Heat treatment method for reducing risk of air gouging cracking of pearlitic wear-resistant liner plate and optimizing comprehensive performance

Abstract

The application discloses a heat treatment method for reducing the risk of air gouging cracking of pearlitic wear-resistant lining plate and optimizing comprehensive performance, which comprises the following steps: high-temperature normalizing, preheating to 250-300 DEG C and keeping for 2-3 hours; heating to 600-650 DEG C and keeping for 3-4 hours; heating to (100-150) DEG C of Acm+ and keeping; spheroidizing annealing, air cooling to 450-500 DEG C and keeping for 2-3 hours, heating to (10-20) DEG C of Ac1+ and keeping, slow cooling to (10-20) DEG C of Ar1- and keeping for 2-3 hours; root of riser planing, air cooling to 300-350 DEG C and keeping, carrying out root of riser planing operation in the keeping stage, returning to the furnace for keeping after planing, slow cooling to <= 150 DEG C in the furnace and discharging to cool to room temperature; performance heat treatment, comprising a subcritical normalizing stage and a tempering stage, in the subcritical normalizing stage, preheating to 250-300 DEG C and keeping for 2-3 hours, heating to 600-650 DEG C and keeping for 3-4 hours, heating to (30-50) DEG C of Ac1+ and keeping, in the tempering stage, preheating to 200 DEG C and keeping for 2 hours, heating to 500-550 DEG C and keeping for 6 hours, and slow cooling to <= 200 DEG C and discharging to air cool. The application reduces the risk of air gouging cracking of the pearlitic wear-resistant lining plate in the process, and improves the wear resistance, strength and fracture toughness of the pearlitic wear-resistant lining plate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel heat treatment, and more particularly relates to a heat treatment method for reducing the risk of gas planing cracking of pearlitic wear-resistant lining plate and optimizing comprehensive performance. BACKGROUND

[0002] Pearlitic wear-resistant lining plate has been widely used in mining machinery due to its high hardness, good toughness and impact fatigue resistance, and has become an indispensable important component in mining equipment. For example, the pearlitic wear-resistant lining plate can be used as the lining plate of mining crusher, semi-autogenous mill, ball mill and other equipment to improve the wear resistance and service life of the equipment; in the material conveying system, the pearlitic wear-resistant lining plate can withstand the impact and wear of high-drop hoppers and other equipment to protect the system equipment from damage.

[0003] In the prior art, the pearlitic wear-resistant lining plate is mostly formed by casting. In order to ensure the installation and use effect of the lining plate, the pearlitic wear-resistant lining plate needs to be subjected to arc gas planing treatment at the root of the riser after being hit by the riser to remove excess material, burrs or uneven surface. However, cracks often occur during the gas planing process. The reason for the cracking is that the pearlitic wear-resistant lining plate is heated during the gas planing process, the molten metal is blown away by the high-speed airflow, the adjacent matrix undergoes austenite transformation, and the micro-cracks are formed after cooling and transformation into martensite. In addition, the uneven cooling of the casting and residual stress cause the cracks to expand and increase.

[0004] The production process of the pearlitic wear-resistant lining plate casting after shakeout is as follows: hitting the riser-normalizing-repairing-tempering-finishing-inspecting-repairing-normalizing-inspecting. In order to avoid gas planing cracking, the workpiece is usually air-cooled to 500 DEG C and then heated to 500 DEG C for gas planing. After gas planing, the workpiece is immediately heated to room temperature. However, due to the high temperature of the workpiece, the operator cannot stay close for a long time, so intermittent work is often adopted, which is low in efficiency. In addition, the performance heat treatment heating temperature is set above the complete austenitizing temperature, and the hardness of the pearlitic wear-resistant lining plate after normalizing is high, but the toughness is poor.

[0005] Therefore, it is necessary to consider the material quality and process and other factors, and to propose a new heat treatment process for the pearlitic wear-resistant lining plate to reduce the risk of gas planing cracking of the pearlitic wear-resistant lining plate, so as to realize efficient and high-quality gas planing operation, and at the same time improve the wear resistance, strength and toughness and other comprehensive performance of the pearlitic wear-resistant lining plate. SUMMARY

[0006] In order to solve the above-mentioned technical problems in the prior art, the present application provides a heat treatment method for reducing the risk of gas planing cracking of pearlitic wear-resistant lining plate and optimizing comprehensive performance, which comprises the following steps:

[0007] (I) high-temperature normalizing, after sanding the riser of the pearlitic wear-resistant lining plate, high-temperature normalizing treatment is performed, the high-temperature normalizing is performed in a three-stage heating mode, including: in the first stage of heating, the pearlitic wear-resistant lining plate is preheated to 250-300 DEG C, and the temperature is kept for 2-3 h; in the second stage of heating, the pearlitic wear-resistant lining plate is heated to 600-650 DEG C, and the temperature is kept for 3-4 h; in the third stage of heating, the pearlitic wear-resistant lining plate is heated to Ac1 + (100-150) DEG C and kept, and after the temperature keeping is finished, the pearlitic wear-resistant lining plate is taken out of the furnace and air-cooled;

[0008] (II) spheroidizing annealing, the pearlitic wear-resistant lining plate after high-temperature normalizing is subjected to spheroidizing annealing treatment, including: the pearlitic wear-resistant lining plate is air-cooled to 450-500 DEG C after normalizing, is taken into the furnace and kept for 2-3 h, is then heated to Ac1 + (10-20) DEG C and kept, after the temperature keeping is finished, is slowly cooled to Ar1 - (10-20) DEG C, is kept for 2-3 h, and then is taken out of the furnace and air-cooled;

[0009] (III) riser root planing, after the pearlitic wear-resistant lining plate is spheroidizing annealed and taken out of the furnace and air-cooled to 300-350 DEG C, the pearlitic wear-resistant lining plate is taken into the furnace and kept, and in the temperature keeping stage, the riser root planing operation is performed while the pearlitic wear-resistant lining plate is hot, the pearlitic wear-resistant lining plate is taken back into the furnace and kept after the riser root planing of the lining plate is completed, and then the pearlitic wear-resistant lining plate is slowly cooled to ≤150 DEG C in the furnace and taken out of the furnace and cooled to room temperature, and subsequent finishing, flaw detection and repair procedures are performed;

[0010] (IV) performance heat treatment, the pearlitic wear-resistant lining plate after the riser root planing is performed is subjected to performance heat treatment, including a subcritical normalizing stage and a tempering stage, wherein the subcritical normalizing stage includes: the pearlitic wear-resistant lining plate is preheated to 250-300 DEG C and kept for 2-3 h; the pearlitic wear-resistant lining plate is heated to 600-650 DEG C and kept for 3-4 h; the pearlitic wear-resistant lining plate is heated to Ac1 + (30-50) DEG C and kept, and after the temperature keeping is finished, the pearlitic wear-resistant lining plate is taken out of the furnace and air-cooled to ≤150 DEG C; the tempering stage includes: the pearlitic wear-resistant lining plate is preheated to 200 DEG C and kept for 2 h; the pearlitic wear-resistant lining plate is heated to 500-550 DEG C and kept for 6 h; after the temperature keeping is finished, the pearlitic wear-resistant lining plate is slowly cooled to ≤200 DEG C, taken out of the furnace and air-cooled.

[0011] Further, in the above heat treatment method for reducing the air planing cracking risk of the pearlitic wear-resistant lining plate and optimizing the comprehensive performance:

[0012] in the second stage of heating of the high-temperature normalizing step, the pearlitic wear-resistant lining plate is heated to 600-650 DEG C at a temperature rising speed of ≤80 DEG C / h;

[0013] in the spheroidizing annealing step, the pearlitic wear-resistant lining plate is heated to Ac1 + (10-20) DEG C at a temperature rising speed of ≤100 DEG C / h, and the pearlitic wear-resistant lining plate is slowly cooled to Ar1 - (10-20) DEG C at a temperature falling speed of ≤20 DEG C / h;

[0014] In the riser root trimming step, the pearlitic wear-resistant lining plate is slowly cooled with the furnace at a cooling rate of ≤30℃ / h to ≤150℃;

[0015] In the performance heat treatment step, the pearlitic wear-resistant lining plate is heated to 600-650℃ at a heating rate of ≤80℃ / h in the intercritical normalizing stage, heated to 500-550℃ at a heating rate of ≤80℃ / h in the tempering stage, and slowly cooled to ≤200℃ at a cooling rate of ≤30℃ / h.

[0016] Further, in the above heat treatment method for reducing the pearlitic wear-resistant lining plate air gouging cracking risk and optimizing the comprehensive performance, in the riser root trimming step, a part of the pearlitic wear-resistant lining plate is hoisted out of the furnace for hot trimming, after trimming, it is put back into the furnace in time, then another part of the pearlitic wear-resistant lining plate is trimmed, after the trimming of all the pearlitic wear-resistant lining plates in the furnace is completed, it is put into the furnace for 1h, and then slowly cooled to ≤150℃ and cooled to room temperature.

[0017] As a specific embodiment, in the above heat treatment method for reducing the pearlitic wear-resistant lining plate air gouging cracking risk and optimizing the comprehensive performance, the pearlitic wear-resistant lining plate is a pearlitic wear-resistant lining plate with a material of 80Cr2Mo and an equivalent cross-sectional thickness of 300mm, and:

[0018] In the high-temperature normalizing step, the first stage heating preheats the pearlitic wear-resistant lining plate to 250℃ and keeps it for 2h; the second stage heating heats the pearlitic wear-resistant lining plate to 600-650℃ at a heating rate of ≤80℃ / h and keeps it for 3h; the third stage heating heats the pearlitic wear-resistant lining plate to 960-980℃ and keeps it for 8h, and after the end of the keeping, it is taken out of the furnace for air cooling;

[0019] In the spheroidizing annealing step, the pearlitic wear-resistant lining plate is air cooled to 450-500℃ after normalizing, put into the furnace for 2h, heated to 810-820℃ at a heating rate of ≤100℃ / h, kept for 8h, then slowly cooled to 670-680℃ at a cooling rate of ≤20℃ / h, kept for 2h, and then taken out of the furnace for air cooling;

[0020] In the riser root trimming step, the pearlitic wear-resistant lining plate is air cooled to 300℃ after spheroidizing annealing, put into the furnace for keeping, in the keeping stage at 300℃, a part of the pearlitic wear-resistant lining plate is hoisted out of the furnace for hot trimming, after trimming, it is put back into the furnace in time, then another part of the pearlitic wear-resistant lining plate is trimmed, after the trimming of all the pearlitic wear-resistant lining plates in the furnace is completed, it is put into the furnace for 1h, then slowly cooled to ≤150℃ at a cooling rate of ≤30℃ / h, taken out of the furnace for cooling to room temperature, and then finished, inspected, and repaired;

[0021] In the performance heat treatment step, the intercritical normalizing stage comprises: preheating the pearlitic wear-resistant lining plate to 300 DEG C, and keeping for 2h; heating the pearlitic wear-resistant lining plate to 600-650 DEG C at a heating rate of ≤80 DEG C / h, and keeping for 3h; heating the pearlitic wear-resistant lining plate to 830-850 DEG C, and keeping for 6h, and after the keeping, taking out the lining plate and air cooling to below 150 DEG C; the tempering stage comprises: preheating the pearlitic wear-resistant lining plate to 200 DEG C, and keeping for 2h; heating the pearlitic wear-resistant lining plate to 500-520 DEG C at a heating rate of ≤80 DEG C / h, and keeping for 6h; after the keeping, slowly cooling the pearlitic wear-resistant lining plate to below 200 DEG C at a cooling rate of ≤30 DEG C / h, and taking out the lining plate and air cooling.

[0022] Further, in the heat treatment method for reducing the gas planing cracking risk of the pearlitic wear-resistant lining plate and optimizing the comprehensive performance, the hardness of the pearlitic wear-resistant lining plate treated by the heat treatment method is HBW 340-370, the yield strength is 702 Mpa, the tensile strength is 1197 Mpa, and the 0 DEG C impact toughness is 16J, 20J or 22J.

[0023] The heat treatment method for reducing the gas planing cracking risk of the pearlitic wear-resistant lining plate and optimizing the comprehensive performance has the following advantages and beneficial effects:

[0024] By adopting the heat treatment process of post-riser head high-temperature normalizing + spheroidizing annealing + intercritical normalizing + tempering, the as-cast grains of the pearlitic wear-resistant lining plate are refined, the composition and the structure are homogenized, the carbide in the lining plate is spheroidized, the spherical or granular carbide is uniformly distributed on the ferrite, the overheating sensitivity of the adjacent matrix structure during the heating in the gas planing process is reduced, the plasticity and the toughness are better, the cracking risk of the pearlitic wear-resistant lining plate in the gas planing process is reduced, the treated pearlitic wear-resistant lining plate has a fine austenite grain and unsolved carbide, the unsolved carbide is in the form of fine spherical and uniformly distributed on the matrix, the wear resistance, the strength and the fracture toughness of the pearlitic wear-resistant lining plate are significantly improved, and because the workpiece temperature during the riser root planing operation is lower than that in the prior art, the riser root planing operation is convenient, the planing efficiency is improved, and the high-efficiency and high-quality gas planing operation is realized. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0026] Figure 1is a process timing diagram of the heat treatment method for reducing the risk of air gouging cracking of pearlitic wear-resistant lining plate and optimizing comprehensive performance of the present application;

[0027] Figure 2 is a process timing diagram of the heat treatment method for reducing the risk of air gouging cracking of pearlitic wear-resistant lining plate and optimizing comprehensive performance of the present application. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described below in conjunction with specific embodiments of the present application and corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] As shown in Figure 1 The heat treatment method for reducing the risk of air gouging cracking of pearlitic wear-resistant lining plate and optimizing comprehensive performance provided by the present application comprises the following steps:

[0030] (1) High-temperature normalizing After sanding and pouring of the pearlitic wear-resistant lining plate, high-temperature normalizing is performed, the purpose of which is to refine the overheated coarse grains of the pearlitic wear-resistant lining plate, eliminate network carbide, and make the composition and structure more uniform, thereby laying a good organizational foundation for subsequent spheroidizing annealing. In addition, high-temperature normalizing can also eliminate internal stress generated during casting and remaining in the refined pearlitic wear-resistant lining plate. High-temperature normalizing is performed in a three-stage heating manner, including: first stage heating, preheating the pearlitic wear-resistant lining plate to 250-300℃ for 2-3h; second stage heating, heating the pearlitic wear-resistant lining plate to 600-650℃ at a heating rate of ≤80℃ / h for 3-4h; third stage heating, heating the pearlitic wear-resistant lining plate to Acm temperature above 100-150℃ (i.e. Acm+(100-150)℃) according to the power of the heat treatment heating furnace, and then holding, the specific holding time is determined according to the actual loading amount, and after holding, the pearlitic wear-resistant lining plate is taken out of the furnace and air cooled.

[0031] (ii) spheroidizing annealing, the spheroidizing annealing treatment is performed on the pearlitic wear-resistant lining plate after high-temperature normalizing, the purpose is to transform the lamellar pearlite structure of the pearlitic wear-resistant lining plate into granular pearlite, so as to reduce the pearlite phase boundary area, enhance the stability of the pearlite, and meanwhile, uniformize the structure and improve the plasticity and toughness of the matrix. The spheroidizing annealing includes: the pearlitic wear-resistant lining plate is normalized and air-cooled to 450-500℃, then after entering the furnace and being preserved for 2-3h, it is heated to 10-20℃ above the Ac1 temperature (i.e. heated to Ac1+(10-20)℃) at a heating rate of ≤100℃ / h, and then preserved, the specific preservation time is determined according to the actual charging amount, after the preservation is finished, it is slowly cooled to 10-20℃ below the Ar1 temperature (i.e. cooled to Ar1-(10-20)℃) at a cooling rate of ≤20℃ / h, and then preserved for 2-3h for preservation transformation, and then air-cooled out of the furnace. In the spheroidizing annealing process, isothermal spheroidizing annealing is adopted, which can shorten the spheroidizing annealing cycle and improve the production efficiency.

[0032] (iii) root of the riser is planed, after the pearlitic wear-resistant lining plate is spheroidizing annealed and air-cooled out of the furnace to 300-350℃, it is entered into the furnace and preserved, the root of the riser is planed while being hot during this preservation stage, after the root of the riser of the lining plate is planed, it is returned to the furnace and preserved in time, then it is slowly cooled with the furnace at a cooling rate of ≤30℃ / h to ≤150℃, and then it is cooled out of the furnace to room temperature to perform the subsequent finishing-inspection-repair process. For the case that the charging amount is large, first, a part of the pearlitic wear-resistant lining plate is hoisted out of the furnace and planed while being hot, after the planing is finished, it is returned to the furnace in time, then another part of the pearlitic wear-resistant lining plate is planed, after the planing of all the pearlitic wear-resistant lining plates is finished, it is entered into the furnace and preserved for 1h, and then slowly cooled to below 150℃ and cooled out of the furnace to room temperature.

[0033] (iv) performance heat treatment, the pearlitic wear-resistant lining plate after the root of the riser is finished is subjected to performance heat treatment, including a subcritical normalizing stage and a tempering stage. The subcritical normalizing stage includes: preheating the pearlitic wear-resistant lining plate to 250-300℃ and maintaining for 2-3h; heating the pearlitic wear-resistant lining plate to 600-650℃ at a heating rate of ≤80℃ / h and maintaining for 3-4h; heating the pearlitic wear-resistant lining plate to Ac1 temperature above 30-50℃ (i.e. heating to Ac1+(30-50)℃) according to the heating furnace power and maintaining, and the specific maintaining time is determined according to the actual loading amount, the maintaining temperature can make most of the base body of the pearlitic wear-resistant lining plate transform into austenite with fine grains, and a part of undissolved granular carbide is also retained, and after the maintaining is finished, the pearlitic wear-resistant lining plate is taken out of the furnace and air-cooled to ≤150℃, pearlite and uniformly distributed spherical carbide are obtained, and such a structure not only has high strength and hardness, but also has good toughness. The tempering stage includes: preheating the pearlitic wear-resistant lining plate to 200℃ and maintaining for 2h; heating the pearlitic wear-resistant lining plate to 500-550℃ at a heating rate of ≤80℃ / h and maintaining for 6h; after the maintaining is finished, the pearlitic wear-resistant lining plate is slowly cooled to ≤200℃ at a cooling rate of ≤30℃ / h and taken out of the furnace and air-cooled, and through the tempering treatment, the residual stress of the pearlitic wear-resistant lining plate is reduced.

[0034] As described above, the heat treatment method for reducing the gas planing cracking risk and optimizing the comprehensive performance of the pearlitic wear-resistant lining plate of the present application adopts the heat treatment process of high-temperature normalizing after encountering the riser + spheroidizing annealing + subcritical normalizing + tempering, the as-cast grains of the pearlitic wear-resistant lining plate are refined through high-temperature normalizing, the composition and structure are uniform, then spheroidizing annealing is performed to spheroidize the carbide in the lining plate, spherical or granular carbide is uniformly distributed on the ferrite, the cutting performance is improved, and compared with the lamellar pearlite after normalizing, through spheroidizing annealing, the overheating sensitivity of the adjacent base body structure during heating in the gas planing process is reduced, the principle lies in that the lamellar pearlite has many phase interfaces and large phase interface area, the nucleation rate is high during austenitizing, and the austenite forms faster, so that the austenite can form in a short time, after the austenite is formed, it enters the growth stage too early, so that the finally obtained austenite grains are coarse; and through spheroidizing annealing, the austenite is uniformly formed by heating, the internal stress caused by the uneven structure is reduced, and the spheroidized structure has better plasticity and toughness than the lamellar structure, so that the material is not easy to crack under external force, therefore, through the spheroidizing annealing heat treatment, not only the gas planing cracking risk of the pearlitic wear-resistant lining plate is reduced, but also after the spheroidizing annealing, the subsequent normalizing treatment adopts subcritical heating, the heating state is fine austenite grains and undissolved carbide, the undissolved carbide is in the form of fine spherical and uniformly distributed on the base body after normalizing, which is helpful to improve the wear resistance, strength and fracture toughness of the pearlitic wear-resistant lining plate after performance heat treatment.

[0035] The heat treatment method for reducing the risk of air gouging cracking and optimizing the comprehensive performance of the pearlitic wear-resistant lining plate is described in detail below in combination with specific examples. The following examples are applied to a pearlitic wear-resistant lining plate with a material of 80Cr2Mo and an equivalent cross-sectional thickness of 300 mm, which can effectively prevent air gouging cracking of the pearlitic wear-resistant lining plate while improving the wear resistance of the pearlitic wear-resistant lining plate. As shown in Figure 2 The specific implementation process of the heat treatment method provided by the example of the present application is as follows:

[0036] (I) high-temperature normalizing, including: first-stage heating, preheating the pearlitic wear-resistant lining plate to 250℃, and holding for 2h; second-stage heating, heating the pearlitic wear-resistant lining plate to 600-650℃, and holding for 3h; third-stage heating, heating the pearlitic wear-resistant lining plate to 960-980℃, and holding for 8h, and then air cooling after the holding is completed.

[0037] (II) spheroidizing annealing, including: air cooling the pearlitic wear-resistant lining plate to 450-500℃ after normalizing, holding for 2h after entering the furnace, heating to 810-820℃, holding for 8h, then slowly cooling to 670-680℃, holding for 2h for transformation, and then air cooling after exiting the furnace.

[0038] (III) riser root planing, air cooling the pearlitic wear-resistant lining plate to 300℃ after spheroidizing annealing, holding in the furnace at 300℃, first hoisting a part of the pearlitic wear-resistant lining plate out of the furnace for hot planing, promptly returning to the furnace after planing is completed, then planing another part of the pearlitic wear-resistant lining plate, and after planing of all the pearlitic wear-resistant lining plates in the furnace is completed, holding in the furnace for 1h, then slowly cooling to below 150℃, and exiting the furnace to cool to room temperature for finishing, flaw detection, and repair procedures.

[0039] (IV) performance heat treatment, including a subcritical normalizing stage and a tempering stage. In the subcritical normalizing stage, the pearlitic wear-resistant lining plate is preheated to 300℃, held for 2h, heated to 600-650℃, held for 3h, heated to 830-850℃, held for 6h, and then air cooled to below 150℃ after the holding is completed. In the tempering stage, the pearlitic wear-resistant lining plate is preheated to 200℃, held for 2h, heated to 500-520℃, held for 6h, and then slowly cooled to below 200℃ after the holding is completed, and air cooled after exiting the furnace.

[0040] According to the embodiment of the present application, 24 pieces of pearlitic wear-resistant lining plates with 80Cr2Mo material and 300mm equivalent cross-section thickness are produced in 3 batches, according to the actual production condition, the root of the riser is conveniently operated and the planing efficiency is obviously improved; only 2 pieces are cracked, the crack depth is 2-3mm, and the crack can be removed after subsequent polishing; the performance test measured data is: hardness HBW 340-370, which is basically unchanged compared with the prior art process, the yield strength is increased from 610Mpa of the prior art process to 702Mpa, the tensile strength is increased from 1092Mpa of the prior art process to 1197Mpa, and the 0℃ impact toughness is increased from 3J, 3J and 4J of the prior art process to 16J, 20J and 22J; the metallographic test measured results are: the base body structure grain size grade of the pearlitic wear-resistant lining plate is higher, the undissolved cementite is granular and dispersedly distributed, and no carbide is precipitated along the crystal.

[0041] In summary, compared with the prior art, the heat treatment method for reducing the pearlitic wear-resistant lining plate air planing cracking risk and optimizing the comprehensive performance has the following advantages and beneficial effects:

[0042] By adopting the heat treatment process of high-temperature normalizing after bumping the riser + spheroidizing annealing + subcritical normalizing + tempering, the as-cast grains of the pearlitic wear-resistant lining plate are refined, the composition and structure are homogenized, the carbide in the lining plate is spheroidized, the spherical or granular carbide is uniformly distributed on the ferrite, the overheating sensitivity of the adjacent base body structure during the air planing process is reduced, the plasticity and toughness are better, the cracking risk of the pearlitic wear-resistant lining plate during the air planing process is reduced, and the structure of the treated pearlitic wear-resistant lining plate is fine austenite grains and undissolved carbide, the undissolved carbide is fine and spherical and uniformly distributed on the base body, the wear resistance, strength and fracture toughness of the pearlitic wear-resistant lining plate are significantly improved, and since the workpiece temperature during the root of the riser planing operation is lower than that of the prior art, the operator of the root of the riser planing operation is convenient, thereby improving the planing efficiency and realizing efficient and high-quality air planing operation.

[0043] It should be noted that in this paper, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the term "include", "contain" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. In addition, "front", "back", "left", "right", "up", "down" in this paper are with reference to the placement state shown in the drawings.

[0044] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features therein can be replaced by equivalents; and such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A heat treatment method for reducing the risk of air gouging cracking in pearlitic wear-resistant liners and optimizing their overall performance, characterized in that, Includes the following steps: (i) High-temperature normalizing: After cleaning the sand and contacting the riser, the pearlitic wear-resistant liner is subjected to high-temperature normalizing treatment. The high-temperature normalizing is carried out in three stages, including: the first stage of heating, preheating the pearlitic wear-resistant liner to 250~300℃ and holding for 2~3 hours; the second stage of heating, heating the pearlitic wear-resistant liner to 600~650℃ and holding for 3~4 hours; the third stage of heating, heating the pearlitic wear-resistant liner to Acm+(100~150)℃ and holding for 3 hours, and then air cooling after the holding is completed. (ii) Spheroidizing annealing: The pearlitic wear-resistant liner after high-temperature normalizing is subjected to spheroidizing annealing treatment, including: the pearlitic wear-resistant liner is air-cooled to 450~500℃ after normalizing, then heated to Ac1+(10~20)℃ and held for 2~3 hours, and after holding for 2 hours, it is slowly cooled to Ar1-(10~20)℃ and held for 2~3 hours, and then air-cooled after being taken out of the furnace. (III) Riser root trimming: After the pearlitic wear-resistant liner is spheroidized and annealed, it is air-cooled to 300~350℃ and then put into the furnace for heat preservation. During the heat preservation stage, the riser root trimming is carried out while it is hot. After the riser root trimming is completed, the liner is put back into the furnace for heat preservation, and then slowly cooled to ≤150℃ with the furnace. It is then taken out of the furnace and cooled to room temperature for subsequent finishing-flaw detection-rework processes. (iv) Performance heat treatment: The pearlitic wear-resistant liner after the riser root is trimmed is subjected to performance heat treatment, including a sub-temperature normalizing stage and a tempering stage. The sub-temperature normalizing stage includes: preheating the pearlitic wear-resistant liner to 250~300℃ and holding it for 2~3h; heating the pearlitic wear-resistant liner to 600~650℃ and holding it for 3~4h; heating the pearlitic wear-resistant liner to Ac1+(30~50)℃ and holding it for 2h; after holding it for 2h, removing it from the furnace and air cooling it to ≤150℃. The tempering stage includes: preheating the pearlitic wear-resistant liner to 200℃ and holding it for 2h; heating the pearlitic wear-resistant liner to 500~550℃ and holding it for 6h; after holding it for 2h, slowly cooling the pearlitic wear-resistant liner to ≤200℃ and air cooling it for 2h.

2. The heat treatment method for reducing the risk of air gouging cracking and optimizing the overall performance of pearlitic wear-resistant liners according to claim 1, characterized in that: In the second stage of heating during the high-temperature normalizing process, the pearlitic wear-resistant lining is heated to 600~650℃ at a heating rate of ≤80℃ / h. In the spheroidizing annealing step, the pearlitic wear-resistant liner is heated to Ac1+(10~20)℃ at a heating rate of ≤100℃ / h, and then slowly cooled to Ar1-(10~20)℃ at a cooling rate of ≤20℃ / h. During the riser root trimming step, the pearlitic wear-resistant liner is slowly cooled with the furnace to ≤150℃ at a cooling rate of ≤30℃ / h. In the performance heat treatment steps, the pearlitic wear-resistant liner is heated to 600~650℃ at a heating rate of ≤80℃ / h during the sub-temperature normalizing stage, and then heated to 500~550℃ at a heating rate of ≤80℃ / h during the tempering stage, and then slowly cooled to ≤200℃ at a cooling rate of ≤30℃ / h.

3. The heat treatment method for reducing the risk of air gouging cracking and optimizing the overall performance of pearlitic wear-resistant liners according to claim 1, characterized in that, In the riser root trimming step, a portion of the pearlitic wear-resistant liner is first lifted out of the furnace and trimmed while still hot. After trimming, it is promptly returned to the furnace. Then, another portion of the pearlitic wear-resistant liner is trimmed. After all the pearlitic wear-resistant liners in the furnace have been trimmed, they are placed back into the furnace and kept warm for 1 hour. Then, they are slowly cooled to below 150°C and taken out of the furnace to cool to room temperature.

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