heat treatment process is to make all kinds of metal materials to obtain the excellent properties of important means. Many reasonable choice materials and various forming process in the actual application and can't meet the requirements of metal artifacts of mechanical properties, physical properties and chemical properties, the heat treatment process is indispensable.

but the heat treatment process in addition to outside, it can play a positive role in the process also inevitably produce more or less deformation, and this is must be avoided in the mechanical processing, the relationship between the two is coexist and need to avoid, can only adopt the appropriate method to control the deformation within the scope of the small as far as possible.

a, temperature measurement and control

the industrial application of heat treatment process on form very much, but the basic process of them are hot process, is consists of three stages: heating, heat preservation and cooling. The whole process can be used heating speed, heating temperature, holding time, cooling rate and described several parameters such as heat treatment cycle.

in the heat treatment process, to use all kinds of heating furnace, metal heat treatment in the heating furnace ( Such as basic heat treatment of annealing, quenching, tempering, carburizing chemical heat treatment, seepage ammonia, aluminized, chromizing or hydrogen and oxygen, etc. ) 。 Therefore, the measurement of temperature in the furnace becomes an important heat treatment process parameters measurement.

each heat treatment process in the specification, the temperature is an important content. If you don't accurate temperature measurement, heat treatment process specification is not correct, so that product quality declining even scrapped. Temperature measurement and control is the key to the heat treatment process, is also the key factors influencing the deformation.

two WenZheng fire control and isothermal annealing

high quenching hardness, mixed crystal, a large number of sorbite or widmanstatten structure can make inner hole deformation increases, so use WenZheng fire control and isothermal annealing to deal with forgings. Metal normalizing, annealing, and before the quenching tempering, to the final metal deformation have influence, directly affects the change of metal structure.

the practice proved that in normalizing the isothermal quenching can effectively make the metal structure tend to be uniform, so as to reduce the deformation.

3, reasonable cooling method

metal cooling process after quenching effect on the deformation is also important a reason. Hot oil quenching oil quenching than cold deformation is small, general control in 20 ℃ to 100 ℃ +. Oil cooling ability of deformation is also very important. The mixing way and speed of the quenching influence the deformation.

the faster the cooling rate of metal heat treatment, the uneven cooling, the stress, the greater the deformation of the mould. Under the premise of can ensure that the mold hardness requirements, as far as possible use precooling; Using hierarchical cooling quenching can significantly reduce the metal thermal stress and organization stress formed during quenching, is the effective method to reduce some of the more complex shape workpiece deformation; For some special complex or higher accuracy of workpiece, using isothermal quenching can significantly reduce the deformation.

4, the reasonable structure of parts

metal during cooling after heat treatment, is always the thin part soon cold, the thick part of the cold slowly. In meet the need of actual production situation, we should try to reduce the workpiece thickness disparity, parts of section to uniform, to reduce the transition region due to stress concentration produce distortion and cracking tendency;

artifacts should keep the structure and material composition and microstructure of symmetry, in order to reduce the distortion caused by uneven cooling. Artifacts should try to avoid sharp edges, grooves, etc. , in addition, the thickness of the workpiece on the border, the steps to place with rounded transition; As far as possible to reduce the workpiece hole and slot on the reinforcement structural asymmetry; Adopt the method of reserve was uneven thickness of parts.

5, the reasonable way of clamping and jig

the purpose to make uniform cooling/heating work, in order to reduce the thermal stress, organizational stress, to reduce the deformation, can change the way the clamping, plate parts and the oil level of the vertical shaft parts made, using the compensation washer, bearing washer, stack washer and so on, spline parts available carburized spindle etc.

6, mechanical processing

when heat treatment is the last step of workpiece machining process, heat treatment distortion of the allowable values should satisfy is provided in the pattern of the size, and the amount of distortion according to the working procedure processing size is determined. Therefore, we should according to the distortion rule of the workpiece, to modification of the size of the before heat treatment, heat treatment distortion squarely in the qualified range.

when heat treatment is the intermediate process, heat treatment before the machining allowance shall be deemed to be machining allowance and the sum of quantity of heat treatment distortion. Usually machining allowance is easy to determine, and heat treatment due to the influence factors is more complex, more so for machining to set aside enough machining allowance, the others all can be used as heat treatment distortion quantity is allowed. After heat treatment processing, according to the laws of the deformation of the workpiece, the application of the pre expanding hole deformation, shrinkage, end, improve after quenching deformation rate.

7, use appropriate medium

on the premise of guarantee the same hardness requirements, as far as possible the oily medium, experiment and practice has proved, and other conditions under the premise of no difference, the slower cooling rate of oily medium, and the cooling speed of water medium is relatively faster. And compared with those of oily medium temperature change on the influences of aqueous medium cooling characteristics, under the condition of the same heat treatment, relatively oily medium aqueous medium after quenching deformation is relatively small.