CN113416834A - Steel wire heat treatment quenching process - Google Patents
Steel wire heat treatment quenching process Download PDFInfo
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- CN113416834A CN113416834A CN202110103700.3A CN202110103700A CN113416834A CN 113416834 A CN113416834 A CN 113416834A CN 202110103700 A CN202110103700 A CN 202110103700A CN 113416834 A CN113416834 A CN 113416834A
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- steel wire
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- heating
- heat treatment
- furnace
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 183
- 239000010959 steel Substances 0.000 title claims abstract description 183
- 238000010438 heat treatment Methods 0.000 title claims abstract description 108
- 238000010791 quenching Methods 0.000 title claims abstract description 49
- 230000000171 quenching effect Effects 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims abstract description 40
- 230000008569 process Effects 0.000 title claims abstract description 31
- 238000001816 cooling Methods 0.000 claims abstract description 23
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 19
- 235000002639 sodium chloride Nutrition 0.000 claims abstract description 16
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 11
- 150000003839 salts Chemical class 0.000 claims abstract description 11
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims abstract description 10
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 10
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 claims abstract description 10
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims abstract description 10
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims abstract description 5
- 239000001110 calcium chloride Substances 0.000 claims abstract description 5
- 229910001628 calcium chloride Inorganic materials 0.000 claims abstract description 5
- 235000011148 calcium chloride Nutrition 0.000 claims abstract description 5
- 239000000203 mixture Substances 0.000 claims abstract description 5
- 239000001103 potassium chloride Substances 0.000 claims abstract description 5
- 235000011164 potassium chloride Nutrition 0.000 claims abstract description 5
- 235000010333 potassium nitrate Nutrition 0.000 claims abstract description 5
- 239000004323 potassium nitrate Substances 0.000 claims abstract description 5
- 239000011780 sodium chloride Substances 0.000 claims abstract description 5
- 235000010344 sodium nitrate Nutrition 0.000 claims abstract description 5
- 239000004317 sodium nitrate Substances 0.000 claims abstract description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 30
- 238000005496 tempering Methods 0.000 claims description 24
- 238000010622 cold drawing Methods 0.000 claims description 22
- 238000000137 annealing Methods 0.000 claims description 18
- 230000009466 transformation Effects 0.000 claims description 14
- 238000005482 strain hardening Methods 0.000 claims description 12
- 238000011282 treatment Methods 0.000 claims description 10
- 229910001567 cementite Inorganic materials 0.000 claims description 8
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 claims description 8
- 230000000704 physical effect Effects 0.000 claims description 8
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical group OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 claims description 5
- 239000000654 additive Substances 0.000 claims description 4
- 230000000996 additive effect Effects 0.000 claims description 4
- 238000005452 bending Methods 0.000 claims description 4
- 230000009286 beneficial effect Effects 0.000 claims description 4
- 230000002349 favourable effect Effects 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 239000011513 prestressed concrete Substances 0.000 claims description 4
- 238000003303 reheating Methods 0.000 claims description 4
- 239000000243 solution Substances 0.000 claims description 4
- 230000000087 stabilizing effect Effects 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 239000003513 alkali Substances 0.000 claims description 3
- 239000002585 base Substances 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 230000007423 decrease Effects 0.000 claims description 3
- 238000005098 hot rolling Methods 0.000 claims description 3
- 238000001953 recrystallisation Methods 0.000 claims description 3
- 239000012266 salt solution Substances 0.000 claims description 3
- 229910000859 α-Fe Inorganic materials 0.000 claims description 3
- 230000008859 change Effects 0.000 claims description 2
- 239000012535 impurity Substances 0.000 claims description 2
- 229910000734 martensite Inorganic materials 0.000 claims description 2
- 239000000344 soap Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000002253 acid Substances 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000005491 wire drawing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
Abstract
The invention discloses a steel wire heat treatment quenching process, which comprises the following steps: leading out a steel wire by a roller of a pay-off machine, horizontally outputting the steel wire after passing through a positioning device, heating the steel wire to 900-950 ℃ to enable the structure to be transformed into austenite, then quenching and preserving heat in molten lead or salt (a mixture of sodium nitrate and potassium nitrate or calcium chloride, sodium chloride and potassium chloride) at the temperature of 480-550 ℃ for a period of time to enable the austenite to be transformed into fine pearlite isothermally, heating the steel wire to a temperature above a critical point, preserving heat for a certain time, rapidly cooling to a standard value temperature, and preserving heat for a sufficient time to form a required spheroidized structure; heating to a temperature above the upper critical point, rapidly cooling to a temperature above the standard value by about 30 ℃, and cooling to a temperature below the lower critical point (about 650 ℃) at a rate of 5 ℃/h; heating to the lower critical point or slightly lower temperature, keeping the temperature for enough time to form the required spheroidized structure (usually 8-12 h), and heating the steel wire to the temperature 30-50 ℃ above the upper critical point.
Description
Technical Field
The invention relates to the technical field of steel wire heat treatment quenching, in particular to a steel wire heat treatment quenching process.
Background
The steel wire is a reprocessed metal product made by cold drawing hot rolled wire rod, and has wide application in various industries. Heat treatment is an important step in the production of steel wire. Because the steel wire is generally used for applying tensile force, the steel wire is required to have stronger tensile strength and better mechanical property, and the purpose is achieved by carrying out heat treatment on the steel wire; meanwhile, certain internal stress or structural stress can be generated among tissues in the steel wire manufacturing process, the steel wire is used in a reaction mode, and the internal stress can be eliminated through heat treatment.
At present, the heat treatment of the steel wire is carried out in a middle heat treatment mode, but the problems of low production efficiency, high production cost and low steel wire cost and quality exist due to unreasonable arrangement of intermediate heat treatment process links. Particularly, in the process of heat treatment, the surface phosphating process is improper in selection, such as unreasonable arrangement of total acidity, free acidity, acid ratio, phosphating temperature, phosphating time and the like, so that the surface corrosion resistance and lubricity of the steel wire are not high, and the requirements of steel wire rope heat treatment wire drawing production cannot be well met.
Disclosure of Invention
The invention aims to provide a steel wire heat treatment quenching process to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme: a steel wire heat treatment quenching process comprises the following steps:
the method comprises the following steps: leading out the steel wire through a roller of a pay-off machine, and horizontally outputting the steel wire after passing through a positioning device;
step two: heating the steel wire to 900-950 ℃ to convert the structure into austenite, quenching in molten lead or salt (mixture of sodium nitrate and potassium nitrate or calcium chloride, sodium chloride and potassium chloride) at 480-550 ℃ and keeping the temperature for a period of time to convert the austenite into fine pearlite isothermally;
step three: then spheroidizing annealing is carried out, the steel wire is heated to the temperature above the upper critical point, the temperature is preserved for a certain time, the steel wire is rapidly cooled to the standard value temperature, and the temperature is preserved for a long time enough to form the required spheroidized structure; heating to a temperature above the upper critical point, rapidly cooling to a temperature above the standard value by about 30 ℃, and cooling to a temperature below the lower critical point (about 650 ℃) at a rate of 5 ℃/h; heating to a lower critical point or a slightly lower temperature, and keeping the temperature for enough time to form a required spheroidized structure (usually 8-12 h);
step four: quenching and tempering, namely heating the steel wire to be 30-50 ℃ above the upper critical point, preserving heat for a certain time, then quenching in oil, and reheating in molten lead. The quenching and tempering of steel wire is usually carried out by the spread method, except that particularly thick steel wire is treated by the forming of a disc. Compared with the cold-drawn steel wire, the quenching and tempering steel wire has the following characteristics: higher strength (when the diameter is more than 2 mm) and elasticity, higher physical property uniformity, longer service life and smaller deformation;
step five: and tempering, namely heating the steel wire to a temperature lower than the transformation temperature, and then cooling to room temperature to eliminate internal stress generated during cold drawing of the steel wire. Tempering is commonly used for steel wires for prestressed concrete and tire edge steel wires. The tempering treatment can improve the elongation of the cold-drawn steel wire, reduce the relaxation value and improve the ratio of yield point to strength, but can reduce the tensile strength and the bending value of the steel wire;
step six: and (3) stabilizing treatment, namely heating the steel wire subjected to multi-pass drawing for a period of time under a certain load so as to achieve the purpose of improving the deformation resistance of the steel wire.
Preferably, the heating temperature decreases with an increase in the carbon content and increases with an increase in the filament diameter. The temperature of lead or salt solution is reduced along with the increase of the wire diameter, and apart from the coil forming treatment of the steel wire with the diameter larger than 12mm, an expansion furnace is generally adopted, namely, the steel wire is discharged from a pay-off rack, continuously passes through a heating furnace, a quenching tank and a cooling tank and then is coiled into a coil by a take-up machine.
Preferably, the annealing is aimed at mainly homogenizing the structure of the wire rod, eliminating work hardening and brittleness, softening the finished steel wire, changing the toughness, ductility, tensile strength, yield point, elongation and other physical properties of the material, and forming a specific microstructure.
Preferably, the heat treatment eliminates work hardening of the steel wire in the previous cold drawing process to facilitate the cold drawing to be continued. When the wire rod or the steel wire is subjected to cold drawing, the tensile strength and the brittleness are continuously increased due to work hardening, and the wire rod or the steel wire cannot be smoothly drawn and can be broken when the certain degree is reached. At this time, the steel wire should be heat-treated to regain the condition favorable for cold drawing, so that the hot-rolled wire rod has a structure suitable for drawing and can be normally drawn. For example, after hot rolling, hypereutectoid steel wire rods have free cementite, are brittle and cannot be drawn normally, spheroidizing annealing enables the cementite to be spheroidized so as to be suitable for drawing, and enables steel wires to have special structures.
Preferably, the steel wire heat treatment is mostly to heat the steel wire above the eutectoid temperature to transform pearlite to austenite and then to cool it in different ways to obtain various textures and properties. Some heat treatments, such as recrystallization annealing or spheroidizing annealing, heat the steel wire only to a temperature near or below the eutectoid temperature.
Preferably, the steel wire is cooled to about 650 ℃ in the first water tank, leaves the water tank 1 before the steam film is broken, is organized into super-cooled austenite, is cooled to about 620 ℃ in the air, and starts to transform the super-cooled austenite into fine pearlite/sorbite; because the transformation is a heat release process, the temperature of the steel wire rises, in order to ensure the mechanical property of the electroplated steel wire, the steel wire is introduced into a second water tank for cooling, more strand body transformation is realized, the transformation of the steel wire is basically completed after leaving the water tank 2, and the steel wire structure after water bath is mainly of the strand body and is accompanied with a small amount of ferrite.
Preferably, the heat treatment is carried out by using an open-hearth furnace, the open-hearth furnace heating process adopts a sectional heating mode, the open-hearth furnace heating furnace is divided into four sections, the heating temperature of the first section furnace is 975-985 ℃, the heating temperature of the second section furnace is 960-; in the lead quenching process, the temperature of the two sections of the lead pot is 560-.
Preferably, the quenching medium water generally has the temperature not exceeding 40 ℃, and impurities such as oil, soap and the like cannot be obtained; aqueous salt and base solutions: 5-10 percent of salt or alkali is added into the water.
Preferably, the heat treatment is performed using a heat treatment furnace, which is generally lower in temperature than a heating furnace, requires strict control of the furnace temperature and furnace atmosphere, and includes a furnace body, a heating device, a mechanical device, an electrical device, and the like.
Compared with the prior art, the invention has the beneficial effects that:
1. the steel wire heat treatment quenching process eliminates the work hardening of the steel wire in the previous cold drawing procedure by heat treatment so as to be beneficial to continuously carrying out cold drawing. When the wire rod or the steel wire is subjected to cold drawing, the tensile strength and the brittleness are continuously increased due to work hardening, and the wire rod or the steel wire cannot be smoothly drawn and can be broken when the certain degree is reached. At this time, the steel wire should be heat-treated to regain the condition favorable for cold drawing, so that the hot-rolled wire rod has a structure suitable for drawing and can be normally drawn. For example, after the hypereutectoid steel wire rod is hot-rolled, free cementite exists, the hypereutectoid steel wire rod is brittle and cannot be normally drawn, spheroidizing annealing enables the cementite to be spheroidized so as to be suitable for drawing, so that the steel wire has a special structure, and after the hypereutectoid steel wire rod is cold-drawn, the steel wire has good performance, so that a finished steel wire has the structure and performance required by a user;
2. the steel wire heat treatment quenching process has the advantages that annealing is mainly carried out on the structure of a uniform wire rod, work hardening and brittleness are eliminated, a steel wire finished product is softened, the toughness, the ductility, the tensile strength, the yield point, the elongation and other physical properties of the material are changed, and a specific microstructure is formed.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a technical scheme that: a steel wire heat treatment quenching process comprises the following steps:
the method comprises the following steps: leading out the steel wire through a roller of a pay-off machine, and horizontally outputting the steel wire after passing through a positioning device;
step two: heating the steel wire to 900-950 ℃ to convert the structure into austenite, quenching in molten lead or salt (mixture of sodium nitrate and potassium nitrate or calcium chloride, sodium chloride and potassium chloride) at 480-550 ℃ and keeping the temperature for a period of time to convert the austenite into fine pearlite isothermally;
step three: then spheroidizing annealing is carried out, the steel wire is heated to the temperature above the upper critical point, the temperature is preserved for a certain time, the steel wire is rapidly cooled to the standard value temperature, and the temperature is preserved for a long time enough to form the required spheroidized structure; heating to a temperature above the upper critical point, rapidly cooling to a temperature above the standard value by about 30 ℃, and cooling to a temperature below the lower critical point (about 650 ℃) at a rate of 5 ℃/h; heating to a lower critical point or a slightly lower temperature, and keeping the temperature for enough time to form a required spheroidized structure (usually 8-12 h);
step four: quenching and tempering, namely heating the steel wire to be 30-50 ℃ above the upper critical point, preserving heat for a certain time, then quenching in oil, and reheating in molten lead. The quenching and tempering of steel wire is usually carried out by the spread method, except that particularly thick steel wire is treated by the forming of a disc. Compared with the cold-drawn steel wire, the quenching and tempering steel wire has the following characteristics: higher strength (when the diameter is more than 2 mm) and elasticity, higher physical property uniformity, longer service life and smaller deformation;
step five: and tempering, namely heating the steel wire to a temperature lower than the transformation temperature, and then cooling to room temperature to eliminate internal stress generated during cold drawing of the steel wire. Tempering is commonly used for steel wires for prestressed concrete and tire edge steel wires. The tempering treatment can improve the elongation of the cold-drawn steel wire, reduce the relaxation value and improve the ratio of yield point to strength, but can reduce the tensile strength and the bending value of the steel wire;
step six: and (3) stabilizing treatment, namely heating the steel wire subjected to multi-pass drawing for a period of time under a certain load so as to achieve the purpose of improving the deformation resistance of the steel wire.
The heating temperature decreases with increasing carbon content and increases with increasing filament diameter. The temperature of lead or salt solution is reduced along with the increase of the wire diameter, except that the steel wire with the diameter larger than 12mm is treated by coiling, an expansion furnace is generally adopted, namely, the steel wire is discharged from a pay-off rack and continuously passes through a heating furnace, a quenching tank and a cooling tank and then is coiled into a coil by a take-up machine, the annealing aims to mainly homogenize the structure of a wire rod, eliminate the work hardening and brittleness, soften the finished product of the steel wire, change the toughness, the ductility, the tensile strength, the yield point, the elongation and other physical properties of the material, form a specific microstructure, and eliminate the work hardening of the steel wire in the previous cold drawing process by heat treatment so as to be beneficial to continuously carrying out cold drawing. When the wire rod or the steel wire is subjected to cold drawing, the tensile strength and the brittleness are continuously increased due to work hardening, and the wire rod or the steel wire cannot be smoothly drawn and can be broken when the certain degree is reached. At this time, the steel wire should be heat-treated to regain the condition favorable for cold drawing, so that the hot-rolled wire rod has a structure suitable for drawing and can be normally drawn. For example, after hot rolling, hypereutectoid steel wire rods have free cementite, are brittle and cannot be drawn normally, spheroidizing annealing makes the cementite spheroidized so that the steel wires are suitable for drawing, and makes the steel wires have special structures, after cold drawing, the steel wires have good performance, and makes finished steel wires have structures and performance required by users, most of steel wire heat treatment is to heat the steel wires to a temperature above eutectoid temperature to make pearlite transform to austenite, and then to cool the steel wires in different modes to obtain various structures and performance. Some heat treatments (such as recrystallization annealing or spheroidizing annealing) only heat the steel wire to a temperature near or below the eutectoid temperature, and the steel wire and pure water are directly cooled, so that hard martensite is generally obtained, and the steel wire cannot be drawn at all. However, after the high molecular additive capable of improving the water viscosity is added into water, water molecules and the additive are well combined, the surface tension of a water vapor interface is increased, and the heat conduction coefficient rate is greatly reduced, so that the slow and stable cooling of the steel wire is realized, a required sorbite structure suitable for drawing and with the distance between sheets being about 20-40 mu m is obtained, the steel wire is cooled to about 650 ℃ in a first water tank, and is separated from the water tank 1 before the steam film is broken, the structure is super-cooled austenite, the steel wire is cooled to about 620 ℃ in air, and the transformation from the super-cooled austenite to fine pearlite/sorbite begins to occur; because the transformation is a heat release process, the temperature of the steel wire rises, in order to ensure the mechanical property of the electroplated steel wire, the steel wire is introduced into a second water tank for cooling, more cable body transformation is realized, the transformation of the steel wire is basically completed after leaving the water tank 2, the steel wire tissue after water bath is mainly cable body and accompanied by a small amount of ferrite, the heat treatment adopts open-hearth furnace heating, the open-hearth furnace heating process adopts a sectional heating mode, the open-hearth furnace heating process is divided into four sections, the heating temperature of the first section furnace is 975-; in the lead quenching process, the temperature of the two sections of the lead pot is 560-; aqueous salt and base solutions: 5-10 percent of salt or alkali is added into water, a heat treatment furnace is required for heat treatment, the temperature of the heat treatment furnace is generally lower than that of a heating furnace, the furnace temperature and the furnace atmosphere are required to be strictly controlled, and the heat treatment furnace comprises a furnace body, a heating device, a mechanical device, electrical equipment and the like.
The working principle is as follows: the method comprises the following steps: leading out the steel wire through a roller of a pay-off machine, and horizontally outputting the steel wire after passing through a positioning device;
step two: heating the steel wire to 900-950 ℃ to convert the structure into austenite, quenching in molten lead or salt (mixture of sodium nitrate and potassium nitrate or calcium chloride, sodium chloride and potassium chloride) at 480-550 ℃ and keeping the temperature for a period of time to convert the austenite into fine pearlite isothermally;
step three: then spheroidizing annealing is carried out, the steel wire is heated to the temperature above the upper critical point, the temperature is preserved for a certain time, the steel wire is rapidly cooled to the standard value temperature, and the temperature is preserved for a long time enough to form the required spheroidized structure; heating to a temperature above the upper critical point, rapidly cooling to a temperature above the standard value by about 30 ℃, and cooling to a temperature below the lower critical point (about 650 ℃) at a rate of 5 ℃/h; heating to a lower critical point or a slightly lower temperature, and keeping the temperature for enough time to form a required spheroidized structure (usually 8-12 h);
step four: quenching and tempering, namely heating the steel wire to be 30-50 ℃ above the upper critical point, preserving heat for a certain time, then quenching in oil, and reheating in molten lead. The quenching and tempering of steel wire is usually carried out by the spread method, except that particularly thick steel wire is treated by the forming of a disc. Compared with the cold-drawn steel wire, the quenching and tempering steel wire has the following characteristics: higher strength (when the diameter is more than 2 mm) and elasticity, higher physical property uniformity, longer service life and smaller deformation;
step five: and tempering, namely heating the steel wire to a temperature lower than the transformation temperature, and then cooling to room temperature to eliminate internal stress generated during cold drawing of the steel wire. Tempering is commonly used for steel wires for prestressed concrete and tire edge steel wires. The tempering treatment can improve the elongation of the cold-drawn steel wire, reduce the relaxation value and improve the ratio of yield point to strength, but can reduce the tensile strength and the bending value of the steel wire;
step six: and (3) stabilizing treatment, namely heating the steel wire subjected to multi-pass drawing for a period of time under a certain load so as to achieve the purpose of improving the deformation resistance of the steel wire.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A steel wire heat treatment quenching process comprises the following steps:
the method comprises the following steps: leading out the steel wire through a roller of a pay-off machine, and horizontally outputting the steel wire after passing through a positioning device;
step two: heating the steel wire to 900-950 ℃ to convert the structure into austenite, quenching in molten lead or salt (mixture of sodium nitrate and potassium nitrate or calcium chloride, sodium chloride and potassium chloride) at 480-550 ℃ and keeping the temperature for a period of time to convert the austenite into fine pearlite isothermally;
step three: then spheroidizing annealing is carried out, the steel wire is heated to the temperature above the upper critical point, the temperature is preserved for a certain time, the steel wire is rapidly cooled to the standard value temperature, and the temperature is preserved for a long time enough to form the required spheroidized structure; heating to a temperature above the upper critical point, rapidly cooling to a temperature above the standard value by about 30 ℃, and cooling to a temperature below the lower critical point (about 650 ℃) at a rate of 5 ℃/h; heating to a lower critical point or a slightly lower temperature, and keeping the temperature for enough time to form a required spheroidized structure (usually 8-12 h);
step four: quenching and tempering, namely heating the steel wire to be 30-50 ℃ above the upper critical point, preserving heat for a certain time, then quenching in oil, and reheating in molten lead. The quenching and tempering of steel wire is usually carried out by the spread method, except that particularly thick steel wire is treated by the forming of a disc. Compared with the cold-drawn steel wire, the quenching and tempering steel wire has the following characteristics: higher strength (when the diameter is more than 2 mm) and elasticity, higher physical property uniformity, longer service life and smaller deformation;
step five: and tempering, namely heating the steel wire to a temperature lower than the transformation temperature, and then cooling to room temperature to eliminate internal stress generated during cold drawing of the steel wire. Tempering is commonly used for steel wires for prestressed concrete and tire edge steel wires. The tempering treatment can improve the elongation of the cold-drawn steel wire, reduce the relaxation value and improve the ratio of yield point to strength, but can reduce the tensile strength and the bending value of the steel wire;
step six: and (3) stabilizing treatment, namely heating the steel wire subjected to multi-pass drawing for a period of time under a certain load so as to achieve the purpose of improving the deformation resistance of the steel wire.
2. The steel wire heat treatment quenching process according to claim 1, characterized in that: the heating temperature decreases with increasing carbon content and increases with increasing filament diameter. The temperature of lead or salt solution is reduced along with the increase of the wire diameter, and apart from the coil forming treatment of the steel wire with the diameter larger than 12mm, an expansion furnace is generally adopted, namely, the steel wire is discharged from a pay-off rack, continuously passes through a heating furnace, a quenching tank and a cooling tank and then is coiled into a coil by a take-up machine.
3. The steel wire heat treatment quenching process according to claim 1, characterized in that: the purpose of the annealing is to mainly homogenize the structure of the wire rod, eliminate work hardening and brittleness, soften the finished steel wire, change the toughness, ductility, tensile strength, yield point, elongation and other physical properties of the material, and form a specific microstructure.
4. The steel wire heat treatment quenching process according to claim 1, characterized in that: the heat treatment eliminates the work hardening of the steel wire in the previous cold drawing process, so as to be beneficial to continuously carrying out cold drawing. When the wire rod or the steel wire is subjected to cold drawing, the tensile strength and the brittleness are continuously increased due to work hardening, and the wire rod or the steel wire cannot be smoothly drawn and can be broken when the certain degree is reached. At this time, the steel wire should be heat-treated to regain the condition favorable for cold drawing, so that the hot-rolled wire rod has a structure suitable for drawing and can be normally drawn. For example, after hot rolling, hypereutectoid steel wire rods have free cementite, are brittle and cannot be drawn normally, spheroidizing annealing enables the cementite to be spheroidized so as to be suitable for drawing, and enables steel wires to have special structures.
5. The steel wire heat treatment quenching process according to claim 1, characterized in that: the steel wire heat treatment is mostly to heat the steel wire above the eutectoid temperature to transform pearlite to austenite and then to cool it in different ways to obtain various structures and properties. Some heat treatments, such as recrystallization annealing or spheroidizing annealing, heat the steel wire only to a temperature near or below the eutectoid temperature.
6. The steel wire heat treatment quenching process according to claim 1, characterized in that: the steel wire and pure water are directly cooled, hard martensite is generally obtained, and drawing is not performed at all. However, after the high molecular additive capable of improving the water viscosity is added into the water, the water molecules and the additive are well combined, the surface tension of a water vapor interface is increased, and the heat conduction coefficient rate is greatly reduced, so that the slow and stable cooling of the steel wire is realized, and the required sorbite structure suitable for drawing and with the sheet spacing of about 20-40 mu m is obtained.
7. The steel wire heat treatment quenching process according to claim 1, characterized in that: the steel wire is cooled to about 650 ℃ in a first water tank, leaves the water tank 1 before the steam film is broken, is organized into super-cooled austenite, is cooled to about 620 ℃ in the air, and begins to transform the super-cooled austenite into fine pearlite/sorbite; because the transformation is a heat release process, the temperature of the steel wire rises, in order to ensure the mechanical property of the electroplated steel wire, the steel wire is introduced into a second water tank for cooling, more strand body transformation is realized, the transformation of the steel wire is basically completed after leaving the water tank 2, and the steel wire structure after water bath is mainly of the strand body and is accompanied with a small amount of ferrite.
8. The steel wire heat treatment quenching process according to claim 1, characterized in that: the heat treatment adopts open-hearth heating, the open-hearth heating process adopts a sectional heating mode, the open-hearth heating furnace is divided into four sections, the heating temperature of the first section furnace is 975-985 ℃, the heating temperature of the second section furnace is 960-; in the lead quenching process, the temperature of the two sections of the lead pot is 560-.
9. The steel wire heat treatment quenching process according to claim 1, characterized in that: the quenching medium water is generally not higher than 40 ℃, and impurities such as oil, soap and the like cannot be obtained; aqueous salt and base solutions: 5-10 percent of salt or alkali is added into the water.
10. The steel wire heat treatment quenching process according to claim 1, characterized in that: the heat treatment needs to utilize a heat treatment furnace, the temperature of the heat treatment furnace is generally lower than that of a heating furnace, the furnace temperature and the atmosphere in the furnace are strictly controlled, and the heat treatment furnace comprises a furnace body, a heating device, a mechanical device, an electrical device and the like.
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