Treatment method for emergency situation during forging of high-nitrogen stainless steel material

Abstract

The invention discloses a processing method for emergency situations during forging of a high-nitrogen stainless steel material, and belongs to the technical field of bearing ring forging processing, and the processing method comprises the following steps: determining fault duration and setting a processing threshold value, and carrying out staged processing according to the fault duration time: if the fault duration time is smaller than a first threshold value, keeping the furnace temperature of equipment unchanged; processing is continued after the fault is removed; the temperature is between the first threshold value and the second threshold value, the preheating furnace temperature is kept unchanged, the final heating furnace and the secondary heating furnace are cooled, the temperature is increased to the process temperature after failure recovery, heat preservation is conducted for 10-20 min, and then machining is conducted; if the second threshold value is exceeded, manually taking out the in-furnace material section or the forge piece for slow cooling, and reprocessing according to the original process after the fault is recovered; by the adoption of the treatment method for the emergency situation occurring during forging of the high-nitrogen stainless steel material, the quality defects such as forge piece cracks and internal twin-crystal-shaped carbides which are prone to occurring during treatment of an original technology are effectively overcome, and the product quality of the high-nitrogen stainless steel forge piece is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of bearing ring forging technology, and in particular to a method for handling emergency situations that occur during the forging of high-nitrogen stainless steel. Background Technology

[0002] High-nitrogen stainless steel possesses high hardness and corrosion resistance. Compared to high-carbon chromium stainless steel bearings under the same conditions, high-nitrogen stainless steel exhibits higher impact toughness. Therefore, in recent years, high-nitrogen stainless steel has been widely used in high-end bearings.

[0003] High-nitrogen stainless steel has a relatively narrow forging temperature range. In actual production, the initial forging temperature is controlled between 1080 and 1120℃, and the final forging temperature is ≥ 950℃. If the final forging temperature is low, deformation during forging becomes difficult, and internal stress increases, making cracks more likely. High-nitrogen stainless steel is a martensitic stainless steel, which is particularly sensitive to cooling rate. After forging, air cooling or wind cooling will result in the formation of some martensitic structures inside the forging. The uneven distribution of the structure leads to high internal stress and a tendency to crack.

[0004] The forging process for high-nitrogen stainless steel includes: preheating of the forging section, final heating of the forging section, forging, secondary heating of the forging, rolling and expanding, and slow cooling after forging. If an emergency occurs during the forging process (emergencies include: malfunction of the preheating furnace or high-temperature heating furnace, sudden power outage, malfunction of forging and ring rolling equipment, damage to forging and ring rolling dies, etc.), improper handling can easily lead to quality problems in the forging process of high-nitrogen stainless steel, or even product scrap. Summary of the Invention

[0005] The purpose of this invention is to provide a method for handling emergency situations that occur during the forging of high-nitrogen stainless steel materials, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this invention provides a method for handling emergency situations that occur during the forging of high-nitrogen stainless steel materials, wherein the high-nitrogen stainless steel materials include domestically produced 40Cr15Mo2VN high-nitrogen stainless steel and imported Cronidur30 high-nitrogen stainless steel; the method includes the following steps: S1. When an emergency occurs during the forging process, determine the duration of the fault, set a threshold for handling the fault duration, and take graded handling measures according to the duration of the fault. S2. If the duration of the fault is less than the first threshold, keep the furnace temperature of the preheating furnace, the final heating furnace and the secondary heating furnace unchanged, and continue processing after the fault is cleared. S3. If the duration of the fault is between the first threshold and the second threshold, keep the temperature of the preheating furnace constant, lower the temperature of the final heating furnace and the secondary heating furnace to 1000±10℃ for heat preservation, and after the fault is recovered, raise the temperature of the final heating furnace and the secondary heating furnace to the process temperature and keep it at that temperature for 10~20 minutes to continue processing. S4. If the fault lasts longer than the second threshold time, manually open the furnace door to remove the material section or forging and perform slow cooling. After the fault is restored, reprocess according to the original process.

[0007] Preferably, the emergency includes electrical or mechanical failures in the preheating furnace, final heating furnace, secondary heating furnace, forging press, and ring rolling mill, sudden power outages in the workshop, or damage to the forging or ring rolling molds.

[0008] Preferably, when an emergency occurs due to electrical or mechanical failure of the preheating furnace, final heating furnace, secondary heating furnace, forging press, or ring rolling mill, or damage to the forging or ring rolling mold, a first threshold of 20 minutes and a second threshold of 40 minutes are set.

[0009] Preferably, when the emergency is a sudden power outage in the workshop, the first threshold is set to 0 minutes and the second threshold is set to 30 minutes.

[0010] Preferably, the process temperature range in S3 is 1080~1120℃.

[0011] Preferably, the slow cooling treatment of S4 involves burying the material segment and forging in a lime box containing dry lime, ensuring that they do not come into contact with the lime box wall after burying, and slowly cooling the material segment and forging in the dry lime to below 300°C before removing them.

[0012] Preferably, the material segment that has undergone slow cooling in S4 is placed in the preheating furnace and forged according to the original process. The forging is placed in the preheating furnace and, after reaching the process time, is transferred to the final heating furnace for direct rolling and expanding forming.

[0013] Preferably, all heating processes are carried out under a nitrogen protective atmosphere.

[0014] Therefore, the present invention employs the above-mentioned method for handling emergency situations that occur during the forging of high-nitrogen stainless steel materials, which has the following beneficial effects: (1) Addressing the shortcomings of the original process in handling emergencies such as equipment failure and mold damage: The original process requires air cooling after removing the material section / forging from the furnace. However, high-nitrogen stainless steel (martensitic type) has a high alloy content and is sensitive to cooling rate. Air cooling can easily lead to the formation of local martensitic structure, generating internal stress or even cracks, ultimately resulting in product scrap. This invention accurately judges the maintenance time or mold replacement time and matches differentiated coping measures such as "maintaining furnace temperature, cooling and maintaining temperature, and slow cooling", which avoids the structural defects caused by air cooling from the root. Practical application has verified that no crack defects are generated during the forging process, which greatly improves the product qualification rate.

[0015] (2) Regarding the defects of the original process in handling sudden power outages: The original process uses furnace cooling. If the cooling time exceeds 30 minutes, high-nitrogen stainless steel is prone to forming twinned carbide structures inside. These structures will significantly reduce the material's impact resistance and may cause the bearings manufactured later to fail prematurely. The present invention clearly defines the graded handling for power outages: When the power outage exceeds 30 minutes, the furnace door is manually opened to remove the material section / forging and the material is slowly cooled by burying it in a dry lime ash box (consistent with the slow cooling process after forging). After the power is restored, the material is reprocessed according to the original process. Actual production verification shows that no twinned carbide structures were generated due to the power outage, which effectively ensures the mechanical properties of high-nitrogen stainless steel and ensures the reliability of subsequent bearing products.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for handling emergency situations that occur during the forging of high-nitrogen stainless steel materials according to the present invention; Figure 2 The images show a comparison of the microstructures of high-nitrogen stainless steel ring forgings for power outage handling according to the present invention. (a) shows the microstructure of the high-nitrogen stainless steel forging after existing processing, where twinned carbide structures appear inside; (b) shows the microstructure of the high-nitrogen stainless steel forging after processing with the new process of the present invention, where the microstructure is qualified. Detailed Implementation

[0018] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] Example like Figure 1 As shown, the present invention provides a method for handling emergencies that occur during the forging of high-nitrogen stainless steel materials, applicable to the handling of emergencies that occur during the forging of domestic 40Cr15Mo2VN high-nitrogen stainless steel and imported Cronidur30 high-nitrogen stainless steel.

[0020] This invention is based on a complete high-nitrogen stainless steel forging process, which includes the following steps: 1. Material section preheating A preheating furnace is used to preheat the high-nitrogen stainless steel material segment. Nitrogen gas is introduced during the preheating process as a protective atmosphere to prevent oxidation of the material segment. The preheating temperature is controlled at 900-950℃. After the material segment is fully transparent (i.e., the temperature inside and outside the material segment is uniform), it is kept at the temperature according to the standard of "1.0×φDmin" (where φD represents the diameter of the material segment in mm). During the holding period, the temperature inside the furnace is monitored in real time to ensure that the temperature is stable within the set range and to avoid temperature fluctuations affecting the preheating effect of the material segment.

[0021] 2. Final heating of material section After the material segment has been preheated and held for the set time, it is removed from the preheating furnace and transferred to the final heating furnace for final heat treatment. Nitrogen gas is also introduced into the final heating furnace as a protective atmosphere, and the heating temperature is controlled at 1080-1120℃. After the material segment is translucent again, it is held at the standard of "0.2×φDmin". During the final heating process, it is necessary to ensure that the material segment is heated evenly to avoid local overheating or insufficient temperature, so as to ensure that the material segment has good plasticity during subsequent forging processing.

[0022] 3. Forging process Forging is carried out using a press or free forging equipment. Before forging, the forging die needs to be preheated, with the preheating temperature controlled between 150 and 300°C. This prevents a sudden drop in the local temperature of the material section when the cold die comes into contact with the high-temperature material section, which would affect the forging quality. During forging, the material section after final heating is first upset to increase its cross-section and decrease its height. Then, it is formed into a preliminary ring shape. Finally, punching is performed to obtain a ring-shaped forging. During the forging process, an infrared thermometer is used to measure the final forging temperature in real time to ensure that the final forging temperature is ≥950°C. If the temperature is lower than this value, forging must be stopped and the material section must be transferred back to the final heating furnace for reheating. Forging can continue after the temperature reaches the standard.

[0023] 4. Secondary heating of forgings The forged ring-shaped forging is placed in a secondary heating furnace and protected with nitrogen gas. The heating temperature is controlled at 1080-1120℃. After the forging is fully colored, it is kept at a temperature of "0.6×Smin" (where S represents the effective wall thickness of the ring-shaped forging in mm). The purpose of secondary heating is to eliminate the internal stress generated during forging and to increase the temperature of the forging, thus providing good conditions for subsequent rolling and expansion forming.

[0024] 5. Rolling and expanding molding A vertical pneumatic or hydraulic rolling mill is used to roll and expand the ring-shaped forging after secondary heating. During the rolling process, the parameters of the rolling mill are adjusted according to the process size requirements of the ring to ensure that the inner diameter, outer diameter, wall thickness and other dimensions of the forging after rolling meet the design standards. After rolling is completed, the temperature of the forging is controlled to be ≥900℃. Then, the rolling shaft and the matching tooling are immediately water-cooled to prevent the tooling temperature from being too high and affecting the subsequent rolling process. At the same time, it is to avoid the residual heat of the tooling from being transferred to the forging and causing local abnormal temperature of the forging.

[0025] 6. Slow cooling after forging Place a ash box next to the rolling mill in advance. The size of the ash box is determined according to the size and quantity of the forgings to be slowly cooled. The bottom of the ash box is supported by heat-resistant furnace bricks to prevent the bottom of the ash box from being damaged by heat. Immediately bury the rolled and expanded forgings in the ash box containing dry lime, ensuring that the forgings do not come into contact with the walls of the ash box to avoid excessive local cooling of the forgings. After the forgings have been slowly cooled to below 300°C in the dry lime, remove them from the ash box to complete the entire forging process.

[0026] In the event of an emergency such as equipment failure, power outage, or mold damage during normal production, the following emergency response procedure shall be activated, including the following steps: S1. When an emergency occurs during the forging process, determine the duration of the fault, set a threshold for handling the fault duration, and take graded handling measures according to the duration of the fault. S2. If the duration of the fault is less than the first threshold, keep the furnace temperature of the preheating furnace, the final heating furnace and the secondary heating furnace unchanged, and continue processing after the fault is cleared. S3. If the duration of the fault is between the first threshold and the second threshold, keep the temperature of the preheating furnace constant, lower the temperature of the final heating furnace and the secondary heating furnace to 1000±10℃ for heat preservation. After the fault is recovered, raise the temperature of the final heating furnace and the secondary heating furnace to the process temperature and keep it at that temperature for 10~20 minutes to continue processing. The process temperature range is 1080~1120℃. S4. If the fault lasts longer than the second threshold time, manually open the furnace door to remove the material section or forging and perform slow cooling treatment. After the fault is restored, reprocess according to the original process. The slow cooling treatment involves burying the material section and forging in a lime box containing dry lime, ensuring that they do not contact the lime box wall. The material section and forging are slowly cooled in the dry lime to below 300°C and then removed. The material section that has undergone slow cooling treatment is placed in the preheating furnace and forged according to the original process. The forging is placed in the preheating furnace and, after the process time is reached, is transferred to the final heating furnace for direct rolling and expanding forming.

[0027] All of the above heating processes were carried out under a nitrogen protective atmosphere.

[0028] The following three examples illustrate different types of emergency situations in detail: Example 1: Equipment experiences electrical or mechanical failure When electrical or mechanical malfunctions occur in the preheating furnace, final heating furnace, secondary heating furnace, forging press, or ring rolling mill, preventing normal processing, the following methods should be used: 1. First, determine the cause of the malfunction and the repair time; 2. If the maintenance time is less than 20 minutes, the furnace temperatures of the preheating furnace, final heating furnace, and secondary heating furnace shall remain unchanged. Forging shall continue after the equipment maintenance is completed and the equipment is ready for use.

[0029] 3. If the maintenance time is 20 to 40 minutes, the temperature of the preheating furnace remains unchanged, while the temperature of the final heating furnace and the secondary heating furnace is reduced to 1000±10℃ for heat preservation. After the equipment is repaired and ready for use, the final heating furnace and the secondary heating furnace are heated up. After reaching the process temperature, they are held for 10 to 20 minutes before forging.

[0030] 4. If the maintenance time exceeds 40 minutes, manually open the furnace door of the preheating furnace / final heating furnace / secondary heating furnace, remove the material sections and forgings from the furnace, and allow them to cool slowly using the post-forging slow cooling method. Once the equipment is repaired and ready for processing, place the material sections into the preheating furnace and forge them according to the original process; place the forgings into the preheating furnace, and after the process time is reached, transfer them to the final heating furnace. After the process time is reached, they can be directly rolled and expanded for further processing.

[0031] Example 2: Sudden Power Outage in the Workshop Determine the cause of the power outage and estimate its duration: 1. If the expected power outage time is less than 30 minutes, the material sections in the preheating furnace and final heating furnace should be cooled down along with the furnace, and the forgings in the secondary heating furnace should also be cooled down along with the furnace. After power is restored, the material sections in the preheating furnace and final heating furnace should be heated up along with the furnace, and the forgings in the secondary heating furnace should also be heated up along with the furnace. After the furnace temperature reaches the process temperature, hold it at that temperature for 10-20 minutes, and then proceed with the forging process according to the original procedure.

[0032] 2. If the expected power outage time is 30 minutes or more, manually open the furnace door, remove the material or forging from the furnace, and immediately use the post-forging slow cooling method described above for slow cooling. After power is restored, place the slow-cooled material into the preheating furnace and re-forge it according to the original process; place the slow-cooled forging into the preheating furnace, and after the process time is reached, transfer it to the final heating furnace for direct rolling and subsequent processing.

[0033] Example 3: Damage to forging or rolling die When a forging or rolling die is damaged, preventing the forging of a preheated section from being forged or the reheated forging from being rolled, the following methods should be used: 1. Determine the time required to change the mold; 2. If the mold change time is less than 20 minutes, keep the furnace temperatures of the preheating furnace, final heating furnace, and secondary heating furnace constant. After replacing the mold with a new one, continue forging.

[0034] 3. If the mold change time is 20 to 40 minutes, keep the preheating furnace temperature constant, while lowering the temperatures of the final heating furnace and the secondary heating furnace to 1000±10℃ and holding them there. After the mold change is complete and the mold is ready for use, raise the temperatures of the final heating furnace and the secondary heating furnace to the process temperature of 1080~1120℃ and hold them there for 10~20 minutes before forging.

[0035] 4. If the mold change takes more than 40 minutes, manually open the furnace door, remove the material or forging from the furnace, and immediately use the post-forging slow cooling method described above for slow cooling. After the mold is changed and the processing conditions are met, place the slow-cooled material into the preheating furnace and re-forge it according to the original process; place the slow-cooled forging into the preheating furnace, and after the process time is reached, transfer it to the final heating furnace for direct rolling and subsequent processing.

[0036] To demonstrate the beneficial effects of the emergency handling method provided in this embodiment, a comparative example and an implementation case will be used to illustrate the following in detail.

[0037] Comparative Example This example demonstrates the consequences of using the existing "furnace cooling-furnace heating" method to handle prolonged power outages.

[0038] Comparative Example 1: Emergency handling methods during the forging of high-nitrogen stainless steel materials in existing processes 1. Forging process 1.1 Material segment preheating: A preheating furnace is used for material segment preheating. Material segment diameter: 50mm; preheating temperature: 900~950℃; holding time after color penetration: 50min; protective atmosphere: nitrogen.

[0039] 1.2 Final heating of material segments: Final heating of material segments is carried out using a final heating furnace. When the material segment reaches the set preheating time, it is automatically taken out from the preheating furnace and transferred to the final heating furnace. Heating temperature: 1080~1120℃, holding time after color clearance: 10min, protective atmosphere: nitrogen.

[0040] 1.3 Forging: The forging of the material section is carried out using a J31-315 press. Before forging, the forging die needs to be preheated to 250℃. The forging process includes: upsetting, forming, punching, and obtaining a ring-shaped forging. The final forging temperature should be ≥950℃, and the final forging temperature is measured using an infrared thermometer.

[0041] 1.4 Secondary heating of forgings: a secondary heating furnace is used; the effective wall thickness of the ring forging is 16mm; the secondary heating temperature is 1100℃; the holding time after color penetration is 10min; the protective atmosphere is nitrogen.

[0042] 1.5 Rolling and Expanding: A vertical pneumatic rolling and expanding machine is used for rolling and expanding. After rolling and expanding, a ring forging conforms to the process dimensions is obtained. The temperature after rolling and expanding is ≥900℃. After rolling and expanding, the rolling and expanding shaft and tooling are water-cooled.

[0043] 1.6 Slow Cooling After Forging: The forgings, after rolling and expanding, are immediately buried in a lime box containing dry lime. The lime box is 60cm long, 40cm wide, and 40cm high. The lime box is placed next to the rolling and expanding machine, with heat-resistant furnace bricks supporting the bottom. After the forgings are buried, they must not come into contact with the lime box wall. The forgings can be removed when they are slowly cooled in the dry lime to below 300℃.

[0044] 2. Due to a power outage in the workshop, the entire production workshop experienced a power supply interruption. The emergency response measures were as follows: the material sections in the preheating furnace and final heating furnace were cooled down along with the furnace, and the forgings in the secondary heating furnace were also cooled down along with the furnace. The power restoration time was 5 hours. After power was restored, the furnace temperature of the preheating furnace was reduced to 700℃, the furnace temperature of the final heating furnace was reduced to 920℃, and the furnace temperature of the secondary heating furnace was reduced to 915℃. At this time, the three heating furnaces began to heat up, and the material sections and forgings in the furnaces heated up along with the furnaces. After reaching the holding time specified in the process, they were processed according to the original forging process.

[0045] 3. After annealing, the high-nitrogen stainless steel forgings underwent physical and chemical testing. The microstructure inside the forgings was uneven, and some fields of view showed severe twinned carbides. Since twinned carbides are very harmful and affect the mechanical properties of the bearings, this batch of forgings was deemed scrapped, resulting in significant economic losses.

[0046] Implementation Case 1: Emergency Handling Methods During High-Nitrogen Stainless Steel Forging 1. Forging process 1.1 Material segment preheating: A preheating furnace is used for material segment preheating. Material segment diameter: 110mm; preheating temperature: 900℃; holding time after color penetration: 110min; protective atmosphere: nitrogen.

[0047] 1.2 Final heating of material segments: Final heating of material segments is carried out using a final heating furnace. When the material segment reaches the set preheating time, it is automatically taken out from the preheating furnace and transferred to the final heating furnace. Heating temperature: 1100℃, holding time after color clearance: 22min, protective atmosphere: nitrogen.

[0048] 1.3 Forging: The forging of the material section is carried out using a 1T free forging hammer. Before forging, the free forging die needs to be preheated to 250℃. The forging process includes: upsetting, forming, punching, and obtaining a ring-shaped forging. The final forging temperature should be ≥950℃, and the final forging temperature is measured using an infrared thermometer.

[0049] 1.4 Secondary heating of forgings: a secondary heating furnace is used; the effective wall thickness of the ring forging is 24 mm; the secondary heating temperature is 1100℃; the holding time after color penetration is 15 min; the protective atmosphere is nitrogen.

[0050] 1.5 Rolling and Expanding: A vertical hydraulic rolling and expanding machine is used for rolling and expanding. After rolling and expanding, a ring forging conforms to the process dimensions is obtained. The temperature after rolling and expanding is ≥900℃. After rolling and expanding, the rolling and expanding shaft and tooling are water-cooled.

[0051] 1.6 Slow Cooling After Forging: The forgings, after rolling and expanding, are immediately buried in a lime box containing dry lime. The lime box is 80cm long, 60cm wide, and 60cm high. The lime box is placed next to the ring rolling mill, supported by heat-resistant furnace bricks at the bottom. After the forgings are buried, they must not come into contact with the lime box wall. The forgings are slowly cooled in the dry lime until they reach a temperature below 300°C before being removed.

[0052] 2. During on-site production, the ring rolling mill was expanding the forging. Before the forging was fully expanded, the large wheel wall of the rolling mill's die broke, preventing further processing. The unexpanded forging was returned to the secondary heating furnace for reheating. The preceding forging process also ceased. The repair time for the large wheel of the rolling mill's die was determined. Due to the broken wheel wall, repair was impossible, and a suitable wheel was unavailable; a new wheel needed to be machined, which would take approximately 3 hours. According to the new process method, the die replacement time is greater than 40 minutes. The furnace door was opened, and the forging section / piece was removed for slow cooling.

[0053] For slow cooling of the material section, the following method is used: The ash box dimensions are 60cm long, 40cm wide, and 40cm high. The ash box is placed next to the final heating furnace, supported by heat-resistant furnace bricks. After the material section is embedded, it must not contact the ash box wall. The material section is slowly cooled in dry lime until it reaches a temperature below 300℃ before being removed. For slow cooling of forgings, the following method is used: The ash box dimensions are 80cm long, 60cm wide, and 60cm high. The ash box is placed next to the ring rolling mill, supported by heat-resistant furnace bricks. After the forgings are embedded, they must not contact the ash box wall. The forgings are slowly cooled in dry lime until they reach a temperature below 300℃ before being removed. After the large roller of the ring rolling mill mold is replaced and the processing conditions are met, the material section is placed in the preheating furnace and forged according to the original process. The forging is placed in the preheating furnace and heated to 900℃ for 25 minutes. After the heating period, it is manually transferred to the final heating furnace and heated to 1100℃ for 5 minutes. After the heating period, it is rolled and expanded and then slowly cooled after forging.

[0054] 3. After annealing, the high-nitrogen stainless steel forgings underwent physical and chemical testing. The internal microstructure of the forgings consisted of uniformly distributed spherical and fine-grained pearlite. Fluorescent magnetic particle testing revealed no cracks or defects in the forgings, indicating that the product quality was up to standard and could proceed with further processing.

[0055] like Figure 2 As shown, the results are magnified by 500×. (a) shows the result after the existing process, where twinned carbides appear inside the forging. (b) shows the result after the process in this embodiment, where the forging has qualified spherical shapes inside.

[0056] Therefore, the present invention adopts the above-mentioned method for handling emergencies during the forging of high-nitrogen stainless steel materials. By addressing emergencies such as preheating furnace / final heating furnace / secondary heating furnace failures, forging and rolling equipment failures, sudden power outages, and damage to forging and rolling dies during the forging of high-nitrogen stainless steel rings, graded handling measures are taken according to the failure repair time, power outage duration, or die replacement time. This effectively avoids quality defects such as forging cracks and internal twinned carbides that are prone to occur in the original process, thus ensuring the product quality of high-nitrogen stainless steel forgings.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method of handling an emergency during forging of a high-nitrogen stainless steel material, characterized by, The high-nitrogen stainless steel material includes domestic 40Cr15Mo2VN high-nitrogen stainless steel and imported Cronidur30 high-nitrogen stainless steel; the method comprises the following steps: S1, when an emergency occurs in the forging process, the duration of the fault is determined, a fault duration processing threshold is set, and hierarchical processing measures are taken according to the duration of the fault; S2, if the duration of the fault is less than the first threshold, the furnace temperature of the preheating furnace, the final heating furnace and the secondary heating furnace is kept unchanged, and the processing is continued after the fault is eliminated; S3, if the duration of the fault is between the first threshold and the second threshold, the preheating furnace temperature is kept unchanged, the final heating furnace and the secondary heating furnace are lowered to 1000±10℃ for heat preservation, after the fault is restored, the final heating furnace and the secondary heating furnace are heated to the process temperature and heat preserved for 10-20 minutes for continuous processing; S4, if the duration of the fault exceeds the second threshold time, the furnace door is manually opened to take out the material section or the forging, and the slow cooling treatment is carried out, and after the fault is restored, the original process is used for processing.

2. The method for handling an emergency situation during forging of a high nitrogen stainless steel material according to claim 1, characterized in that: The emergency includes electrical and mechanical faults of the preheating furnace, the final heating furnace, the secondary heating furnace, the forging press and the ring rolling machine, sudden power failure in the workshop or damage of the mold for forging and ring rolling.

3. The method of claim 2, wherein the high nitrogen stainless steel material is forged. When the emergency is electrical and mechanical faults of the preheating furnace, the final heating furnace, the secondary heating furnace, the forging press and the ring rolling machine or damage of the mold for forging and ring rolling, the first threshold is set to 20 minutes and the second threshold is set to 40 minutes.

4. The method of claim 2, wherein the high nitrogen stainless steel material is forged. When the emergency is sudden power failure in the workshop, the first threshold is set to 0 minute and the second threshold is set to 30 minutes.

5. The method of claim 1, wherein the high nitrogen stainless steel material is forged. The process temperature range in S3 is 1080-1120℃.

6. The method of claim 1, wherein the high nitrogen stainless steel material is forged. The slow cooling treatment in S4 is that the material section and the forging are buried in a lime box filled with dry lime, and after being buried, the material section and the forging do not contact the wall of the lime box, and the material section and the forging are slowly cooled to below 300℃ in the dry lime and taken out.

7. The method of claim 6, wherein the high nitrogen stainless steel material is forged. The material section after the slow cooling treatment in S4 is put into the preheating furnace for forging processing according to the original process, and the forging is put into the preheating furnace, and after reaching the process time, the forging is transferred to the final heating furnace for ring expansion forming processing.

8. The method of claim 7, wherein the high nitrogen stainless steel material is forged. All heating processes are carried out in a nitrogen protective atmosphere.

Images