A heat treatment method for improving the low temperature impact toughness of 630 material

Abstract

The present application discloses a heat treatment method for improving the low-temperature impact toughness of 630 material, which relates to the field of metal heat treatment, and includes the following steps: S1: preparing a valve stem blank, which is refined by AOD; S2: solution heat treatment; S3: adjusting the heat treatment, the holding time at 840±10℃ is calculated according to the maximum wall thickness of the part, the holding time is 0.5mm / min, at least 2h, and air cooling to room temperature after the holding is completed; S4: aging heat treatment, the holding time at 580±10℃ is calculated according to the maximum wall thickness of the part, the holding time is 1mm / min, at least 4h, and air cooling to room temperature after the holding is completed; S5: testing, after the part is heat treated, the tensile strength, yield strength, elongation, cross-sectional shrinkage, hardness and -52℃ low-temperature impact value are tested to verify whether the 630 material after heat treatment meets the -52℃ low-temperature working condition requirements. The present application is helpful to improve the low-temperature impact toughness of 630 material.

Description

Technical Field

[0001] The present application relates to the field of metal heat treatment, and in particular to a heat treatment method for improving the low-temperature impact toughness of 630 material. Background Art

[0002] When the valve is used in high-cold areas with a temperature of -52℃, in addition to the low-temperature impact value of the materials of the valve body, valve cover and other pressure-bearing parts being ≥27J, the matching valve stem must also meet the requirements. At present, the valve stem materials of valves in high-cold areas are often selected from 304, 316, 304L, 316L austenitic stainless steel or nitrogen-strengthened stainless steel XM-19. At -52℃, although the low-temperature impact value of austenitic stainless steel or nitrogen-strengthened stainless steel can meet ≥27J, the strength and hardness are both low, and the valve stem is prone to deformation or bending, affecting the switching and sealing performance of the valve. Therefore, it is necessary to find a material with high strength and hardness and a low-temperature impact value of ≥27J to solve the problem of valve stem deformation or bending.

[0003] 630 material is a precipitation hardening stainless steel, also known as 17-4PH, with high strength, high hardness and good corrosion resistance. The latest product standard for bar material is ASTM A564 / A564M-2019a, which is often used as valve stem material. The standard stipulates that 630 material can be solution treated or age hardened, and also stipulates the room temperature mechanical properties requirements after solution treatment or age hardening. Through testing, the low temperature impact value of 630 material at -52°C is less than 18J, which cannot meet the requirement of ≥27J. That is, the valve stem made of 630 material can meet the requirements of strength and hardness, but its low temperature impact toughness is not up to standard. Summary of the invention

[0004] In order to improve the low-temperature impact toughness of 630 material, that is, to improve the low-temperature impact toughness of the valve stem, the present application provides a heat treatment method for improving the low-temperature impact toughness of 630 material.

[0005] The present application provides a heat treatment method for improving the low temperature impact toughness of 630 material using the following technical solution: A heat treatment method for improving the low-temperature impact toughness of 630 material comprises the following steps: S1: prepare valve stem blanks, the blanks are refined by AOD, and the nickel content is controlled at the upper limit of 3.0-5.0wt% according to the standard requirements; S2: Solution heat treatment, furnace temperature ≤ 200℃, heating rate 120℃ / h, holding time at 1050±10℃ is calculated according to the maximum wall thickness of the part, holding time is 0.5mm / min, at least 2h, water cooling after the holding period; S3: Adjust heat treatment, furnace temperature ≤ 200℃, heating rate 120℃ / h, holding time at 840±10℃ is calculated according to the maximum wall thickness of the part, holding time is 0.5mm / min, at least 2h, after holding, air cool to room temperature; S4: Aging heat treatment, furnace temperature ≤ 150℃, heating rate 120℃ / h, holding time at 580±10℃ is calculated according to the maximum wall thickness of the part, holding time is 1mm / min, at least 4h, after the holding is completed, air cool to room temperature; S5: Testing: After the parts are heat treated, the tensile strength, yield strength, elongation, cross-sectional shrinkage, hardness and -52℃ low-temperature impact value are tested to verify whether the 630 material after heat treatment meets the -52℃ low-temperature working condition requirements.

[0006] By adopting the above technical scheme, the billet is refined by AOD, which significantly improves the cleanliness and inclusion distribution of the steel and reduces the content of harmful gases. In addition to controlling each element according to the provisions of ASTM A564 standard, the nickel content is controlled according to the upper limit of 3.0-5.0wt% required by the standard, and the control value is required to be 4.0-5.0wt%. Increasing the nickel content can toughen the structure and significantly improve the low-temperature impact toughness of the valve stem billet; adjusting the heat treatment to an additional heat treatment process, which is carried out immediately after the solution heat treatment, can make the original austenite grain boundaries and martensite lath boundaries-subgrain boundaries produce more reverse transformation austenite during the heat treatment process, which has the effect of toughening the structure and can significantly improve the low-temperature impact toughness of the valve stem billet.

[0007] Preferably, in step 2, a solid solution furnace is used for heat treatment, the solid solution furnace comprises a furnace body, a feed port is provided on one side of the furnace body, a discharge port is provided on the other side of the furnace body, and a hot air assembly is arranged in the furnace body; a plurality of conveying rollers are laid in the furnace body, a plurality of annular conveying grooves are provided on the conveying rollers along the length direction, and the valve stem blank is overlapped in the conveying grooves of the conveying rollers; a transmission wheel is rotatably arranged in the conveying roller, an avoidance opening is provided on the bottom wall of the conveying groove where the conveying roller is located, and the transmission wheel is located at the avoidance opening.

[0008] By adopting the above technical scheme, a conveying track is laid at the feeding port of the solid solution furnace to convey the valve stem blank into the furnace body. The conveying track is composed of a plurality of drive rollers, and a conveying groove like that on the conveying roller is also formed on the drive roller. The valve stem blank is located in the conveying groove for conveying, which can prevent the valve stem blank from slipping on the conveying roller, thereby ensuring that the valve stem blank is stably conveyed into the furnace body; in practice, the rotation angle of the conveying roller is fixed, that is, after the conveying roller conveys the valve stem blank into the furnace body, the final state of the conveying roller is that the avoidance port is set upward, and at this time, the bottom of the valve stem blank is pressed against the drive wheel. During the heating process, the drive wheel moves, and the drive wheel drives the valve stem to rotate by friction, thereby making the valve stem blank heated evenly, preventing the contact part between the valve stem blank and the conveying roller from being shielded, resulting in uneven heating, thereby affecting the heat treatment effect.

[0009] Preferably, the hot air assembly comprises a burner and a spiral conveying rod rotatably arranged in a vertical direction, the burner is mounted on a side wall of the furnace body, and the air outlet of the burner is located at an upper end of the spiral conveying rod.

[0010] By adopting the above technical solution, the high-temperature hot air generated by the burner passes through the upper end of the spiral conveying rod, and the spiral conveying rod rotates, which, on the one hand, allows the hot air to quickly spread throughout the furnace body, and on the other hand, can generate a downward conveying force on the upper layer of hot air, thereby allowing the hot air to quickly spread to the valve stem blank for heating operations. The hot air in the furnace body can form a circulation, which helps to improve the heating effect on the valve stem blank.

[0011] Preferably, the conveying roller has two arc-shaped plates that slide relative to each other at the avoidance opening, and the arc-shaped plates slide along the length direction of the conveying roller. A synchronization component that drives the two arc-shaped plates to slide synchronously is arranged inside the conveying roller.

[0012] By adopting the above technical scheme, the arrangement of the arc plate can make the annular bottom wall of the conveying groove continuous, which helps to ensure the stability of the valve stem blank when the conveying roller conveys the valve stem blank; when the conveying roller drives all the valve stem blanks into the furnace body, the conveying roller stops rotating, and the valve stem blank is overlapped on the arc plate, and the synchronization component drives the two arc plates to slide in the direction of separation, at which time the avoidance opening is exposed, and then the valve stem blank will drop and abut against the transmission wheel, and then the rotation of the transmission wheel can drive the valve stem blank to rotate.

[0013] Preferably, sliding grooves are opened in both side walls of the conveying groove, and the conveying roller is slidingly connected to the abutment wheel in the two sliding grooves. In the initial state, the abutment wheel is located in the sliding groove. When the arc plate slides into the conveying roller, the abutment wheel slides out of the sliding groove and abuts against the valve stem blank.

[0014] By adopting the above technical scheme, after the avoidance opening is exposed due to the sliding of the arc plate, the transmission wheel is exposed, that is, the highest point of the transmission wheel is lower than the arc plate. Therefore, in order to ensure that the valve stem blank contacts the transmission wheel when it descends, that is, when the valve stem blank overlaps the arc plate, the distance between the two side walls of the conveying groove is greater than the diameter of the valve stem blank. Therefore, after the arc plate slides into the conveying roller, the valve stem blank will descend and abut against the transmission wheel; but because the distance between the two side walls of the conveying groove is greater than the valve stem blank, the contact between the valve stem blank and the transmission wheel is not reliable. At this time, the valve stem blank is positioned by sliding the two abutment wheels outward and abutting against the valve stem blank, and the abutment point between the abutment wheel and the valve stem blank is located at a position slightly above the center of the valve stem blank, that is, the abutment wheel can also generate downward pressure on the valve stem blank, thereby ensuring that the abutment between the valve stem blank and the transmission wheel is stable, which is convenient for the subsequent transmission wheel to drive the valve stem blank to rotate.

[0015] Preferably, the synchronization component includes a movable plate, two connecting rods and a driving cylinder for driving the movable plate to slide, the two connecting rods correspond one-to-one to the two arc-shaped plates, one end of the connecting rod is hinged to the movable plate, and the other end of the connecting rod is hinged to the corresponding arc-shaped plate.

[0016] By adopting the above technical solution, the driving cylinder is a high temperature resistant cylinder, the piston rod of the driving cylinder is extended, and the connecting rod moves, thereby realizing the synchronous backward movement of the two arc plates.

[0017] Preferably, the conveying roller is located in the sliding groove and is slidably connected to a sliding block, the abutment wheel is rotatably connected to the end of the sliding block, a first rack portion is formed on the upper side of the arc plate, the conveying roller is located on the upper side of the first rack portion and is rotatably connected to a linkage gear, and the linkage gear is meshed with the first rack portion, and a second rack portion meshed with the linkage gear is formed on the lower side of the sliding block.

[0018] By adopting the above technical solution, when the arc plate slides into the conveying roller, the first rack portion on the arc plate drives the linkage gear to slide, and the linkage gear drives the sliding block to slide through the first rack portion, so that the abutment wheel extends out of the sliding groove and abuts against the valve stem blank.

[0019] Preferably, the conveying roller is rotatably connected with a plurality of first rotating shafts, the number of the first rotating shafts is the same as the number of transmission wheels and corresponds one to one, the transmission wheel is coaxially fixed on the first rotating shaft, a first sprocket is also coaxially fixed on the first rotating shaft, a first chain is wound around all the first sprockets, and a tensioning sprocket is provided in the conveying roller, the tensioning sprocket is distributed between adjacent first sprockets and meshes with the first chain; the end of the conveying roller is rotatably connected with a second rotating shaft, a second sprocket is coaxially fixed on the second rotating shaft, a third sprocket is also coaxially fixed on the first rotating shaft located at the end of the conveying roller, a second chain is wound around the first sprocket and the third sprocket; the end of the conveying roller is provided with a driving component for driving the second rotating shaft to rotate.

[0020] By adopting the above technical solution, the second shaft rotates, driving the third sprocket to rotate, the second sprocket drives the third sprocket to rotate through the second chain, and then drives one of the first shafts to rotate, and the first sprocket on the first shaft rotates accordingly. Under the action of the first chain, the synchronous rotation of all the first shafts can be achieved, and then the rotation of the transmission wheel is achieved. The tensioning wheel makes the first chain between adjacent first sprockets in a tensioned state, thereby ensuring the meshing effect of the first chain and the first sprocket, which helps to ensure the rotation stability of the transmission wheel.

[0021] Preferably, the driving assembly includes a linkage shaft, a first bevel gear and a second bevel gear. The linkage shaft is rotatably matched with the end of the conveying roller, and the linkage shaft extends into the conveying roller. The first bevel gear is coaxially fixed to the linkage shaft, and the second bevel gear is coaxially fixed to the second rotating shaft, and the first bevel gear and the second bevel gear are meshed. A one-way wheel is coaxially fixed to the linkage shaft, a pawl is hinged on the one-way wheel, and an abutment spring is also provided on the one-way wheel, and the end of the abutment spring is connected to the pawl. A ratchet is provided at the end of the conveying roller, and the pawl is meshed with the ratchet. A driving motor for driving the linkage shaft to rotate is provided on the furnace body.

[0022] By adopting the above technical solution, when the conveying roller rotates, the linkage shaft will be driven to rotate synchronously under the action of the ratchet pawl. When the conveying roller stops, the driving motor drives the linkage shaft to rotate. At this time, the conveying roller will not rotate. The linkage shaft drives the second bevel gear to rotate through the first bevel gear, thereby realizing the rotation of the second rotating shaft.

[0023] In summary, the present application includes at least one of the following beneficial technical effects: 1. The billet is refined by AOD, which significantly improves the cleanliness and inclusion distribution of the steel and reduces the content of harmful gases. In addition to controlling each element according to the ASTM A564 standard, the nickel content is controlled at the upper limit of 3.0-5.0wt% according to the standard requirements, and the control value is required to be 4.0-5.0wt%. Increasing the nickel content can toughen the structure and significantly improve the low-temperature impact toughness of the valve stem billet; 2. Adjust the heat treatment to an additional heat treatment process, which is carried out immediately after the solution heat treatment. This can produce more reversed austenite at the original austenite grain boundaries and martensite lath boundaries-subgrain boundaries during the heat treatment process, which has the effect of toughening the structure and can significantly improve the low-temperature impact toughness of the valve stem blank; 3. The conveying groove on the conveying roller can limit the position of the valve stem blank to prevent the valve stem blank from slipping during the conveying process; 4. When the conveying roller stops, the transmission wheel rotates, driving the valve stem blank to rotate, so that the valve stem blank can be heated evenly, preventing the contact part between the valve stem blank and the conveying roller from being shielded, resulting in uneven heating, thereby affecting the heat treatment effect; 5. In the initial state, the two arc plates support the valve stem blank. The two arc plates make the bottom wall of the conveying groove continuous, thereby preventing the valve stem blank from constantly moving when the conveying roller conveys the valve stem blank. When the conveying roller stops rotating, the two arc plates slide, the avoidance opening is exposed, and the valve stem blank abuts against the transmission wheel. When the arc plates slide, the abutment wheel is synchronously driven to slide outward and abut against the valve stem blank, positioning the valve stem blank, which helps to ensure the transmission effect between the transmission wheel and the valve stem blank; 6. Under the action of the guide cover, the hot air in the heating space can enter the inclined part of the first sealing plate under the action of pressure to replenish the hot air, so that the hot air can directly act on the valve stem blank on the outside, thereby helping to ensure that all valve stem blanks are heated evenly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flowchart of the heat treatment method in the embodiment of the present application; Figure 2 This is a cross-sectional view of the overall structure of the solution furnace in the embodiment of the present application; Figure 3 This is a schematic cross-sectional view of the solid solution furnace in the embodiment of the present application; Figure 4 This is a schematic cross-sectional structural diagram of a conveying roller in an embodiment of the present application; Figure 5 for Figure 4 A partial enlarged view of middle A; Figure 6 It is a partial structural schematic diagram of an embodiment of the present application; Figure 7 It is a partial structural schematic diagram of an embodiment of the present application, mainly showing the structure of the ratchet and the pawl; Figure 8 This is a schematic diagram showing the direction of hot air flow in the embodiment of the present application.

[0025] Figure numerals: 1, furnace body; 11, feed port; 12, discharge port; 2, hot air assembly; 21, burner; 22, spiral conveying rod; 3, conveying roller; 31, conveying trough; 32, avoidance port; 33, sliding groove; 35, tensioning sprocket; 36, linkage gear; 37, ratchet; 4, transmission wheel; 5, arc plate; 51, sliding part; 52, first rack part; 6, sliding block; 61, abutment wheel; 62, second rack part; 7, synchronization assembly; 71, moving plate; 72, connecting rod; 73, driving cylinder; 8, first Rotating shaft; 81, first sprocket; 82, first chain; 83, third sprocket; 9, second rotating shaft; 91, second sprocket; 10, second chain; 20, driving assembly; 201, linkage shaft; 2011, one-way wheel; 2012, ratchet; 2013, abutment spring; 202, first bevel gear; 203, second bevel gear; 30, air guide cover; 40, air guide plate; 401, first sub-plate; 4011, vertical portion; 4012, heat supplement hole; 402, second sub-plate; 50, rotation gap; 60, heat supplement space. DETAILED DESCRIPTION

[0026] The following is combined with Figure 1 -Attached Figure 8 This application is described in further detail.

[0027] The embodiment of the present application discloses a heat treatment method for improving the low-temperature impact toughness of 630 material.

[0028] Reference Figure 1 The heat treatment method for improving the low temperature impact toughness of 630 material includes the following steps: S1: Prepare the valve stem blank. The blank is refined by AOD to significantly improve the cleanliness and inclusion distribution of the steel and reduce the content of harmful gases. In addition to controlling each element according to the ASTM A564 standard, the nickel content is controlled at the upper limit of 3.0-5.0wt% according to the standard requirements, and the control value is required to be 4.0-5.0wt%. Increasing the nickel content can toughen the structure and significantly improve the low-temperature impact toughness of the parts.

[0029] S2: Solution heat treatment, charging temperature ≤200℃, heating rate 120℃ / h, holding time at 1050±10℃ is calculated according to the maximum wall thickness of the part, holding time is 0.5mm / min, at least 2h, water cooling after the holding is completed.

[0030] S3: Adjust the heat treatment, the furnace temperature is ≤200℃, the heating rate is 120℃ / h, the holding time at 840±10℃ is calculated according to the maximum wall thickness of the part, the holding time is 0.5mm / min, and the minimum is 2h. After the holding is completed, air cool to room temperature; adjust the heat treatment to an additional heat treatment process, which is carried out immediately after the solution heat treatment. During the heat treatment process, more reverse transformation austenite can be produced at the original austenite grain boundaries and martensite lath boundaries-subgrain boundaries, which has the effect of toughening the organization and can significantly improve the low-temperature impact toughness of the parts.

[0031] S4: Aging heat treatment, furnace temperature ≤150℃, heating rate 120℃ / h, holding time at 580±10℃ is calculated according to the maximum wall thickness of the part, holding time is 1mm / min, at least 4h, air cool to room temperature after the holding period.

[0032] S5: Testing: After the parts are heat treated, the tensile strength, yield strength, elongation, cross-sectional shrinkage, hardness and -52℃ low-temperature impact value are tested to verify whether the 630 material after heat treatment meets the -52℃ low-temperature working condition requirements.

[0033] Specifically, the chemical composition of the 630 material is controlled as shown in Table 1 below: Solution heat treatment method: furnace charging temperature 160℃, heating rate 120℃ / h, keep warm at 1040℃ for 4h, and water cool after the end of the heat preservation.

[0034] Adjust the heat treatment method: furnace temperature 150℃, heating rate 120℃ / h, keep warm at 840℃ for 4h, and air cool to room temperature after the end of the heat preservation.

[0035] Aging heat treatment method: furnace loading temperature 120℃, heating rate 120℃ / h, keep warm at 580℃ for 8h, and air cool to room temperature after the end of the heat preservation.

[0036] The test results are shown in Table 2 below: According to the contents of Table 1 and Table 2, by adopting a heat treatment method for improving the low-temperature impact toughness of 630 material provided by the present invention, the low-temperature impact toughness of 630 material can be greatly improved to meet the requirement of low-temperature impact value ≥ 27J at -52°C.

[0037] In step S2, a solution furnace is used for heat treatment, referring to Figure 2 , Figure 3 and Figure 4The solid solution furnace includes a furnace body 1, a feed port 11 is provided on one side of the furnace body 1, a discharge port 12 is provided on the other side of the furnace body 1, and furnace doors are installed at the feed port 11 and the discharge port 12 of the furnace body 1. A hot air assembly 2 is provided in the furnace body 1, and a plurality of conveying rollers 3 are laid in the furnace body 1. The ends of the conveying rollers 3 extend out of the furnace body 1. The rotation of all the conveying rollers 3 is driven by a pulley assembly, which will not be described in detail here. The conveying rollers 3 are provided with a plurality of annular conveying grooves 3 along the length direction. 1. The valve stem blank is overlapped on the bottom wall of the conveying groove 31, and a transmission wheel 4 is rotatably arranged in the conveying roller 3. The conveying roller 3 is located on the bottom wall of the conveying groove 31 and an avoidance opening 32 is opened, and the conveying roller 3 is located at the avoidance opening 32 and is provided with two opposite arc plates 5 for sliding. The arc plates 5 slide along the length direction of the conveying roller 3. When the two arc plates 5 slide toward each other and abut, the bottom wall of the conveying groove 31 is continuous. When the two arc plates 5 slide back to back, the transmission wheel 4 is exposed at the avoidance opening 32.

[0038] Transmission rollers are also laid on the outside of the feeding port 11 of the solid solution furnace. The transmission rollers are also provided with conveying grooves 31, and the positions thereof correspond to those of the conveying rollers 3. The valve stem blank is placed in the conveying grooves 31 of the transmission rollers, and then the transmission rollers rotate to convey the valve stem blank to the conveying rollers 3. The valve stem blank is located in the conveying grooves 31 of the conveying rollers 3. Since the valve stem blank is cylindrical and prone to slipping, the valve stem blank can be limited by the conveying grooves 31 to prevent it from slipping on the conveying rollers 3. In practice, the rotation angle of the conveying rollers 3 is fixed, that is, after the conveying rollers 3 convey the valve stem blank into the furnace body 1, the final state of the conveying rollers 3 is that the avoidance opening 32 is set upward. When the heating operation is performed, the two arc plates 5 move back to back to expose the avoidance opening 32, and the valve stem blank abuts against the transmission wheel 4. The transmission wheel 4 rotates, driving the valve stem blank to rotate, which helps to make the valve stem heated more evenly, thereby improving the heat treatment effect.

[0039] Reference Figure 3 and Figure 4 The conveying groove 31 is expanded in the direction away from the rotation axis of the conveying roller 3. The conveying roller 3 is provided with sliding grooves 33 on both sides of the conveying groove 31. The conveying roller 3 is slidingly connected with a sliding block 6 in the sliding groove 33. The end of the sliding block 6 is rotatably connected with an abutment wheel 61. In the initial state, the abutment wheel 61 is located in the sliding groove 33. When the two arc plates 5 slide back to back, the abutment wheel 61 slides out of the sliding groove 33 and abuts against the valve stem blank.

[0040] The transmission wheel 4 can be exposed only after the arc plate 5 slides to expose the avoidance opening 32. Therefore, the highest point of the transmission wheel 4 is lower than the arc plate 5. Therefore, the valve stem blank needs to drop a certain distance before it can contact the transmission wheel 4. If the valve stem blank is to move downward in the conveying groove 31, when the valve stem blank is overlapped on the arc plate 5, the maximum diameter of the valve stem blank in the horizontal direction is smaller than the distance between the conveying grooves 31. In this way, after the arc plate 5 slides, the valve stem blank will drop and abut against the transmission wheel 4. However, because the two side walls of the conveying groove 31 are The materials are not always in contact with each other, so the contact between the valve stem blank and the driving wheel 4 is not reliable and may be skewed; at this time, the two abutment wheels 61 slide outward and abut against the valve stem blank to position the valve stem blank, thereby ensuring that the valve stem blank and the driving wheel 4 are tightly abutted, and the abutment point between the abutment wheel 61 and the valve stem blank is located above the center of the valve stem blank, that is, there will be a certain downward pressure on the valve stem blank, which helps to ensure the stable abutment between the valve stem blank and the driving wheel 4, thereby ensuring the transmission effect between the driving wheel 4 and the valve stem blank.

[0041] Reference Figure 4 and Figure 5 A sliding portion 51 is formed on the arc-shaped plate 5, a sliding groove that slides with the sliding portion 51 is provided in the conveying roller 3, and a synchronization component 7 that drives the two arc-shaped plates 5 to slide synchronously is provided in the conveying roller 3. The synchronization component 7 includes a moving plate 71, two connecting rods 72, and a driving cylinder 73 that drives the moving plate 71 to slide. The driving cylinder 73 is fixedly installed in the conveying roller 3, and the moving plate 71 is fixedly installed at the end of the piston rod of the driving cylinder 73. The two connecting rods 72 correspond to the two arc-shaped plates 5 one by one. One end of the connecting rod 72 is hinged to the moving plate 71, and the other end is hinged to the corresponding arc-shaped plate 5. The driving cylinder 73 is a high-temperature resistant cylinder. The piston rod of the driving cylinder 73 is extended, and the connecting rod 72 moves, thereby realizing the synchronous back-to-back movement of the two arc-shaped plates 5, and the piston rod contracts to realize the opposite movement of the two arc-shaped plates 5.

[0042] Reference Figure 4 and Figure 6, a plurality of first rotating shafts 8 are rotatably connected in the conveying roller 3, the number of the first rotating shafts 8 is the same as the number of the transmission wheels 4 and corresponds one to one, the transmission wheel 4 is coaxially fixed on the first rotating shaft 8, and a first sprocket 81 is also coaxially fixed on the first rotating shaft 8, and a first chain 82 is wound around all the first sprockets 81, and a tensioning sprocket 35 is also installed in the conveying roller 3, and the tensioning sprocket 35 is distributed between adjacent first sprockets 81 and meshes with the first chain 82, which helps to make the first chain 82 in a tensioned state, thereby ensuring the transmission effect of the transmission wheel 4; a second rotating shaft 9 is rotatably connected in the end of the conveying roller 3 extending out of the furnace body 1, and a second sprocket 91 is coaxially fixed on the second rotating shaft 9, and a third sprocket 83 is coaxially fixed on the first rotating shaft 8 located at the end of the conveying roller 3, and a second chain 10 is wound around the second sprocket 91 and the third sprocket 83, and a driving component 20 for driving the second rotating shaft 9 to rotate is provided at the end of the conveying roller 3.

[0043] The second rotating shaft 9 rotates, driving the third sprocket 83 to rotate. The second sprocket 91 drives the third sprocket 83 to rotate through the second chain 10, thereby driving one of the first rotating shafts 8 to rotate. The first sprocket 81 on the first rotating shaft 8 rotates accordingly. Under the action of the first chain 82, the synchronous rotation of all the first rotating shafts 8 can be achieved, thereby realizing the rotation of the transmission wheel 4.

[0044] The driving assembly 20 includes a linkage shaft 201, a first bevel gear 202, and a second bevel gear 203. The linkage shaft 201 is rotatably matched with the end of the conveying roller 3, and the linkage shaft 201 extends into the conveying roller 3. The first bevel gear 202 and the linkage shaft 201 are coaxially fixed, and the second bevel gear 203 is coaxially fixed on the second rotating shaft 9, and the first bevel gear 202 and the second bevel gear 203 are meshed. A driving motor for driving the linkage shaft 201 to rotate is installed on the outer wall of the furnace body 1. The linkage shaft 201 rotates, and the second rotating shaft 9 is rotated through the first bevel gear 202 and the second bevel gear 203.

[0045] Reference Figure 3 , Figure 6 and Figure 7 A one-way wheel 2011 is coaxially fixed on the linkage shaft 201, a ratchet 2012 is hinged on the one-way wheel 2011, and an abutting spring 2013 is also installed on the one-way wheel 2011, and the other end of the abutting spring 2013 is connected to the ratchet 2012. The end of the conveying roller 3 is fixedly connected with a ratchet 37, which is arranged around the one-way wheel 2011, and the ratchet 2012 is meshed with the ratchet 37. When the conveying roller 3 rotates, the ratchet 37 and the ratchet 2012 will synchronously drive the linkage shaft 201 to rotate together. When the conveying roller 3 stops rotating, the driving motor drives the linkage shaft 201 to rotate, and the conveying roller 3 will not rotate at this time.

[0046] Reference Figure 4 and Figure 5The arc plate 5 is formed with a first rack portion 52 on the upper side of the sliding portion 51, and the conveying roller 3 is rotatably connected with a linkage gear 36 on the upper side of the first rack portion 52. The linkage gear 36 is meshed with the first rack portion 52, and a second rack portion 62 meshed with the linkage gear 36 is formed on the lower side of the sliding block 6. When the arc plate 5 slides into the conveying roller 3, the first rack portion 52 on the arc plate 5 drives the linkage gear 36 to slide, and the linkage gear 36 drives the sliding block 6 to slide through the first rack portion 52, so that the abutting wheel 61 extends out of the sliding groove 33 and abuts against the valve stem blank.

[0047] Reference Figure 2 and Figure 3 The hot air assembly 2 includes a burner 21 and a screw conveying rod 22. A guide cover 30 is also installed in the furnace body 1, and the screw conveying rod 22 is arranged to rotate in the guide cover 30 along the vertical direction. The screw conveying rod 22 is driven to rotate by a motor. The burner 21 is installed on the side wall of the furnace body 1, and the air outlet of the burner 21 is located at the upper end of the screw conveying rod 22.

[0048] Reference Figure 3 and Figure 8 The guide cover 30 is composed of two guide plates 40, which are symmetrically arranged. The guide plates 40 are composed of a first partition plate 401 and a second partition plate 402. The first partition plate 401 is located on the inner side. A vertical portion 4011 is formed on the upper side of the first partition plate 401. The vertical portions 4011 of the two first partition plates 401 are surrounded to form a rotation gap 50 for the screw conveying rod 22 to rotate. The lower side of the first partition plate 401 is inclined downward and inclined toward the inner wall of the furnace body 1. The hot air can be guided to diffuse outward, and then can contact all valve stem blanks in the length direction of the conveying roller 3; the second partition plate 402 is arranged at an angle, and the lower end of the second partition plate 402 is fixedly connected to the lower end of the first partition plate 401, and the second partition plate 402 is inclined from bottom to top toward the middle of the furnace body 1, and a heat supplement space 60 is formed between the second partition plate 402 and the first partition plate 401, and a heat supplement hole 4012 connected to the heat supplement space 60 is opened at the inclined part of the first partition plate 401.

[0049] When the spiral conveying rod 22 rotates, the hot air in the upper layer of the furnace body 1 can be conveyed downward, and the hot air passes through the rotating gap 50 and moves to the inclined portion of the first partition plate 401. Under the guidance of the inclined portion, the hot air contacts all the valve stem blanks to achieve heating, and then the hot air flows from the bottom and flows upward from the outside of the second partition plate 402 to form a hot air circulation. In practice, because the spiral conveying rod 22 generates a conveying force on the hot air, that is, after the hot air flows out of the rotating gap 50, the hot air initially has a certain initial velocity of flowing downward, that is, it will not diffuse outward uniformly along the inclined portion on the lower side of the first partition plate 401, which ultimately causes the valve stem blank in the middle to be heated more, while the valve stem blank on the side is heated less, resulting in uneven heating of the valve stem blank.

[0050] However, during the hot gas circulation process, the hot gas will continue to enter the supplementary heating space 60. When the hot gas enters the lower side of the first partition plate 401 at a certain speed, part of the hot gas will diffuse outward at a certain speed. According to Bernoulli's principle, the greater the flow rate, the smaller the pressure. That is, relative to the flow rate in the supplementary heating space 60, the flow rate at the inclined portion of the first partition plate 401 is greater than the flow rate in the supplementary heating space 60. At this time, the pressure in the supplementary heating space 60 is greater than the pressure in the inclined portion of the first partition plate 401. That is, the hot gas in the supplementary heating space 60 will flow out from the supplementary heating hole 4012 and contact with the hot gas in the inclined portion of the first partition plate 401, thereby heating the valve stem blank located on the outside. That is, in this way, it is possible to ensure that all valve stem blanks are heated evenly as much as possible.

[0051] The implementation principle of a heat treatment method for improving the low-temperature impact toughness of 630 material in an embodiment of the present application is as follows: the billet is refined by AOD to significantly improve the cleanliness and inclusion distribution of the steel and reduce the content of harmful gases. In addition to controlling each element as specified in the ASTM A564 standard, the nickel content is controlled at an upper limit of 3.0-5.0wt% as required by the standard, and the control value is required to be 4.0-5.0wt%. Increasing the nickel content can toughen the structure and significantly improve the low-temperature impact toughness of the valve stem billet; adjusting the heat treatment to an additional heat treatment step, which is performed immediately after the solution heat treatment, can cause more reverse transformed austenite to be produced at the original austenite grain boundaries and the martensite lath boundaries-subgrain boundaries during the heat treatment process, which has the effect of toughening the structure and can significantly improve the low-temperature impact toughness of the valve stem billet.

[0052] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A heat treatment method for improving the low temperature impact toughness of 630 material, characterized by: The steps include: S1: prepare valve stem blanks, the blanks are refined by AOD, and the nickel content is controlled at the upper limit of 3.0-5.0wt% according to the standard requirements; S2: Solution heat treatment, furnace temperature ≤ 200℃, heating rate 120℃ / h, holding time at 1050±10℃ is calculated according to the maximum wall thickness of the part, holding time is 0.5mm / min, at least 2h, water cooling after the holding period; S3: Adjust heat treatment, furnace temperature ≤ 200℃, heating rate 120℃ / h, holding time at 840±10℃ is calculated according to the maximum wall thickness of the part, holding time is 0.5mm / min, at least 2h, after holding, air cool to room temperature; S4: Aging heat treatment, furnace temperature ≤ 150℃, heating rate 120℃ / h, holding time at 580±10℃ is calculated according to the maximum wall thickness of the part, holding time is 1mm / min, at least 4h, after the holding is completed, air cool to room temperature; S5: Testing: After the parts are heat treated, the tensile strength, yield strength, elongation, cross-sectional shrinkage, hardness and -52℃ low-temperature impact value are tested to verify whether the 630 material after heat treatment meets the -52℃ low-temperature working condition requirements.

2. A heat treatment method for improving the low temperature impact toughness of 630 material according to claim 1, characterized in that: In step 2, a solid solution furnace is used for heat treatment, the solid solution furnace comprises a furnace body (1), a feed port (11) is provided on one side of the furnace body (1), a discharge port (12) is provided on the other side of the furnace body (1), and a hot air assembly (2) is arranged in the furnace body (1); a plurality of conveying rollers (3) are arranged in the furnace body (1), a plurality of annular conveying grooves (31) are provided in the conveying roller (3) along the length direction, and the valve stem blank is overlapped in the conveying groove (31) of the conveying roller (3); a transmission wheel (4) is rotatably arranged in the conveying roller (3), a avoidance opening (32) is provided on the bottom wall of the conveying groove (31) of the conveying roller (3), and the transmission wheel (4) is located at the avoidance opening (32).

3. A heat treatment method for improving the low temperature impact toughness of 630 material according to claim 2, characterized in that: The hot air assembly (2) comprises a burner (21) and a screw conveying rod (22) arranged to rotate in a vertical direction; the burner (21) is mounted on a side wall of the furnace body (1); and an air outlet of the burner (21) is located at the upper end of the screw conveying rod (22).

4. A heat treatment method for improving the low temperature impact toughness of 630 material according to claim 2, characterized in that: The conveying roller (3) has two arc-shaped plates (5) that slide relative to each other at the avoidance opening (32), and the arc-shaped plates (5) slide along the length direction of the conveying roller (3). A synchronous component (7) that drives the two arc-shaped plates (5) to slide synchronously is arranged inside the conveying roller (3).

5. A heat treatment method for improving the low temperature impact toughness of 630 material according to claim 4, characterized in that: The conveying roller (3) is located in the conveying groove (31) and has sliding grooves (33) on both side walls. The conveying roller (3) is located in the two sliding grooves (33) and is slidingly connected to the abutment wheel (61). In the initial state, the abutment wheel (61) is located in the sliding groove (33). When the arc plate (5) slides into the conveying roller (3), the abutment wheel (61) slides out of the sliding groove (33) and abuts against the valve stem blank.

6. A heat treatment method for improving the low temperature impact toughness of 630 material according to claim 4, characterized in that: The synchronization component (7) comprises a moving plate (71), two connecting rods (72) and a driving cylinder (73) for driving the moving plate (71) to slide, the two connecting rods (72) corresponding to the two arc-shaped plates (5) one by one, one end of the connecting rod (72) is hinged to the moving plate (71), and the other end of the connecting rod (72) is hinged to the corresponding arc-shaped plate (5).

7. A heat treatment method for improving the low temperature impact toughness of 630 material according to claim 5, characterized in that: The conveying roller (3) is located in the sliding groove (33) and is slidably connected to a sliding block (6); the abutting wheel (61) is rotatably connected to the end of the sliding block (6); a first rack portion (52) is formed on the upper side of the arc plate (5); the conveying roller (3) is located on the upper side of the first rack portion (52) and is rotatably connected to a linkage gear (36), and the linkage gear (36) is meshed with the first rack portion (52); and a second rack portion (62) meshed with the linkage gear (36) is formed on the lower side of the sliding block (6).

8. A heat treatment method for improving the low temperature impact toughness of 630 material according to claim 2, characterized in that: A plurality of first rotating shafts (8) are rotatably connected in the conveying roller (3), the number of the first rotating shafts (8) is the same as the number of the transmission wheels (4) and corresponds to each other, the transmission wheels (4) are coaxially fixed on the first rotating shafts (8), a first sprocket (81) is also coaxially fixed on the first rotating shaft (8), a first chain (82) is wound around all the first sprockets (81), and a tensioning sprocket (35) is arranged in the conveying roller (3), the tensioning sprocket (35) is distributed between adjacent first sprockets (8 1) and meshed with a first chain (82); the end of the conveying roller (3) is rotatably connected to a second rotating shaft (9), a second sprocket (91) is coaxially fixed on the second rotating shaft (9), a third sprocket (83) is coaxially fixed on the first rotating shaft (8) located at the end of the conveying roller (3), a second chain (10) is wound between the first sprocket (81) and the third sprocket (83); the end of the conveying roller (3) is provided with a driving component (20) for driving the second rotating shaft (9) to rotate.

9. A heat treatment method for improving the low temperature impact toughness of 630 material according to claim 8, characterized in that: The driving assembly (20) comprises a linkage shaft (201), a first bevel gear (202) and a second bevel gear (203); the linkage shaft (201) is rotatably matched with the end of the conveying roller (3), and the linkage shaft (201) extends into the conveying roller (3); the first bevel gear (202) is coaxially fixed to the linkage shaft (201), and the second bevel gear (203) is coaxially fixed to the second rotating shaft (9); the first bevel gear (202) and the second bevel gear (203) are meshed; the linkage A one-way wheel (2011) is coaxially fixed on the shaft (201), a ratchet (2012) is hinged on the one-way wheel (2011), and an abutment spring (2013) is also provided on the one-way wheel (2011), the end of the abutment spring (2013) is connected to the ratchet (2012), a ratchet (37) is provided at the end of the conveying roller (3), and the ratchet (2012) is meshed with the ratchet (37); and a driving motor for driving the linkage shaft (201) to rotate is provided on the furnace body (1).

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