A quenching device and method for preventing quenching cracking of a cylindrical workpiece

Abstract

The present application belongs to quenching technical field, and relates to a quenching device and method for preventing quenching cracking of a cylindrical workpiece. On the basis of the inner spraying mechanism being capable of stopping the inner spraying water, a water baffle is additionally arranged outside the inner spraying mechanism to more effectively prevent the residual water of the inner spraying from continuously flowing into the inner hole of the cylindrical workpiece, thereby avoiding the problem of uneven cooling at the end. After the cylindrical workpiece is quenched by using the device and method, the flaw detection qualified rate is obviously improved, and there is no obvious difference in performance after tempering heat treatment. Furthermore, the device and method reduce the blow-drying mechanism, keep the continuous rotation of the rotating drag pulley after quenching, and utilize the residual heat of the cylindrical workpiece for drying and cooling. Not only the compressed air cost is reduced, but also the material yield is obviously improved. The device and method are worthy of popularization and application in the quenching (water quenching) mode of the cylindrical workpiece such as a steel pipe.

Description

Technical Field

[0001] This invention belongs to the field of quenching technology and relates to a quenching device and method for preventing cracking of cylindrical workpieces during quenching. Background Technology

[0002] In the steel pipe production process, water quenching is an important step in the tempering treatment of steel pipes. The quality of water quenching has a significant impact on the performance of steel pipe products. Currently, the commonly used tempering treatment for steel pipes is an internal spraying and external quenching device. The existing internal spray and external rinsing quenching device includes: a roller conveyor and a turning hook, through which the cylindrical workpiece can move along its axial direction and move to the vicinity of the turning hook, and is turned into the quenching machine by the turning hook; a rotating roller, which can rotate while the cylindrical workpiece is being quenched to avoid uneven cooling and bending during quenching; an internal spray mechanism and an external rinsing mechanism, in which the internal spray mechanism injects water into the inner hole of the cylindrical workpiece in a columnar shape during quenching, and the external rinsing mechanism sprays water onto the outer wall of the workpiece during quenching. The internal spray mechanism and the external rinsing mechanism spray water internally and spray water externally simultaneously during the quenching of the cylindrical workpiece to ensure uniform cooling of the inner and outer walls; and a drying mechanism, which is connected to compressed air and can further dry the residual moisture in the inner hole after quenching of the cylindrical workpiece after natural drainage.

[0003] Currently, end-heat quenching cracking is a very common phenomenon in the quenching process of medium carbon and medium thick wall CrMo alloy seamless quenched and tempered pipes. Since many users require delivery in fixed lengths, end-heat quenching often results in the scrapping of the entire pipe, causing great trouble to the quality on site.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] This invention aims to provide a quenching device and method to prevent cracking of cylindrical workpieces during quenching. Based on existing conventional quenching devices and methods, the drying mechanism is reduced, an external internal spray water control mechanism (water baffle) is added, existing rotating trolleys are fully utilized, the cooling method after quenching is optimized, and its function is improved. It can effectively solve the problem of end cracking of cylindrical workpieces, especially medium carbon and / or medium-thick wall seamless steel pipes, during quenching (water quenching), and ultimately achieve the purpose of improving the yield and reducing material loss during heat treatment.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, a quenching device for preventing cracking of cylindrical workpieces during quenching includes: a turning hook for turning the cylindrical workpiece into the quenching mechanism.

[0008] Rotating rollers are used to rotate cylindrical workpieces during the quenching process and during cooling after quenching.

[0009] An internal spray mechanism is used to inject water into the inner hole of a cylindrical workpiece;

[0010] An external spraying mechanism is used to spray water onto the outer wall of a cylindrical workpiece.

[0011] The internal spray water control mechanism includes a baffle plate located outside the internal spray mechanism. The baffle plate is used to prevent residual water generated when the internal spray mechanism stops spraying from contacting the cylindrical workpiece.

[0012] Furthermore, the internal spray mechanism is equipped with a shut-off valve, which is used to control the opening and closing of the internal spray water of the internal spray mechanism.

[0013] And / or, the baffle plate is controlled by hydraulic or pneumatic pressure to move along the radial direction of the cylindrical workpiece, so as to prevent the residual water sprayed by the internal spraying mechanism from flowing into the inner hole of the cylindrical workpiece after the quenching is completed, at the same time as the internal spraying mechanism stops spraying water.

[0014] Furthermore, the quenching device also includes a roller conveyor, through which the cylindrical workpiece moves along its axial direction to the vicinity of the turning hook, and is turned into the quenching mechanism from the roller conveyor by the turning hook.

[0015] Secondly, a quenching method for preventing quenching cracks in cylindrical workpieces using the aforementioned quenching apparatus includes:

[0016] The internal spraying mechanism, the external spraying mechanism, and the rotating tow wheel operate simultaneously to perform internal spraying on the inner wall, external spraying on the outer wall, and overall rotary quenching on the cylindrical workpiece. After quenching, the operation of the internal spraying mechanism and the external spraying mechanism is stopped, but the rotating tow wheel continues to rotate to keep the cylindrical workpiece rotating. A baffle plate prevents residual internal spray water from contacting the cylindrical workpiece, and the residual heat of the cylindrical workpiece is used to complete the drying and cooling process to prevent quenching cracks.

[0017] Furthermore, the rotating tug continues to rotate for 10-20 seconds after quenching is completed.

[0018] Furthermore, the rotating tug continues to rotate at a speed of 1-2.5 revolutions per second after quenching.

[0019] Furthermore, the cylindrical workpiece has a pre-quenching temperature of 830-890℃ and a post-quenching residual temperature of 100-220℃.

[0020] Furthermore, the cylindrical workpiece is a hollow tube.

[0021] Furthermore, the hollow tube is one or more of the following types: alloy tube, medium carbon tube, or medium-thick wall tube.

[0022] Furthermore, the hollow tube is a medium-carbon, medium-thick-walled CrMo alloy series seamless quenched and tempered tube;

[0023] And / or, in the aforementioned medium carbon fiber tube type, the carbon content of the hollow tube is 2.5-6%;

[0024] And / or, in the medium-thickness wall type, the medium-thickness wall of the hollow tube is ≥15mm.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention, based on the ability to stop internal water spraying within the internal spraying mechanism, further adds a baffle plate on the outside to more effectively prevent residual water from continuing to flow into the inner hole of the cylindrical workpiece, thus avoiding uneven cooling at the ends. Using the device and method of this invention, the flaw detection pass rate of cylindrical workpieces after quenching is significantly improved, and there is no significant difference in performance after tempering heat treatment. Furthermore, the device and method of this invention reduce the need for a drying mechanism, and by maintaining the continuous rotation of the rotating trolley after quenching, utilizing the residual heat of the cylindrical workpiece for drying and cooling, not only are compressed air costs reduced, but the material yield is also significantly improved. This invention is worthy of widespread application in the quenching (water quenching) of cylindrical workpieces such as steel pipes. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the quenching device of the present invention;

[0028] Explanation of reference numerals in the attached drawings: 1. Internal spray mechanism; 2. Internal spray water control mechanism; 3. Rotating tow wheel; 4. External spray mechanism. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. The embodiments of this invention are implemented based on the technical solutions of this invention, and detailed implementation methods and processes are given. However, the scope of protection of this invention is not limited to the following embodiments. Those skilled in the art should understand that the embodiments are merely helpful in understanding this invention and should not be considered as specific limitations on this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0031] In this invention, unless otherwise specified and / or stated, all numerical values ​​relating to component amounts are "by weight or weight percentage" throughout. Process parameters in the following examples, unless otherwise specified, are generally performed under conventional conditions. The raw materials described in the following examples are all available from publicly available commercial sources.

[0032] Seamless quenched and tempered pipes made of medium-carbon, medium-thick-walled CrMo alloys often experience end-quenching cracks during the quenching process, frequently resulting in the scrapping of the entire pipe. This causes significant on-site quality losses and makes it difficult to meet customer's length delivery requirements. Through in-depth on-site monitoring, the inventors discovered that end-quenching cracks are often closely related to uneven cooling of the inner wall or the end. Therefore, based on existing conventional quenching equipment and methods, by reducing the drying mechanism and adding an external internal spray water control mechanism, the quenching method can be optimized, and related functions can be assembled and improved, effectively solving the problem of end-quenching cracks. The specific technical solution is as follows:

[0033] In a first aspect, a quenching device for preventing cracking of cylindrical workpieces during quenching includes: a turning hook for turning the cylindrical workpiece into the quenching mechanism.

[0034] Rotating rollers are used to rotate cylindrical workpieces during the quenching process and during cooling after quenching.

[0035] An internal spray mechanism is used to inject water into the inner hole of a cylindrical workpiece;

[0036] An external spraying mechanism is used to spray water onto the outer wall of a cylindrical workpiece.

[0037] The internal spray water control mechanism includes a baffle plate located outside the internal spray mechanism. The baffle plate is used to prevent residual water generated when the internal spray mechanism stops spraying from contacting the cylindrical workpiece.

[0038] This invention relates to a quenching device that, based on existing quenching devices, reduces the drying mechanism. Utilizing an existing rotating roller, it ensures that cylindrical workpieces, such as pipes, continue to rotate after quenching, promoting continuous water movement within the pipe and preventing water accumulation. The residual heat of the pipe allows for uniform evaporation of the spread-out water, reducing the cost of compressed air used in the drying mechanism. Simultaneously, an external internal spray water control mechanism, i.e., a baffle plate, is added to prevent the small amount of residual water already sprayed from continuing to flow into the pipe's inner hole after the shut-off valve on the internal spray mechanism is closed, thus avoiding uneven cooling at the end. While closing the shut-off valve ideally stops the internal spray from continuing to flow in, in actual operation, a small amount of residual water still flows into the inner hole, accumulating at one end without pressure. This invention, through the combined use of an internal shut-off valve and an external baffle plate, effectively prevents the continued flow of internally sprayed water and residual water into the pipe's inner hole. The rotation of the rotating roller and the residual heat of the pipe ensure uniform drainage of water from the inner hole and uniform cooling of the end.

[0039] As an optional embodiment of the quenching device of the present invention, the baffle plate is hydraulically controlled to move along the radial direction of the cylindrical workpiece. After quenching is completed, while the internal spraying mechanism stops spraying water (the opening and closing of the internal spraying mechanism can be controlled by existing water control components such as shut-off valves), it prevents the remaining water sprayed by the internal spraying mechanism from flowing into the inner hole of the cylindrical workpiece.

[0040] In the above technical solution, the baffle plate is positioned between the internal spray mechanism and the rotating trolley, near the water spray point of the internal spray mechanism. It is hydraulically controlled to move along the radial direction of the cylindrical workpiece (the radial direction refers to the direction of the straight line containing the diameter of the cylindrical workpiece, perpendicular to the axis). For an extended period (the entire quenching period), it remains in the lower limit position to prevent obstruction of the internal spray water from entering the inner hole of the cylindrical workpiece for quenching. Only after quenching is completed, and simultaneously with the shut-off valve stopping the internal spray, does the baffle plate rise to a position between the outlet of the internal spray mechanism and the inner hole of the cylindrical workpiece, preventing any residual internal spray water that was sprayed before stopping from flowing into the inner hole and affecting end cooling. Furthermore, hydraulic pressure can be replaced by pneumatic pressure, such as compressed air, but hydraulic control makes the baffle plate's operation more stable than pneumatic control. Preferably, the baffle plate is generally square, with its width slightly larger than the diameter of the internal spray nozzle of the internal spray mechanism. When it rises to its highest position, the center of the square should be at the same height as the center of the internal spray nozzle to block residual internal spray water. This design is suitable for cylindrical workpieces of all specifications, such as cylindrical workpieces with different outer diameters and wall thicknesses.

[0041] As an optional embodiment of the quenching device of the present invention, the quenching device further includes a roller conveyor, through which the cylindrical workpiece moves along its axial direction to the vicinity of the turning hook, and is turned into the quenching mechanism from the roller conveyor by the turning hook.

[0042] In the above technical solution, the axial direction refers to the direction of the straight line containing the central axis of the cylindrical workpiece, which is perpendicular to the radial direction.

[0043] Secondly, a quenching method for preventing quenching cracks in cylindrical workpieces using the aforementioned quenching apparatus includes:

[0044] The internal spraying mechanism, the external spraying mechanism, and the rotating tow wheel operate simultaneously to perform internal spraying on the inner wall, external spraying on the outer wall, and overall rotary quenching on the cylindrical workpiece. After quenching, the operation of the internal spraying mechanism and the external spraying mechanism is stopped, but the rotating tow wheel continues to rotate to keep the cylindrical workpiece rotating. A baffle plate prevents residual internal spray water from contacting the cylindrical workpiece, and the residual heat of the cylindrical workpiece is used to complete the drying and cooling process to prevent quenching cracks.

[0045] The quenching method of this invention is used for quenching. Before quenching, the cylindrical workpiece is quenched at a temperature of 830-890℃ (e.g., 835℃, 845℃, 855℃, 865℃, 875℃, 885℃, etc.) depending on the carbon content. During quenching, the inner wall is sprayed internally by an internal spraying mechanism, and the outer wall is sprayed externally by an external spraying mechanism, ensuring uniform cooling of both the inner and outer walls. Simultaneously, a rotating roller is used to rotate the workpiece, preventing uneven cooling and bending. The processing time for internal spraying and external spraying is directly related to the outer diameter and wall thickness of the cylindrical workpiece. Generally, the specific time is based on the residual temperature after quenching. Quenching is complete when the residual temperature reaches 100-220℃ (e.g., 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, etc.). After quenching, while closing the internal and external spray systems, a baffle plate is used to prevent a small amount of residual water from the internal spray from continuing to flow into the inner hole and accumulating under no pressure, which could cause uneven cooling and cracking at the ends during the cooling process. Furthermore, the rotating roller is kept in continuous rotation to facilitate the even drainage of moisture from both ends of the inner hole. The residual heat of the cylindrical workpiece after quenching also allows residual water on the inner and outer walls to evaporate at a uniform rate, preventing a small amount of water from accumulating in the inner hole for an extended period and causing quenching cracks. This invention's quenching method ensures uniform drainage of moisture from the inner hole of the cylindrical workpiece and uniform cooling at the ends, avoiding the need for complete scrapping, solving on-site quality loss problems, and meeting the user's requirements for fixed-length delivery.

[0046] As an optional embodiment of the quenching method of the present invention, the rotating trolley continues to rotate for 10-20s (such as 11s, 13s, 15s, 17s, 19s, etc.) after quenching is completed.

[0047] In the above technical solution, the rotating tug continues to rotate for several seconds after quenching to ensure that the moisture (including water vapor) on the inner wall of the steel pipe is drained at a uniform speed.

[0048] As an optional embodiment of the quenching method of the present invention, the rotating trolley continues to rotate at a speed of 1-2.5 revolutions / second after quenching (such as 1.1 revolutions / second, 1.3 revolutions / second, 1.5 revolutions / second, 1.7 revolutions / second, 1.9 revolutions / second, 2.1 revolutions / second, 2.3 revolutions / second, etc.).

[0049] In the above technical solution, different rotation speeds are determined according to the different outer diameters of the pipes, so that pipes of different outer diameters can be cooled at a uniform speed. Generally, the linear velocity of the rotating roller and the steel pipe usually has a slight difference due to friction, but this is negligible. Therefore, it is assumed that the linear velocity of the rotating roller is the same as that of the steel pipe. The linear velocity of the steel pipe is controlled by adjusting the linear velocity of the roller, thereby controlling its cooling. For example, taking a rotating roller with a diameter of 400mm as an example, a rotation speed of 1 revolution / second is suitable for cooling pipes with an outer diameter of not less than 100mm but less than 200mm; a rotation speed of 1.5 revolutions / second is suitable for cooling pipes with an outer diameter of not less than 200mm but less than 300mm; a rotation speed of 2 revolutions / second is suitable for cooling pipes with an outer diameter of not less than 300mm but less than 400mm; and a rotation speed of 2.5 revolutions / second is suitable for cooling pipes with an outer diameter of not less than 400mm but less than 500mm.

[0050] As an optional embodiment of the quenching method of the present invention, the cylindrical workpiece is a hollow tube. Further, the hollow tube is one or more types of medium-carbon tube, alloy tube, or medium-thick-walled tube; even further, the tube is a seamless quenched and tempered tube of the medium-carbon, medium-thick-walled CrMo alloy series.

[0051] In this invention, medium-thick wall tubes refer to seamless tubes with a wall thickness ≥15mm, and medium carbon tubes generally refer to seamless tubes with a carbon content of 2.5-6%. This quenching method is applicable to various types of seamless tubes such as medium carbon tubes, medium-thick wall tubes, and alloy tubes. However, it is more effective in preventing cracking caused by the quenching process for medium carbon and medium-thick wall CrMo (CrMnMo) alloy series tempered tubes.

[0052] As an optional embodiment of the quenching method of the present invention, the chemical composition of the CrMo alloy series seamless quenched and tempered tube, by mass percentage, includes: C 0.38~0.45% (e.g., 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, etc.); Si 0.17~0.37% (e.g., 0.18%, 0.20%, 0.22%, 0.24%, 0.26%, 0.28%, 0.30%, 0.32%, 0.34%, 0.36%, etc.); Mn 0.50~0.80% (e.g., 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, etc.); S≤0.035%; P≤0.035%; Cr 0.90~1.20% (e.g., 0.95%, 1.00%, 1.05%, 1.10%, 1.15%, etc.); Ni≤0.30% (e.g., 0.30%, 0.25%, 0.20%, 0.15%, 0.10%, etc.); Cu≤0.30% (e.g., 0.30%, 0.25%, 0.20%, 0.15%, 0.10%, etc.); Mo0.15~0.25%.

[0053] As an optional embodiment of the quenching method of the present invention, after the rotating trolley stops, the baffle plate no longer needs to block the space between the internal spraying mechanism and the cylindrical workpiece.

[0054] In the above technical solution, the baffle plate can detach from the internal spray mechanism and the cylindrical workpiece after a 3-second delay after the rotating tow wheel stops, and no longer plays a blocking role.

[0055] The present invention will now be described in further detail with reference to specific embodiments.

[0056] Examples 1-4

[0057] A method for quenching steel pipes, the method involving the use of a quenching apparatus, such as... Figure 1 As shown, the quenching device includes:

[0058] Roller conveyor and tipping hook: The cylindrical workpiece can move along its axial direction via the roller conveyor and move to the vicinity of the tipping hook, where it is tipped from the roller conveyor into the quenching machine using the tipping hook.

[0059] The rotating roller 3 (rotating support roller) allows the cylindrical workpiece to rotate during the quenching process and during the cooling process after quenching;

[0060] The internal spraying mechanism 1 can inject internal spray water into the inner hole of the cylindrical workpiece in a columnar shape for internal spray quenching; the internal spraying mechanism is equipped with a shut-off valve, which is used to control the opening and closing of the internal spray water of the internal spraying mechanism.

[0061] The external spraying mechanism 4 (external spraying water tank) can spray external spraying water onto the outer wall of the cylindrical workpiece for external spraying quenching.

[0062] The internal spray water control mechanism 2 includes a baffle plate (baffle head) located outside the internal spray mechanism. The baffle plate is located between the internal spray mechanism and the rotating towing wheel, near the water spraying point of the internal spray mechanism. It is hydraulically controlled and can move along the radial direction of the cylindrical workpiece. It remains in the lower limit state for a long time and only rises when the quenching is completed and the internal spraying stops, so as to prevent the residual internal spraying water that was sprayed before the spraying stopped from continuing to flow into the inner hole.

[0063] The method for quenching steel pipes using the above-mentioned quenching device includes:

[0064] By operating the internal spraying mechanism, the external spraying mechanism, and the rotating trolley simultaneously, the cylindrical workpiece is internally sprayed and externally sprayed during quenching, resulting in uniform cooling of the inner and outer walls. Furthermore, the workpiece rotates while being internally sprayed and externally sprayed to prevent uneven cooling in certain areas from causing bending.

[0065] After quenching using the internal spray + external spray + rotation method, stop the internal spray and external spray but do not stop the rotation. Simultaneously, the external baffle rises to prevent residual water from the internal spray from continuing to flow into the inner hole of the cylindrical workpiece. At the same time, the cylindrical workpiece is not immediately removed from the quenching machine; it continues to rotate on the rotating roller at a speed of 1 revolution / second for 10-20 seconds, utilizing the residual temperature of 100-220℃ to evaporate the moisture on its inner wall at a uniform rate. After the cylindrical workpiece has finished rotating, it is removed from the quenching machine, and the baffle lowers after a 3-second delay.

[0066] Examples of quenching treatment are given for cylindrical workpieces made of medium-thick-walled, medium-carbon CrMo alloy series seamless quenched and tempered tubes (42CrMo seamless tubes and 40CrMnMo seamless tubes) with high risk of quenching cracking (Examples 1-4).

[0067] Both 42CrMo and 40CrMnMo seamless steel pipes underwent corresponding quenching heat treatment before quenching. The quenching heat treatment temperature was 860℃. The quenching holding time (min) for 42CrMo seamless steel pipes was calculated as 2 min per 1 mm of wall thickness; the quenching holding time (min) for 40CrMnMo seamless steel pipes was calculated as 3 min per 1 mm of wall thickness. After quenching heat treatment, the above-mentioned quenching equipment and methods were used for further quenching. After quenching, ultrasonic flaw detection was performed. Subsequently, a tempering heat treatment was performed at 620℃ for 1 hour. After tempering heat treatment, tensile properties (yield strength, tensile strength) and impact energy were tested according to GB / T228 and GB / T229. The steel grades, specifications, and test results of Examples 1-4 are detailed in Tables 1 and 2.

[0068] Table 1. Examples 1-4 and Comparative Examples 1-4: Cylindrical workpieces and flaw detection results.

[0069]

[0070] Table 2. Examples 1-4 and Comparative Examples 1-4: Cylindrical workpieces and tempering heat treatment.

[0071]

[0072] Comparative Examples 1-4

[0073] The difference from Examples 1-4 is that conventional quenching equipment and methods are used to quench the cylindrical workpieces in Examples 1-4 respectively.

[0074] The specific difference between the conventional quenching device and the quenching device in the embodiment is that the conventional quenching device includes a drying mechanism but does not have an internal spray water control mechanism (water baffle), while the rest of the mechanism is the same as in the embodiment.

[0075] The specific difference between the conventional quenching method and the quenching method in the embodiment is that: after quenching, the water baffle is not used to block the residual water sprayed inside, and the continuous rotation of the rotating tow wheel is not continued. In addition to natural drainage, the cylindrical workpiece is further dried by compressed air through a drying mechanism to dry the residual moisture in the inner hole after quenching. The compressed air pressure is controlled at about 0.4MPa, and the drying time is 3-5 seconds. The rest of the quenching treatment is the same as in the embodiment.

[0076] The steel grades, specifications, and test results for Comparative Examples 1-4 are detailed in Tables 1 and 2.

[0077] As can be seen from the above, when using the quenching device and method of this invention for production, the pass rate of flaw detection of medium carbon and medium thick wall CrMo alloy series tempered pipes with high risk of quenching cracking is significantly improved after quenching. There is no significant difference in performance after tempering heat treatment. At the same time, the drying mechanism is reduced during the quenching process, reducing the cost of compressed air and significantly improving the material yield. The annual yield increased by an average of 2.56% per month. It is worth promoting its application in steel pipe quenching (water quenching) methods.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A quenching method for preventing cracking of cylindrical workpieces during quenching using a quenching device, characterized in that, The quenching device includes: a turning hook for turning the cylindrical workpiece into the quenching mechanism; Rotating rollers are used to rotate cylindrical workpieces during the quenching process and during cooling after quenching. An internal spray mechanism is used to inject water into the inner hole of a cylindrical workpiece; An external spraying mechanism is used to spray water onto the outer wall of a cylindrical workpiece. An internal spray water control mechanism includes a baffle plate disposed outside the internal spray mechanism. The baffle plate is used to prevent residual water generated when the internal spray mechanism stops spraying from contacting the cylindrical workpiece. The baffle plate is controlled by hydraulic or pneumatic pressure to move along the radial direction of the cylindrical workpiece. After quenching, it is used to prevent the residual water sprayed by the internal spraying mechanism from flowing into the inner hole of the cylindrical workpiece when the internal spraying mechanism stops spraying water. The quenching device also includes a roller conveyor, through which the cylindrical workpiece moves along its axial direction to the vicinity of the turning hook, and is turned from the roller conveyor into the quenching mechanism by the turning hook. The internal spray mechanism is equipped with a shut-off valve, which is used to control the opening and closing of the internal spray water of the internal spray mechanism. The quenching method includes: The internal spraying mechanism, the external spraying mechanism, and the rotating tow wheel operate simultaneously to perform internal spraying on the inner wall, external spraying on the outer wall, and overall rotary quenching on the cylindrical workpiece. After quenching, the operation of the internal spraying mechanism and the external spraying mechanism is stopped, but the rotating tow wheel continues to rotate to keep the cylindrical workpiece rotating. A baffle plate prevents residual internal spray water from contacting the cylindrical workpiece, and the residual heat of the cylindrical workpiece is used to complete the drying and cooling process to prevent quenching cracks. The rotating tug continues to rotate for 10-20 seconds after quenching is completed; The rotational speed of the rotating roller after quenching is determined based on the outer diameter of the pipe. For a 400mm diameter rotating roller, a rotational speed of 1 revolution / second is suitable for cooling pipes with an outer diameter of not less than 100mm but less than 200mm; a rotational speed of 1.5 revolutions / second is suitable for cooling pipes with an outer diameter of not less than 200mm but less than 300mm; a rotational speed of 2 revolutions / second is suitable for cooling pipes with an outer diameter of not less than 300mm but less than 400mm; and a rotational speed of 2.5 revolutions / second is suitable for cooling pipes with an outer diameter of not less than 400mm but less than 500mm. The cylindrical workpiece is a hollow tube; The hollow tube is a medium-carbon, medium-thick-walled CrMo alloy series seamless quenched and tempered tube; The chemical composition of the CrMo alloy series seamless quenched and tempered tubes, by mass percentage, includes: C 0.38~0.45%; Si 0.17~0.37%; Mn 0.50~0.80%; S≤0.035%; P≤0.035%; Cr 0.90~1.20%; Ni≤0.30%; Cu≤0.30%; Mo 0.15~0.25%; The hollow tube has a wall thickness of ≥15mm.

2. The quenching method according to claim 1, wherein The cylindrical workpiece has a pre-quenching temperature of 830-890℃ and a residual temperature of 100-220℃ after quenching.

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