CN110614289A - Slow cooling method for large-scale extruded thick-wall blank made of Ni-Cu alloy heat-resistant steel - Google Patents
Slow cooling method for large-scale extruded thick-wall blank made of Ni-Cu alloy heat-resistant steel Download PDFInfo
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- CN110614289A CN110614289A CN201910940033.7A CN201910940033A CN110614289A CN 110614289 A CN110614289 A CN 110614289A CN 201910940033 A CN201910940033 A CN 201910940033A CN 110614289 A CN110614289 A CN 110614289A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C29/00—Cooling or heating work or parts of the extrusion press; Gas treatment of work
- B21C29/003—Cooling or heating of work
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Abstract
The invention discloses a slow cooling method for a large-scale extruded thick-wall blank made of Ni-Cu alloy heat-resistant steel, which comprises the following steps: charging blanks into a furnace, waiting for the blanks, preserving heat, cooling the furnace, and discharging from the furnace for air cooling; wherein, the wall thickness of the blank is 200 mm-500 mm, the blank is cooled in air to more than 500 ℃ and then is put into a furnace, the temperature of the material waiting is 350-400 ℃, and the temperature of the material waiting is kept for 2.5-5 hours; after the temperature of the furnace is raised, the heat preservation temperature is 640-660 ℃, the heat preservation time is 30-50 hours, the furnace cooling speed is less than or equal to 40 ℃/h, and the tapping temperature is less than or equal to 400 ℃. The invention solves the defects of high surface hardness, stress cracking and white point organization caused by slowly cooling various blank blanks of low alloy and high alloy from a high-temperature thermal state to room temperature, and avoids the problem that the blank surface is too hard or scrapped when the blank is cooled from the high temperature to the room temperature.
Description
Technical Field
The invention relates to a hot working method suitable for large-scale extrusion forming, in particular to a slow cooling method for a large-scale extrusion thick-wall blank of Ni-Cu alloy heat-resistant steel.
Background
The extrusion is successfully carried out once in 7 months in 2009, and the domestic first set of 3.6 ten thousand tons of vertical extruders and 1.5 ten thousand tons of vertical blank making machines are built, which marks that the high-end forming and manufacturing technology in China obtains a major breakthrough and breaks through the technical monopoly in the field of blank making and extrusion of large-sized workpieces abroad.
The steel ingot is used as the raw material for extrusion, and the processes of upsetting and perforating are carried out on a 150MN blank making press to provide the extrusion blank for a 360MN extruder, and the practice proves that: the quality of the pierced blank directly determines the surface quality of the extruded tube. The early-stage extrusion process generally adopts a 'blank making-extrusion' mode to form a blank steel pipe at one time, and the formed pipe blank has the phenomena of large wall thickness difference and serious surface quality defect.
However, for various blanks made of low alloy and high alloy, the defects of high surface hardness, stress cracking and white point texture are generated when the blanks are slowly cooled from a high-temperature thermal state to room temperature, and the blanks are cooled from the high temperature to the room temperature to cause the problems of over-hard surfaces or scrappage of the blanks.
Disclosure of Invention
The invention aims to provide a slow cooling method for a large-scale extruded thick-wall blank made of Ni-Cu alloy heat-resistant steel, which solves the problems of high surface hardness, stress cracking and white-point tissue defects caused by slow cooling of various blank making blanks of low alloy and high alloy from a high-temperature thermal state to room temperature, and avoids the problem that the blank surface is too hard or scrapped when the blank is cooled from the high temperature to the room temperature.
The technical scheme is as follows:
a slow cooling method for a large-scale extruded thick-wall blank made of Ni-Cu alloy heat-resistant steel comprises the following steps: charging blanks into a furnace, waiting for the blanks, preserving heat, cooling the furnace, and discharging from the furnace for air cooling; wherein, the wall thickness of the blank is 200 mm-500 mm, the blank is cooled in air to more than 500 ℃ and then is put into a furnace, the temperature of the material waiting is 350-400 ℃, and the temperature of the material waiting is kept for 2.5-5 hours; after the temperature of the furnace is raised, the heat preservation temperature is 640-660 ℃, the heat preservation time is 30-50 hours, the furnace cooling speed is less than or equal to 40 ℃/h, and the tapping temperature is less than or equal to 400 ℃.
Further, the billet material is WB36 billet containing Ni and Cu low alloy or 15Ni1MnMoCu billet.
The invention has the technical effects that:
1. the invention solves the problems of high surface hardness, stress cracking, high white surface hardness and difficult processing of various blank making blanks of low alloy and high alloy from a high-temperature thermal state to room temperature, and avoids the problem of over-hard or scrapped blank surface when the blank is cooled from high temperature to room temperature.
By the slow cooling method, the internal stress of the blank is eliminated, the surface hardness is reduced, the internal structure of the blank is optimized, the hydrogen diffusion effect is achieved, and the stress cracking and white point structure limitation are avoided.
2. The economic benefit and the social benefit are high.
The quality of the surface of the tube blank extruded after the blank slow cooling machine is adopted for heating is greatly improved, and the surface cracks and the wall thickness difference of more than 10mm are reduced from 70 percent to 20 percent. The raw material loss cost, energy cost, labor cost and other auxiliary costs caused by the wall thickness difference and the grinding of the tube blank are about 30.08 ten thousand yuan/year. Before the blank slow cooling machine is not used for heating, the scrapped tube blank accounts for 1.3 percent (year) of surface cracks and wall thickness differences, after the blank slow cooling is adopted, the surface cracks and the wall thickness differences caused by blank-free reasons directly generate tube blank scrapping, and the economic loss of the direct year is recovered as follows: 2760 × 1.3% × 6550 yuan × 8 tons, so the total saving value of the extruded tube blank after the blank is processed by the slow cooling machine is about 24.89 ten thousand yuan. Aiming at a novel blank extrusion process, a set of large thick-wall blank slow cooling process which accords with the blank extrusion of a 150MN blank-making press is compiled, a solid foundation is laid for the extrusion of the novel technology to break through the quality problem of the extruded blank, and support is provided for the innovation of the extrusion mode of the large-diameter seamless steel pipe.
Drawings
FIG. 1 is a drawing of the slow cooling process of WB36 and 15Ni1MnMoCu blanks containing Ni and Cu alloy in the invention.
Detailed Description
The following description sufficiently illustrates specific embodiments of the invention to enable those skilled in the art to practice and reproduce it.
The slow cooling method for the large-scale extruded thick-wall blank made of the Ni-Cu alloy heat-resistant steel comprises the following steps: charging blanks into a furnace, waiting for the blanks, preserving heat, cooling the furnace, and discharging from the furnace for air cooling; wherein, the wall thickness of the blank is 200 mm-500 mm, the blank is cooled in air to more than 500 ℃ and then is put into a furnace, the temperature of the material waiting is 350-400 ℃, and the temperature of the material waiting is kept for 2.5-5 hours; the temperature of the furnace is raised under full power, the heat preservation temperature is 640-660 ℃, the heat preservation time is 30-50 hours, the furnace cooling speed is less than or equal to 40 ℃/h, and the tapping temperature is less than or equal to 400 ℃.
As shown in FIG. 1, it is a slow cooling process diagram of WB36 and 15Ni1MnMoCu blanks containing Ni and Cu alloy in the invention.
In order to improve the surface quality of the extruded tube blank, the extrusion procedure adopts a mode of blank making, machining and extrusion; the process flow is as follows: steel ingot blank making, perforating, heating, extruding and tube blank annealing.
The method comprises the steps of cooling a high-temperature blank manufactured by a 150MN blank manufacturing machine to room temperature to prepare for subsequent machining, wherein the purpose of slow cooling of the blank is to cool the high-temperature blank to the room temperature, ensure the hardness of the blank to meet the requirement of subsequent machining, and simultaneously prevent the blank from generating cracks due to overlarge internal stress and prevent the blank from generating tissue defects such as white spots and the like in the blank. Secondly, the blank making is carried out on the first 150 blank making machines in China, and the forming method is different from the traditional forging and has the characteristics of quick forming and large deformation. In terms of mechanism, because the components and the forming method of the blank are different from the traditional forged piece, the components determine different tissues and tissues, the deformation capability is different, and the internal stress and the hydrogen diffusion capability of the blank after deformation are different; the different deformation modes and the different deformation energy inside the blank result in different recrystallization temperature and recovery time.
The method aims at large-scale extrusion thick-wall blank, the forming mode of the workpiece is different from common forging, and the method is independently developed by breaking through foreign technology blockages for the first time in our factory. Because of different forming methods, the annealing slow cooling method is naturally different from the dehydrogenation annealing after the common forging. The slow cooling method comprises the following steps: comprises charging blank, waiting at low temperature, keeping temperature, cooling in furnace, and air cooling; the wall thickness of the blank is 200 mm-500 mm, the blank is cooled in air to more than 500 ℃ and then is put into a furnace, and the temperature is kept for 2.5-5 hours when the temperature of the blank is 350-400 ℃; the temperature of the furnace is raised under full power, the heat preservation temperature is 640-660 ℃, the heat preservation time is 30-50 hours, the furnace cooling speed is less than or equal to 40 ℃/h, and the tapping temperature is less than or equal to 400 ℃.
The Ni and Cu alloy materials are produced in small batches, and three furnaces are selected for test verification, and the details are shown in table 1.
TABLE 1 batch wall thickness selection and Process execution
And (4) after the blank is discharged from the furnace, detecting white spots, wherein no white spots are generated. The surface hardness of the blank is detected before the blank is processed, and the WB36 hardness is 160-170 HB. On the other hand, the blank machining process is tracked and observed, and the metal cutting is normal and no crack is generated in the blank machining process. For further examination and verification, the high-alloy tube blank and the low-alloy tube blank are respectively subjected to physical and chemical detection, the detection items comprise macrostructure, metallographic phase test and mechanical property test, the test meets the technical index requirements, and the details are shown in tables 2 and 3.
TABLE 2 macrostructure test results
TABLE 3 Performance and high magnification tissue test results
According to the small-batch trial production condition: after the blank is slowly cooled according to the process, the blank has moderate hardness and is suitable for machining; the blank and the tube blank have no cracks and white spots; the performance of the subsequent tube blank is qualified. Further verifies the rationality of the calculation principle of the slow cooling temperature and the heat preservation time. Practice proves that the method can meet the technical requirements, can achieve the expected effect, and ensures the product quality.
The terminology used herein is for the purpose of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.
Claims (2)
1. A slow cooling method for a large-scale extrusion thick-wall blank made of Ni-Cu alloy heat-resistant steel is characterized by comprising the following steps: charging blanks into a furnace, waiting for the blanks, preserving heat, cooling the furnace, and discharging from the furnace for air cooling; wherein, the wall thickness of the blank is 200 mm-500 mm, the blank is cooled in air to more than 500 ℃ and then is put into a furnace, the temperature of the material waiting is 350-400 ℃, and the temperature of the material waiting is kept for 2.5-5 hours; after the temperature of the furnace is raised, the heat preservation temperature is 640-660 ℃, the heat preservation time is 30-50 hours, the furnace cooling speed is less than or equal to 40 ℃/h, and the tapping temperature is less than or equal to 400 ℃.
2. The slow cooling method for large extruded thick-walled blank of Ni-Cu alloy containing heat-resistant steel as claimed in claim 1, wherein the blank material is WB36 blank containing Ni and Cu low alloy or 15Ni1MnMoCu blank.
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| CN201910940033.7A CN110614289A (en) | 2019-09-30 | 2019-09-30 | Slow cooling method for large-scale extruded thick-wall blank made of Ni-Cu alloy heat-resistant steel |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5456030A (en) * | 1977-10-12 | 1979-05-04 | Sumitomo Metal Ind | Steel lump cooling method |
| JP2009030131A (en) * | 2007-07-30 | 2009-02-12 | Seiken Ryu | Method for improving surface hardness of martensitic stainless steel |
| CN106180245A (en) * | 2016-07-18 | 2016-12-07 | 内蒙古北方重工业集团有限公司 | A kind of slow cooling method containing Ni, Cu alloy large-size extruding heavy wall steps of manufacturing blanks |
| CN106834946A (en) * | 2017-02-27 | 2017-06-13 | 江阴兴澄特种钢铁有限公司 | Big thickness protects Testing Tensile Strength at Elevated Temperature steel plate SA299GrB and preparation method thereof |
| CN108998650A (en) * | 2018-07-10 | 2018-12-14 | 内蒙古北方重工业集团有限公司 | 630 DEG C of extra-supercritical unit G115 method for manufacturing large-diameter thick-wall seamless steel pipe |
-
2019
- 2019-09-30 CN CN201910940033.7A patent/CN110614289A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5456030A (en) * | 1977-10-12 | 1979-05-04 | Sumitomo Metal Ind | Steel lump cooling method |
| JP2009030131A (en) * | 2007-07-30 | 2009-02-12 | Seiken Ryu | Method for improving surface hardness of martensitic stainless steel |
| CN106180245A (en) * | 2016-07-18 | 2016-12-07 | 内蒙古北方重工业集团有限公司 | A kind of slow cooling method containing Ni, Cu alloy large-size extruding heavy wall steps of manufacturing blanks |
| CN106834946A (en) * | 2017-02-27 | 2017-06-13 | 江阴兴澄特种钢铁有限公司 | Big thickness protects Testing Tensile Strength at Elevated Temperature steel plate SA299GrB and preparation method thereof |
| CN108998650A (en) * | 2018-07-10 | 2018-12-14 | 内蒙古北方重工业集团有限公司 | 630 DEG C of extra-supercritical unit G115 method for manufacturing large-diameter thick-wall seamless steel pipe |
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