The technology details of tap heat treatment

In machining, tap is tool of the commonnest a kind of cutting, use the whorl inside treatment to buckle, by cutting part and petiole composition. Divide in cutting process still be chafed strongly outside a variety of stress action action. Accordingly, requirement tap has high intensity, hardness, wearability and lesser distortion after heat treatment. According to above requirement, the material of production tap chooses steel of tool of element of carbon of T12A, T10A commonly, steel of CrWMn steel, 9CrSi and W18Cr4V high-speed steel, W6Mo5Cr4V2. In the process of heat treatment production of tap, as a result of people often oversight among them a few detail, create distortion of tap heat treatment, even craze discards as useless, appear taller percent defective, cause bigger pecuniary loss. For this aborning should note the following problem: The material of production tap should undertake before machining quality is checked, the microstructure of material should be the ball changes an organization, carbide is petty and distributing even. If the microstructure of material is a shape pearlite and carbide dimension too big, inhomogenous spend put high in meshy carbide even, the plasticity of tap is reduced, quench distortion craze tendency increases, and the brittleness that increases point of a knife, easy collapse blade, lower the service life of tap. In tendency of craze of the distortion when before tap quenchs, quenching to decrease, ask to precision taller tap should eliminate the machining stress of the generation in early days working procedure especially. Tap is in before quenching, all should undertake warm-up, reduce thermal stress in order to drop difference in temperature, reduce the distortion liability of tap. Especially to W18Cr4V high-speed steel, because quench,heat temperature is higher, if put the tap of cold conditions into the bath furnace of high temperature salt that is as high as 1280 ℃ to heat directly, because heat rate is rapidder, can cause very great thermal stress, increase distortion craze liability. So tap is in quench warm-up all should undertake before heating, in order to reduce difference in temperature, reduce thermal stress. When tap heat treatment, can quench to its blade ministry and petiole only, and among transfer not to quench partly. Can make transfer to have tenacity partly so, with benefit at undertaking correctively later. Quench heat temperature should choose inferior temperature as far as possible, in case grain is bulky, reduce the intensity of tap, plasticity and tenacity. Especially small diameter tap, would rather reduce a few hardness, also must make its maintain certain tenacity, avoid high temperature to quench absolutely. Quench meanwhile heat time also should not grow too, heat exorbitantly otherwise temperature and heat preservation time, also can bring about tap grain bulky, decarbonization, overheat burns a phenomenon too even, affect its function and service life, discard as useless even. The tap after quenching should instantly temper, prevent to be placed for long. Temper temperature should ask according to the hardness of tap and decide, and still need to notice the following at 2 o'clock: ① basis quenchs the circumstance is timely adjust temper temperature; The area of the first kind of temper brittleness of ② escape steel, the temper temperature that is like CrWMn steel is 250 ℃ ～ 300 ℃ . Time of temper heat preservation should grow as far as possible a few. The hardness after carbolic steel and heat treatment of awl of alloy steel wire with 61 ～ 63HRC advisable, high-speed steel with 63 ～ 66HRC advisable. Practice proves " detail decides success or failure " , if above detail notices in the manufacturing process of tap, can reduce the heat treatment blemish of tap and distortion and craze greatly, improve the percent of pass of tap and service life, reduce manufacturing cost to increase economic benefits. CNC Milling