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Large gear ring replaced induction heat treatment carburizing

Large gear ring replaced induction heat treatment carburizing

Ring gear shantui construction machinery company limited in important parts of anew final drive of bulldozers, high accuracy, abrasion resistance and fatigue resistance. Penetration heat treatment can make the work with high hardness and wear resistance of the surface layer, and the Center section of the workpiece remains toughness and ductility of low carbon steel. Original process for carburizing and quenching, but the technology to produce the ring gear tooth deformation, resulting in artifacts scrapped. Our company through the analysis of the structure of internalgear ring and heat treatment, have developed a programme of induction heat treatment technology.

1. internal gear deformation survey
Inner gear ring made of 20CrMnTi, hardening depth 1.8~2.4mm, surface hardness58~63HRC. The main processes of the inner gear ring: material forging → → → →→ fine car gear rough car fire carburizing throwing → → → → → quenching and tempering fine cars.

Determine the ring gear as shown in the heat treatment process. Normalization procedure was in a box-type resistance furnace thermal insulation 2H; in IPSEN controlled atmosphere carburizing and quenching process in the oven; Tempering Tempering furnace IPSEN; hardening procedure in IPSEN in multipurpose furnace withcontrolled atmosphere, to prevent carbon dioxide removal. In order to reduce thering gear quenching distortion design special quenching bulging tires to stop theshrinkage of the ring gear, add, after the fast expansion of the workpiece fetal quenching, quenching medium for good k-rich oil, tempering temperature 150 ℃.

Test results after quenching, tempering, hardness to meet the requirements, but the changes in the value of m ≥ 1.2mm, deformation and maximum 2.6mm. Varyingdegrees of elliptical deformation of the workpiece to meet Assembly requirements. Internal gear Jin Xiangru shown in Figure 4, martensite and carbides, level 3 level of martensite, carbide grade 1, to meet the requirements.

2. cause analysis and process improvement
Within tooth circle by 920 ℃ high temperature heating overall carburizing, carburizing time up to 30h, artifacts in high temperature district time too long, hot stress larger, deformation larger; quenching Shi within tooth circle surface, and heart Department cooling not while, surface cooling more fast, heart Department cooling more slow, caused stress larger, and for the tooth circle size larger, and tooth Department size more thin, even joined quenching expansion tire block within tooth circle deformation, also cannot control quenching process in the of artifacts size changes and the stress release. Because subsequent tooth is no longer processing, deformation cannot be repaired, causing artifacts scrap.

As a result of rapid quenching technology for quickly heating the workpiece, can reduce the deformation of ring gear. In response to these circumstances, we decided to adopt a programme of induction heat treatment technology. Induction heat treatment heat up fast, only the wear and fatigue resistance of tooth surface is heated, plastic that can still maintain good elsewhere, and the heating time is short (about 40s), greatly reduce the deformation and since only teeth are heated, another location is not heated, and other locations when play a supporting role to preventtooth deformation, which reduces the deformation.

Based on the above analysis, instead of 45 steel inner ring material, process adjustments are as follows.

(1) the technical requirements 52~60HRC surface hardness, hardness 248~293HBW, top 1.9~12.4mm, 2.4~5.0mm pitch hardened layer depth of the hardened toothroot hardened 1.5~3.0mm.

(2) route cutting saddle → → → → normalizing of forging and tempering throwing→ → → → → cutting induction hardening and tempering fine cars.

(3) induction hardening induction 1200kW large gear induction hardening machinepower supply using IGBT transistor intermediate frequency power supply and the ring gear structural design of internal gear ring of the sensor, as shown in Figure 6.Work hardening inductor using liquid jet device of centralized heating sensor, after the end of the workpiece heating, direct liquid injection quenching; using5%~7%AQ251 quenching medium.

(4) the effective quenching after tempering, test items and results. Necropsy results shown in the microstructure, hardened tissue of tempered martensite grain level9; heart tissue for tempered sorbite, grain size for grade 8; tooth hardening, hardening; design of microstructure and hardening test results meet the technologicalrequirements. While changes in the value of m ≤ 0.4mm, greatly reduced compared with 20CrMnTi carburizing gear ring, satisfy the demand for Assembly and use.

3. the effect of confirmation
(1) the effect of the passage of the analysis, experimental induction hardening can be seen to be the ring gear are up to requirements developed by heat treatment,slightly lower compared with the carburizing heat treatment surface hardness of the workpiece, but hardened layer depth is deep, and martensite grain size at the same level, but carbide with high wear resistance. So I installed verification company,hosts 3000h inspection, internal gear wear is very small, no problem, fully meet therequirements.
(2) the processing efficiency of two kinds of manufacturing processes of various machining processes and normalizing same 20CrMnTi material high temperature tempering after carburizing gear ring and reheated quenching after tempering timerequired for 46h,45 steel gear hardening and tempering, induction hardening tempering is only 9.5h. Induction hardening process the workpiece is greatly reducedmanufacturing cycles, improving production efficiency.

(3) 20CrMnTi steel production cost price higher than that of steel 45 and 45 steel can be used to reduce the cost of production; carburizing heat treatment need to consume large amounts of energy, infiltrating agents, high production costs and environmental pollution by emissions; induction heat treatment only consumes a small amount of electrical energy, no emissions, no pollution, are environmentally-friendly technology, heat treatment industry is focused on the promotion of energy saving, emission reduction technologies.

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