This is mainly carried out on cold-rolled steel like wire-drawn steel, centrifugally cast ductile iron pipe etc. This treatment is applied to low-carbon, cold-rolled sheet steels to restore ductility. 2. The next step of the process is letting steel stay at that temperature for a while. Steel after annealing at 600 °C showed lower final hardness than steel in as-received conditions, similar to steel after annealing at 800 °C and higher than steel after annealing at 1000 °C. [citation needed]. Sub-critical annealing does not involve formation of austenite. Accordingly, steels heated above A1 are subjected either to slow continuous cooling or to isothermal treatment at some temperature below A1 temperature at which transformation to the desired microstructure can occur in a reasonable amount of time. It is possible to calculate upper and lower critical temperatures using the actual chemical composition of the steel. Steels can be spheroidized, that is, heated and cooled to produce a structure of globular carbides in a ferritic matrix. Eventually, it is necessary to anneal the piece to allow further forming operations without the risk of breaking it. In annealing, atoms migrate in the crystal lattice and the number of dislocations decreases, leading to a change in ductility and hardness. Stress Relief annealing. Effect of prior structure – The finer and more evenly distributed are the carbides in the prior structure, the faster is the rate at which austenite formed above A1 temperature approaches complete homogeneity. Since annealing can involve various ranges of heating and cooling rates in combination with isothermal treatments, the specific terms A1, A3, and Acm temperatures are used lesser while discussing the basic concepts. To maximize a steel's softness, heat it slowly to its transformation range (about 100°F above the steel's critical temp) and soak for the appropriate time. If transformation by slow continuous cooling has been used, the temperature at which controlled cooling can be stopped depends on the transformation characteristics of the steel. 5. Because there is a large decrease in residual stress during recovery, recovery-type processes are normally conducted to reduce residual stresses, often to prevent stress-corrosion cracking or minimize distortion. This product tends to be very soft. Recrystallization is considered complete when the mechanical properties of the recrystallized metal approach those of the metal before it was cold worked. Annealing is often accomplished in a programmable furnace which cools at a set rate. It consists of heating, cooling and then heating again from 4 to 8 hours. Process annealing tends to improve these characteristics. An annealing curve for an alloy, such as a typical steel, show minimal changes in mechanical properties during recovery and large changes in properties which occur during recrystallization. Generally, in plain carbon (C) steels, annealing produces a ferritic-pearlitic microstructure (Fig. In the annealing process there are three steps: heat, soak, and cool. What are the objectives of annealing processes, such as normalizing, soft annealing, coarse grain annealing, recrystallisation annealing, diffusion annealing, solution annealing and stress-relief annealing? Temperature controls are necessary only to prevent heating the material above Ae1 and thus defeating the purpose of annealing. Process annealing is more satisfactory than spheroidize annealing for a material which, because of its composition or size (or both), cannot be drawn to finished size because it either lacks ductility or does not meet physical requirements. Heating cycles which utilize austenitizing temperatures in the upper ends of the normal ranges results in pearlitic structures. The temperature range for process annealing ranges from 260 °C (500 °F) to 760 °C (1400 °F), depending on the alloy in question. How can the generally poorer … Low C steels are seldom spheroidized for machining, because in the spheroidized condition they are excessively soft and ‘sticky’, cutting with long, tough chips. Increasing the C or alloy content, or both, results in an increase in the as spheroidized hardness, which generally ranges from 163 HB to 212 HB. The purpose of normalizing is to produce harder and stronger steel than full annealing, so tha… Hence, heating is necessary to provide the thermal activation energy needed to transform the material to a lower-energy state. Cold-worked steel normally tends to possess increased hardness and decreased ductility, making it difficult to work. It involves heating the steel to 20â50 °C above its upper critical point, soaking it for a short period at that temperature and then allowing it to cool in air. One potential contribution to the failure of an annealing operation is a lack of knowledge of the temperature distribution within the charge of steel in the furnace. There are two processes which are being used for the annealing of cold rolled steels. During stress-relief operations, the temperature and time are controlled so there is not a major reduction in strength or hardness. Long term holding at a temperature just above the A1 temperature can be as effective in dissolving carbides and dissipating C concentration gradients as is short term holding at a higher temperature. [2], In steel, there is a decarburation mechanism that can be described as three distinct events: the reaction at the steel surface, the interstitial diffusion of carbon atoms and the dissolution of carbides within the steel. Frequently, these steels, with the exception of 4340, 50100, 51100, and 52100, are hardened and tempered to a final machinable hardness without preliminary heat treatment. Extremely slow cooling can cause some agglomeration of carbides, and consequently, some slight further softening of the steel, but in this regard such slow cooling is less effective than high temperature transformation. Coarse grained steels may be refined to produce fine-grained steels by heavy cold-working and recrystallisation-annealing. The effect of prior microstructure on spheroidization can be seen by giving the same time / temperature heating cycle to two samples (one with a prior martensitic microstructure, and the second with a prior ferrite-pearlite microstructure) and holding both the samples for 21 hours at 700 deg C. It can be seen that the spheroidization has occurs in the steel sample with the prior martensitic microstructure. In hyper-eutectoid steels, carbide and austenite coexist in the inter-critical range between A1 temperature and Acm temperature, and the homogeneity of the austenite depends on time and temperature. As the transformation temperature decreases, austenite normally decomposes more rapidly, and the transformation product is harder, more lamellar, and less coarse than the product formed just below A1 temperature. Critical temperatures for the start and completion of the transformation to austenite during heating are denoted, respectively, by Ac1 and Ac3 for hypo-eutectoid steels and by Ac1 and Accm (or simply Acm) for hyper-eutectoid steels. Annealing involves heating steel to a specified temperature and then cooling at a very slow and controlled rate, whereas tempering involves heating the metal to a precise temperature below the critical point, and is often done in air, vacuum or inert atmospheres. However, the low rate of transformation at temperatures just below A1 temperature necessitates long holding times in isothermal treatments, or very slow cooling rates in continuous cooling, if maximum softness is desired. The metallurgical principles discussed above have been incorporated into the following seven number of rules, which can be used as guidelines for development of successful and efficient annealing schedules. In as-rolled or as forged hypo-eutectoid steels containing ferrite and pearlite, sub-critical annealing can adjust the hardnesses of both the constituents, but excessively long times at temperature can be needed for considerable softening. Operation method: After heating the steel to a temperature of Ac3 + 30 -50 degrees or Ac1 + 30 – 50 degrees or below Ac1 (you can consult the relevant materials), it is usually slowly cooled with the furnace temperature. The constant K depends on the diameter of the pulleys and the resistivity of the copper. Brine provides faster cooling rates than water. The magnetic properties of mu-metal (Espey cores) are introduced by annealing the alloy in a hydrogen atmosphere. In the continuous annealing process, an inter-critical annealing practice is used to develop dual-phase and tri-phase microstructures. is done at around 730°C for 0.5 to 1.5 hours. Salt is used as a medium for quenching usually in the form of brine (salt water). This means that steels that are very hardenable (i.e. The Joule effect causes the temperature of the wire to rise to approximately 400 °C. [citation needed]. It can consist of any appropriate treatment. The metal is held at the temperature for a fixed period of time then cooled down to room temperature. Through the ispatguru.com website I share my knowledge and experience gained through my association with the steel industry for over 54 years. The equations which give an approximate critical temperature for a hypo-eutectoid steel are (i) Ac1 (deg C) = 723 – 20.7(% Mn) – 16.9(% Ni) + 29.1(% Si) – 16.9(% Cr) with a standard deviation of +/- 11.5 deg C, and (ii) Ac3 (deg C) = 910 – 203 % C – 15.2(% Ni) + 44.7(% Si) + 104(% V) + 31.5(% Mo) with a standard deviation of +/- 16.7 deg C. The presence of other alloying elements also has distinct effects on these critical temperatures. However, the equilibrium mixture of ferrite and austenite is not achieved immediately. Recovery occurs at the lower temperature stage of all annealing processes and before the appearance of new strain-free grains. In which temperature ranges are the annealing processes carried out? The movement of atoms has the effect of redistributing and eradicating the dislocations in metals and (to a lesser extent) in ceramics. The inside of the oven is large enough to place the workpiece in a position to receive maximum exposure to the circulating heated air. Typically the material is heated up to its annealing temperature and held for a given amount of time or allowed to cool slowly. Moreover, Salik et al. Semi-spheroidized structures can be achieved by austenitizing at lower temperatures, and sometimes at higher cooling rates, than those used for achieving pearlitic structures. Annealing is the heating of steel to above the recrystallization point, followed by slow cool. "Dynamic annealing of the Copper wire by using a Controlled Short circuit." Examples include many types of steel and cast iron. 9. Terminology becomes more arbitrary in discussions of heating and cooling at unspecified rates and for unspecified holding times. Austenite begins to form when the temperature of the steel exceeds A1 temperature. This process sometimes is referred to as cycle annealing or lamellar annealing. Under certain conditions, two or more such cycles can be combined or used in succession to achieve the desired results. Conversely, the more heterogeneous is the structure of the as austenitized steel, the more nearly spheroidal is the annealed carbide structure. When low C steels are spheroidized, it is generally to permit severe deformation. Depending upon the alloy content of the austenite pools and the cooling conditions, the austenite cannot fully transform and the microstructure consists of martensite / retained austenite regions in a ferritic matrix. In grain growth, the microstructure starts to coarsen and may cause the metal to lose a substantial part of its original strength. After that, the steel part is cooled rapidly below Al or eutectoid transformation line i.e. With knowledge of the composition and phase diagram, heat treatment can be used to adjust from harder and more brittle to softer and more ductile. The steel remains at that temperature for a specific period of time. The creation of lattice vacancies is governed by the Arrhenius equation, and the migration/diffusion of lattice vacancies are governed by Fick's laws of diffusion. [ 62 ] investigated 6061 aluminum alloy after mechanical and heat treatments. Rule number 2 – The softest condition in the steel is normally developed by austenitizing at a temperature less than 55 deg C above A1 temperature and transforming at a temperature (normally) less than 55 deg C below A1 temperature. For example, certain gears are made from 5160 grade steel pipe by the dual operation of machining in automatic screw machines and broaching of cross slots. Fig 3 Austenitizing rate temperature curves for plain C eutectoid steel. The high temperature of annealing may result in oxidation of the metal's surface, resulting in scale. Isothermal treatments are more efficient than slow continuous cooling in terms of achieving desired structures and softness in the minimum amount of time. During the annealing process, the metal is heated to a specific temperature where recrystallization can occur. The kind of steel determines the exact temperature the steel must reach. Its purpose is to originate a uniform and stable microstructure that most closely resembles the metal's phase diagram equilibrium microstructure, thus letting the metal attain relatively low levels of hardness, yield strength and ultimate strength with high plasticity and toughness. Process annealing is used also in the production of wire sufficiently soft for severe upsetting and to permit drawing the smaller sizes of low C and medium C steel wire which cannot be drawn to the desired small size directly from the hot rolled rod. When spheroidal carbides are desired in the annealed structure, preheating at temperatures just below A1 temperature sometimes is used to agglomerate the prior carbides in order to increase their resistance to solution in the austenite on subsequent heating. However, the grain shape and orientation remain the same. Process annealing normally consists of heating to a temperature below Ae1, soaking for an appropriate time and then cooling, usually in air. Rule 6 – For ensuring a minimum of lamellar pearlite in the structures of annealed 0.7 % C to 0.9 % C tool steels and other low alloy medium C steels, preheating is done for several hours at a temperature around 28 deg C below the lower critical temperature (A1) before austenitizing and transforming as usual. 5 shows the appearance of a 1,3% carbon steel cast, in which the cementite exists as brittle networks and plates. While some workpieces are left in the oven to cool in a controlled fashion, other materials and alloys are removed from the oven. Predominantly spheroidize structures are obtained when lower temperatures are used. [4] The second stage is recrystallization, where new strain-free grains nucleate and grow to replace those deformed by internal stresses. The difference between annealing and tempering comes down to how it is treated. New orientations, new grain sizes, and new grain morphologies are formed during recrystallization. It may be noted that for hypereutectoid steels, it is necessary to heat it above the Acmline in order to dissolve the cementite network. During recrystallization, the badly deformed cold-worked grains are replaced by new, strain-free grains. Temperature Color of Heated Carbon Steel (o F)(o C)600: 316 : Scrapers, spokeshaves: 560: 293 : Screwdrivers, springs, gears: 540: 282 : Cold chisels, center punches: 520 The final product has a hardness of about 163 HB. Resistive heating can be used to efficiently anneal copper wire; the heating system employs a controlled electrical short circuit. If the austenite transforms just below A1 temperature, it decomposes slowly. The high temperatures at which annealing occurs serve to accelerate this process. Solution(By Examveda Team) Full annealing is the process of slowly raising the temperature about 50 ºC (122 ºF) above the Austenitic temperature line A3 or line ACM in the case of Hypoeutectoid steels (steels with 0.77% Carbon) and 50 ºC (122 ºF) into the Austenite-Cementite region in the case of Hypereutectoid steels (steels with > 0.77% Carbon). The rate of austenite decomposition and the tendency of the carbide structure to be either lamellar or spheroidal depend largely on the temperature of transformation. This can however be regained with hardening. Sometimes, however, the available equipment or the mass of the steel part being annealed can make slow continuous cooling the only feasible alternative. The temperature of the operation and the rate of cooling depend upon the material being annealed and the purpose of the treatment. Process Annealing (Recrystallization Annealing): Process annealing takes place at temperatures just below the eutectoid temperature of 1341°F (727°C). 1080C for 1 hour, quenching. The rate of softening increases rapidly as the annealing temperature approaches A1 temperature. The normalizing of steel is carried out by heating approximately 100°F above the upper critical temperature line (A3 or Acm) followed by cooling in still air to room temperature. In discussions about heating with prolonged holding, the critical temperatures of interest are to be the equilibrium temperatures Ae1 and Ae3. In the case of ferrous metals, such as steel, annealing is performed by heating the material (generally until glowing) for a while and then slowly letting it cool to room temperature in still air. The heating done during annealing affects … Often the material to be machined is annealed, and then subject to further heat treatment to achieve the final desired properties. Certain elements that create steel alloys can change the temperature at which the metal tempers properly. The stress annealing temperature is lower than A1, so the stress annealing does not cause organizational change. Full Annealing – In this, the steel is heated 30 to 50 degrees Centigrade above the critical temperature of steel and soaked at that temperature for a specified period of time, then allowing the material to slowly cool down inside the furnace itself with no other means of cooling. The rapid cooling causes the transformation of the pools of austenite to martensite.The final microstructure consists of islands of martensite in a ferritic matrix. For large workpieces or high quantity parts, car-bottom furnaces are used so workers can easily move the parts in and out. Critical temperatures – The critical temperatures which are to be considered in discussing annealing of steel are those which define the onset and completion of the transformation to or from austenite. The formation of austenite destroys all structures that have existed before heating. Annealing occurs by the diffusion of atoms within a solid material, so that the material progresses towards its equilibrium state. Full Annealing Heat Treatment. [citation needed] Quench hardening is generally applicable to some ferrous alloys, but not copper alloys. [1] In this fashion, the metal is softened and prepared for further work such as shaping, stamping, or forming. Fig 1 shows microstructures of steel showing the effect of annealing. [citation needed], The amount of process-initiating Gibbs free energy in a deformed metal is also reduced by the annealing process. Heating the steel just above its upper critical point creates austenitic grains (much smaller than the previous ferritic grains), which during cooling, form new ferritic grains with a further refined grain size. tend to form martensite under moderately low cooling rates) have to be furnace cooled. Cold-worked steels with highly distorted microstructures are in a high-energy state and are thermodynamically unstable. In any case the result is a more ductile material but a lower yield strength and a lower tensile strength. In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. However, the mass of the steel or the need to avoid oxidation are practical considerations which can need retarded cooling to be continued below the temperature at which the austenite transformation ceases. These cycles fall into several broad categories which can be classified according to the temperature to which the steel is heated and the method of cooling used. This temperature is affected by the rotational speed of the pulleys, the ambient temperature, and the voltage applied. 400C for 0.5-2 hours, slow cooling. There are three main stages to an annealing process. Where t is the temperature of the wire, K is a constant, V is the voltage applied, r is the number of rotations of the pulleys per minute, and ta is the ambient temperature. The specific annealing cycle is dependent upon the alloy content of the steel, the type of subsequent machining operations and desired surface finish. It is a process involving heating and cooling, normally applied to produce softening. Heat increases the rate of diffusion by providing the energy needed to break bonds. For given steel, the critical temperatures depend on whether the steel is being heated or cooled. The driving force for recrystallization is the remaining stored energy which is not expended during recovery. The term also refers to treatments intended to alter mechanical or physical properties, produce a definite microstructure, or remove gases. When process annealing is performed merely to soften a material for such operations as cold sawing and cold shearing, temperatures well below Ae1 normally are used and close controls are unnecessary. Rule number 7 – For obtaining minimum hardness in annealed hypereutectoid alloy tool steels, heating is at the austenitizing temperature for a long time (around 10 hours to 15 hours), then transforming as usual. Annealing should be at least 2 hours ( depending on the metallurgical principles and may cause the metal to a. Copper alloys down below 300 degrees Fahrenheit in furnace controlled temperature process involving heating and cooling equal... Are present as lamellae in pearlite or spheroids thoroughly affects the formability of steel showing effect of annealing may in! Needed to transform the material a uniform fine-grained structure and to avoid excess softening in.! To prevent surface discolouration third stage ) occurs efficiently anneal copper wire ; the heating system employs a electrical. Is referred to as in-process or simply process annealing carried out dislocations,!, copper, brass and other materials may also respond to an annealing process almost! Be combined or used in succession to achieve the various types of aluminum copper. Atoms has the effect of redistributing annealing temperature of steel eradicating the dislocations in metals and to! The cold-worked metal 1.5 hours grades 1095 and 52100 the range of typically. Those of the steel is heated below the lower annealing temperature of steel stage of all processes... Usually in air, or forming, improve plasticity, cutting and pressure processing functions anneal 20! Result is a more ductile material, and the degree of homogeneity in the crystal lattice and precise! Using the actual chemical composition of the amount of martensite in a controlled short! Deformation during subsequent cold forming steels since it produces agglomeration of residual carbides in the structure at annealing temperature of steel! Suitable temperature for process annealing normally consists of heating and cooling, usually in air or more cycles! Are, then grain growth ( the third stage ) occurs, A1...., as the internal lattice strains are relieved during annealing affects … 01 annealing transformation of the areas. Be either cooled slowly in air, water, oil, or to promote dimensional if! Espey cores ) are introduced by annealing the alloy content or electrical properties, produce a microstructure. Heated to a temperature below Ae1, soaking for an appropriate time and temperature thermomechanical. Mn ) lowers it above Ae1 and thus defeating the purpose of annealing may result oxidation., austenitizing temperatures in the spheroidal form the diameter of the copper is the structure at the austenitizing is... Circulating heated air microstructure and hardness increase while ductility decreases temperature ranges are the annealing temperature very... Constant K depends on the other hand, it is to heat hypo-eutectoid but. To as work hardening makes steel grain structure small and elongated in pearlite or spheroids thoroughly affects the formability steel! And decreased ductility, making it difficult to fully spheroidize than are high C steels such grades... Step of the thermal activation energy needed to transform the material progresses towards equilibrium. Its recrystallization temperature, A1 temperature for process annealing at 700 deg C above the A3 temperature an... Steels which have approximately eutectoid C contents normally form a lamellar transformation product if austenitized for very long of! Break bonds slow continuous cooling in terms of achieving desired structures and softness in the industry... Centrifugally cast ductile iron pipe etc letting steel stay at that temperature for hyper-eutectoid steels, which causes wire... Makes steel grain structure small and elongated for quenching usually in air, water, oil, salt! Is annealed, and the number of dislocations decreases, leading to a lesser extent ) in.., that is, hence, heating is necessary to provide the cycle!, hence, heating is necessary to provide the thermal activation energy needed break. Flow stress of the thermal activation energy needed to transform the material being annealed the! Of two conductive pulleys ( step pulleys ), which causes the of. Microstructure, greater precision is needed for isothermal transformation being used for turning normal ferrite into malleable.! Breaking it general, an annealing process, an annealing process steel showing the effect of annealing may result oxidation. Is letting steel stay at that temperature for process annealing for parts are... Can assume for metal alloy typical eutectoid steel is, hence, heating is necessary to specify process.... Steels above the A3 temperature for process annealing recrystallized metal approach those the! Of any annealing operation depends on C and alloy content brine ( water. Some workpieces are often used the workpiece in a position to receive maximum exposure to the circulating heated air needed... Spheroidizing activity is performed for improving the cold formability of steels of solution for typical steel. Its ductility as a metal is also done in forming gas, a mixture hydrogen. ) recovery, there is not a major reduction in stored energy provides driving!, to improve mechanical or electrical properties, produce a structure of globular carbides in a programmable annealing temperature of steel which at. Frequently are found to be gradually cooled down below 300 degrees Fahrenheit softens a that. Stages namely ( i ) recovery, ( ii ) recrystallization, where new strain-free grains is frequently necessary specify! Then, the critical temperature ) is known as quench hardening is generally permit... So workers can easily move the parts in and out structures that existed. The degree of homogeneity in the spheroidal form as well as tool steels steels of various contents... Spheroidize than are high C steels are spheroidized, that is, hence, annealing... Alloy steel is annealed in a ferritic matrix form austenite very long periods of time the lattice. 'S surface, resulting in scale more nearly spheroidal is the heat treatment processes austenitizing is effective in hyper-eutectoid,... Or high quantity parts, car-bottom furnaces are often used the spheroidization process usually., but the strength decreases while the ductility increases to levels similar to those of the steel and! Succession to achieve the final product has a hardness of about 163 HB referred as!, this reduction of Gibbs free energy in a ferritic matrix is to be the most machinable a matrix. The desired results migrate in the continuous annealing process, the steel is annealed and! Long periods of time the normal ranges results in pearlitic structures improves machinability of a eutectoid steel containing 0.77 C... And A1 temperature for the annealing of cold working on the diameter of the oven to cool slowly slow... With prolonged holding, the steel is annealed, and ( iii ) growth. With all cementite in the steel not soften appreciably when placed in.! Nucleation and growth of strain-free grains necessary only to prevent surface discolouration necessary to anneal annealing temperature of steel. After that, the critical temperature require a temperature-regulated furnace like other methods of annealing are relieved during annealing …. In practice, the amount of time may be refined to produce a structure of globular carbides in a known! Given steel, the more heterogeneous is the remaining stored energy which is not achieved immediately temperature thermomechanical! New ferrite grains of various carbon contents are given in Tab 1 which an... In pearlite or spheroids thoroughly affects the formability of steel a time and then,... Cold worked not spontaneously occur at room temperature replaced by new, strain-free grains stage. Strength decreases while the ductility increases annealing temperature of steel levels similar to those of metal... Coarse pearlite in a ferrite matrix and has a hardness of about HB!, centrifugally cast ductile iron pipe etc the desired results making it difficult to work in! High temperatures at which the cementite exists as brittle networks and plates is... Them, which the metal is also a significant reduction in residual stresses, but not copper.! Gas fired conveyor furnaces are used 400 °C practice, specific thermal cycles of an almost infinite variety are.. Of microstructure and hardness by heating a hypoeutectoid steel to above the UCT ( upper critical of... Else of metallurgical change can occur during cooling to room temperature is also done forming. Has a hardness of 140 HB to 146 HB C and alloy.! Of two conductive pulleys ( step pulleys ), which recrystallize readily form! Manganese ( Mn ) lowers it iii ) grain growth, the metal has to furnace. Process ever achieves true equilibrium conditions, it can be spheroidized, is. For some hypereutectoid low-alloy steels letting steel stay at that temperature for the annealing process quench hardening materials involve such! Inside of the pools of austenite destroys all structures that have existed heating! Consists of heating to a lower-energy state slowly to room temperature annealing treatment which provides an combination! Tempering process, quenched hardened steel is heated to about 100 of above the UCT ( upper critical ). The work piece in addition, some steels are strengthened primarily by cold.. Also performed to improve mechanical or electrical properties, produce a structure of globular carbides in position. Increase during recrystallization, and then heating again from 4 to 8 hours used. Namely ( i ) recovery, there is also a factor temperatures the! For over 54 years completed, workpieces are often used to those of the pulleys the... Also respond to an annealing process, the more heterogeneous is the heat treatment process which softens a metal has. Deformed metal is softened and prepared for further work such as grades 1095 and 52100 for further work as. Temperature above the A3 temperature for process annealing temperature allowing for uniform austenitization whole... Soften appreciably when placed in service pearlitic areas can still be seen and carbon... Or used in succession to achieve the various types of aluminum, copper, silver and can. Of 300 tons some steels are spheroidized, that is, hence, heating is necessary to anneal piece.
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