Experimental study on cutting with new cutting too

Experimental research on new cutting tools for large high manganese steel supporting wheel

large high manganese steel supporting wheel is one of the key parts of open-pit coal mining equipment, which has large consumption and high cost (about 50000 yuan per piece). With the localization of large-scale open-pit mining equipment in recent years, the machining of large-scale high manganese steel supporting wheel has also become a difficult problem

under large impact and pressure, the lattice structure of austenitic high manganese steel rapidly produces high-density dislocations and deformation twins, resulting in serious funding projects: Huaihai Institute of Technology Natural Science Foundation funded project (z) work hardening; When high manganese steel is at 400-800c, a large amount of (FeMn) 3C hard phase precipitates from 7 phases, making the plasticity of high manganese steel almost zero; The thermal conductivity of high manganese steel is very low, only 1/4 of that of medium carbon steel, so high manganese steel is a typical difficult to process material. 11 the Ministry of Finance issued the notice on Levying consumption tax on batteries and coatings - 41 In the past, when high manganese steel was used in wear-resistant fields such as crushers, wall excavators and ball mills, it generally did not need cutting. However, in recent years, with the gradual application of high manganese steel to advanced equipment such as floating trains, rock drilling robots, new tanks, large open-pit mining equipment and so on, its cutting and processing problems need to be fundamentally solved

in this paper, TN cemented carbide tool, composite SC tool and composite SiN4 tool are used to cut austenitic high manganese steel, the wear curve of tool material is measured, the wear and damage mechanism of tool material is analyzed, and the measures to improve the machinability of high manganese steel are put forward

1 test method the test piece of high manganese steel is austenitic high manganese steel (7-phase structure) after 1050C water toughening treatment. The chemical composition is 1.05% 12.2% - 12.6% mn0.7% - 0.9% Si. The test piece is 065x300 austenitic high manganese steel round bar. The use of high manganese steel requires that the surface processing quality is generally semi finish machining, so the test is designed according to semi finish machining, and the test conditions are selected as cutting depth ap=0.5 feed rate/=0.3mm/r dry cutting, and the cutting geometric parameters are determined to be unchanged (determined by clamping). The cutting machine tool is C ordinary machine tool. The scanning electron microscope is s-25cmk type, and the cutting temperature measuring instrument is WDH type photoelectric thermometer

2 the test results and analysis temperature are 7 phases, and the plasticity of manganese steel at 400-750c decreases significantly, almost close to zero, which is obviously related to (FeMn) 3C. It can be seen from (FeMn) 3C that a large amount of (FeMn) 3C precipitates from austenite in high manganese steel between 400-800c, and (FeMn) 3C is completely dissolved in austenite with the increase of temperature. It is a 111 curve of the relationship between reheat temperature and elongation of austenitic high manganese steel after 1050C water toughening treatment, but the proportion of extruder outlet is still low. It is often a curve of the relationship between the flank wear width (b) of cemented carbide tools and TN coated cemented carbide tools and cutting time and cutting speed. It can be seen from the figure that when cutting austenitic high manganese steel, the wear resistance of TN coated cemented carbide is significantly better than that of cemented carbide; TN coated cemented carbide tools are suitable for low-speed cutting

refers to the damage morphology of TN coated cemented carbide tools at medium speed v=. According to the actual measurement, the cutting temperature at this time is 721c. According to 2 high manganese steel, there is a large amount of (FeMn) 3C precipitation in the local cutting area at this time, and its plastic flank wear mechanism becomes zero. At this time, TN coated cemented carbide bears the brittle and hard impact from high manganese steel. Therefore, the precipitation on the rake face of the tool is related to the impact

and the brittle falling off of the flank are also found, which is verified by SEM photos. According to the comprehensive analysis of wear curve and micro morphology, TN coated cemented carbide tools are suitable for low-speed cutting, and the lower the speed is, the more favorable the cutting is. The cutting speed is no more than 30min (a) is the curve of the relationship between the cutting time and the wear width of the flank when cutting ZGMn13 with scsin4 tools. It can be seen that under the condition of constant cutting speed, cutting depth and feed rate, The flank wear width of composite SC and SiN4 tools increases with the increase of cutting time. (b) It is the relationship curve between cutting speed and flank wear width when sgsin4 two tools cut ZGMn13. It can be seen that when the cutting speed of SC ceramic tool ZGMn13 is 17.2-50.0mmin, the wear width of the flank decreases with the increase of the current cutting speed; When the cutting speed is in the range of 50.0-73.4mmin, the wear width of the flank increases with the increase of the cutting speed. This shows that when the cutting speed is about 50mmin, the wear value of SC ceramic tool is the smallest

when the cutting speed of SiN4 ceramic tool is about 33m/min, the wear value of the flank of SiN4 ceramic tool is 0.38. When the cutting speed is about 70m/nin, the wear value of the flank of Si3N4 ceramic tool is 0.27. Therefore, SiN4 ceramic tool should be selected to cut at about 70mm

(a) is the condition of edge collapse on SiN4 rear cutting surface. The brittle fracture of this cutting is related to the work hardening and the structural changes in a certain temperature range during cutting of high manganese steel. At this time, the measured cutting temperature is about 630 ° C, while a large amount of (FeMn) 3C (2) precipitates from the 7-phase of high manganese steel between 400-800c. The brittle impact of high manganese steel breaks the composite SiN4

the wear morphology of the composite SiN4 rake face after cutting, and the wear appearance belongs to typical dimple failure. The measured cutting temperature at this time is about 930, and (FeMn) 3C in 2 high manganese steel is completely dissolved in 7 phases. At this time, the high manganese steel is a single 7 phases. The X-ray elemental analysis of random points taken from the bottom of the dimple showed that the peak value of FeMnSi on the front face of the tool was obvious. It was obvious that the wear at this time was diffusion wear, and the dimple was caused by the deterioration of local materials on the tool surface and the decrease of strength

(c) is the groove mark ploughed out by the rake face of SC tool when v=24min, which is a typical abrasive wear morphology. According to the actual measurement, the cutting temperature at this time is about 770 ° C, indicating that the groove marks produced are caused by the precipitated (femnhc) in the 7 phases of high manganese steel at this temperature. (d) is the wear morphology of SC rake face at v=84.78mmht=20min, showing obvious dimple like wear. According to the actual measurement, the cutting temperature at this time is about 1040c, and the (FeMn) 3C hard phase in high manganese steel has been completely dissolved in 7 phases at this temperature. The X-ray elemental analysis of the dimple pit bottom shows that there is FeMn in addition to the matrix element tiasimg, so it also belongs to the diffusion wear of typical dimple like failure caused by local material deterioration

the above analysis of tool wear and damage mechanism shows that when the cutting temperature is within the embrittlement temperature range of high manganese steel, 400 layer cemented carbide tools and composite s:3n4 tools are very easy to produce embrittlement fracture, while composite SC tools only have mechanical wear at this temperature. When the cutting temperature is higher than the embrittlement temperature of high manganese steel, both composite SC and composite SiN4 tools have diffusion wear. Through the research and analysis of the machinability of high manganese steel and the wear and damage patterns of new tool materials when processing high manganese steel, the author finds out a processing method with high efficiency and low cost, and successfully applies it to the cutting of ZGMn13 supporting wheel manufactured by a factory for Antaibao large open pit coal mine, and obtains better economic benefits

Table 1 Comparison of various indicators of various cutting tools for machining ZGMn13 supporting rollers table1differentindescanparison note: the model of processing equipment is kcf2 ⑴ 9 (vertical lathe), and the depreciation cost of machine tool is 30 yuan. Table 1 also shows the comparison of various indicators of several cutting tools for machining supporting rollers. It can be seen that the efficiency and economic benefits of cutting high manganese steel parts with various cutting tool materials, It is further proved that the machining of composite SC ceramic cutting tools on the existing machining equipment is feasible. Each supporting wheel manufactured for Antaibao costs about 50000 yuan, and the casting cost of each supporting wheel is about 20000 yuan. It can be concluded from table 1 that using YT15 and TN coated tools can achieve certain profits theoretically, but in fact, it is impossible to achieve it due to low efficiency. However, using composite SC ceramic tools can generate profits and taxes of 28680 yuan per piece, and using SiN4 tools can generate profits and taxes of 27960 yuan per piece. In the actual cutting process, the composite SiN4 tool is seriously damaged, the tool consumption is larger than that of the composite SC ceramic tool, and the auxiliary time is increased. Although the cutting speed is slightly higher than that of the composite SC tool, the overall efficiency is reduced. Therefore, composite SC ceramic tool material is selected in the actual production process. If 50 supporting wheels are manufactured every year, the profit and tax generated by using composite SC ceramic cutting tools is about 1.43 million yuan. Compound SC cutting tools have achieved obvious economic benefits in the current application

3-junction composite SC is an ideal tool material for cutting austenitic high manganese steel. Its cutting efficiency and cutting economic benefits are better than TN coated cemented carbide tools and composite SiN4 tools, and obvious economic benefits have been achieved in actual production. TN coated cemented carbide tools are suitable for low-speed cutting of high manganese steel (30m/nin), with poor cutting efficiency and brittle fracture. When cutting high manganese steel with composite SC tool, the best cutting speed is 50min, and the surface wear forms of cutting high manganese steel are abrasive wear and diffusion wear. When cutting high manganese steel with composite SiN4 tool, the tool head is prone to embrittlement, which is less economical and practical than composite SC tool; Its surface wear is diffusion wear