CN-116117065-B - Forging method for improving grain size of austenitic stainless steel strip nozzle pipeline

CN116117065BCN 116117065 BCN116117065 BCN 116117065BCN-116117065-B

Abstract

The invention relates to a forging method for improving grain size of austenitic stainless steel strip pipe nozzle pipes, which comprises the steps of discharging electroslag ingots with diameters phi of 1000-1200 mm after heat preservation for 9-12 hours at 1180+/-10 ℃ to form billets through integral drawing, discharging the billets after furnace return to 1200+/-10 ℃ and fully preserving heat for 7-8 hours, discharging the billets with flat upsetting caps for upsetting, discharging the flat billets after flat billets are fully preserving heat for 3-4 hours at 1180+/-10 ℃, discharging the billets after drawing both ends and dislocating pipe nozzles to form billets after dislocating pipe nozzles, discharging the billets after dislocating pipe nozzles after heat preservation for 3-4 hours at 1150-1180+/-10 ℃, and discharging the billets after finishing by fire. By adopting the forging method of the pipe with the nozzle finished by four firings, the grain size of the forging body is more than or equal to 4 grades, and the overall grain size of the austenitic stainless steel pipe with the nozzle is greatly improved.

Inventors

XIONG WU
WU XIANLONG
YU HAIJUAN
LIN CHEN
LU QIAO
XIAO HAISHENG
DUAN LAISHAN
Sun Saigang
LIU XIUHUAN
BAI YU

Assignees

武汉重工铸锻有限责任公司

Dates

Publication Date: 20260505
Application Date: 20230209

Claims (2)

1. A forging method for improving grain size of austenitic stainless steel strip nozzle pipeline is characterized by comprising the following steps: 1) The electroslag ingot with the diameter phi of 1000-1200 mm is discharged from the furnace after heat preservation for 9-12 hours at 1180+/-10 ℃ and integrally drawn to form a blank; 2) After the blank is returned to the furnace, the furnace temperature is raised to 1200+/-10 ℃ and is fully kept for 7-8 hours, then the blank is discharged and is provided with a flat upsetting cap for upsetting, and a flat square blank is formed by drawing a flat square and stamping; 3) Fully preserving heat of the flat square blank for 3-4 hours at 1180+/-10 ℃, discharging, drawing two ends and dislocating the pipe mouth to form a blank with dislocated pipe mouth, and reserving deformation of the blank with dislocated pipe mouth; 4) The blank after the nozzle is shifted is discharged after being insulated for 3-4 hours at the temperature of 1150-1180+/-10 ℃, the discharging is finished by one fire, the finishing is finished sequentially from the bottom end to the clamp handle end, the bottom round rod part is firstly formed, the nozzle is then formed, the nozzle part must respectively press the reserved deformation in the height and thickness directions by one anvil large pressing amount to be close to the process size, the small deformation is finished and formed, and the round rod part at the clamp handle end is then formed after the nozzle large pressing amount is finished to obtain the forge piece; placing a blank in an upsetting drain pan, placing a flat upsetting cap on the blank for upsetting, and then pulling a flat anvil to form a flat blank, wherein the cross section height of the flat blank=the process nozzle height+the deformation reserved by the last fire+the shrinkage, the shrinkage is 150-200 mm, and the cross section thickness of the flat blank=the process nozzle thickness+the deformation reserved by the last fire+150-200 mm; in the step 3), the calculation method of the final fire reserved deformation of the nozzle and the rod part is that the deformation of the flat square nozzle= (area before finishing-area after finishing)/(area before finishing)/(deformation of the round rod part= (diameter before finishing-diameter after finishing)/(diameter before finishing); In the step 4), if the total length of the forging piece is more than or equal to 3m, the heating temperature of the last fire is 1180+/-10 ℃, if the total length of the forging piece is less than 3m, the heating temperature of the last fire is 1150-1180 ℃, the temperature of the final forging surface of the last fire is controlled to be 800-900 ℃, and the deformation of the last fire is controlled to be 30% -45%; the upsetting diameter is required to ensure that the forging ratio of the nozzle is 6-10.
2. The forging method for improving the grain size of the austenitic stainless steel strip nozzle pipeline is characterized in that the concrete process of the step 1) comprises the steps of sawing off two ends of an electroslag ingot with the diameter phi of 1000-1200 mm respectively, keeping the temperature of the electroslag ingot at 300-350 ℃ for 4-5 hours, heating to 850+/-10 ℃ at the heating rate of less than or equal to 50 ℃ per hour for 5-7 hours, heating to 1180+/-10 ℃ at the heating rate of less than or equal to 60 ℃ per hour for 9-12 hours, discharging, clamping the bottom of the electroslag ingot on a press with the tonnage of 8000t or more, stepping on a body pressing clamp of the electroslag ingot at the riser end of the electroslag ingot by using a flat anvil, turning over the electroslag ingot after the clamping, and integrally drawing out the body of 10-30 mm to form a blank.

Description

Forging method for improving grain size of austenitic stainless steel strip nozzle pipeline Technical Field The invention belongs to the technical field of forging, and particularly relates to a forging method for improving grain size of austenitic stainless steel strip nozzle pipelines. Background The stainless steel pipeline is one of important parts of a nuclear power station, is an austenitic stainless steel forge piece, has extremely high technical requirements, and generally requires that the austenitic grain size is equal to or larger than level 4 as a whole, and has extremely high forging difficulty. The middle of the pipeline is provided with a nozzle except for the round rod parts at the two ends, the nozzle part is a large-section flat square, and the grain size control difficulty is larger than that of the round rod parts at the two ends. Because austenitic stainless steel is in the unorganized transformation in heating and cooling process, can only refine the crystal grain through forging deformation, and the nozzle cross section is larger, and the nozzle needs to be heated with the furnace by multiple fires, so that the whole grain size of the nozzle is harder to meet the requirement. Disclosure of Invention The invention aims to solve the technical problem that the grain size of an austenitic stainless steel strip nozzle pipeline is difficult to be larger than or equal to 4 levels integrally, and provides a forging method for improving the grain size of the austenitic stainless steel strip nozzle pipeline. The invention achieves the following purposes: the invention comprises heating austenitic stainless steel electroslag ingot at different temperatures and forging forming with four fires, and the specific process is as follows: 1) The electroslag ingot with the diameter phi of 1000-1200 mm is discharged from the furnace after heat preservation for 9-12 hours at 1180+/-10 ℃ and integrally drawn to form a blank; 2) After the blank is returned to the furnace, the furnace temperature is raised to 1200+/-10 ℃ and is fully kept for 7-8 hours, then the blank is discharged and is provided with a flat upsetting cap for upsetting, and a flat square blank is formed by drawing a flat square and stamping; 3) Fully preserving heat of the flat square blank for 3-4 hours at 1180+/-10 ℃, discharging, drawing two ends and dislocating the pipe mouth to form a blank with dislocated pipe mouth, and reserving deformation of the blank with dislocated pipe mouth; 4) And (3) discharging the blank after the nozzle is shifted by mistake after the blank is insulated for 3-4 hours at 1150-1180+/-10 ℃, finishing by one fire after discharging, finishing sequentially finishing from the bottom end to the clamp handle end, forming the bottom round rod part firstly, forming the nozzle again, pressing the reserved deformation amounts in the height and thickness directions to be close to the process size by one anvil large pressing amount respectively by the nozzle part, finishing and forming by small deformation amount, and forming the round rod part of the clamp handle end after finishing the nozzle large pressing amount to obtain the forge piece. The method comprises the specific steps of firstly, sawing off both ends of an electroslag ingot with the diameter phi of 1000-1200 mm for 40-50 mm, after the electroslag ingot is kept at 300-350 ℃ for 4-5 hours, heating to 850+/-10 ℃ according to the heating rate of less than or equal to 50 ℃ per hour, keeping the temperature for 5-7 hours, heating to 1180+/-10 ℃ according to the heating rate of less than or equal to 60 ℃ per hour, keeping the temperature for 9-12 hours, discharging, clamping the bottom of the electroslag ingot on a press with the tonnage of 8000t or more, stepping a body pressing clamp handle on the riser end of the electroslag ingot by using a flat anvil, turning the pressed electroslag ingot around, and integrally drawing out a single side of the ingot body by 10-30 mm to form a blank. Further, the concrete process of the step 2) is that the blank is placed in an upsetting drain pan, a flat upsetting cap is placed on the blank for upsetting, a flat anvil is used for drawing a flat square blank, the section height of the flat square is equal to the process nozzle height, the reserved deformation of the last fire and the pulling and shrinking amount, the pulling and shrinking amount is 150-200 mm, and the section thickness of the flat square is equal to the process nozzle thickness, the reserved deformation of the last fire and the pulling and shrinking amount is equal to 150-200 mm. Further, the upset diameter is required to ensure a forging ratio of 6 to 10 for the nozzle. Further, in the step 3), the final fire reserve deformation amount of the nozzle and the stem is calculated by the deformation amount of the flat square nozzle= (area before finishing-area after finishing)/(area before finishing), and the deformation amount of the circular stem= (diameter befo