of the poured molten steel is not lower than 1450 ℃, and the temperature of the initial pouring is not lower than 1550 ℃.

9. The method of claim 8, wherein the heat treatment process comprises: heating the casting from room temperature to 650-670 ℃ at a temperature of 80-100 ℃/h, preserving heat for 5 hours, heating to 1080-1100 ℃ at a temperature of 110-150 ℃/h, preserving heat for 4 hours, and carrying out water toughening treatment; and then the ultrahigh manganese steel is prepared by tempering treatment.

10. The preparation method of claim 9, wherein the time from opening the furnace door to the water entering of the casting is controlled to be completed within 30 seconds, so that the water entering temperature of the casting is ensured to be higher than 1080 ℃; the temperature of the circulating cooling water is kept below 30 ℃, and the highest temperature of the circulating cooling water after water toughening is not more than 50 ℃; the cooling speed of the casting is 30 ℃/second;