Quenching&annealing and Tempering’s different

Quenching&annealing and Tempering’s different

When the term “annealing” is applied to ferrous alloys without qualification, full annealing is applied. Precision metal parts This is achieved by heating above the alloy’s transformation temperature, then applying a cooling cycle which provides maximum softness. This cycle may vary widely, depending on composition and characteristics of the specific alloy.

   Quenching is a rapid cooling of a steel or alloy from the austenitizing temperature by immersing the workpiece in a liquid or gaseous medium. Quenching medium commonly used include water, 5% brine, 5% caustic in an aqueous solution, oil, polymer solutions, or gas (usually air or nitrogen).

  Selection of a quenching medium depends largely on the hardenability of material and the mass of the material being treating (principally section thickness).

  Precision metal parts The cooling capabilities of the above-listed quenching media vary greatly. In selecting a quenching medium, it is best to avoid a solution that has more cooling power than is needed to achieve the results, thus minimizing the possibility of cracking and warp of the parts being treated. Modifications of the term quenching include direct quenching, fog quenching, hot quenching, interrupted quenching, selective quenching, spray quenching, and time quenching.

  Tempering. Precision metal parts In heat treating of ferrous alloys, tempering consists of reheating the austenitized and quench-hardened steel or iron to some preselected temperature that is below the lower transformation temperature (generally below 1300 ℃ or 705 ℃). Tempering offers a means of obtaining various combinations of mechanical properties. Tempering temperatures used for hardened steels are often no higher than 300 ℃(150 ℃). The term “tempering” should not be confused with either process annealing or stress relieving. Even though time and temperature cycles for the three processes may be the same, the conditions of the materials being processed and the objectives may be different.

 

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Classification of Heat Treating Processes

Classification of Heat Treating Processes

 Precision CNC machining parts In some instances，heat treatment procedures are clear-cut in terms of technique and application．whereas in other instances，descriptions or simple explanations are insufficient because the same technique frequently may be used to obtain different objectives．For example, stress relieving and tempering are often accomplished with the same equipment and by use of identical time and temperature cycles．The objectives，however，are different for the two processes．

 The following descriptions of the principal heat treating processes are generally arranged according to their interrelationships．

 Normalizing consists of heating a ferrous alloy to a suitable temperature (usually 50°F to 100°F or 28℃ to 56℃) above its specific upper transformation temperature．This is followed by cooling in still air to at least some temperature well below its transformation temperature range．For low-carbon steels, the resulting structure and properties are the same as those achieved by full annealing；for most ferrous alloys, normalizing and annealing are not synonymous.

 Precision CNC machining parts  Normalizing usually is used as a conditioning treatment, notably for refining the grains of steels that have been subjected to high temperatures for forging or other hot working operations. The normalizing process usually is succeeded by another heat treating operation such as austenitizing for hardening, annealing, or tempering.

  Precision CNC machining parts Annealing is a generic term denoting a heat treatment that consists of heating to and holding at a suitable temperature followed by cooling at a suitable rate. It is used primarily to soften metallic materials, but also to simultaneously produce desired changes in other properties or in microstructure. The purpose of such changes may be, but is not confined to, improvement of machinability, facilitation of cold work (known as in-process annealing), improvement of mechanical or electrical properties, or to increase dimensional stability. When applied solely to relive stresses, it commonly is called stress-relief annealing, synonymous with stress relieving.

    

Heat treatment of metal

Heat treatment of metal 

  Precision CNC machining parts The generally accepted definition for heat treating metals and metal alloys is “heating and cooling a solid metal or alloy in a way so as to obtain specific conditions or properties.” Heating for the sole purpose of hot working (as in forging operations) is excluded from this definition．Likewise，the types of heat treatment that are sometimes used for products such as glass or plastics are also excluded from coverage by this definition．

 Transformation Curves 

 Precision CNC machining parts The basis for heat treatment is the time-temperature-transformation curves or TTT curves where，in a single diagram all the three parameters are plotted．Because of the shape of the curves，they are also sometimes called C-curves or S-curves．

 To plot TTT curves，the particular steel is held at a given temperature and the structure is examined at predetermined intervals to record the amount of transformation taken place．It is known that the eutectoid steel (T80) under equilibrium conditions contains，all austenite above 723℃，whereas below，it is the pearlite．To form pearlite，the carbon atoms should diffuse to form cementite．The diffusion being a rate process，would require sufficient time for complete transformation of austenite to pearlite．From different samples，it is possible to note the amount of the transformation taking place at any temperature．These points are then plotted on a graph with time and temperature as the axes．Through these points，transformation curves can be plotted as shown in Fig.1 for eutectoid steel． Precision CNC machining parts The curve at extreme left represents the time required for the transformation of austenite to pearlite to start at any given temperature．Similarly，the curve at extreme right represents the time required for completing the transformation．Between the two curves are the points representing partial transformation. The horizontal lines Ms and Mf represent the start and finish of martensitic transformation.

  

Drilling and Milling Machines

Drilling and Milling Machines 

      Precision CNC machining parts Upright drilling machines or drill presses are available in a variety of sizes and types, and are equipped with a sufficient range of apindle speeds and automatic feeds to fit the neds of most industries. Speed ranges on a typical machine are from 76 to 2025 rpm., with drill feed from 0.002 to 0.020 in.per revolution of the spindle.   

  Radial drilling machines are used to drill workpieces that are too large or cumbersome to conveniently move. The spindle with the speed and feed changing mechanism is mounted on the radial arm; by combining the movement of the radial arm around column and the movement of the spindle assembly along the arm, it is possible to align the spindle and the drill to any position within reach of the machine. For work that is too large to conveniently support on the base, the spindle assembly can be swung out over the floor and the workpiece set on the beside the machine.    

 Plain radial drilling machines provide only for vertical movement of the spindle; universal machines allow the spindle to swivel about an axis normal to the radial arm and the radial arm to rotate about a horizontal axis, thus permitting drilling at any angle. 

 A multispindle drilling machine has one or more heads that drive the spindles through universal joints and telescoping splined shafts. All spindles are usually driven by the same motor and fed simultaneously to drill the desired number of holes. In most machines each spindle is held in an adjustable plate so that it can be moved relative to the others. The area covered by adjacent spindles overlap so that the machine can be set to drill holes at any location within its range. 

   Precision CNC machining parts The milling operation involves metal removal with a rotating cutter. It includes removal of metal from the surface of a workspiece, enlarging holes, and form cutting, such as threads and gear teeth. 

Within an knee and column type of milling machine the column is the main supporting member for the other components, and includes the base containing the drive motor, the spindle, and the cutters. The cutter is mounted on an arbor held in the spindle, and supported on its outer extremity by a bearing in the overarm. The knee is held on the column in dovetail slots, the saddle is fastened to the knee in dovetail slots, and the table is attached to the saddle. Thus, the build-up the knee and column machine provides three motions relative to the cutter. A four motion may be provided by swiveling the table around a vertical axis provided on the saddle. 

 Precision CNC machining partsFixed-bed milling machines are designed to provide more rigidity than the knee and column type. The table is mounted directly on the machine base, which provides the rigidity necessary for absorbing heavy cutting load, and allows only longitudinal motion to the table. Vertical motion is obtained by moving the entire cutting head.   

  Tracer milling is characterized by coordinated or synchronized movements of either the paths of the cutter and tracing elements, or the paths of the workpiece and model. In a typical tracer mill the tracing finger follow the shape of the master pattern, and the cutter heads duplicate the tracer motion.

Operational safety and environmental protection

Operational safety and environmental protection

 Precision wire cutting Along with advance in technology and human culture development, the people are more and more high to the working condition improvement and the environmental protection request. The electric spark forming processing as a result of its own characteristic, can have the driving fluid splash, the smog, the noise, the electromagnetic radiation, the noxious gas inevitably in the processing process and so on the safety factor and the pollution, is noticeable to the operator personal safety and the environment harm. Therefore, for the guarantee electrical finishing industry sustainable development, must act according to “the green manufacture principle”, the realization resources most effective use and the reject threshold produces with the emissions. Should take following measure specifically:

①         Precision wire cutting Seal engine bed work area. This is advantageous to the improvement driving fluid, the smog, the electromagnetic radiation and so on to the human body, the engine bed, the working conditions pollution, is advantageous in the operating process prevented receives an electric shock the danger as well as to the noxious gas centralized processing emissions;

 ②Precision wire cutting Vicarious technical utilization. For example, the environmental pollution which creates for the reduced use driving fluid, may in the guarantee processing efficiency, the processing precision, the processing cost as well as under the processing process stable premise, selects the pollution small driving fluid as far as possible, simultaneously should study, the development vigorously does not use the driving fluid the formed processing technology;

  ③ Reject post-processing. The waste liquid, the waste gas produces which after the processing in must pass through processing to be able to discharge. Needs to point out specially, has pollutant reasonable processing to the processing process, not only is advantageous to the enhancement work security, the reduction environmental pollution, but also is advantageous in improves operator's working conditions, causes when the operator work the mood is happy, this regarding enhances the electrical finishing industry the social image and the market competitive power also is extremely beneficial.

  

Electric spark forming processing craft trend of development

Electric spark forming processing craft trend of development

 Through processes the mechanism to the electric spark forming the research, further promulgates the electric discharge process the inherent laws, and take this as the instruction, impels the electric spark forming processing craft to the high efficiency, the high accuracy, the low loss direction to develop, meanwhile should pay attention to the micro refinement processing aspect the development. 

(1) processing process highly effective

 Precision wire cuttingNot only the processing process highly effective manifests in through the improvement electric spark machining servosystem, the control system, the driving fluid system, the engine bed structure and so on, reduces the above factor to the electric spark forming processing efficiency influence, enhances, the precision work efficiency thickly in under the guarantee processing precision premise, meanwhile should reduce the non-cutting time as far as possible (for example programming time, electrode and work piece localization time, maintenance time and so on), this needs to strengthen the engine bed the automatic programming function, expands the engine bed online backstage programming ability, the improvement and the development suitable electrode and the work piece positioning device.

 In the engine bed maintenance aspect, should strengthen the engine bed the multimedia functions and the online help function, regarding the common breakdown, the operator may act according to the computer prompt realization trouble shooting directly, simultaneously this is also advantageous in strengthens the engine bed the feasibility and operator's operation skill.

 (2) processing process precision 

Precision wire cutting Through uses a series of advanced processing technology and the technique, at present the electric spark forming processing precision had the comprehensive enhancement, some has been possible to achieve the mirror surface processing level. But looked from the overall that, the vanguard technology insufficiently is also mature in the actual production application and widespread, therefore has the necessity comprehensive impetus to have the vanguard technology further consummation and to develop to the industrial production direction. In the guarantee processing speed, under the processing cost premise, makes the electric spark forming processing the precision level further to enhance, causes the electric spark forming to process into some major parts, the essential components finally processing way. At the same time, to processes the precision the weight not to be able to limit merely to the work piece size precision and the surface roughness, but also should include the profile the GDOP, deterioration level thickness as well as the microscopic crack, the oxidation, the corrosion and so on. 

(3) processing process micro refinement

Precision wire cutting  An electric spark forming processing important application domain is the narrow trough, the deep cavity, the tiny components processing, therefore the processing process micro refinement will be the next important development direction. The electric spark processes the mechanism and the conventional electric spark forming processing tiny is same, but has own craft characteristic: Each pulse electric discharge energy is very small, driving fluid circulation difficulty, stable electric discharge gap scope small and so on. Based on these craft characteristic, the tiny electric spark forming processing processing equipment, the driving fluid circulatory system, the electrode preparation and so on inevitably and the conventional electric spark forming processing has the very big difference. Therefore, needs key to study the non-mechanical action

 and the disturbance to the processing process influence and so on, further enhances the processing efficiency, the processing precision and the processing process stability. 

(4) application scope expansion 

At present, not only the electric spark forming processing may process each kind of electric conduction metal material and the complex die space, but also can realize to the semiconducting material, the non-conducting material processing, and has obtained the good processing effect. At the same time, the electrode material type also unceasingly increases. This aspect main trend of development is: Further studies the semiconducting material, the non-conducting material electric spark machining mechanism, promotes its processing efficiency, the processing precision, the processing process stable enhancement, the expansion to be possible to process the material the scope; Besides the processing complex die space, further realizes to the three dimensional die space, the complex profile processing; Development performance superior new electrode material.

   

Electric spark forming processing theory trend of development

Electric spark forming processing theory trend of development

Precision wire cuttingIn recent years, the electric spark forming processing basic theory research not yet made the substantive progress, although some scholars to the processing process electric discharge trace, the material eclipse eliminated the principle and so on to propose some new views, but obtained the significant breakthrough by no means in the electric spark machining mechanism research aspect. The more active research area mainly concentrates in the processing craft theory and the control theory aspect.

  Precision wire cuttingIn the processing craft fundamental research aspect, how does the research hot spot mainly is enhance the electric spark forming processing the surface quality and the processing speed, reduces the loss, the development electric spark machining scope, as well as exploration complex, tiny structure processing method and so on. Will apply through the research results in the production practice, will comprehensively enhance the electric spark forming processing workability. In the control fundamental research aspect, the intelligent control always is the research key. The domestic and foreign production new electric spark forming processing engine bed mostly has used the intelligent control technology, this technical application makes the engine bed operation to be easier, requests to the operator lowly. At the same time, the intelligence control system has from the learning capability, but the online automatic monitor, the adjustment processing process, realizes the processing process optimized control.

 Although the electric spark forming processing fundamental research in aspects and so on basic theory, processing craft theory, control theory all has certain development and the enhancement, but the processing craft theory, the control theory need to obtain the further full scale development, must have the breakthrough in the entire electric discharge process mechanism research. Therefore, the electric spark forming processing fundamental research trend of development will be further is discussing the processing craft theory and the control theory, enhances the electric spark forming processing workability and the processing scope, obtains the better control effect at the same time, key research electric discharge process mechanism.

 The electric spark forming processing mechanism research has not made the unprecedented progress the primary cause except outside the electric discharge process itself complexity, randomness, but also because the research technique and the method lack the innovation. Therefore, it is necessary to profit from other research area the success experience, directs the human advanced research technique and the experimental technology, the victory tradition research technique limitation, the deep person analysis and the revelation entire electric discharge process intrinsic essence, the establishment may reflect objectively the electric discharge process rule the theoretical model, instructs the electric spark forming processing craft theory and the control theory research, but the computer simulation technical possibilities realizes this process effective tool

 electric spark forming processing equipment structure improvement

  Precision wire cutting The model modern machining engine bed development experience, the electric spark forming processing equipment develops to the numerical control direction is a irreversible tendency. On the one hand should by the high accuracy, the high velocity, change into the pursue goal automatically, seizes the market by the technical superiority; On the other hand should consider fully the equipment the performance price compared to, through to the engine bed function reasonable localization, makes the structure improvement and the modular design, uses the open numerical control system, enhances rationality which the engine bed designs, provides by the lowest price and the enough function to the user may satisfy each kind of electric spark forming processing engine bed which the different processing needs.

  Modern machining technological development impact, before suits uses the electric spark machining a part of processing domain to substitute gradually for the machining way. But, the modern science and technology development proposed to the components manufacture precision a higher request, each kind of high performance material application is day by day widespread, simultaneously, some components structure tends to the complication, the microminiaturization, thinly, this all causes the machining technology to be restricted in certain processing domain application, but these are exactly the electric spark forming processing technical superiority, also is it has the existing space and the development potential reality basis.