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CN-121988992-A - Preparation method suitable for hard jacket of refractory high-temperature alloy and hard jacket

CN121988992ACN 121988992 ACN121988992 ACN 121988992ACN-121988992-A

Abstract

The invention discloses a preparation method suitable for a hard jacket of a difficult-to-deform superalloy and the hard jacket, which relate to the technical field of metal material pressure processing and aim to solve the problems of high rolling forming difficulty, easiness in cracking and low yield of the difficult-to-deform superalloy, and the preparation method comprises the following steps of S1, preprocessing a blank, performing surface turning, end precision machining and polishing on the difficult-to-deform superalloy rolled blank to enable two ends to be exposed by 5-12 mm ends and the roughness Ra to be less than or equal to 1.6 mu m; S2, preparing a hard sheath with the wall thickness of 5-12 mm, tightly wrapping blanks, folding two ends of the sheath to form tight occlusion with ends, S3, welding a blank assembly and an additional end block into a whole by friction welding, S4, heating to 1050-1180 ℃ and preserving heat for 2-4 hours, carrying out multi-pass rolling with the total deformation of 50% -70%, and S5, machining and removing the sheath and the end block to obtain finished products.

Inventors

  • SONG BIN
  • ZHAN XIAOHONG
  • FU RENLI
  • Tian Qianren
  • WANG YANLIANG

Assignees

  • 南京航空航天大学

Dates

Publication Date
20260508
Application Date
20260326

Claims (7)

  1. 1. The preparation method of the hard alloy sheath suitable for the difficult-to-deform high temperature alloy is characterized by comprising the following steps of: step S1, blank pretreatment, namely performing surface turning on a high-temperature alloy rolled blank difficult to deform, removing oxide scales and surface defects, and performing precision machining on end surfaces of two ends of the blank to expose the ends with the height of 5-12 mm at the two ends of the blank; Polishing and descaling the surface of the end head to ensure that the surface roughness R a is less than or equal to 1.6 mu m; S2, preparing and assembling a hard jacket, namely preparing the hard jacket with the wall thickness of 5-12 mm and the wall thickness uniformity tolerance of +/-0.5 mm by adopting pure iron, low carbon steel or easy-deformation iron base and nickel base alloy with the thermal expansion coefficients similar to those of difficult-deformation high-temperature alloy blanks; tightly wrapping the hard sheath on the outer surface of the blank processed in the step S1, inwards folding two ends of the sheath, and tightly pressing the sheath on the exposed ends at two ends of the blank, so that the inner surface of the folded part of the sheath and the side surface and the end surface edge of the exposed end of the blank form tight mechanical engagement and coverage; s3, end welding, namely performing friction welding on two ends of the blank assembly subjected to the sheath treatment in the step S2 and an additional end block made of carbon steel, alloy steel, pure iron or a combination material thereof by adopting a friction welding process to form an integrated rolling blank; Wherein the upsetting pressure of friction welding is 250-400 MPa, the friction time is 10-40 s, and the initial rotating speed is 500-1500 r/min; S4, heating and rolling, namely heating the welded integrated rolled blank to 1050-1180 ℃, preserving heat for 2-4 hours, and then carrying out multi-pass rolling deformation with the total deformation of 50-70%; s5, after finishing rolling, removing the external hard sheath and the additional end block in a machining mode to obtain a difficult-to-deform high-temperature alloy bar or profile with a target size; the difficult-to-deform superalloy includes, but is not limited to, GH4720Li, GH4738 superalloy.
  2. 2. The method for preparing a hard jacket of a refractory superalloy according to claim 1, wherein in step S1, the exposed ends at both ends of the blank are identical in height to the wall thickness of the subsequent hard jacket.
  3. 3. The method for preparing the hard jacket suitable for the refractory superalloy according to claim 1, wherein in the step S2, the two ends of the jacket are folded and then pre-fixed by mechanical pressing or spot welding.
  4. 4. The method for preparing the hard alloy sheath suitable for the difficult-to-deform superalloy is characterized in that the mechanical pressurization is that an annular clamp is adopted to clamp a folding area, the pressurization pressure is 30-80 MPa, and the dwell time is 5-15 s; The spot welding is to evenly distribute 4-8 point-shaped welding seams along the circumferential direction, the distance between adjacent welding points is 30-50 mm, the diameter of each welding point is 5-8 mm, and the spot welding position is located on the outer side of the folded wrap end part so as to avoid interference to the subsequent friction welding area.
  5. 5. The method for preparing the hard refractory alloy sheath according to claim 1, wherein in the step 2, the two ends of the sheath are folded inwards in one of a right-angle fold, an inclined plane fold or an arc transition fold; The end face of the sheath formed after folding is basically flush with the end face of the exposed end of the blank or slightly pressed in, and the pressing-in amount is 0.1-0.5 mm.
  6. 6. The method for preparing the hard jacket suitable for the refractory superalloy is characterized in that in the step S1, exposed ends processed at two ends of a blank are processed with chamfers or fillets on the end faces, and transition fillets of 1-3 mm are arranged at the joint of the ends and the jacket so as to facilitate folding and bonding of the ends of the jacket and reduce stress concentration.
  7. 7. A hard jacket suitable for refractory superalloy is characterized by being applied to the preparation method as claimed in any one of the claims 1-6; the sheath is of a cylindrical structure which is suitable for a difficult-to-deform high-temperature alloy rolled blank, and is made of pure iron, low-carbon steel or easy-to-deform iron base and nickel base alloy which have similar thermal expansion coefficients with the difficult-to-deform high-temperature alloy rolled blank; The wall thickness of the sheath is 5-12 mm, and the uniformity tolerance of the wall thickness is controlled within +/-0.5 mm; the fit clearance between the inner diameter of the sheath and the outer diameter of the pretreated blank is 0.1-0.3 mm, and the length of the sheath is 10-24 mm longer than that of the pretreated blank; the two ends of the sheath can be folded inwards, the folded sheath can form tight mechanical engagement with the ends of the blank, the folding angle is 90-120 degrees, and the width of the folding edge is 3-8 mm.

Description

Preparation method suitable for hard jacket of refractory high-temperature alloy and hard jacket Technical Field The invention relates to the field of metal material pressure processing, in particular to a preparation method suitable for a hard jacket of a high-temperature alloy difficult to deform and the hard jacket. Background The iron-based, nickel-based and cobalt-based refractory superalloy is widely applied to the preparation of key hot end components in the fields of aerospace, energy and the like by virtue of excellent high-temperature strength, creep resistance and corrosion resistance. However, the alloy has obvious inherent defects in hot working, particularly in the roll forming process, such as extremely high deformation resistance, for example, GH4720Li and GH4738 nickel-based difficult-to-deform high-temperature alloy, the deformation resistance at 1050-1180 ℃ can reach 800-1200 MPa (refer to GB/T14992-2005 related study on classification and brand of high-temperature alloy and intermetallic compound high-temperature materials and metal school report 2018), far exceeds that of common steel, the plastic working window is extremely narrow, cracks can be easily generated only at 40-80 ℃, the temperature deviation exceeds +/-20 ℃, and the thermal deformation activation energy can reach 850-990kJ.mol -1 (according to the study on the thermal deformation behavior and dynamic recrystallization characteristics of coarse-grain GH4720Li alloy in the period 1 of the rare metal materials and engineering 2020), the thermal working difficulty is extremely high, the surface and end defects are easy to generate, and the high-quality production of the alloy is restricted. In the prior art, the sheath rolling process is a main means for relieving the problems, but the traditional soft sheath (such as high-temperature asbestos) has obvious defects, firstly has low strength, is easy to break and lose heat preservation effect when the rolling deformation reaches 25% -35% by combining with industrial engineering practice data (refer to high-temperature alloy hot working process specifications), is difficult to improve alloy deformation behavior, secondly has the advantages that the sheath is not tightly combined with a blank, a gap of 0.5% -1.0 mm exists, the heat conduction efficiency is greatly reduced, the temperature difference between the center and the surface of the blank in the rolling process can reach 120-180 ℃, the temperature drop rate exceeds 5 ℃ per minute (refer to industrial engineering practice data, refer to high-temperature alloy processing technology report of Shanghai Kai metallurgical products Co., ltd.), the blank deformation is uneven, thirdly has poor end sealing performance, the end heat dissipation speed of the blank is 3-4 times faster than the middle part, the end part and the surface are easy to generate, the rolling yield is only 30% -55% (according to the research on the current situation that the cast-forge refractory turbine for a wheel disc and the crack is easy to be developed) and the blank is greatly scraped due to the defect of the high-temperature requirement of the cast turbine alloy is researched and formed in the rolling process. In summary, the existing sheath rolling process cannot effectively solve the problems of temperature drop, uneven deformation and cracks in the rolling forming of the difficult-to-deform superalloy, and severely restricts the rolling forming of the superalloy with high quality and high efficiency, so a preparation method suitable for the difficult-to-deform superalloy hard sheath and the hard sheath are provided for solving the problems. Disclosure of Invention The invention overcomes the defects of the prior art and provides a preparation method suitable for a hard jacket of a high-temperature alloy which is difficult to deform and the hard jacket. In order to achieve the aim, the technical scheme adopted by the invention is that the preparation method suitable for the hard alloy sheath difficult to deform comprises the following steps: step S1, blank pretreatment, namely performing surface turning on a high-temperature alloy rolled blank difficult to deform, removing oxide scales and surface defects, and performing precision machining on end surfaces of two ends of the blank to expose the ends with the height of 5-12 mm at the two ends of the blank; Polishing and descaling the surface of the end head to ensure that the surface roughness R a is less than or equal to 1.6 mu m; S2, preparing and assembling a hard jacket, namely preparing the hard jacket with the wall thickness of 5-12 mm and the wall thickness uniformity tolerance of +/-0.5 mm by adopting pure iron, low carbon steel or easy-deformation iron base and nickel base alloy with the thermal expansion coefficients similar to those of difficult-deformation high-temperature alloy blanks; tightly wrapping the hard sheath on the outer surface of the blank processed in the step S1, inwards fo