A forging process for a fxm-19 reactor shaft forging

Abstract

The present application belongs to the technical field of special steel forging, and particularly relates to a forging process for a FXM-19 reactor shaft forging. The process is characterized by the following steps: performing surface finishing treatment on raw materials, selecting a suitable heating furnace, designing a reasonable heating process, performing twice forging by using a 1800-ton radial precision forging machine, reasonably designing the deformation process of each heating, and controlling the hammering amount and pulling speed of each pass of the precision forging machine, so as to meet the surface quality and grain size requirements of the FXM-19 reactor shaft forging. The process is suitable for the forging of special steel with a surface prone to cracking and a length not less than 10 meters.

Description

Technical Field

[0001] This invention belongs to the field of special steel forging technology, specifically relating to a forging process for FXM-19 reactor shaft forgings. This process is suitable for forging special steels with surfaces that are extremely prone to cracking and lengths not less than 10 meters. Background Technology

[0002] FXM-19 steel is a high-alloy austenitic stainless steel with the following chemical composition: C≤0.06%, Si≤1.0%, Mn: 4.0%~6.0%, P≤0.035%, S≤0.02%, Cr: 20.5%~23.5%, Mo: 1.5%~3.0%, Ni: 11.5%~13.5%, V: 0.1%~0.3%, N: 0.2%~0.4%, Nb: 0.01%~0.3%, Al≤0.03%.

[0003] The FXM-19 reactor shaft forging has a diameter of 230mm and a length of 11 meters. It belongs to the high-alloy slender bar forging category, making it difficult to forge. The surface is extremely prone to cracking, and its long length, coupled with the requirement for a post-forging grain size of at least grade 5, further increases the forging difficulty. Currently, forging companies frequently encounter surface cracking and scrapping issues or substandard grain size after forging when forging this product, making it a forging challenge within the industry. Summary of the Invention

[0004] In view of the above, the purpose of this invention is to overcome the shortcomings of the prior art and provide a forging process for FXM-19 reactor shaft forgings that solves the problems of forging cracking and scrapping and unqualified grain size in FXM-19 reactor shaft forgings, so as to solve the forging difficulties of FXM-19 reactor shaft forging products.

[0005] The objective of this invention is achieved as follows: a forging process for an FXM-19 reactor shaft forging, wherein the forging process is carried out according to the following procedure:

[0006] Step 1) Perform surface finishing treatment on the electroslag ingot. Finishing requirements: The entire surface of the electroslag ingot is polished to remove visible defects such as surface cracks, pores, pits, residues, and scabs. If there are slag grooves, joint marks, or truncated marks on the surface, or pits that do not have a smooth transition with the substrate, they must be polished clean. The height, width, and length ratio of the cleaned ingot should be 1:6:10.

[0007] Step 2) Heat the finished electroslag ingot. The heating process curve is as follows: hold at 350℃~400℃ for 4 hours, then heat to 1220℃ at a rate of 80℃ per hour and hold for 6 hours. The heating furnace should be no more than 20 meters away from the precision forging machine. After heating, quickly remove the electroslag ingot from the furnace for forging.

[0008] Step 3) Use an 1800-ton radial precision forging machine for the first forging. Before forging this product, forge other products first to ensure that the loading track, control machine jaws, and hammer head of the precision forging machine are in a hot state. Set the forging frequency of the precision forging machine to 180 times per minute. Use R280 hammer head. The final forging temperature is ≥960℃. Use an Optos temperature gun to measure the temperature. If the part temperature is lower than 960℃, immediately return it to the furnace for reheating. Use a hydraulic press to flatten the ingot tail after forging and use the residual heat of the ingot for hot straightening. The curvature should not exceed 3mm per meter. Air cool the ingot to room temperature.

[0009] Step 4) Use a lathe to peel off the surface cracks of the billet and smooth the transition at the steps.

[0010] Step 5) Select one or two heating furnaces to heat the stripped billet. The heating process curve is as follows: hold at 350℃~400℃ for 3 hours, then heat up to 1220℃ at a rate of 80℃ per hour and hold for 5 hours. The heating furnace should be no more than 20 meters away from the precision forging machine. After heating, quickly remove the billet from the furnace for forging.

[0011] Step 6) Use an 1800-ton radial precision forging machine for secondary forging. Before forging this product, forge other products first to ensure that the forging machine's feeding track, operating machine jaws, and hammer head are in a hot state. Set the forging frequency of the precision forging machine to 180 times per minute and select R180 hammer head.

[0012] Step 7) Air cooling treatment of the forged billet.

[0013] Furthermore, in step 3), in order to minimize the occurrence of cracks on the surface of the forging during the first forging process, the first forging is performed by forging the end of the electroslag ingot to the junction with the precision forging machine, forging in 3 passes. The hammer drop in the first pass is 30mm, and the hammer drop in the remaining passes is 40-50mm. The junction ramp is divided into 3 steps. The riser end is forged in 1 pass with a hammer drop of 30mm. After the first forging, the billet is returned to the furnace for heating and held at 1220℃ for 2 hours. In the remaining passes, the billet is forged to the diameter specified in the process, with a hammer drop of 40-50mm in each pass. The length of the forged billet is controlled within the range of the effective heating length of the heating furnace minus 200-300mm, so as to ensure that the billet can be loaded into the heating furnace during the second forging and that the second forging time is controlled within 8 minutes.

[0014] Furthermore, in step 5), in order to ensure that the forgings have a high initial forging temperature during the secondary forging, if one heating furnace is selected to heat the stripped billet, the first billet is taken out of the furnace for forging, and the next billet is kept warm for 1 hour before being taken out of the furnace for forging. If two heating furnaces are selected to heat the stripped billet, the billets in the two heating furnaces are taken out of the furnace in turn for forging.

[0015] Furthermore, in step 6), to ensure the completion of the second forging in one pass, after the first forging, the length of the billet is controlled within the effective heating length of the heating furnace minus 200-300mm. To ensure the completion of the second forging in one pass and the quality of the forging, the second forging is controlled to be completed within 8 minutes for 2-3 passes on the precision forging machine. The forging speed of the first pass is greater than 4 meters per minute, and the last pass is forged at 2-3 meters per minute. The hammer depth of each pass is 30-50mm.

[0016] The positive effects of this invention are as follows:

[0017] 1. The forging process of this invention can effectively solve the problems of forging cracking and scrapping and unqualified grain size in FXM-19 reactor shaft forgings.

[0018] 2. The forging process concept of this invention has been extended to the forging of special steels with surfaces that are extremely prone to cracking and a length of not less than 10 meters. Detailed Implementation

[0019] To fully understand the inventiveness of this invention, a forging process for an FXM-19 reactor shaft forging will be described in detail in the embodiments to fully illustrate the invention.

[0020] A forging process for an FXM-19 reactor shaft: The forging process is carried out according to the following procedure:

[0021] FXM-19 reactor shaft forgings, with a forging diameter of 250mm, a length of 11700mm, an electroslag ingot weight of 5.85 tons, and a central diameter of ∅690mm. Quantity: 6 pieces.

[0022] Step 1) Perform surface finishing treatment on the electroslag ingot. Finishing requirements: The entire surface of the electroslag ingot should be polished to remove visible defects such as surface cracks, pores, pits, residues, and scabs. If there are slag grooves, joint marks (or cut marks), or pits that do not have a smooth transition with the substrate, they should be polished clean. The height, width, and length ratio of the cleaned ingot should be 1:6:10.

[0023] Step 2) Select heating furnace No. 3 to heat the 6 finished electroslag ingots. The heating curve is as follows: hold at 350℃ for 4 hours, then heat up to 1220℃ at a rate of 80℃ per hour and hold for 6 hours. Heating furnace No. 3 is a trolley regenerative heating furnace with an effective heating length of 6.8 meters and a distance of 15 meters from the 1800-ton radial precision forging machine. After heating, quickly remove the electroslag ingots from the furnace for forging.

[0024] Step 3) Use an 1800-ton radial precision forging machine for the first forging. Before forging this product, forge other products first. The feeding track, operating machine jaws, and hammer head are in a hot state. Set the forging frequency of the precision forging machine to 180 times per minute. Use R280 hammer head. The final forging temperature is ≥960℃. Use an Optos temperature measuring gun to measure the temperature. If the part temperature is lower than 960℃, immediately return it to the furnace for reheating.

[0025] The tail end of the electroslag ingot was forged to ∅560mm in the first firing, with the deformation process as follows: -∅660-∅610-∅560. The transition ramp has three steps. The riser end was forged once to ∅660mm, with the deformation process as follows: -∅660. The part temperatures measured using an Optos thermometer were 962℃, 967℃, 963℃, 962℃, 965℃, and 964℃, respectively. After the first firing forging, three billets were returned to furnace No. 4 for reheating. Heating furnace No. 1 was held at 1220℃ for 2 hours. Heating furnace No. 4 was a trolley-type regenerative heating furnace with an effective heating length of 6.8 meters and a distance of 18 meters from the 1800-ton radial precision forging machine. After the holding period, the second heating was performed. First, the riser end was forged to ∅480mm, with a deformation process of -∅610-∅560-∅520-∅480. Then, the ingot tail end was forged to ∅480mm, with a deformation process of -∅520-∅480. The part temperature was measured using an Optics temperature gun. 974℃, 983℃, 975℃, 967℃, 972℃, 971℃; After the second forging, three billets were returned to furnace No. 4 for heating, and three billets were returned to furnace No. 3 for holding at 1220℃ for 2 hours; After the holding period, the third forging was performed, forging the entire piece to ∅380mm. The deformation process was: -∅430-∅380. The part temperatures were measured using an Optics temperature gun: 984℃, 983℃, 978℃, 981℃, 979℃, 981℃. At this temperature, the billet lengths were 6580mm, 6600mm, 6620mm, 6580mm, 6608mm, 6620mm, and 6605mm, respectively. The forged billets were then leveled using a hydraulic press, and hot straightening was performed using the residual heat of the billets. After straightening, the measured curvatures were 1mm / m, 1.10mm / m, 1.12mm / m, 1.13mm / m, 1.09mm / m, and 1.05mm / m, respectively. The billets were then air-cooled to room temperature.

[0026] Step 4) Use a lathe to peel off the surface cracks of the billet and smooth the transition at the steps.

[0027] Step 5) Select heating furnaces No. 3 and No. 4 to heat the stripped billets. The heating curve is as follows: hold at 350℃ for 3 hours, then increase the temperature to 1220℃ at a rate of 80℃ per hour and hold for 5 hours. The billets from heating furnaces No. 3 and No. 4 are taken out of the furnaces in turn for forging.

[0028] Step 6) Secondary forging is performed using an 1800-ton radial precision forging machine. Prior to forging this product, 38CrMoAl products had already been forged. The forging machine's loading track, operating jaws, and hammers were in a hot state. The forging frequency of the precision forging machine was set to 180 strokes per minute, and R180 hammers were selected. The 1800-ton radial precision forging machine forged the billet to ∅254mm. The deformation process was: -∅335-∅290-∅254. The forging speeds for the first pass were 6 m / min, 5.8 m / min, 5.6 m / min, 5.6 m / min, 5.6 m / min, and 5. The forging speeds for the first pass were 7 meters per minute, 5.5 meters per minute, 5.5 meters per minute, 5.3 meters per minute, 5.3 meters per minute, 5.3 meters per minute, and 5.3 meters per minute for the second pass, and 2.4 meters per minute, 2.3 meters per minute, 2.3 meters per minute, 2.3 meters per minute, 2.3 meters per minute, and 2.3 meters per minute for the third pass, with forging times of 6 minutes 52 seconds, 7 minutes 02 seconds, 6 minutes 58 seconds, 6 minutes 55 seconds, 7 minutes 12 seconds, and 7 minutes 06 seconds, respectively.

[0029] Step 7: Air cooling treatment of the forged billet.

[0030] The FXM-19 reactor shaft forgings were inspected. The flaw detection standard was ASTM A745, acceptance level QL2, and the grain size detection standard was ASTM E112, with a minimum grade of 5. The inspection results are shown in Table 1.

[0031] Table 1: Post-forging inspection results of six FXM-19 reactor shaft forgings in the implementation case.

[0032] Furnace ingot number Surface quality Flaw detection results Grain size after forging 9A22452 There are 3 surface cracks throughout the body, with a crack depth of 4mm. qualified Level 5.5 9A22448 There are 4 surface cracks throughout the body, with a crack depth of 3mm. qualified Level 6 9A22451 There are two surface cracks throughout the body, with a crack depth of 3mm. qualified Level 6.5 9A22446 Multiple surface cracks throughout the body, with a crack depth of 5mm. qualified Level 6 9A22447 There is one surface crack throughout the entire body, with a crack depth of 2mm. qualified Level 6 9A22453 There are two surface cracks throughout the body, with a crack depth of 3mm. qualified Level 6.5 .

Claims

1. A forging process for a FXM-19 reactor shaft forging, characterized by: The forging process is carried out according to the following process: Step 1), surface finishing treatment is carried out on the electroslag ingot, and the finishing requirements are as follows: the surface of the electroslag ingot is polished, and the visible defects such as surface cracks, pores, pits, residues and scabs are cleaned; if there are slag grooves, joint marks or notch marks on the surface, they need to be polished clean; the cleaning ratio of height, width and length is 1:6:10; Step 2), the electroslag ingot after finishing is heated, and the heating process curve is as follows: 4 hours of heat preservation at 350-400℃, then heating to 1220℃ at a temperature rising rate of 80℃ per hour, heat preservation for 6 hours; the heating furnace requires a distance of not more than 20 meters from the precision forging machine; after heating is completed, the electroslag ingot is quickly taken out of the furnace for forging; Step 3), the first forging is carried out by using a 1800-ton radial precision forging machine; before forging the product, other products are forged to ensure that the feeding track of the precision forging machine, the clamping jaw of the manipulator and the hammer head are in a hot state; the forging frequency of the precision forging machine is set to 180 times per minute; the R280 hammer head is selected; the final forging temperature is greater than or equal to 960℃; the temperature is measured by using the Oupusi temperature gun; if the temperature of the workpiece is lower than 960℃, it is immediately returned to the furnace for heating; the forged blank is straightened by using the oil press; the bending degree is not more than 3mm per meter; the blank is air cooled to room temperature; Step 4), the blank is treated by using a lathe to peel off the skin, and the surface cracks are peeled off clean; the steps are smoothly transitioned; Step 5), one or two heating furnaces are selected to heat the blank after peeling; the heating process curve is as follows: 3 hours of heat preservation at 350-400℃, then heating to 1220℃ at a temperature rising rate of 80℃ per hour, heat preservation for 5 hours; the heating furnace requires a distance of not more than 20 meters from the precision forging machine; after heating is completed, the blank is quickly taken out of the furnace for forging; Step 6), the second forging is carried out by using a 1800-ton radial precision forging machine; before forging the product, other products are forged to ensure that the feeding track of the precision forging machine, the clamping jaw of the manipulator and the hammer head are in a hot state; the forging frequency of the precision forging machine is set to 180 times per minute; the R180 hammer head is selected; Step 7), the blank after forging is air cooled.

2. A process for forging of a FXM-19 reactor shaft forging as claimed in claim 1, wherein: In step 3, in order to avoid cracks on the surface of the forged piece as much as possible during the first forging, the ingot tail end of the electroslag ingot is forged to the intersection of the precision forging machine in the first heating, and the forging is carried out for 3 passes; the first pass is 30mm, and the remaining passes are 40-50mm; the intersection inclined table is divided into 3 steps; the end of the ingot is forged for 1 pass, and the hammering amount is 30mm; after the first heating, the blank is returned to the furnace for heating, and the temperature is kept at 1220℃ for 2 hours; the blank is forged to the specified diameter in the process; the hammering amount of each pass is 40-50mm; the length of the forged blank is controlled within the range of the effective heating length of the heating furnace minus 200-300mm, so that the blank can be loaded into the heating furnace during the second forging, and the time for the second forging is controlled within 8 minutes.

3. A forging process for a FXM-19 reactor shaft forging as claimed in claim 1, wherein: In step 5), in order to ensure high initial forging temperature of the forged piece during secondary forging, if one heating furnace is selected to heat the peeled blank, the previous blank is taken out for forging, and the next blank is taken out for forging after 1 hour of heat preservation; if two heating furnaces are selected to heat the peeled blank, the blanks in the two heating furnaces are taken out for forging in turns.

4. A forging process for a FXM-19 reactor shaft forging as claimed in claim 1, wherein: In step 6), in order to ensure completion of one-time forging in secondary forging, the length of the blank after the first forging is controlled within the effective heating length of the heating furnace minus 200-300 mm, in order to ensure completion of one-time forging in secondary forging and the quality of the forged piece, the secondary forging is controlled to be completed within 8 minutes of 2-3 passes of the precision forging machine, the forging speed of the previous pass is greater than 4 meters per minute, the forging speed of the last pass is 2-3 meters per minute, and the hammering amount of each pass is 30-50 mm.