Conversion

Introduction

Deformation Strengthening and Combination of phase change strengthening. It includes the normilation and solid state phase of the metal material, and the two are organically combined, and the metal material is used to organize the structure in the deformation process, affect the phase change process and the phase change product to obtain the desired Organization and performance.

Classification of type

Classification of worms in the formation of heat treatment process, mainly low-temperature refactive heat treatment, high temperature refractive heat treatment, changeable steel shaped heat transfer treatment, and pre-type heat transfer treatment.

(1) Low temperature type heat transfer treatment. It is mainly divided into low-temperature variable quenched (deformation quenching) and low temperature variable. (1) Low temperature variable quenching. Heating the steel to the austenite state, keeping a certain time, then quench to the AR1 (Austenitic Squiration Temperature Line), while the temperature (about 500 ~ 600 ° C) above the MS (upper horse point), to be temperature After uniform, a deformation (pressure processing) is performed, then quenched to obtain martensite tissue. This method is mainly used in structural steel, tool steel, and alloying element content, and a stable steel species of cold bombs. (2) Low temperature variable isothermal quenching. Similar to the previous segment of the low-temperature variable quenching process, but deformation, the same temperature is carried out in the lower beekest area, and the lower Beikestone tissue is obtained after quench. Compared to low-temperature variable quenching, it can be used for steel types with a slightly low content of alloying elements. The low-temperature refrigeration treatment can keep the steel to keep the workpiece with better strength, toughness, and improve its life in the case where the plastic is substantially similar. Its process features are done before the phase changes.

(2) High temperature refactive heat treatment (stabilizing the deformation of the austenite). It is mainly divided into high temperature variable quenching and high temperature variable contour. (1) High temperature variable quenching. The steel is heated to a stable state in which the martensite tissue is obtained in this state. This method is widely used, and there is no special requirement for materials. General carbon steel, low alloy steel can be applied. (2) High temperature variable isothermal quenching. After heating the steel to a stable austenitic state and a deformation, isoelectric or lowerbeikest region is larper or the lower beegan tissue. This method is also widely used. The deformation process of high temperature refactive heat treatment is also completed before the phase transition.

(3) Plasticized steel shaped heat treatment. The heat treatment process of martensite transition is caused by solid-soluble and phase change in phase-induced phase change and phase-induced plasticity, after solid-solubilization treatment, Austeniticization, debris treatment, etc. This fracture is made in phase transitions, which is more complicated.

(4) Pre-shaped heat transfer process. Steel parts that will be in an annealed, normalized or conditioned condition, is enhanced at room temperature or at room temperature, and after tempering, the heat treatment process of quenching and final tempering is rapidly heated. The deformation occurs at room temperature. For structural steel, tool steel pre-refactive heat treatment can achieve improvement, improve plasticity.

Main advantages

1 combine the formation of the metal material and the final performance of the obtained material, simplifying the production process, saving energy consumption and equipment investment.

2 compared to ordinary heat treatment, the metal material can achieve better intensity and toughness of the mechanical properties. Some steels, especially micro-gold steel, only adopted a deformation heat treatment to give full play to the role of alloy elements in steel, high strength, good plastic performance. Due to the above reasons, the deformation of the widespread heat is widely used in the production of metal and alloy plates, strip, pipe, silk materials, and various parts such as leaf spring, connecting rod, blade, tool, mold, etc..

Deformation Process

The plastic deformation (modal variation) in the type revolving process can be used in various forms such as rolling, forging, squeezing, drawing, and It has a loosening decomposition, martensite phase change, denseness, and the like. The order of deformation and phase change is also varied: there is a transformation phase change; or a deformation during the phase change; it can also be deform between one two phases.

When the actual application of the heat treatment process, it is not only necessary to combine the composition and performance requirements of the material, and determine the heat treatment process parameters after the deformation, but more importantly, according to the tissue structure and the phase change after the mother phase shape. And the role of the phase change product, correctly determine the process parameters of the deformation, in order to obtain the desired mother-phase structure and the changed tissue to achieve the desired performance.

Deformation effect

Deformation of the effects of the mother phase

Temperature, the shape changes the tissue structure of the mother phase before the phase change, even changes. The phase transition in the deformation or deformation process is different from general heat treatment in the type, morphology, etc. of phase change kinetics and phase change products, thereby obtaining good performance.

Deformation changes the change in the changes of the mother-phase tissue (deformation temperature, the parameter variable, the total variable variable, the deformation speed, etc.) and the components of the metal material, according to the opposite phase The role of the change, the tissue structure after the phaserable structure is substantially three categories:

1 deformation, the path-shaped variable, such as exceeding the recrystallization critical deformation, the mother phase dynamics or Static recrystallization allows the grain to refine; if multi-channel variation is performed, multiple recrystallization occurs, and the grains of the mother phase are significantly refined (see reply and recrystallization).

2 is changed in the recrystallization temperature of the material, and the mother phase does not recrystallize, and a large number of crystal defects, or only the reply process, forming a multilateral structure.

3-form variable induced second phase is precipitated by the mother phase, the precipitated second phase is interacting with the dislocation, making the ingredients and structures of the mother phase and the structure.

Deformation effects on phase change

Temperature treatment, the mother phase tissue after deformation is often the synthesis of the above types. Now the austenite of steel is an example, the austenitic pair of austenitic pairs and phase transition products afterwards are explained.

The action of ferrite-pearllar phase changes

deformation, produced recrystallized fine-heart grains, so that the ferrite after the cooling transition is correspondingly obtained. Refine. A large amount of crystal defects in austenite in austenite occurred after the deformation, and the transition of ferrite provided a large number of nucleation locations after the transformation of ferrite, and the thermal activation process of ferrite core is easier. Ferrite grain refinement; in addition to the austenite has an accelerated diffusion process, accelerate ferritic transition speed, improve the temperature of the temperature of ferrite (see Type 2 in the Schedule).

If there is a second phase induced in austenite, the fine ferrite grain is more effective. Low carbon, contains micro-gold steel of Nb, V, and Ti alloy elements of the Nb, V, and Ti alloy, belongs to this situation. The deformation causes the austenite to generate poly-side crystals, and more dislocations in the austenite circle boundary, and the deformation induces Nb (CN) or other alloy elements carbon, nitride. The small second phase is first precipitated at the Aushurithic boundary and the crystal boundary, and the picked grain boundary and the grain boundaries, so that the growth of the crystalline and the migration of the grain boundaries are hindered, resulting in austenite recrystallization. The core is difficult to generate it in this point, even if it is not easy to grow, thereby suppressing the occurrence of austenite recrystallization. Only when it is given to a larger deformation, the recrystallization, resulting in the recrystallization, resulting in the recrystallization of Austenitic grains, is smaller than ordinary low carbon steel. About 950 ° C or less, the shape induced the precipitate, which can completely prevent the austenite from recrystallization, so that the austenite unsecolved temperature range is expanded, which is conducive to increasing the shape of the uncludeless zone. Variables make the austenites produce a greater amount of crystal defects. In the austenite re-crystalline region and the unsearched zone, it is obtained by fine austenite grains and high defects of crystal defects. Such austenite transition formed of ferrite crystal grains and uniform, and a ferrite having a 5 μm diameter of 5 μm (laboratory can obtain a ferrite of 2 μm diameter).

Only in terms of grain refinement, the yield strength of the steel is increased by 10 to 15 kgf / mm 2 , while improving the low temperature toughness of steel, making the toughness-brittle transformation The temperature drops to -70 ° C. The refinement of ferritic grains can also offset the brittleness caused by the second phase of the phase precipitation and ferrite, retain its precipitation, and further improve the yield of steel on the basis of good low temperature toughness. strength. Austenites, which can only refine the transformed martensite or bainite tissue for the modified martensite and bainite phase change.

A large number of crystal defects in austenite makes a martensite that grows in a working method, and the bainite crystals are greatly blocked, so that the change in the transition is refined. The crystal defect in the austenite can be converted by the martensite, bainite, so that the transitional martensite or bainite tissue is higher than the general heat treatment Martensite and Bay. The dislocation density of the body. This phenomenon is particularly protruding when the austenite generates formation induced by formation. Phase induced the second phase of the precipitation, nailed austenite existing stereotable error; in further formation, promoting a large number of new dishes in the austenite proliferation, greatly increase the dislocation density in the austenite. Correspondingly increases the dislocation density of the martensite after the transition. Martensite, the median dislocation density in bainite is increased, and it is the main reason for the strength of the steel to improve the strength of steel. Such a martensite tissue is in a backfire, and due to the high dislocation density, the carbide provides a large number of nucleation positions, and as a result, make the carbonizing material in the back of the fire, more uniform distribution. The variable-induced second phase is precipitated from the austenite, reducing the content of carbon and alloys in the austenite, which is advantageous to reduce the number of twin martensite and increase the number of plate strips. The refinement of martensite tissue, the decrease in twin martensite, and the uniform carboned carbide distribution during tempering is a good reason for the toughness of the formation.

Austenitic shape formed in the epitaxial grains, which is more stable, not only for direct formation of martensite, but also genes to re-heat quenching, martensite tissue formed again, The strength of the steel after deformation of the quench is still higher than the general quenching steel.

The austenite removal can refine the transformed bainite, and the transformed bainite tissue type can also be changed. Austenitic austenite in low carbon shellen steel is transformed into an upper bainite tissue, and the austenite varies into particulate bainite tissue. The plasticity of this tissue is better than the upper bisquis.

Conversion induced Martensitic phase change in m s ~ m d temperature range Internal variable energy induced austenite transition into martensite, and martensite transition occurs above m s . M D is called a deformation induced martensite to start transition points. The formation of induced martensite can improve the strength of the steel, more importantly, in the stress concentration in the austenite matrix, due to the generation of induced martensite, avoiding the production and expansion of microcracks, improve steel Plasticity.

The rules of the above austenite have basically been applied to other alloys.

Application

Dimensating heat treatment is effective in efficient use of deformation and phase transformation in metal materials, combining pressure processing and heat treatment operation, allowing the forming process to obtain ultimate performance A process method that is unified. The deformation heat treatment can not only achieve high strength, high plasticity, and high toughness of the general machining treatment, but also greatly simplify the production process of steel or parts, resulting in considerable economic benefits. Therefore, deformation heat treatment has been widely valued by metallurgical industries, mechanical manufacturing and cutting-edge sectors, which is extremely rapid. The theoretical research and practical applications in this area are increasingly in-depth. Since the early 1960s, especially in the 1980s, many factories, research units, and higher industrial colleges have also made a lot of research work in the formation of heat treatment process, actual application effects and strong toughness mechanism. It has begun to use in steel plates, wire, pipe, leaf spring, connecting rod, blade, work and agricultural machine parts.

Although countries in the 1980s have studied a lot of research on various deformation heat treatment, some deformation heat treatment processes have only conducted a positive exploration, and there is no prevailing in the production of universal applications. The main difficulties in practical applications are: Some deformation heat treatment processes apply and develop, depending on the progress of material forming technology; it is also necessary to make certain dedicated, powerful and effective deformation equipment. Nevertheless, certain types of heat treatment processes have many advantages in material performance and economic aspects.

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