Heat treatment method for preventing deformation of thin-wall long cylindrical workpiece and special auxiliary tool

Abstract

The invention relates to a heat treatment method for preventing deformation of a thin-wall long cylindrical workpiece and a special auxiliary tool, and belongs to the technical field of heat treatment of metal workpieces. The heat treatment method for preventing the deformation of the thin-wall long cylindrical workpiece comprises the following steps: vertically putting the thin-wall long cylindrical workpiece into a heating furnace by utilizing a special auxiliary tool; the thin-wall long cylindrical workpiece is subjected to heating, heat preservation, cooling and tempering; or carrying out heating, heat preservation and cooling on the thin-wall long cylindrical workpiece; the special auxiliary tool comprises a base, a pull rod and an upper cover, limiting grooves are formed in the base and the upper cover respectively, the two ends of the thin-wall long-barrel-shaped workpiece are located in the limiting grooves of the base and the upper cover respectively, and the pull rod penetrates through the base, the thin-wall long-barrel-shaped workpiece and the upper cover. The special auxiliary tool can reduce the deformation of the thin-wall long cylindrical workpiece, so that the deformation rate of the thin-wall long cylindrical workpiece is below 2.5%, the overall performance of the thin-wall long cylindrical workpiece is uniform, and smooth delivery of the workpiece is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of metal workpieces, and in particular to a heat treatment method for preventing deformation of a thin-walled long cylindrical workpiece and a special auxiliary tool. Background Art

[0002] Heat treatment of metal materials is a process in which a metal or alloy workpiece is heated to a suitable temperature, kept at this temperature for a certain period of time, and then cooled at different speeds in different media to control its performance by changing the surface or internal microstructure of the metal material.

[0003] The heat treatment process is generally divided into three processes: heating, heat preservation and cooling. The heat treatment process can change the structure of the workpiece and improve the performance of the workpiece. However, during the heat treatment process, the workpiece is subjected to a complex stress process, and the combined effect of multiple stress fields such as thermal stress, phase change stress and organizational stress causes the workpiece to deform. Especially for thin-walled long cylindrical workpieces, because their walls are thin and long, they are very easy to deform during heat treatment, and subsequent processing adjustments are required. If they cannot be adjusted, they can only be scrapped.

[0004] Therefore, there is an urgent need for a heat treatment method to prevent the deformation of thin-walled long cylindrical workpieces and ensure that the size of the thin-walled long cylindrical workpieces meets the processing requirements. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a heat treatment method and a special auxiliary tool for preventing deformation of thin-walled long cylindrical workpieces, which can prevent deformation of thin-walled long cylindrical workpieces without affecting the performance of thin-walled long cylindrical workpieces.

[0006] In a first aspect, the present invention provides a heat treatment method for preventing deformation of a thin-walled long cylindrical workpiece, wherein the thin-walled long cylindrical workpiece is vertically placed in a heating furnace using a special auxiliary tool; the thin-walled long cylindrical workpiece is heated, kept warm, and cooled, or the thin-walled long cylindrical workpiece is heated, kept warm, cooled, and tempered;

[0007] The special auxiliary tool includes a base, a pull rod and an upper cover. Limiting grooves are respectively provided on the base and the upper cover. The two ends of the thin-walled long cylindrical workpiece are respectively located in the limiting grooves of the base and the upper cover. The pull rod passes through the base, the thin-walled long cylindrical workpiece and the upper cover.

[0008] Furthermore, the thin-walled long cylindrical workpiece rotates around its own central axis during the heating, heat preservation and cooling processes.

[0009] Furthermore, the heating temperature is 750-1080° C. and is kept warm for 1-5 hours.

[0010] Furthermore, the heat treatment method for preventing deformation of thin-walled long cylindrical workpieces comprises the following steps:

[0011] S1: Set the size of the upper limit grooves of the base and upper cover and the length of the pull rod according to the diameter, wall thickness and length of the thin-walled long cylindrical workpiece;

[0012] S2: Place the base on the limit block of the pull rod;

[0013] S3: Pass the pull rod through the thin-walled long cylindrical workpiece so that one end of the thin-walled long cylindrical workpiece is located in the limiting groove of the base;

[0014] S4: Pass the pull rod through the upper cover, insert the other end of the thin-walled long cylindrical workpiece into the limiting groove of the upper cover, and install the lifting ring on the pull rod;

[0015] S5: hoist the special auxiliary tool and the thin-walled long cylindrical workpiece and place them vertically into the heating furnace; heat them to a predetermined temperature and keep them warm;

[0016] S6: Lift the special auxiliary tools and thin-walled long cylindrical workpiece vertically out of the heating furnace and cool them.

[0017] In a second aspect, the present invention provides a thin-walled elongated cylindrical workpiece, which is prepared by the heat treatment method of the present invention.

[0018] Furthermore, the deformation rate of the thin-walled long cylindrical workpiece is below 2.5%.

[0019] In the third aspect, the present invention provides a special auxiliary tool for implementing the heat treatment method described in the present invention, wherein the special auxiliary tool comprises a base, a pull rod and an upper cover, wherein limiting grooves are respectively provided on the base and the upper cover, and the limiting grooves on the base are arranged opposite to the openings of the limiting grooves on the upper cover; a limiting block is provided at one end of the pull rod, and the other end of the pull rod passes through the base and the upper cover, and the base and the upper cover move along one direction on the pull rod.

[0020] Furthermore, the base and the upper cover are both radially symmetrical, including a central portion and a plurality of support portions radially distributed around the central portion; an axial through hole is provided in the central portion for the pull rod to pass through.

[0021] Furthermore, the support portion is provided with a plurality of limiting grooves in sequence, and the limiting grooves on the plurality of support portions that are equidistant from the symmetry center are located on the same concentric circle.

[0022] Furthermore, the end of the pull rod is connected with a lifting ring, and the lifting ring is located on a side of the upper cover away from the base.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. The present invention utilizes a special auxiliary tool to vertically heat and cool a thin-walled long cylindrical workpiece, thereby reducing the influence of gravity on both ends of the thin-walled long cylindrical workpiece. In addition, the special auxiliary tool includes a base, a pull rod and an upper cover, and the base and the upper cover are respectively provided with limiting grooves, and the two ends of the thin-walled long cylindrical workpiece are respectively located in the limiting grooves of the base and the upper cover; during the heating, cooling and / or tempering stages, the limiting grooves can limit the deformation of the thin-walled long cylindrical workpiece in the radial direction, but do not hinder the free expansion and contraction in the length direction. Therefore, the special auxiliary tool can reduce the deformation of the thin-walled long cylindrical workpiece, so that the deformation rate of the thin-walled long cylindrical workpiece is below 2.5%, thereby ensuring the smooth delivery of the workpiece.

[0025] 2. The special auxiliary tool in the present invention includes a base, a pull rod and an upper cover. The base and the upper cover are respectively provided with limit grooves, and the limit groove on the base is arranged opposite to the opening of the limit groove on the upper cover; a limit block is arranged at one end of the pull rod, and the other end of the pull rod passes through the base and the upper cover, and the base and the upper cover move along one direction on the pull rod. The special auxiliary tool can not only limit the deformation of thin-walled long cylindrical workpieces, but also play the role of a lifting auxiliary tool, saving materials.

[0026] 3. In the heating, cooling and tempering stages of the present invention, the thin-walled long cylindrical workpiece can rotate around its own central axis under the action of the rotating mechanism, so that the overall temperature of the thin-walled long cylindrical workpiece is uniform, thereby ensuring the uniform overall performance of the thin-walled long cylindrical workpiece.

[0027] 4. During the cooling process of the thin-walled long cylindrical workpiece of the present invention, the thin-walled long cylindrical workpiece is in a vertical state and enters the coolant, and the base and the upper cover are both cross structures, which do not hinder the cooling of the inner circumference of the thin-walled long cylindrical workpiece by the coolant, ensuring that the inner and outer circumferences of the thin-walled long cylindrical workpiece are cooled at the same time, and the temperature difference between the inner and outer circumferences of the workpiece is small, reducing the deformation tendency of the thin-walled long cylindrical workpiece. It is ensured that the thin-walled long cylindrical workpiece is heated evenly and has a uniform structure.

[0028] 5. The base and the upper cover of the present invention are provided with limiting grooves of multiple specifications, which can be suitable for thin-walled long cylindrical workpieces of different specifications, including thin-walled long cylindrical workpieces with different diameters and heights, and can also be suitable for thin-walled long cylindrical workpieces with different diameters at both ends.

[0029] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0031] Figure 1 It is a schematic diagram of assembling a special auxiliary tool and a thin-walled long cylindrical workpiece;

[0032] Figure 2 This is a schematic diagram of the upper cover in the special auxiliary tool;

[0033] Figure 3 This is a schematic diagram of the base in the special auxiliary tool;

[0034] Figure 4 It is a top view of the base in the special auxiliary tool;

[0035] Figure 5 This is a schematic diagram of the position of a thin-walled long cylindrical workpiece in a heat treatment furnace;

[0036] In the figure, 1. pull rod; 2. upper cover; 3. base; 4. limit groove; 5. thin-walled long cylindrical workpiece; 6. limit block; 7. lifting ring. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0038] Thin-walled long cylindrical workpieces have the structural characteristics of large diameter, thin wall thickness and long length. They often deform during heat treatment, especially at the two ends of the workpiece, where deformation is particularly serious. The existing heat treatment process for thin-walled long cylindrical workpieces is mainly to place the thin-walled long cylindrical workpiece horizontally on a tray for heating and cooling. After heat treatment, the two ends of the workpiece will deform under the action of gravity and stress, and the deformation rate is relatively large. Thin-walled workpieces cannot be repaired by mechanical processing.

[0039] The present invention provides a heat treatment method for preventing deformation of a thin-walled long cylindrical workpiece, which comprises vertically placing the thin-walled long cylindrical workpiece into a heating furnace using a special auxiliary tool; heating, heat-insulating, cooling and tempering the thin-walled long cylindrical workpiece; or heating, heat-insulating and cooling the thin-walled long cylindrical workpiece;

[0040] The special auxiliary tool includes a base, a pull rod and an upper cover. Limiting grooves are respectively provided on the base and the upper cover. The two ends of the thin-walled long cylindrical workpiece are respectively located in the limiting grooves of the base and the upper cover. The pull rod passes through the base, the thin-walled long cylindrical workpiece and the upper cover.

[0041] Compared with the prior art, the present invention uses a special auxiliary tool to hoist the thin-walled long cylindrical workpiece, and the thin-walled long cylindrical workpiece is always in a vertical state during the heating and cooling process, so that the temperature distribution of the thin-walled long cylindrical workpiece is uniform during heating and cooling, ensuring the uniform organization of the thin-walled long cylindrical workpiece and the uniform overall performance of the workpiece. At the same time, during the cooling process, the stress distribution is relatively uniform, reducing the deformation tendency of the thin-walled long cylindrical workpiece.

[0042] In addition, the special auxiliary tool includes a base, a pull rod and an upper cover, and limited slots are respectively provided on the base and the upper cover to limit the deformation of the thin-walled long cylindrical workpiece in the radial direction. However, the upper cover in the special auxiliary tool can move on the pull rod, so the thin-walled long cylindrical workpiece can freely expand and contract along the length direction during the heating and cooling process, release stress, and reduce the deformation rate of the diameter of the two ends of the thin-walled long cylindrical workpiece.

[0043] Specifically, the thin-walled long cylindrical workpiece has a wall thickness of 20-150 mm, a length of 1200-6000 mm, and an outer diameter of 2000-3000 mm. The thin-walled long cylindrical workpiece can be made of stainless steel, such as ultra-low carbon stainless steel SA508-3, such as austenitic stainless steel 316LN.

[0044] It should be noted that during the heating stage, the heating temperature of the thin-walled long cylindrical workpiece is 750-1080℃, and the holding time is 1-5h. Heat until the material is completely austenitized, and keep it warm for a certain period of time to ensure that the material is completely austenitized. When the temperature is lower than 750℃, the material cannot be completely austenitized, affecting the final performance; when the heating temperature is higher than 1080℃, it will cause some material grains to grow and affect the performance.

[0045] Exemplarily, the heating temperature of the thin-walled long cylindrical workpiece can be 750℃, 780℃, 800℃, 820℃, 850℃, 880℃, 900℃, 910℃, 930℃, 950℃, 980℃, 1000℃, 1020℃, 1040℃, 1060℃ or 1080℃.

[0046] Specifically, the heating temperature of the thin-walled long cylindrical workpiece is 800-1060°C.

[0047] Specifically, the heating temperature of the thin-walled long cylindrical workpiece is 890-1000°C.

[0048] In the cooling stage, the heated and heat-insulated thin-walled long cylindrical workpiece is directly placed in the air for air cooling to room temperature, or placed in a coolant for liquid cooling to room temperature. The coolant mainly includes cooling water and cooling oil.

[0049] In the tempering stage, the thin-walled long cylindrical workpiece is heated again for tempering treatment. The heating temperature is 150-700℃ and the holding time is 1-10h. The role of tempering is to eliminate the quenching stress of the material and adjust the material strength and toughness matching. When the heating temperature is lower than 150℃, the low-temperature tempering does not completely eliminate the stress; when the heating temperature is higher than 700℃, it has a greater impact on the material strength.

[0050] Exemplarily, the heating temperature for tempering the thin-walled long cylindrical workpiece can be 150°C, 180°C, 200°C, 250°C, 280°C, 300°C, 320°C, 350°C, 370°C, 390°C, 400°C, 420°C, 430°C, 450°C, 480°C, 500°C, 530°C, 550°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C or 700°C.

[0051] Specifically, the heating temperature for tempering the thin-walled long cylindrical workpiece is 200-660°C.

[0052] Specifically, the heating temperature for tempering the thin-walled long cylindrical workpiece is 350-500°C.

[0053] According to the experimental results, the thinner the wall thickness of the thin-walled long cylindrical workpiece is and the larger the diameter is, the greater the deformation tendency of the thin-walled long cylindrical workpiece is, that is, the greater the deformation rate of the thin-walled long cylindrical workpiece is, and in severe cases, it cannot be adjusted by its own processing allowance, resulting in waste of the workpiece. The heat treatment method of the present invention is used to treat the thin-walled long cylindrical workpiece, which can be applied to the thin-walled long cylindrical workpiece with a wall thickness of 20-150mm, a length of 1200-6000mm, and a diameter of 2000-3000mm. After testing, the deformation rate of the thin-walled long cylindrical workpiece is below 2.5%.

[0054] It should be noted that the thin-walled elongated cylindrical workpiece rotates around its own central axis during the heating, heat preservation and cooling process, so that the thin-walled elongated cylindrical workpiece is heated evenly, ensuring the overall temperature of the workpiece to be consistent, and ultimately ensuring the overall uniform performance of the workpiece.

[0055] Reference Figure 1 The present invention provides a special auxiliary tool, which includes a base 3, a pull rod 1 and an upper cover 2. Limiting grooves 4 are respectively provided on the base 3 and the upper cover 2, and the limiting grooves 4 on the base 3 are arranged opposite to the openings of the limiting grooves 4 on the upper cover 2; a limiting block 6 is provided at one end of the pull rod 1, and the other end of the pull rod 1 passes through the base 3 and the upper cover 2, and the base 3 and the upper cover 2 move along one direction on the pull rod 1.

[0056] Compared with the existing technology, the special auxiliary tool provided by the present invention can reduce the deformation tendency of the thin-walled long cylindrical workpiece 5 in the radial direction without hindering its free extension in the length direction; it can also be used as a lifting auxiliary tool to heat and cool together with the thin-walled long cylindrical workpiece 5.

[0057] Reference Figure 2 and Figure 3 The base 3 and the upper cover 2 are both radially symmetrical, including a central portion and a plurality of support portions radially distributed around the central portion. An axial through hole is provided in the central portion, and a plurality of limiting grooves 4 are sequentially provided on the support portions in a radial direction away from the central portion. The limiting grooves 4 on the plurality of support portions at equal distances from the symmetry center are located on the same concentric circle. The number of the limiting grooves 4 can be increased and adjusted according to actual production needs.

[0058] Specifically, the lower end surface of the upper cover 2 is a plane, which can ensure that the limiting groove 4 is at the same horizontal position, so as to facilitate the smooth insertion of the thin-walled long cylindrical workpiece 5; the upper end surface can be a plane or a cone. When the upper end surface of the upper cover 2 is a plane, the overall weight of the upper cover 2 is relatively light, which avoids excessive weight being applied to the thin-walled long cylindrical workpiece 5, causing deformation tendency; when the upper end surface of the upper cover 2 is a cone, it can generate tension on the edge of the upper cover 2, preventing the upper cover 2 from being deformed by gravity during the heating process, thereby affecting the size of the thin-walled long cylindrical workpiece 5.

[0059] Specifically, the cross-axis section of the base 3 is a trapezoid, which minimizes its own weight while ensuring that it can withstand a certain stress. At the same time, the cross-axis section is a trapezoidal design, which is conducive to reducing the radial deformation of the base 3 itself, thereby reducing the radial deformation of the thin-walled long cylindrical workpiece 5.

[0060] Both the base 3 and the upper cover 2 are provided with through holes for inserting the pull rod 1. In order to smoothly insert the pull rod 1 and prevent the base 3 and the upper cover 2 from shifting during use, the diameter of the through hole is the diameter of the pull rod 1 + (10-20) mm.

[0061] Preferably, the base 3 and the upper cover 2 are both cross structures, and a plurality of limit slots 4 are provided on the base 3 and the upper cover 2, and the number of the limit slots 4 can be increased and adjusted according to actual production needs. A through hole for inserting the pull rod 1 is provided on the base 3 and the upper cover 2, and the central axis of the through hole coincides with the center of the base 3 and the upper cover 2, respectively, and the size of the through hole is adapted to the diameter of the pull rod 1.

[0062] During the cooling process, the cooling medium needs to cool the inner and outer peripheral surfaces of the thin-walled long cylindrical workpiece 5, and the temperature of the inner and outer peripheral surfaces needs to be consistent or slightly different to ensure that the deformation tendency is small. Therefore, the base 3 and the upper cover 2 of the special auxiliary tool of the present invention are both cross structures, which can ensure that the cooling medium can smoothly enter the inner peripheral surface of the thin-walled long cylindrical workpiece 5 to cool it, and on the other hand, it can save materials and reduce costs, and at the same time, it does not affect the heating and cooling process of the workpiece 5 during the heating and cooling stages.

[0063] Specifically, the base 3 and the upper cover 2 may also be a cross-shaped structure.

[0064] Specifically, the thickness of the base 3 is greater than the thickness of the upper cover 2 .

[0065] In the present invention, the thickness of the base 3 is greater than that of the upper cover 2, and the base 3 bears the weight of the thin-walled long cylindrical workpiece 5 and the upper cover 2. The thicker the base 3 is, the smaller its deformation is during the heating process, thereby ensuring that the thin-walled long cylindrical workpiece 5 does not deform or deforms less. The upper cover 2 mainly functions to limit the radial deformation of the thin-walled long cylindrical workpiece 5, so the thickness of the upper cover 2 is thinner than that of the base 3.

[0066] Reference Figure 4 A plurality of limiting grooves 4 for inserting thin-walled long cylindrical workpieces 5 of different diameters are provided on the base 3 and the upper cover 2. The limiting groove 4 extends in an arc shape as a whole, and the center of the arc curvature coincides with the center of the through hole. The width of the limiting groove 4 is the wall thickness of the thin-walled long cylindrical workpiece 5 + (50-200mm), so that the thin-walled long cylindrical workpiece 5 can be inserted smoothly.

[0067] It should be noted that in the present invention, a plurality of limiting grooves 4 of different specifications are provided on the base 3 and the upper cover 2, which can be suitable for thin-walled long cylindrical workpieces 5 of different diameters, and are also suitable for thin-walled long cylindrical workpieces 5 with different diameters at both ends, so as to limit the deformation of the thin-walled long cylindrical workpiece 5. In addition, during the use of the special auxiliary tool, the upper cover 2 and the pull rod 1 can move relative to each other, which can meet the needs of thin-walled long cylindrical workpieces 5 of different heights. Under the action of gravity and the limiting grooves 4, the thin-walled long cylindrical workpiece 5, the pull rod 1 and the base 3 remain relatively stable, and no relative rotation or radial movement occurs. Due to the action of its own gravity and the limiting grooves 4, the thin-walled long cylindrical workpiece 5 and the upper cover 2 will also not rotate or move radially relative to each other.

[0068] Specifically, a lifting ring 7 is provided on one end of the pull rod 1 away from the base 3 .

[0069] It should be noted that a lifting ring 7 is provided on the pull rod 1 to facilitate the rapid lifting of the entire special auxiliary tool and the thin-walled long cylindrical workpiece 5 by a crane, so that the thin-walled long cylindrical workpiece 5 can be quickly put into water from the heating furnace.

[0070] Specifically, a rotating mechanism is connected to the side of the hanging ring 7 away from the thin-walled long cylindrical workpiece 5 .

[0071] Specifically, the rotating mechanism includes a driving element and a connecting rod, and the driving element and the connecting rod can be belt-driven or gear-driven.

[0072] Specifically, the connecting rod is rotatably connected above the heat treatment furnace, one end of the connecting rod is connected to the driving element, and the other end of the connecting rod is connected to the hanging ring 7.

[0073] Under the action of the driving mechanism, the thin-walled long cylindrical workpiece 5 can be rotated around its own axis at a rotation speed of 0.2 to 3 rad / min. As the heating temperature increases, the rotation speed of the thin-walled long cylindrical workpiece 5 gradually decreases. During the heating, cooling and tempering stages, the temperature of the inner and outer peripheral surfaces of the thin-walled long cylindrical workpiece 5 can be kept uniform, the tendency of the workpiece 5 to deform is reduced, and the uniformity of the performance of the workpiece 5 is ensured.

[0074] The operation process of the special auxiliary tool includes the following steps:

[0075] S1: setting the size of the upper limit groove 4 on the base 3 and the upper cover 2 and the length of the pull rod 1 according to the diameter, wall thickness and length of the thin-walled long cylindrical workpiece 5;

[0076] S2: placing the base 3 on the limit block 6 of the pull rod 1;

[0077] S3: Pass the pull rod 1 through the thin-walled long cylindrical workpiece 5 so that one end of the thin-walled long cylindrical workpiece 5 is located in the limiting groove 4 of the base 3;

[0078] S4: Pass the pull rod 1 through the upper cover 2, insert the other end of the thin-walled long cylindrical workpiece 5 into the limiting groove 4 of the upper cover 2, and install the lifting ring 7 on the pull rod 1;

[0079] S5: hoisting the special auxiliary tool and the thin-walled long cylindrical workpiece 5 and vertically placing them into the heating furnace; heating to a predetermined temperature and keeping the temperature;

[0080] S6: The special auxiliary tool and the thin-walled long cylindrical workpiece 5 are lifted vertically out of the heating furnace for cooling.

[0081] First, pass the pull rod 1 through the base 3, so that the base 3 is placed on the limit block 6 of the pull rod 1, and the opening direction of the limit groove 4 on the base 3 is away from the limit block 6; then pass the pull rod 1 through the thin-walled long cylindrical workpiece 5, so that one end of the thin-walled long cylindrical workpiece 5 is located on the base 3, and one end of the thin-walled long cylindrical workpiece 5 is inserted into the limit groove 4 of the base 3; finally, pass the pull rod 1 through the upper cover 2, with the opening of the limit groove 4 on the upper cover 2 facing the thin-walled long cylindrical workpiece 5, and the other end of the thin-walled long cylindrical workpiece 5 inserted in the limit groove 4 of the upper cover 2, and then install the lifting ring 7, and the assembly is completed.

[0082] During heating: Refer to Figure 5 , use a crane (or overhead crane) to hoist the special auxiliary tool and the thin-walled long cylindrical workpiece 5, so that the thin-walled long cylindrical workpiece 5 is vertically placed in the heating furnace, heated to a predetermined temperature and kept warm;

[0083] During the cooling process: the heated and heat-insulated thin-walled long cylindrical workpiece 5 is lifted by a traveling crane (or overhead crane), kept in a vertical state, and quickly placed in the air or coolant for cooling.

[0084] In order to more clearly describe the present invention, it is further illustrated by the following examples and comparative examples.

[0085] Example 1

[0086] The special auxiliary tool includes a base, a pull rod and an upper cover. Limiting grooves are respectively opened on the base and the upper cover. The two ends of the thin-walled long cylindrical workpiece are respectively located in the limiting grooves of the base and the upper cover. The pull rod passes through the base, the thin-walled long cylindrical workpiece and the upper cover. The length of the pull rod and the size of the limiting groove are opened according to the thin-walled long cylindrical workpiece.

[0087] A heat treatment method for preventing deformation of a thin-walled long cylindrical workpiece comprises the following steps:

[0088] S1: Place the thin-walled long cylindrical workpiece vertically into the heating furnace using a special auxiliary tool; and rotate the thin-walled long cylindrical workpiece around its own axis under the action of a rotating mechanism at a rotation speed of 3 rad / min;

[0089] S2: heating the thin-walled long cylindrical workpiece to 800° C. and keeping the temperature for 5 hours, and reducing the rotation speed to 2 rad / min;

[0090] S3: water cooling the thin-walled long cylindrical workpiece after heat preservation;

[0091] S4: tempering the cooled thin-walled long cylindrical workpiece at a temperature of 520° C. for a holding time of 10 h, and air cooling to room temperature;

[0092] The thin-walled long cylindrical workpiece is a forging made of SA508-3, with an outer diameter of 2600 mm, a wall thickness of 100 mm and a length of 4500 mm.

[0093] Example 2

[0094] Example 2 is substantially the same as Example 1, except that the thin-walled long cylindrical workpiece described in Example 2 is a forging made of 316LN; and in S2, the heating temperature is 1060°C and kept warm for 2 hours, the rotation speed is reduced to 0.8 rad / min, and no tempering treatment is performed.

[0095] Example 3

[0096] Example 3 is substantially the same as Example 1, except that the outer diameter of the thin-walled cylindrical workpiece described in Example 3 is 2900 mm, the wall thickness is 50 mm, and the length is 5500 mm; and in S2, the heating temperature is 900°C and is kept warm for 3 hours.

[0097] Comparative Example 1

[0098] Comparative Example 1 is substantially the same as Example 1, except that, in Comparative Example 1, no special auxiliary tool is used. Instead, four lifting ears (evenly distributed) are provided at the upper end of the thin-walled long cylindrical workpiece to make the thin-walled long cylindrical workpiece in a vertical state for heating, cooling, and tempering treatment.

[0099] Comparative Example 2

[0100] Comparative Example 2 is substantially the same as Example 1, except that Comparative Example 2 uses a universal auxiliary tool tray, and the thin-walled long cylindrical workpiece is horizontally placed on the tray, and then heated, cooled, and tempered.

[0101] Dimensional inspection

[0102] The thin-walled long cylindrical workpieces prepared according to the methods of Examples 1-3 and Comparative Examples 1-2 were subjected to dimensional inspection, the diameters of the two ends of the workpieces before and after heat treatment were measured, and the deformation rates were calculated. The specific inspection results are shown in Table 1. The performance uniformity of the thin-walled long cylindrical workpieces obtained after heat treatment was inspected, and the hardness of the two ends and the middle section of the thin-walled long cylindrical workpieces was tested. The specific inspection results are shown in Table 2.

[0103] Table 1 Dimensional test results

[0104]

[0105]

[0106] With reference to Examples 1-3 and Comparative Examples 1-2 and in combination with Table 1, it can be seen that, according to the method described in Examples 1-3, a special auxiliary tool with a limiting groove is used for lifting, and the thin-walled long cylindrical workpiece is vertically suspended in a heat treatment furnace, and the thin-walled long cylindrical workpiece is heat treated. Before and after the heat treatment, the deformation of both ends of the thin-walled long cylindrical workpiece is small, and the deformation rate is maintained below 2.5%.

[0107] Table 2 Workpiece performance uniformity test

[0108] category Hardness of left end of workpiece HBW Workpiece middle hardness HBW Hardness of the right end of the workpiece HBW Example 1 375 / 378 / 370 375 / 380 / 378 382 / 380 / 378 Example 2 275 / 270 / 273 272 / 276 / 278 270 / 270 / 275 Example 3 395 / 398 / 388 385 / 387 / 390 396 / 385 / 385 Comparative Example 1 365 / 368 / 370 365 / 360 / 365 392 / 393 / 388 Comparative Example 2 395 / 393 / 398 365 / 350 / 355 365 / 367 / 370

[0109] Referring to Examples 1-3 and Comparative Examples 1-2 and in combination with Table 2, it can be seen that the thin-walled long cylindrical workpiece is heat treated according to the method described in Examples 1-3. After the heat treatment, the overall hardness of the thin-walled long cylindrical workpiece is relatively uniform with a small difference.

[0110] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A heat treatment method for preventing deformation of thin-walled long cylindrical workpieces, characterized in that: Using a special auxiliary tool, the thin-walled long cylindrical workpiece is placed vertically into a heating furnace; the thin-walled long cylindrical workpiece (5) is heated, kept warm, and cooled, or the thin-walled long cylindrical workpiece (5) is heated, kept warm, cooled, and tempered; The special auxiliary tool comprises a base (3), a pull rod (1) and an upper cover (2), wherein the base (3) and the upper cover (2) are respectively provided with limit grooves (4), and the two ends of the thin-walled long cylindrical workpiece (5) are respectively located in the limit grooves (4) of the base (3) and the upper cover (2), and the pull rod (1) passes through the base (3), the thin-walled long cylindrical workpiece (5) and the upper cover (2).

2. The heat treatment method for preventing deformation of thin-walled long cylindrical workpieces according to claim 1 is characterized in that: The thin-walled long cylindrical workpiece (5) rotates around its own central axis during the heating, heat preservation and cooling processes.

3. The heat treatment method for preventing deformation of thin-walled long cylindrical workpiece according to claim 1 is characterized in that: The heating temperature is 750-1080° C. and kept warm for 1-5 hours.

4. The heat treatment method for preventing deformation of thin-walled long cylindrical workpiece according to claim 1 is characterized in that: The following steps are included: S1: setting the size of the upper limit groove (4) of the base (3) and the upper cover (2) and the length of the pull rod (1) according to the diameter, wall thickness and length of the thin-walled long cylindrical workpiece (5); S2: placing the base (3) on the limit block (6) of the pull rod (1); S3: Pass the pull rod (1) through the thin-walled long cylindrical workpiece (5) so that one end of the thin-walled long cylindrical workpiece (5) is located in the limiting groove (4) of the base (3); S4: Pass the pull rod (1) through the upper cover (2), insert the other end of the thin-walled long cylindrical workpiece (5) into the limiting groove (4) of the upper cover (2), and install the lifting ring (7) on the pull rod (1); S5: hoisting the special auxiliary tool and the thin-walled long cylindrical workpiece (5) and vertically placing them into a heating furnace; heating them to a predetermined temperature and keeping them warm; S6: The special auxiliary tool and the thin-walled long cylindrical workpiece (5) are lifted vertically out of the heating furnace for cooling.

5. A thin-walled long cylindrical workpiece, characterized in that: The method is prepared by the heat treatment method according to any one of claims 1 to 4.

6. The thin-walled long cylindrical workpiece according to claim 5, characterized in that: The deformation rate of the thin-walled long cylindrical workpiece (5) is below 2.5%.

7. A special auxiliary tool for implementing the heat treatment method for preventing deformation of thin-walled long cylindrical workpieces as described in any one of claims 1 to 4, characterized in that: The special auxiliary tool comprises a base (3), a pull rod (1) and an upper cover (2); a limiting groove (4) is respectively provided on the base (3) and the upper cover (2), and the limiting groove (4) on the base (3) and the opening of the limiting groove (4) on the upper cover (2) are arranged opposite to each other; a limiting block (6) is provided at one end of the pull rod (1), and the other end of the pull rod (1) passes through the base (3) and the upper cover (2), and the base (3) and the upper cover (2) move along one direction on the pull rod (1).

8. The special auxiliary tool according to claim 7, characterized in that: The base (3) and the upper cover (2) are both radially symmetrical and include a central portion and a plurality of support portions radially distributed around the central portion; the central portion is provided with an axial through hole for the pull rod (1) to pass through.

9. The special auxiliary tool according to claim 7, characterized in that: The support portion is provided with a plurality of limiting grooves (4) in sequence, and the limiting grooves (4) on the plurality of support portions that are equidistant from the symmetry center are located on the same concentric circle.

10. The special auxiliary tool according to claim 7, characterized in that: The end of the pull rod (1) is connected to a lifting ring (7), and the lifting ring (7) is located on a side of the upper cover (2) away from the base (3).

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