Development of the hottest high manganese steel we

2022-08-21
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Development of high manganese steel welded composite hammer 1 experimental purpose

Abstract: This paper introduces the production process, service performance and production cost of pckw-1618 reversible impact crusher composite hammer by welding wear-resistant alloy composite plate at the striking part of high manganese steel hammer. The industrial test results show that the service life of the new high manganese steel welded composite hammer is about 3 times that of the modified high manganese steel mn13cr2reti integral hammer and 1.5 times that of the ultra-high manganese steel mnl8cr2more integral hammer. Its production cost is between the above two hammers, but its performance price ratio is the best among the three types of hammers

key words: welding; Crusher; Composite hammer; High manganese steel

pckw-1618 reversible impact crusher is a newly developed high-efficiency crusher mainly used for fine crushing of mineral raw materials such as coking coal, gypsum, limestone, iron ore, dolomite and granite [1]. The crusher is equipped with 84 small hammers, each weighing about 11 kg. Pckw-1618 reversible impact crusher has high power (315 kW), rotor length of 1.8 in, diameter of 1.6 in, and rotating speed of 650 R/min, so the production efficiency is very high. In addition, the crusher rotor can rotate forward or reverse, that is, after the rotor runs in a certain direction for a period of time, if the working surface on one side of the hammer head is seriously worn, there is no need to replace the hammer head at this time, just reverse the rotation direction of the rotor, so it is very convenient to use

at present, it is found that the main factor affecting the normal operation of this new crusher is the wear resistance of the hammer. At present, the hammer head of pckw-1618 reversible impact crusher is mainly made of ultra-high manganese steel and modified high manganese steel mn13cr2reti. Among them, the former is more widely used than the latter. The main reason is that the impact hardening effect of the former is more obvious than the latter in the working process of the hammer head. However, even so, the service life of the ultra-high manganese steel mnl8cr2more hammer is not ideal. For example, when a dolomite mine in Baotou breaks dolomite, the continuous service life of the ultra-high manganese steel mn18cr2more hammer is only about 10 days, while the continuous service life of the modified high manganese steel mn13cr2reti hammer is only about 4 days. The frequent replacement of hammers not only seriously affects the normal operation of crushers, but also increases the labor intensity of workers and the production cost of fine ore raw materials. Therefore, improving the service life of the hammer has become a key technical problem to be solved urgently for pckw-1618 reversible impact crusher. Therefore, the author conducted a series of tests to explore ways to improve the service life of the hammer. At first, medium carbon rare earth bainitic cast steel and medium chromium cast steel with high strength, toughness and hardness (48~52 HRC) were tried to replace high manganese steel, but the effect was not ideal. Instead of significantly improving the wear resistance of the hammer head, the hammer head was broken during use due to insufficient toughness reserves of medium carbon rare earth bainite cast steel or medium chromium cast steel. Later, the composite hammer head of high manganese steel and high chromium cast iron was tested, that is, the hammer handle was made of high toughness high manganese steel mn13cr2reti, and the striking part of the hammer head was made of high wear-resistant high chromium cast iron cr20mo2cu, but the test still ended in failure. The reason was that the small hammer head of pckw-1618 reversible impact crusher made the composite area of high manganese steel and high chromium cast iron smaller, resulting in low composite strength of the hammer head and a U-turn phenomenon; In addition, the rotor speed of pckw-1618 impact crusher is high, which makes the hammer head collide violently with the mineral raw materials entering the crusher in the process of use. High chromium cast iron is a brittle material with poor toughness, so the phenomenon of high chromium cast iron fragmentation occurs in the process of use. Recently, the author solved this problem by welding wear-resistant alloy composite plate at the striking part of the end of high manganese steel mnl3cr2reti hammer. After practical use, the service life of high manganese steel mn13cr2reti hammerhead welded with wear-resistant alloy composite plate is 1.5 times that of ultra-high manganese steel hammerhead mn18cr2m0re and 3 times that of modified high manganese steel mn13cr2reti hammerhead

1 design idea of welded composite hammer

1.1 design principle of welded composite hammer

Figure 1 is the schematic diagram of pckw-1618 reversible impact crusher hammer. It can be seen from the figure that the working principle of this type of crusher is actually the same as that of the hammer crusher with shaft hole. In view of the high speed of the hammer head of pckw-1618 reversible impact crusher and the large impact force received during its operation, and the current hammer head made of a single wear-resistant material and the composite hammer produced by conventional casting process are difficult to meet the requirements, the new pckw-1618 reversible impact crusher hammer head decided to adopt the welding composite method. The basic idea is to significantly improve the wear resistance of the hammer head by welding cemented carbide materials at the striking part of a single hammer head with high toughness, which can not only ensure the integrity, toughness and safety of the hammer head, but also give full play to the excellent wear resistance of cemented carbide. Under the guidance of such a design idea, it is required that the material for making the hammer head should not only have high toughness and certain wear resistance, but also have good welding performance, so as to avoid the occurrence of hammer handle fracture, turning around and cemented carbide falling off at the striking part during the use of the hammer head

1.2 selection of matrix material of welding composite hammer

according to the design idea of welding composite hammer, medium and low carbon steel, medium and low carbon low alloy high strength steel and high manganese steel are likely to become the matrix material of composite hammer. Among them, medium and low carbon steel and medium and low carbon low alloy high strength steel have the advantages of good toughness and excellent welding performance, but their shortcomings are poor wear resistance and poor casting performance. If they are selected, some domestic manufacturers have also adopted high-precision load sensors for force measurement. As the base material of pckw-1618 reversible impact crusher hammer, the hammer handle may be worn first due to intense friction during the use of the hammer, resulting in fracture and turning around. Therefore, Medium and low carbon steel and medium and low carbon low alloy high strength steel are not suitable for the hammer handle of pckw-1618 reversible impact crusher; High manganese steel Mn13 has the characteristics of high toughness, excellent wear resistance and good casting performance. It is an ideal material for making pckw-1618 reversible impact crusher hammer. If the high manganese steel Mn13 is modified or alloyed, its wear resistance will be further improved. Therefore, it is appropriate to choose the modified high manganese steel mn13cr2reti as the material of the welding composite hammer, and the production cost of the modified high manganese steel mn13cr2reti is relatively low; Although the wear resistance of ultra-high manganese steel l8cr2more is better than that of modified high manganese steel mn13cr2reti, its production cost is high, so it is not suitable for welding composite hammer. The only deficiency of high manganese steel as the material of welding composite hammer is its high carbon content and high alloy content, so the welding performance is poor. However, if this deficiency of high manganese steel is overcome by adopting appropriate welding process, high manganese steel will become an ideal matrix material for the production of welding composite hammer

1.3 selection of cemented carbide at the striking part of the welding composite hammer

the cemented carbide at the striking part of the hammer is proposed to adopt a new type of wear-resistant alloy composite plate. The new wear-resistant alloy composite plate takes 25# low carbon steel as the substrate, and generates a wear-resistant cemented carbide layer with a certain thickness on the substrate by using a special fusion welding process. 25 # the thickness of low carbon steel substrate is 5 ~ 11 mm, the thickness of hard wear-resistant alloy layer is 6 ~ 12 mm, and the hardness is 65 ~ 72 HRC. Generally, the carbides in hard wear-resistant alloy layer are MC and M7C3, and the volume percentage is 30 ~ 40. Users can choose the thickness of the substrate, the thickness of the hard wear-resistant alloy layer and the type of carbide in the wear-resistant alloy layer according to their own requirements. Although many countries in the world can produce wear-resistant alloy composite plates at present, it is said that the wear-resistant alloy composite plates produced by Australian alloy steels company have the largest alloy layer thickness and the best quality. The wear-resistant alloy composite plates used in the welding composite hammer in this paper are composite plates produced by Australian alloy steels company with a substrate thickness of 9 mill and a hard wear-resistant alloy layer thickness of 10 RAM (hardness of 65 HRC). Due to the excellent welding performance of 25 # low carbon steel, the welding problem between high manganese steel and cemented carbide at the striking part of the composite hammer originally designed is changed into the welding problem between high manganese steel hammer body and low carbon steel, which greatly reduces the difficulty of welding and improves the bonding strength between wear-resistant alloy composite plate and the base material of the hammer

1.4 composite of welded composite hammers

two key problems need to be solved to successfully weld the high manganese steel hammer body and wear-resistant alloy composite plate. The first is the welding strength. Even if the high manganese steel hammer body is connected with the wear-resistant alloy composite plate by welding, it must have sufficient strength. Otherwise, the hammer head will gradually fall off due to frequent impact during use. According to experience, this problem can be solved by selecting the welding rod and welding process suitable for Mnl3 welding of high manganese steel and embedding carbon steel plate in the body of high manganese steel hammer to improve the welding strength or bonding strength between the body of high manganese steel hammer and wear-resistant alloy composite plate. The method is to select Swiss super2222 or stainless steel electrode on one side of high manganese steel matrix to form the transition layer of the weld, and the welding between the transition layer and wear-resistant alloy clad plate can use ordinary low carbon steel electrode; The embedded steel plate adopts A3 steel plate with a thickness of 10 mm, which is similar to the composition of carbon steel substrate; The second is the welding cracking of high manganese steel. Under the action of high welding heat and thermal stress, high manganese steel in the welding position and surrounding areas will undergo structural transformation and embrittlement, making it crack. Therefore, it should be cooled in time during welding

2 production process of welded composite hammers

the production of high manganese steel mnl3cr2reti hammers for experiments was carried out in a 250 kg medium frequency induction furnace in the metallurgical laboratory of Inner Mongolia University of science and technology. The casting process of the matrix of high manganese steel mnl3cr2reti hammer is completely the same as that of the common high manganese steel castings. The hammer head is formed by vacuum EPC. When making the foam plastic model, the position of the alloy plate of 19 mm and the thickness of the weld of about 10 mm are reserved on the striking surface of the model hammer, and two A3 steel plates of 10 mm x30 itlmx 50 mm, which have been derusted, are inserted in the middle of the foam plastic model perpendicular to the striking surface of the hammer as stiffeners for welding and connecting with the wear-resistant alloy composite plate

1. Principle of false test: 1) when a beam with rectangular section bears the difference of tortuous load, the reasons are: after the casting is cooled to room temperature, turn over the box and drop the sand, knock out the pouring riser, heat the casting to 1050 ℃ for 3 hours, and then put it into the cooling water tank for water toughening treatment

before welding the high manganese steel hammer base and wear-resistant alloy, clean and polish the hammer body, especially the iron oxide scale of the steel plate at the welding position. When welding, first use super2222 or stainless steel electrode to lay and weld about 10 mm thick transition layer on the welding part of high manganese steel hammer body, and then use 256 carbon steel electrode to weld the cut wear-resistant composite alloy plate with the hammer body. In order to prevent cracks in the welding part of the high manganese steel hammer body during welding, the non welding part of the hammer head is always placed in water for cooling. Finally, hard alloy is overlaid on the weld to protect the weld and the carbon steel layer of wear-resistant composite alloy plate from rapid wear

3 service performance of welded composite hammer

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