A method to prevent rack and heat treatment deformation

A 2019 - prevents deformation of the rack and heat treatment method 07 - 22 Liu Hongfeng little hao hao' China non-ferrous ( Shenyang) Metallurgical machinery co. , LTD. ) Rack is one of the gear drive parts, it is tend to gear diameter & infin; A special form. Normally, sector rack before milling machining for the blank forging into the circle, the overall heat treatment, heat treatment after eliminating stress forging ring blank, according to the ring gear set aside machining allowance to each working procedure, in the car to car fan shape into, to prevent deformation, turning after the completion of the natural aging treatment is needed to eliminate stress, then according to the pattern cut actual size, become a single rack, then in milling machining. 1. Technical analysis in the past more than our company produces the rack or steel for structural rack shape mostly linear, tooth surface hardness requirement for 240 ~ 280 HBW. The production of the rack is to use the driving part of the ship's crane crane barge, rack and choose material for forging 42 crmo, tooth surface hardness is 290 ~ 320 HBW, rack shape for 110 & deg; Fan-shaped gear tooth surface, the order quantity is 4 pieces. The new structure, the rack of hard-toothed surface processing is the first time in my company production, if USES the conventional forging, the processing method of blank, three rack blank forged into a circle, three rack shape for 330 & deg; , and the entire forging laps of 360 & deg; , when one by one after cutting, there is a rack will be reduced. If the two rack blank forged into a circle, two rack shape for 220 & deg; , 4 pieces rack forging into two whole ring blank, causes 50% of the waste materials and processing. At the same time as the whole sector rack diameter of 5343 mm ( M = 26, z = 207, D = rack diameter mz + 2 m) , conditioning, need to have large heat treatment equipment, 6. 0 m× 5. 5米) 。 And at present, the company equipment can meet the whole whole ring gear blank conditioning needs, in order to reduce the material and processing cost, improve the company's existing equipment utilization rate, how the rack in the process of heat treatment, on the premise of guarantee the rack hardness, choose a suitable heat treatment deformation, in the form of the rack in the uniform stress release during and after heat treatment, rack and small deformation, is one of the difficult points of the rack processing. To this end, we decided to adopt single rack for forging and machining and heat treatment process, to ensure the quality of rack processing. 2. Conditioning prior to determine the machining allowance in order to prevent the rack can't correction deformation occurring in the process of heat treatment of rack processing method, using the method of heat treatment process, to ensure a single rack with enough after quenched and tempered high strength and hardness, good plasticity and toughness, and high machining accuracy. First of all to the rack and the coarse hobbing, stress release before heat treatment after deformation caused by testing, according to the deformation situation to choose the appropriate machining allowance. Allowance for the choice of: rack adopts thick conditioning open after the tooth, tooth flank remain 8 mm cushion, on each side to the bottom of the tooth have 25 mm allowance, cylindrical left on each side to 16 mm, upper and lower end face of plate respectively 40 mm, 15 mm allowance, to ensure that in the event of deformation after machining allowance will be enough quantity to make up, has provided the safeguard for subsequent processing, figure 1 rack machining allowance. Figure 13. Process method ( 1) Platform and baffle rack placed platform adopts the cast iron parts, cast iron platform is the feature of oil cooling after the heating, the platform thermal deformation is small, it won't rack of deformation caused by the deformation of the platform, at the same time to ensure the rack in the process of quenching deformation is minimal. Six platforms welding piece of baffle, baffle is made of Q235 plain steel plate, specifications for 300 mm & times; 150毫米× 50 mm, location distribution in the rack and arc welding symmetrically on the beam of platform, rack on both sides of the couple, rack and arc length of a third place, as well as the rack ends, limits the rack denotation and arch degree of deformation, effectively prevent the rack up during quenching. Figure 2 platform for rack and baffle. Figure 2 ( 2) Brace brace with rack and steel with the same material, because the steel has the characteristics of high temperature resistance, small thermal deformation, can reduce the rack in the process of quenching deformation. Size: 3700 mm & times; 200毫米× 150mm。 Brace and rack web compound to ensure that the rack in the smooth and minimum deformation in the process of heat treatment. （ 3) Furnace charging way to weld brace rack are put on the platform, the platform of the beam, the rack on the shape of welding, the brace with rigid firebrick underlay, and will contact position cushion, cushion flat rack and platform, then the platform with our rack, load to the mean temperature within the chamber of a stove or furnace, heat treatment of heat insulation. During quenching, lift platform, with rack and quenching in oil. 4. Conclusion the rack and the processing method of preventing deformation process in practical, examined the measurement and size of all the parts before and after the rack in the quenched and tempered, are fully meet the needs of subsequent finishing, mechanical performance testing, satisfies the requirement of drawing technology. By using this method processing rack, effectively prevent the rack in the process of heat treatment of serious distortion; The process method simple operation, low cost, can be reused in similar products in the process of heat treatment, high utilization, has wide popularization value. Source: the metal processing ( Hot working) Magazine,