A roller-pressing gas quenching method for 1-4 mm high-strength steel plates

Abstract

The present invention belongs to the technical field of heat treatment of steel plates, and discloses a roller-pressed gas quenching method for 1-4 mm high-strength steel plates, including a temperature compensation control method, a gas volume distribution method, a roller gap control method, and a roller speed control method; the temperature compensation control method and the gas volume distribution method realize precise control of organizational properties by increasing the cooling temperature and regulating the cooling path, thereby improving the strength and toughness of the steel plate; the roller gap control method realizes constrained quenching by differentially setting the roller gaps of different rollers; and the roller speed control method realizes high uniformity and high flatness quenching by differentially setting the roller speeds of different rollers. The present invention solves the problems of poor quenching shape, large residual stress, substandard strength and toughness, and poor surface quality of 1-4 mm high-strength steel plates, and improves the quenching quality.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of steel plates, and in particular to a roller-pressing gas quenching method for high-strength steel plates with a diameter of 1 to 4 mm. Background Art

[0002] Ultra-thin high-strength steel plates are key raw materials in the fields of equipment manufacturing, transportation, petrochemicals, military industry, etc., and are crucial to the large-scale and lightweight development of equipment. The heat treatment process of such steel plates requires different cooling systems and constrained deformation methods to control the toughness and plate shape to obtain better performance. Since roller quenching machines have the advantages of high cooling intensity, uniform quenching, high control accuracy, and continuous production, they have become the main quenching technology for ultra-thin high-strength steel plates.

[0003] However, as the thickness of steel plates is reduced to 1-4 mm, the width is increased to more than 2 m, and the strength level is increased to more than 960 MPa, the high cooling uniformity and high flatness plate shape control during the quenching process have become insurmountable technical bottlenecks for traditional roller quenching machines, mainly manifested in: high sensitivity to quenching of steel plates, easy to bend after quenching, and difficult to correct; users have strict requirements on the comprehensive service performance of such steel plates and high requirements on the consistency of quenched structural properties of steel plates; the strength of steel plates is significantly improved after quenching, and the uneven distribution of residual stress is prone to cold processing deformation and rebound, affecting the overall structural processing quality and safety of large equipment. Therefore, high uniformity and high flatness quenching of 1-4 mm ultra-thin high-strength steel plates has become a recognized technical problem in the industry.

[0004] When using traditional cooling methods such as low-flow weak water cooling and water mist cooling for quenching, the temperature drop process undergoes heat exchange modes with significant differences in cooling rates, such as film boiling, nucleate boiling, transition boiling, and jet impact, which bring about problems such as uneven local cooling and large fluctuations in cooling rates. It cannot solve the problems of large residual stress, large heat treatment distortion, and poor surface quality of such steel plates. The gas cooling medium has a single heat exchange mode, high cooling uniformity, and good cooling rate controllability. It has been successfully used in the continuous quenching process of cold-rolled strip steel, providing a new idea for solving the plate shape problem during the quenching of thin plates.

[0005] The present invention uses compressed air as a cooling medium for extremely thin high-strength steel plates with a thickness of 1 to 4 mm, and precisely regulates the cooling path and the deformation process, ultimately achieving high cooling uniformity and high flatness plate shape control.

[0006] Among the existing patents, patent CN103233112A discloses a quenching and tempering heat treatment equipment and method for 4-6mm high-strength thin plates, which uses a quenching press to achieve pressurized water spray quenching to reduce the quenching deformation of the steel plate. This patent mainly uses pressure water quenching for quenching, which is quite different from the roller-type gas quenching method of the present invention.

[0007] Patent CN106460081A discloses a method and apparatus for manufacturing strip steel, which uses a gas mixture containing hydrogen as a quenching medium to quench the strip steel and achieve uniform cooling over the width of the strip steel. This patent differs greatly from the present invention in terms of equipment form, quenching medium, and cooling system.

[0008] Patent CN109207884A discloses a low residual stress aluminum alloy plate and its preparation method, wherein the third-stage quenching process utilizes strong wind cooling to reduce the residual internal stress in the plate. This process is quite different from the present invention in terms of cooling rate, cooling temperature range and cooling system.

[0009] Patent CN110760654A discloses a martensitic stainless steel quenching process, which uses vacuum gas quenching heat treatment equipment for vacuum quenching, realizes the quenching process and reduces stress concentration. This process is quite different from the present invention in terms of cooling system, equipment form, etc.

[0010] Patent CN110129543A discloses a roller quenching process for ultra-thin strip steel. The invention realizes high straightness and high uniformity quenching of ultra-thin strip steel through the combination of various control processes. The cooling medium and cooling method of the invention are quite different from those of the present invention.

[0011] Patent CN102534136A discloses a highly wear-resistant bimetallic composite heat treatment process, which realizes the quenching process by strong wind cooling after the furnace. The cooling system of the invention is quite different from that of the present invention. Summary of the invention

[0012] The purpose of the present invention is to provide a roller-pressed gas quenching method for 1-4 mm high-strength steel plates to address the technical bottleneck problems of the existing 1-4 mm high-strength steel plates having great difficulty in regulating the organizational properties, high quenching sensitivity, poor plate shape and large residual stress during the roller-pressed quenching process. The method can achieve high uniformity, high flatness and low residual stress quenching heat treatment production of such steel plates and meet the heat treatment requirements such as the strength and toughness indicators of the steel plates.

[0013] The technical solution of the present invention is as follows: a roller-type gas quenching method for 1-4 mm high-strength steel plates, which is mainly composed of a temperature compensation control method, a gas volume distribution method, a roll gap control method and a roll speed control method; the temperature compensation control method and the gas volume distribution method are set before the steel plate 1 exits the heat treatment furnace 2; the roll gap control method is set after the steel plate 1 exits the heat treatment furnace 2; the roll speed control method is dynamically adjusted between the steel plate 1 exiting the heat treatment furnace 2 and the gas quenching process.

[0014] The temperature compensation control method is as follows: before the steel plate 1 leaves the heat treatment furnace 2, the temperature of the temperature compensation hood 3 is raised to 700-980°C, in preparation for compensating the temperature of the steel plate 1 after leaving the heat treatment furnace 2; when the thickness of the steel plate 1 is large and the roller speed is high, the temperature of the temperature compensation hood 3 is reduced; when the thickness of the steel plate 1 is small and the roller speed is low, the temperature of the temperature compensation hood 3 is increased; the range of decrease or increase of the temperature of the temperature compensation hood 3 is 0-280°C.

[0015] The gas volume distribution method is as follows: before the steel plate 1 leaves the heat treatment furnace 2, the gas volume of each group of gas quenching nozzles is set to decrease from the first group of gas quenching nozzles 5 to the fourth group of gas quenching nozzles 8, and the gas volume of each gas quenching nozzle group is the same, and the gas volume of each group of gas quenching nozzles accounts for 30% to 70%, 20% to 40%, 10% to 30%, and 10% to 30% of the total gas volume respectively; the gas volume of a single gas quenching nozzle ranges from 1000 to 1500m 3 / h, the jet pressure range is 0.1~0.4MPa.

[0016] The roll gap control method is as follows: before the steel plate 1 enters the quenching machine 4, all roll gap values ​​of the quenching machine 4 except the last set of rollers 16 are set to [d-2mm, d+2mm], where d is the thickness of the steel plate; and the roll gap value of the last set of rollers 16 of the quenching machine is set to [d-1.5mm, d+1.5mm] to realize roller-type constrained quenching.

[0017] In the roll gap control method, when the steel plate 1 has a wavy shape in the middle after quenching, the roll gaps of all roller sets are increased; when the steel plate 1 has a wavy shape at the edge after quenching, the roll gaps of all roller sets are reduced, and the reduction or increase amplitude of the roll gap is 0.1 to 1 mm.

[0018] The roller speed control method is that the steel plate 1 leaves the heat treatment furnace 2 at a speed 1.2 to 2.0 times the stable gas quenching speed, and the steel plate 1 reaches the first set of rollers 12 at a speed of -0.01 to -0.15 m / s. 2 / s acceleration is decelerated to a stable gas quenching speed; the speed increase of the steel plate 1 out of the heat treatment furnace 2 increases with the decrease of the thickness of the steel plate, which is specifically calculated by the following formula, where V 1 V is the speed of the steel plate out of the heat treatment furnace, in m / s. 2 is the stable gas quenching speed of the steel plate, in m / s, d is the thickness of the steel plate, in mm;

[0019] V 1 =(3-1.31667d+0.35d 2 -0.03333d 3 )V 2 d∈[1,4].

[0020] The stable gas quenching speed is the speed of the first set of rollers after the last set of rollers bite the steel plate.

[0021] In the roller speed control method, after the head of the steel plate 1 enters the nth group of rollers of the quenching machine 4, n≥1, the roller speed from the n+1th group of rollers to the last group of rollers of the quenching machine 4 along the length direction of the steel plate 1 = the roller speed of the nth group of rollers + 0.0001~0.001m / s, so as to realize micro-tension stretching quenching between adjacent rollers, and the roller speed range of the steel plate 1 during quenching is 0.08~1m / s.

[0022] In the roller speed control method, when the final cooling temperature of the steel plate 1 after passing through the quenching machine 4 is higher than 150°C, the speeds of all rollers are reduced; when the temperature of the steel plate 1 after passing through the quenching machine 4 is lower than 50°C, the speeds of all rollers are increased; the amplitude of the reduction or increase of the roller speed is 0.001 to 0.1 m / s.

[0023] Beneficial effects of the present invention: The present invention precisely controls the cooling path and deformation process during the roller-type gas quenching process of 1-4 mm high-strength steel plates, effectively improving the performance indicators and performance uniformity of 1-4 mm high-strength steel plates after quenching, improving the quenching shape and residual stress of ultra-thin high-strength steel plates after quenching, and improving the quenching quality. Through the temperature compensation control method and the gas volume distribution method, the cooling start temperature is increased, the cooling path is regulated, the generation of non-martensitic structures such as proeutectoid ferrite, pearlite, and bainite is reduced, and the quenching shape, residual stress and toughness of ultra-thin high-strength steel plates after quenching are improved; roller-type constrained quenching is achieved through the roller gap control method, which effectively improves the quenching uniformity and straightness of the steel plate; through the roller speed control method, the cooling efficiency is improved, the difference in uniformity of organizational properties caused by head pre-cooling is reduced, and micro-tension stretch quenching is achieved at the same time, effectively eliminating the quenching shape problems of steel plates such as edge waves and middle waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram showing the implementation scheme of the roller-pressed gas quenching method for 1-4 mm high-strength steel plates in the present invention;

[0025] In the figure: 1-steel plate; 2-heat treatment furnace; 3-temperature compensation hood; 4-quenching machine; 5-first group of gas quenching nozzles; 6-second group of gas quenching nozzles; 7-third group of gas quenching nozzles; 8-fourth group of gas quenching nozzles; 9-roller; 10-roller in furnace; 11-high temperature resistant roller in temperature compensation hood; 12-first group of rollers; 13-second group of rollers; 14-third group of rollers; 15-fourth group of rollers; 16-last group of rollers. DETAILED DESCRIPTION

[0026] Take 2mm thick and 2000mm wide high-strength wear-resistant steel plate NM400 for engineering machinery as an example, combined with Figure 1 , describing the specific implementation method of the roller-pressed gas quenching process for ultra-thin high-strength steel plates of 1 to 4 mm.

[0027] Before the steel plate 1 leaves the heat treatment furnace 2, the temperature compensation control method sets the temperature compensation hood 3 to heat to 700-980°C. When the temperature of the temperature compensation hood 3 is greater than 980°C, the steel plate 1 is rapidly air-cooled at high temperature after the temperature compensation, and the actual temperature compensation efficiency is reduced, resulting in energy waste; when the temperature of the temperature compensation hood 3 is less than 700°C, the steel plate will undergo non-martensitic phase transformation, carbide precipitation and other unfavorable structural transformations before quenching, and the steel plate 1 will be reduced by 300-800MPa. For example, when the heating temperature of the temperature compensation hood 3 is 850°C, the strength of the example NM400 steel plate is 1400MPa; when the heating temperature of the temperature compensation hood 3 is 650°C, the strength of the example NM400 steel plate is 1000MPa.

[0028] In this embodiment, four groups of gas quenching nozzles are designed, namely, the first group of gas quenching nozzles 5, the second group of gas quenching nozzles 6, the third group of gas quenching nozzles 7 and the fourth group of gas quenching nozzles 8; the gas volume distribution method sets the single nozzle flow rate of the first group of gas quenching nozzles 5 to the fourth group of gas quenching nozzles 8 to be 1500m 3 / h、1200m 3 / h、1100m 3 / h、1000m 3 / h, the jet pressure is 0.4MPa, and the gas volume and jet pressure of each group of upper and lower nozzles are the same. At this time, the total gas volume is 9600m 3 / h, the gas volume of the first group of gas quenching nozzles 5 to the fourth group of gas quenching nozzles 8 decreases, accounting for 31%, 25%, 23% and 21% of the total gas volume respectively. This gas volume distribution method improves the cooling rate of the high temperature zone of the steel plate 1, reduces the generation of non-martensitic phase transformation, and accurately controls the cooling path, so that the best microstructure and performance can be obtained under the condition of the same total gas volume. When other distribution methods are used, the strength of the steel plate will be reduced by 200 to 600MPa. For example, when the above-mentioned group-by-group decreasing gas volume distribution method is used, the strength of the example NM400 steel plate is 1400MPa; when the four groups of gas quenching nozzles account for 25% of the total gas volume, and the jet pressure is 0.4MPa, that is, when the above-mentioned group-by-group decreasing gas volume distribution method is not used, the strength of the example NM400 steel plate is 1100MPa.

[0029] The roller speed control method sets the roller speed of the roller 10 in the furnace, the high temperature roller 11 in the heating cover and the first group of rollers 12 to 0.3m / s, and the roller speed of the other groups of rollers to 0.2m / s. The roller speed control method can accelerate the head of the steel plate 1 to enter the quenching machine 4, reduce the non-martensitic phase transformation caused by the precooling of the steel plate head, increase the head strength by 100-500Mpa, and enhance the uniformity of the performance of the steel plate 1. For example, when the above roller speed control method is used, the strength of the steel plate head is 1400MPa; when the roller speed of all groups of rollers is 0.2m / s, that is, when the above roller speed control method is not used, the strength of the steel plate head is 1000MPa.

[0030] The roll gap control method sets the roll gap of the last set of rollers 16 to 2.8mm, and the roll gap of the other sets of rollers to 3mm. This method realizes the whole plate roller pressing constrained quenching process, and the last set of rollers 16 strengthens the constraint, further improving the plate shape quality.

[0031] The steel plate 1 is heated to 900℃ in the heat treatment furnace 2 and kept at this temperature for 10 minutes before being taken out of the furnace at a speed of 0.3m / s. When the head of the steel plate contacts the first set of rollers, the steel plate is moved at a speed of -0.08m / s. 2 / s acceleration to reduce the speed of the roller 10 in the furnace, the high temperature roller 11 in the heating cover and the first group of rollers 12 to 0.2m / s, and the speed of the second group of rollers 13, the third group of rollers 14, the fourth group of rollers 15 and the last group of rollers 16 is adjusted to 0.2001m / s; when the head of the steel plate 1 reaches the second group of rollers 13, the speed of the third group of rollers 14, the fourth group of rollers 15 to the last group of rollers 16 is adjusted to 0.2002m / s; and so on, when the head of the steel plate 1 reaches the last group of rollers 16, the speed of all rollers 9 no longer changes. From then on, micro-tension stretch quenching between rollers 9 is achieved, which effectively improves the quality of the plate shape. When the above roller speed control method is used, the flatness of the example steel plate is less than 4mm / m; when the second group of rollers 13 to the last group of rollers 16 are all 0.2m / s, that is, when the above roller speed control method is not used, the flatness of the example steel plate is greater than 10mm / m.

[0032] When the temperature of the steel plate 1 out of the quenching machine 4 is higher than 150°C, the steel plate has not completed the phase transformation, and a non-martensitic structure is obtained, and the strength of the steel plate is reduced by 200-400MPa, and the speed of all rollers 9 of the next steel plate 1 is reduced to 0.18m / s; when the temperature of this steel plate 1 out of the quenching machine 4 is lower than 50°C, the steel plate has completed the phase transformation, but the cooling time is too long, resulting in energy waste and reduced production efficiency, and the speed of all rollers 9 of the next steel plate 1 is increased to 0.22m / s. Finally, the final cooling temperature of the steel plate is adjusted to 50-150°C, so as to improve the performance and production efficiency of the steel plate 1.

[0033] When the middle wave appears after quenching of this steel plate 1, the gap of the last set of rollers 16 of the next steel plate 1 is increased to 3.0mm, and the gaps of the remaining sets of rollers are increased to 3.2mm, and the gaps of each set of rollers are gradually increased until the middle wave disappears. When the edge wave appears after quenching of this steel plate 1, the gap of the last set of rollers 16 of the next steel plate 1 is reduced to 2.6mm, and the gaps of the remaining sets of rollers are reduced to 2.8mm, and the gaps of each set of rollers are gradually reduced until the edge wave disappears. The straightness of the 2mm NM400 steel plate after final quenching is <4mm / m.

Claims

1. A roller-pressed gas quenching method for 1-4 mm high-strength steel plates, characterized in that: The roller-type gas quenching method mainly comprises a temperature compensation control method, a gas volume distribution method, a roller gap control method and a roller speed control method; the temperature compensation control method and the gas volume distribution method are set before the steel plate (1) exits the heat treatment furnace (2); the roller gap control method is set after the steel plate (1) exits the heat treatment furnace (2); the roller speed control method is dynamically adjusted after the steel plate (1) exits the heat treatment furnace (2) and during the gas quenching process; The temperature compensation control method is as follows: before the steel plate (1) exits the heat treatment furnace (2), the temperature of the temperature compensation cover (3) is raised to 700-980° C., so as to compensate the temperature of the steel plate (1) after exiting the heat treatment furnace (2); When the thickness of the steel plate (1) is large and the roller speed is high, the temperature of the heating cover (3) decreases; when the thickness of the steel plate (1) is small and the roller speed is low, the temperature of the heating cover (3) increases; the range of decrease or increase of the temperature of the heating cover (3) is 0 to 280°C; The gas volume distribution method is as follows: before the steel plate (1) leaves the heat treatment furnace (2), the gas volume of each group of gas quenching nozzles is set to decrease from the first group of gas quenching nozzles (5) to the fourth group of gas quenching nozzles (8), and the gas volume of each gas quenching nozzle group is the same, and the gas volume of each group of gas quenching nozzles accounts for 30% to 70%, 20% to 40%, 10% to 30%, and 10% to 30% of the total gas volume respectively; the gas volume of a single gas quenching nozzle ranges from 1000 to 1500m 3 / h, the jet pressure range is 0.1~0.4MPa; The roller gap control method is as follows: before the steel plate (1) enters the quenching machine (4), all roller gap values ​​except the last group of rollers (16) of the quenching machine (4) are set to [d-2mm, d+2mm], where d is the thickness of the steel plate; and the roller gap value of the last group of rollers (16) of the quenching machine is set to [d-1.5mm, d+1.5mm], so as to realize roller-type constrained quenching; The roller speed control method is that the steel plate (1) leaves the heat treatment furnace (2) at a running speed of 1.2 to 2.0 times the stable gas quenching speed, and when the head of the steel plate (1) reaches the first set of rollers (12), the speed is -0.01 to -0.15 m / s. 2 / s acceleration is decelerated to a stable gas quenching speed; The speed of the steel plate (1) exiting the heat treatment furnace (2) is calculated according to the following formula, wherein V1 is the speed of the steel plate exiting the heat treatment furnace, in m / s, V2 is the stable gas quenching speed of the steel plate, in m / s, and d is the thickness of the steel plate, in mm; <h2 style=";text-align:left;direction:ltr">V1 = (3 - 1.31667d + 0.35d<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -0.03333d<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> )V2 d∈[1,4]。 2. The roller-type gas quenching method for 1-4 mm high-strength steel plates according to claim 1, characterized in that: In the roll gap control method, when the steel plate (1) has a wavy shape in the middle after quenching, the roll gaps of all roller sets are increased; when the steel plate (1) has a wavy shape at the edge after quenching, the roll gaps of all roller sets are reduced, and the amplitude of the reduction or increase of the roll gap is 0.1 to 1 mm.

3. The roller-type gas quenching method for 1-4 mm high-strength steel plates according to claim 1, characterized in that: The stable gas quenching speed is the speed of the first set of rollers after the last set of rollers bite the steel plate.

4. The roller-pressing gas quenching method for 1-4 mm high-strength steel plates according to claim 1, characterized in that: In the roller speed control method, after the head of the steel plate (1) enters the nth group of rollers of the quenching machine (4), n≥1, the roller speed from the n+1th group of rollers to the last group of rollers of the quenching machine (4) along the length direction of the steel plate (1) is equal to the roller speed of the nth group of rollers + 0.0001 to 0.001 m / s, so that micro-tension stretch quenching is achieved between adjacent rollers, and the roller speed range of the steel plate (1) during quenching is 0.08 to 1 m / s.

5. The roller-type gas quenching method for 1-4 mm high-strength steel plates according to claim 4, characterized in that: In the roller speed control method, when the final cooling temperature of the steel plate (1) after passing through the quenching machine (4) is higher than 150°C, the speeds of all rollers are reduced; when the temperature of the steel plate (1) after passing through the quenching machine (4) is lower than 50°C, the speeds of all rollers are increased; the amplitude of the reduction or increase of the roller speed is 0.001 to 0.1 m / s.

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