CN112522479A - Cooling method for steel pipe or round bar - Google Patents
Cooling method for steel pipe or round bar Download PDFInfo
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- CN112522479A CN112522479A CN202011197553.2A CN202011197553A CN112522479A CN 112522479 A CN112522479 A CN 112522479A CN 202011197553 A CN202011197553 A CN 202011197553A CN 112522479 A CN112522479 A CN 112522479A
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- 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
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- 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
- C21D1/28—Normalising
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- 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
- C21D1/62—Quenching devices
- C21D1/63—Quenching devices for bath quenching
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- 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
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
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- 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
- C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
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- 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
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
- C21D9/085—Cooling or quenching
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Abstract
The invention provides a cooling method of a steel pipe or a round bar, which comprises the following steps: firstly, conveying a heated workpiece to a rotating device, wherein the rotating device is positioned above a water quenching tank and drives the workpiece to rotate; and step two, controlling the depth position of the rotating device immersed into the water quenching tank according to the material and the requirement of the workpiece, and simultaneously regulating and controlling the rotating speed of the rotating device to enable the workpiece to rotate according to a set linear speed, so as to realize the cooling of the workpiece. According to the method, a heated workpiece is conveyed to a rotating device through a roller way and a stirring material, the descending distance of the workpiece is controlled through a hydraulic proportional valve and a displacement sensor, the depth h of the workpiece immersed into a quenching tank is accurately controlled, the linear speed v of the workpiece is controlled through a rotating tug, the cooling time t in the whole process is controlled, the cooling speed and the cooling strength of the workpiece can be effectively controlled, the uniform structure and the performance are obtained, and the application range is wide.
Description
Technical Field
The invention belongs to the technical field of heat treatment of steel pipes or bars, and particularly relates to a cooling method of a steel pipe or a round bar.
Background
In recent years, the research on the non-tempered steel and the high-hardenability quenched and tempered steel for the heat treatment of steel pipes and bars has been greatly developed, and simultaneously, new technical problems are faced. For the technical bottleneck of non-tempered steel, the traditional method uses a fan to forcibly cool from the end after austenitizing, so that the problems of uneven overall length cooling and insufficient strength are caused.
A water mist cooling method for a steel pipe (CN108315532B) disclosed in 2018 is successfully applied to a large-diameter and large-wall-thickness steel pipe, the diameter of the steel pipe is larger than 219mm, the wall thickness of the steel pipe is larger than 30mm, and for a small-diameter and thin-wall pipe, the problems of uneven water mist cooling and bending are caused, so that the final performance stability is influenced; 2019, which discloses a water-cooling self-tempering process and device for steel pipes (CN109868352A), the method rapidly cools an austenitized steel pipe from the outer surface to the inner wall to 550-650 ℃, but the continuous rapid cooling reduces the surface temperature of the steel pipe to below 300 ℃ of martensite starting transformation point, and the steel pipe after self-tempering obtains a mixed structure of shallow surface tempered martensite, core pearlite and bainite, so that the hardness and performance of the whole section are greatly fluctuated, and the overall stability is influenced. A water quenching process for a high-hardenability quenched and tempered steel pipe introduces a process requirement of the high-hardenability quenched and tempered steel pipe by controlling the time sequence of internal spraying and external spraying (or external soaking) in a steel pipe water quenching method (CN103146901B) disclosed in 2013, but the method does not consider the influence of the depth and the rotating speed of a workpiece immersed in a quenching tank on cooling, and does not completely solve the problem in the aspect of quench cracking control.
At present, a cooling process of a multipurpose steel pipe or bar is needed, and the cooling process has adjustable cooling speed, small overall section hardness and performance fluctuation and strong stability for non-quenched and tempered steel or high-hardenability quenched and tempered steel pipes or bars with different diameters and wall thicknesses.
Therefore, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.
Disclosure of Invention
The invention aims to provide a cooling method of a steel pipe or a round bar, which aims to solve the problems that the cooling mode is single, the application range is narrow and the cooling speed cannot be controlled in the conventional heat treatment of the steel pipe or the bar.
In order to achieve the above purpose, the invention provides the following technical scheme:
a method of cooling a steel pipe or round bar, the method comprising the steps of:
firstly, conveying a heated workpiece to a rotating device, wherein the rotating device is positioned above a water quenching tank and drives the workpiece to rotate;
and step two, controlling the depth position of the rotating device immersed into the water quenching tank according to the material and the requirement of the workpiece, and simultaneously regulating and controlling the rotating speed of the rotating device to enable the workpiece to rotate according to a set linear speed, so as to realize the cooling of the workpiece.
In the cooling method of the steel pipe or the round bar as described above, preferably, the workpiece is divided into two cooling methods according to the material and the requirement of the workpiece:
for non-quenched and tempered steel, the rotating device drives the workpiece to be positioned at the junction of liquid and air, and the workpiece is cooled by adopting a partial immersion circulating cooling method;
and for the quenched and tempered steel, the rotating device drives the workpiece to be completely immersed into the water quenching tank, and the workpiece is cooled by adopting a full immersion cooling method.
In the cooling method of the steel pipe or the round bar as described above, preferably, for the quenched and tempered steel, the total immersion cooling method is divided into shallow immersion quenching cooling and deep immersion quenching cooling according to the degree of hardenability of the steel type;
dividing the hardenability of steel by the ideal critical hardenability diameter DI of the steel, generally taking the DI value of a 5.2 inch boundary, taking DI more than or equal to 5.2 inches as a steel grade with high hardenability, and taking the rest as a steel grade with general hardenability;
the steel grade with high hardenability is cooled by shallow immersion quenching;
the steel grade with general hardenability adopts deep immersion quenching cooling.
In the method for cooling a steel pipe or a round bar as described above, preferably, the workpiece immersion depth h in the shallow immersion quenching is D + (10mm to 80mm), where D is the diameter of the workpiece and h is the vertical distance from the liquid level position of the quenching tank to the lowest end position of the workpiece; the value range of D is 90-540 mm.
The immersion depth H of the workpiece during deep immersion quenching cooling is (H-150mm) -H, and H is the depth of liquid in the quenching tank; the value range of H is 250 mm-1500 mm.
In the cooling method of the steel pipe or the round bar, preferably, the overall steel temperature of effluent of the non-quenched and tempered steel after the partial immersion in the water-air circulation cooling method is 550-650 ℃;
the whole steel temperature of the outlet water of the quenched and tempered steel after the full-immersion cooling method is 100-200 ℃.
In the above method for cooling a steel pipe or round bar, preferably, the rotating device includes:
the rotary tug system comprises a rotary tug, the rotary tug is in transmission connection with the workpiece, and the rotary tug and the workpiece synchronously lift in the water quenching tank;
the hydraulic system is connected with the rotary tug and comprises a hydraulic proportional valve, and the lifting process of the rotary tug is controlled by opening and closing the hydraulic proportional valve;
and the displacement sensor is arranged on the rotary tug and used for accurately controlling the rotary tug to descend to the depth position in the water quenching tank.
In the method for cooling the steel pipe or the round bar, preferably, the rotary tug system comprises a rotary tug motor, the rotary tug motor is used for driving the rotary tug to rotate, and the frequency of the rotary tug motor is adjustable within the range of 0-50 HZ.
In the above method for cooling a steel pipe or a round bar, it is preferable that a ratio of the angular velocity of the rotary tug and the frequency of the rotary tug motor is a constant a of 2.2;
preferably, the frequency of the rotary tug motor during shallow immersion quenching cooling is 10-25 HZ;
still preferably, the frequency of the rotating tug motor during the deep immersion quenching cooling is 30-45 Hz.
In the method for cooling a steel pipe or a round bar as described above, preferably, the cooling method further comprises performing an internal spray cooling treatment on the inner wall of the steel pipe, and cooling the inner wall of the steel pipe before the steel pipe is cooled as a whole in the water quenching tank.
A cooling device for steel pipes or round bars, the device comprising:
the quenching tank is internally provided with a liquid cooling medium;
the rotating device is arranged above the quenching tank, and can be lifted and positioned in the quenching tank; the rotating device is the rotating device.
Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:
according to the cooling method of the steel pipe or the bar, the heated workpiece is conveyed to a rotating device through a roller way and a stirring material, the rotating device is positioned right above a water quenching tank, the descending distance of the rotating device is controlled through a hydraulic proportional valve and a displacement sensor, the depth h of the workpiece immersed into the water quenching tank is accurately controlled, the linear speed v of the workpiece is controlled through a rotating tug wheel, and finally the cooling time t in the whole process is controlled.
The non-quenched and tempered steel is subjected to a partially immersed circulation cooling method, so that a heat-treated workpiece is subjected to circulation cooling in two media of liquid and air, the liquid-air circulation cooling speed of the workpiece is controlled by controlling the rotating speed and time of a rotary tug, and uniform normalized structure and performance can be obtained.
The quenching and tempering steel adopts a cooling mode of complete immersion, the cooling intensity of the quenching and tempering steel is continuously increased along with the increase of the immersion depth of a heat treatment workpiece in a quenching water tank, the cooling requirements on different hardenability quenching and tempering steel materials are met, an ideal quenching and tempering tissue is obtained, and simultaneously quenching and cracking can be effectively controlled.
The rotary placing can realize two functions of normalizing cooling and quenching and tempering cooling at the same time, can be popularized and applied to two heat treatment lines, and has wide application range.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:
FIG. 1 is a schematic diagram of the position of a workpiece in a quenching tank according to various cooling methods of an embodiment of the invention;
FIG. 2 is a schematic structural view of a partial immersion circulation cooling method according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a shallow immersion quenching according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a deep immersion quenching according to an embodiment of the present invention.
Detailed Description
In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are for convenience of description of the present invention only and do not require that the present invention must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. The terms "connected" and "connected" used herein should be interpreted broadly, and may include, for example, a fixed connection or a detachable connection; they may be directly connected or indirectly connected through intermediate members, and specific meanings of the above terms will be understood by those skilled in the art as appropriate.
The cooling rate control is one of the most important means for controlling the details of the heat treatment process, and the conventional method for controlling the cooling rate is to change the cooling medium (such as furnace cooling, air cooling, water cooling, oil cooling, etc.), or to change the temperature, speed (flow rate), etc. of one of the cooling media. The invention adopts another mode: the positions (depths) of the heat treatment workpieces in the quenching tank are controlled to be different, so that different cooling speeds are realized. When a heat treatment workpiece is contacted with the liquid level of the quenching tank, the heat exchange between the workpiece and the quenching tank is started, the heat exchange area is increased along with the increase of the depth of the heat treatment workpiece immersed into the liquid level of the quenching tank, the cooling speed is accelerated, meanwhile, the workpiece is fixed in the quenching tank and rotates at a certain linear speed, the heat treatment workpiece is cooled circularly in two media of liquid and air, the cooling speed and the cooling time are reasonably controlled, and the non-quenched and tempered steel can obtain uniform normalizing structure and performance. The immersion type water quenching process is realized along with the continuous decline of the heat treatment workpiece and when the heat treatment workpiece is completely immersed into the liquid surface of the quenching tank, the cooling strength is continuously increased along with the different depths of the whole immersion liquid surface, the cooling requirements on different hardenability quenched and tempered steel materials are met, an ideal quenched and tempered tissue is obtained, and the quenching cracking can be effectively controlled.
The embodiment of the invention provides a cooling method of a steel pipe or a round bar, which comprises the following steps:
conveying a heated workpiece to a rotating device, wherein the rotating device is positioned above a water quenching tank and drives the workpiece to rotate;
and step two, controlling the depth position of the rotary device immersed in the water quenching tank according to the material and the requirement of the workpiece, and simultaneously regulating and controlling the rotating speed of the rotary device to enable the workpiece to rotate according to a set linear speed, so as to realize the cooling of the workpiece.
The workpiece heated in the first step of the invention refers to the heating of the workpiece in a specific heat treatment process, for example, in the case of non-quenched and tempered steel, the heating may be the heating in the normalizing heat treatment process, and the second step corresponds to the cooling after the heating in the normalizing heat treatment process. For quenched and tempered steel, heating generally refers to heating in the quenching heat treatment process, and step two corresponds to cooling after heating in the quenching heat treatment process.
In the embodiment of the invention, the workpiece is divided into two cooling modes according to the material and the requirement of the workpiece:
for non-quenched and tempered steel, the rotating device drives the workpiece to be positioned at the junction of liquid and air, and the workpiece is cooled by adopting a partial immersion circulating cooling method;
for quenched and tempered steel, a rotating device drives a workpiece to be completely immersed into a quenching tank, and the workpiece is cooled by adopting a full immersion cooling method. According to the hardenability of the steel, shallow immersion quenching cooling and deep immersion quenching cooling are adopted; the steel grade with high hardenability is cooled by shallow immersion quenching; the steel grade with general hardenability adopts deep immersion quenching cooling, the hardenability is high and low as the ideal critical hardenability diameter DI of the steel, the DI value is generally 5.2 inches dividing line, DI is more than or equal to 5.2 inches, the steel grade with high hardenability is taken as the steel grade with general hardenability, and the rest is the steel grade with general hardenability.
The rotating device includes: the system comprises a rotary tug system, a hydraulic system and a displacement sensor.
The rotary tug system comprises a rotary tug, the rotary tug is in transmission connection with the workpiece, and the rotary tug and the workpiece synchronously ascend and descend in the quenching tank.
The hydraulic system is connected with the rotary tug, comprises a hydraulic proportional valve, and controls the lifting process of the rotary tug through the opening and closing of the hydraulic proportional valve.
The displacement sensor is arranged on the rotary tug and used for accurately controlling the rotary tug to descend to the depth position in the water quenching tank.
The rotating device mainly controls the lifting of the rotating tug through a hydraulic system, when the hydraulic proportional valve is opened, the rotating tug descends or rises (the direction is determined according to the flow direction of a hydraulic oil circuit), when the hydraulic proportional valve is closed, the rotating tug stops lifting, and the displacement sensor directly and accurately controls the stopping position (namely the descending depth h) of the rotating tug device.
In a specific embodiment of the invention, the rotary tug system comprises a rotary tug motor, the rotary tug motor is used for driving the rotary tug to rotate, and the frequency of the rotary tug motor is adjustable within the range of 0-50 HZ. The structure of the rotary tugboat system is consistent with that of a tugboat group used in a steel pipe water-cooling self-tempering process and device (CN 109868352A).
As shown in fig. 1, the rotating device and the quenching tank can be combined to realize four common cooling process models by taking a steel pipe as an example: air cooling, partial immersion circulation cooling, shallow immersion quenching cooling and deep immersion quenching cooling.
The heat treatment workpiece after being heated and austenitized is conveyed to a rotating device above a quenching tank through a roller way and a stirring material, the descending distance of the heat treatment workpiece is controlled through a hydraulic proportional valve and a displacement sensor according to the specifications and process requirements of different steel pipes or bars, the depth of the heat treatment workpiece immersed into the quenching tank is accurately controlled (the arbitrary integer within the depth range of the quenching tank is adjustable), after the descending reaches the required immersion depth, a rotating tug wheel drives the steel pipes or the bars to rotate according to the specified frequency, different linear speeds of the steel pipes or the bars can be realized, and finally, the whole process control purpose is realized by controlling the cooling time. For steel pipes or bars with different diameters D, in the whole cooling process, the key control parameters are the immersion depth h, the rotation linear speed v of the tug (controlled by setting the frequency f of a motor of the rotary tug), and the cooling time t, which are key parameters for realizing the cooling mode.
The control is divided into the following three types according to the position relation of the workpiece in the water quenching tank, and the specific description is given by taking the liquid medium in the water quenching tank as water and taking the depth of the water quenching tank as 800mm as an example. Of course, in other embodiments, the water quenching tank may also contain other liquid cooling mediums, and the invention is not limited thereto.
1. And (4) completely arranging the steel pipe or the bar above the liquid level of the quenching tank, namely performing conventional air cooling.
2. As shown in FIG. 2, the steel tube or rod is partially immersed in the surface of the quenching bath. According to the requirements of the performance and the structure of partial non-quenched and tempered steel, the steel pipe or the steel bar is subjected to full austenitizing heat treatment (the temperature is generally 820-. The most critical step is the process of uniformly and rapidly cooling the austenitized workpiece to 500-650 ℃ in the whole (surface and core), and the process is a partial immersion circulating cooling method.
Taking the immersion depth of the workpiece as 1/4D as an example, the following details are provided: the immersion depth h of the steel pipe or the bar is controlled to be 1/4 of the diameter D of the workpiece, the surface area of the workpiece 1/3 is immersed in the water surface at the moment, 2/3 is exposed outside, and therefore the workpiece is exposed in the air to be uniform integrally, the temperature time is 2 times of the cooling time of the workpiece in the water, and the uniform temperature of the inner surface and the outer surface of the workpiece is ensured. Controlling the rotation linear velocity v of the tug (namely the rotation linear velocity of the workpiece),
wherein t1 is any position A, the steel is influenced by a steam film in static water after rotating for a circle at the temperature of more than 400 ℃, the cooling speed is generally 150-; s is the circumferential length of the section in water, R is the diameter of the rotary tug, and the device R is 250mm in the embodiment; the constant a of the ratio of the angular speed of the rotary tug to the frequency of the rotary tug motor is 2.2, namely when the frequency f of the rotary tug motor is 1HZ, the angular speed of the rotary tug is 2.2r/min, and the frequency of the motor and the angular speed of the rotary tug are in a linear relation; f is the frequency of the motor of the rotary tug; therefore, after the above formula is substituted, the frequency f of the rotary tug motor can be controlled to be 0.073D. The cooling time t is the total time of soaking in water and air for circulating cooling, namely 3t1, namely 1.5 s; finally, the workpiece is uniformly and quickly cooled to 650 ℃ of 500-. In other embodiments, when the immersion depth h is different, the cooling time ratio of single water-air circulation cooling (rotating for one circle) in air and water is changed, the cooling intensity and uniformity are directly influenced, and the corresponding process parameters are correspondingly different.
3. As shown in fig. 3 and 4, the steel pipe or rod is completely immersed (shallow and deep) in the surface of the quenching bath. The key technology of quenching and tempering steel pipes or bars is to obtain a uniform structure by controlling the cooling speed in the quenching process and simultaneously prevent quenching cracking, and the larger the immersion depth is, the stronger the cooling capacity is under the same stirring speed, so that the uniform quenching structure is ensured by adopting deep immersion quenching for steel types with general hardenability (such as 27SiMn, 30CrMo, 35CrMo, 42rMo and the like), and the uniform quenching structure is effectively prevented by adopting shallow immersion quenching for steel types with high hardenability (such as 4340, 4145, 13Cr and the like).
The realization process is as follows: controlling the immersion depth h of the steel pipe or the bar to D +20mm (shallow immersion quenching method) or h to 800mm (deep immersion quenching method). The high-speed rotation can effectively break a water vapor film formed on the surface of the workpiece during cooling at a high-temperature section (the steel temperature is more than 400 ℃) and accelerate the quenching cooling speed, so the rotational linear velocity v of the tug (namely the rotational linear velocity of the workpiece) meets the following formula:
the frequency f is 10-25 HZ (such as 12HZ, 15HZ, 18HZ, 20HZ, 22HZ and 25HZ) during shallow immersion cooling, and preferably is 15 HZ; the frequency f during deep immersion cooling is 30-45 HZ (for example, 32HZ, 35HZ, 38HZ, 40HZ, 42HZ), and f is preferably 40 HZ. Along with the increase of the frequency of the rotary tug motor, the cooling speed of the workpiece is increased, the cooling time is shortened, and the cooling time t is the total time of all immersion cooling so as to finally ensure that the workpiece is uniformly and rapidly cooled to 100-200 ℃.
In other embodiments, the workpiece immersion depth h in the shallow immersion quenching cooling is D + (10mm to 80mm), preferably h is D +20mm, where D is the diameter of the workpiece and D ranges from 90mm to 540 mm; h is the vertical distance from the liquid level height position of the quenching tank to the lowest end position of the workpiece; the immersion depth H of the workpiece during deep immersion quenching cooling is (H-150mm) -H, wherein H is the depth of liquid in a quenching tank and the unit is mm; the value range of H is 250 mm-1500 mm.
The cooling method of the invention also comprises the step of carrying out internal spraying cooling treatment on the inner wall of the steel pipe, and cooling the inner wall of the steel pipe before the steel pipe is wholly cooled in the water quenching tank. The internal spraying control can be executed according to the internal spraying operation in Chinese patent CN103146901B 'Steel tube Water quenching method'.
The embodiment of the invention is limited by the depth of the quenching tank of 800mm, the diameter of the bar is preferably 80-340mm, the outer diameter of the steel pipe is preferably 80-381mm, and the wall thickness of the steel pipe is preferably 5-100 mm.
Example 1
This example provides several exemplary steels that were subjected to the cooling method of the present invention described above to obtain satisfactory steels.
According to the delivery state of the steel grade and the required mechanical property and structure, a corresponding cooling mode is selected, and then the cooling process is controlled according to the corresponding parameters in the following table 1 by combining with the technical scheme of the cooling method in the invention, and a certain tempering process (the normalized delivery does not need tempering) is combined to obtain the steel which finally meets the requirements of the mechanical property and the structure, so that the hardness uniformity of the whole length and the whole section is good, and the impact power is better. In table 1, when the delivery state is normalized, the normalizing heat treatment process corresponds to the corresponding heat preservation temperature and cooling mode in table 1; in the normalizing and tempering delivery state, the corresponding heat preservation temperature and cooling mode in table 1 refer to a normalizing heat treatment process, and the tempering heat treatment process is a conventional heat treatment process.
TABLE 1 Cooling of different types of steel
According to the table, different steel types can be cooled according to different delivery states and mechanical property requirements by using the cooling device of the invention according to different cooling methods, and the steel meeting the requirements can be obtained by controlling the immersion depth, the cooling time and the frequency of the rotary tug motor.
Example 2
Partial immersion cycle cooling is compared with other cooling methods: the steel is represented by steel type AISI1340 and D139.7 multiplied by 32.9mm steel pipes, wherein two of the comparative cases respectively adopt cooling methods in patents CN108315532B 'a steel pipe water spray cooling method' and CN109868352A 'a steel pipe water-cooling self-tempering process and device', the performances and the hardness are shown in the following table after the comparison of the four cooling processes, and the performances are compared in different cooling modes, the impact energy of the partial immersion circulating cooling method is obviously superior to that of the traditional air cooling process, and the hardness uniformity of the whole length and the whole section is obviously superior to that of the other two cooling modes.
TABLE 2 comparison of partial immersion circulation cooling with other cooling methods
Example 3
The shallow immersion cooling is compared with a cooling method in patent CN103146901B 'Steel tube Water quenching method': the steel tube with the diameter of 410-13Cr and D165.1 multiplied by 38.1mm is taken as a representative steel tube, after two cooling processes and tempering together, the performance and the hardness are equivalent to the performance uniformity shown in the following table, but the flaw detection qualification rate of the shallow immersion water quenching method is far higher than that of the conventional steel tube water quenching method.
TABLE 3 comparison of the shallow immersion cooling mode with the cooling mode in the Steel tube Water quenching method
Example 4
The deep immersion cooling is compared with a cooling method in a patent CN103146901B 'Steel tube Water quenching method': the quenched and tempered bars of steel grade 42CrMoS4+ QT and 125mm are taken as a representative, after two cooling processes and tempering together, the performance and the hardness are as shown in the following table, the flaw detection qualification rate of the two is basically consistent, but the deep immersion cooling mode is obviously superior to that of the method shown in the patent CN103146901B in the aspect of uniformity of mechanical properties.
TABLE 4 comparison of deep immersion cooling and cooling in Steel tube Water quenching
In summary, the following steps: according to the cooling method for the steel pipe or the bar, the descending distance of the steel pipe or the bar is controlled through the hydraulic proportional valve and the displacement sensor, the depth h of the workpiece immersed into the quenching tank is accurately controlled, the linear speed v of the workpiece is controlled through the rotary tug, and finally the cooling time t in the whole process is controlled.
The non-quenched and tempered steel is subjected to a partially immersed circulation cooling method, so that a heat-treated workpiece is subjected to circulation cooling in two media of liquid and air, the liquid-air circulation cooling speed of the workpiece is controlled by controlling the rotating speed and time of a rotary tug, and uniform normalized structure and performance can be obtained.
The quenching and tempering steel adopts a cooling mode of complete immersion, the cooling intensity of the quenching and tempering steel is continuously increased along with the increase of the immersion depth of a heat treatment workpiece in a quenching water tank, the cooling requirements on different hardenability quenching and tempering steel materials are met, an ideal quenching and tempering tissue is obtained, and simultaneously quenching and cracking can be effectively controlled.
The rotary placing can realize two functions of normalizing cooling and quenching and tempering cooling at the same time, can be popularized and applied to two heat treatment lines, and has wide application range.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A cooling method of a steel pipe or a round bar is characterized by comprising the following steps:
the method comprises the following steps that firstly, a heated workpiece is conveyed to a rotating device, the rotating device is located above a water quenching tank, and the rotating device is used for driving the workpiece to rotate;
and step two, controlling the depth position of the rotating device immersed into the water quenching tank according to the material and the requirement of the workpiece, and simultaneously regulating and controlling the rotating speed of the rotating device to enable the workpiece to rotate according to a set linear speed, so as to realize the cooling of the workpiece.
2. The cooling method of steel pipe or round bar according to claim 1, wherein the work piece is divided into two cooling methods according to the material and requirement of the work piece:
for non-quenched and tempered steel, the rotating device drives the workpiece to be positioned at the junction of liquid and air, and the workpiece is cooled by adopting a partial immersion circulating cooling method;
and for the quenched and tempered steel, the rotating device drives the workpiece to be completely immersed into the water quenching tank, and the workpiece is cooled by adopting a full immersion cooling method.
3. The cooling method of steel pipe or round bar according to claim 2, wherein the full immersion cooling method is divided into shallow immersion quenching cooling and deep immersion quenching cooling according to the degree of hardenability of the steel type for quenched and tempered steel;
dividing the hardenability of steel by the ideal critical hardenability diameter DI of the steel, taking the DI value of a 5.2 inch boundary, taking DI more than or equal to 5.2 inches as a steel grade with high hardenability, and taking the rest as a steel grade with general hardenability;
the steel grade with high hardenability is cooled by shallow immersion quenching;
the steel grade with general hardenability adopts deep immersion quenching cooling.
4. The method for cooling a steel pipe or a round bar as set forth in claim 3, wherein the work immersion depth h in the shallow immersion quenching cooling is D + (10 mm-80 mm), where D is the diameter of the work and h is the vertical distance from the liquid level position of the quenching tank to the lowermost end position of the work;
the immersion depth H of the workpiece during deep immersion quenching cooling is (H-150mm) -H, and H is the depth of liquid in the quenching tank.
5. The cooling method for the steel pipe or the round bar according to claim 3, wherein the overall temperature of the discharged water of the non-quenched and tempered steel after the partial immersion in the water-air circulation cooling method is 550 to 650 ℃;
the whole steel temperature of the outlet water of the quenched and tempered steel after the full-immersion cooling method is 100-200 ℃.
6. The method for cooling a steel pipe or round bar as set forth in any one of claims 3 to 5, wherein the rotating means comprises:
the rotary tug system comprises a rotary tug, the rotary tug is in transmission connection with the workpiece, and the rotary tug and the workpiece synchronously lift in the water quenching tank;
the hydraulic system is connected with the rotary tug and comprises a hydraulic proportional valve, and the lifting process of the rotary tug is controlled by opening and closing the hydraulic proportional valve;
and the displacement sensor is arranged on the rotary tug and used for accurately controlling the rotary tug to descend to the depth position in the water quenching tank.
7. The method for cooling steel pipes or round bars according to claim 6, wherein the rotary tug system comprises a rotary tug motor for driving the rotary tug to rotate, and the frequency of the rotary tug motor is adjustable within the range of 0-50 HZ.
8. The method for cooling a steel pipe or a round bar according to claim 7, wherein the ratio of the angular velocity of the rotary tug to the frequency of the rotary tug motor is constant a 2.2;
preferably, the frequency of the rotary tug motor during shallow immersion quenching cooling is 10-25 HZ;
still preferably, the frequency of the rotating tug motor during the deep immersion quenching cooling is 30-45 Hz.
9. The method for cooling a steel pipe or a round bar according to claim 1, further comprising subjecting the inner wall of the steel pipe to an internal spray cooling treatment, wherein the inner wall of the steel pipe is cooled before the steel pipe is cooled in the quenching tank as a whole.
10. A cooling device for steel pipes or round bars, characterized in that it comprises:
the quenching tank is internally provided with a liquid cooling medium;
the rotating device is arranged above the quenching tank, and can be lifted and positioned in the quenching tank; the rotating device is the rotating device described in claim 6.
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