CN-121988633-A - Forming method of super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe

CN121988633ACN 121988633 ACN121988633 ACN 121988633ACN-121988633-A

Abstract

A method for forming super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe belongs to the technical field of metal corrugated pipes. The invention aims to solve the problems that the prior traditional multilayer corrugated pipe forming process can cause serious uneven wall thickness, cracking and layering defect among pipe blanks due to uncooled deformation due to large deformation degree, or can cause poor performance of a welding line area of the nickel-titanium-based shape memory alloy and early failure due to adoption of a welding process. The method comprises the steps of preparing a multi-layer tube blank structure, preparing the tube blank before forming, and forming. The invention is used for forming the super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe.

Inventors

ZHANG YANQIU
Yu Chaona
HE XIAOFENG
JIANG SHUYONG
FU WENHAO
GUO KAIRUI
YU WEIQIANG
LIU JINLEI

Assignees

哈尔滨工程大学

Dates

Publication Date: 20260508
Application Date: 20260226

Claims (10)

1. The forming method of the super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe is characterized by comprising the following steps of: 1. Preparing a multi-layer tube blank structure: nesting a plurality of super-elastic nickel-titanium-based shape memory alloy tube blanks to obtain a multi-layer tube blank structure, and calculating the inner diameter size of the innermost tube blank in the multi-layer tube blank structure according to the minimum inner diameter size of the innermost tube in the designed super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated tube; 2. Preparation before forming: Respectively welding a super-elastic nickel-titanium-based shape memory alloy circular plate at two ends of the multilayer tube blank structure to obtain an end-sealed multilayer tube blank structure, perforating the upper end of the end-sealed multilayer tube blank structure and communicating the upper end with an air inlet tube joint by adopting a welding method to obtain a tube blank to be expanded; 3. Shaping: and pre-bulging is carried out on the pipe blank to be bulged, then gas-solid compound bulging is carried out, the corrugated pipe after bulging is obtained, and the super-elastic nickel-titanium-based shape memory alloy circular plate and a section of wave crest adjacent to the super-elastic nickel-titanium-based shape memory alloy circular plate at the two ends of the corrugated pipe after bulging are removed, so that the super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe is obtained.
2. The method for forming the super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe according to claim 1, wherein the total thickness of the multilayer pipe blank structure in the first step is the same as the thickness of the super-elastic nickel-titanium-based shape memory alloy circular plate in the second step, the super-elastic nickel-titanium-based shape memory alloy pipe blank in the first step and the super-elastic nickel-titanium-based shape memory alloy circular plate in the second step are made of NiTi alloy, niTiNb alloy or NiTiFe alloy, and the grain size is 0.2-15 μm.
3. The method for forming the super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe according to claim 1 is characterized in that the heights of all pipe blanks in the multilayer pipe blank structure in the step one are the same, a gap of 0.1 mm-0.2 mm is arranged between adjacent pipe blanks in the multilayer pipe blank structure in the step one, the inner diameter size of the innermost pipe blank in the multilayer pipe blank structure in the step one is set to be D1, the minimum inner diameter size of the innermost pipe in the designed super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe is set to be D2, D1-D2=d, and D is 40% -50% of the difference between the outer diameters of peaks and valleys of the outermost pipe in the designed super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe.
4. The method for forming the super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe according to claim 1 is characterized in that the super-elastic nickel-titanium-based shape memory alloy pipe blank obtained in the first step is subjected to acid washing, and the acid washing is specifically carried out by mechanically pretreating ① by using water sand paper or sand blasting to obtain a mechanically pretreated pipe blank, ② immersing the mechanically pretreated pipe blank in a mixed solution of hydrofluoric acid and nitric acid for 2 min-15 min, wherein the addition amount of HF solution in the mixed solution of hydrofluoric acid and nitric acid is 30 mL/L-90 mL/L, the addition amount of HNO 3 solution is 300 mL/L-530 mL/L, the concentration of the HF solution is 40wt%, the concentration of HNO 3 solution is 68wt%, and after ③, washing is carried out by flowing cold water or warm water, and finally drying is carried out.
5. The method for forming a superelastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe according to claim 1, wherein the diameter of the nickel-titanium-based shape memory alloy circular plate in the second step is the same as the outer diameter of the outermost tube blank in the multi-layer tube blank structure.
6. The method for forming a super elastic nickel-titanium based shape memory alloy multi-layer corrugated pipe according to claim 1, wherein the material of the air inlet pipe joint in the second step is NiTi alloy, niTiNb alloy or NiTiFe alloy, and the wall thickness of the air inlet pipe joint in the second step is larger than the total thickness of the multi-layer pipe blank structure.
7. The method for forming the super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe according to claim 1, wherein the outer surfaces of adjacent pipe blanks in the multilayer pipe blank structure in the first step and the pipe blanks to be expanded in the second step are coated with a solder resist, and the solder resist is TiO 2 、Y 2 O 3 or BN.
8. The method for forming a superelastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe according to claim 1, wherein the pre-bulging in the third step is specifically performed according to the following steps: ① The method comprises the steps of placing a pipe blank to be expanded in a pre-expansion tool, wherein the pre-expansion tool consists of a pre-expansion die sleeve and a plurality of pre-expansion modules, the pre-expansion modules are arranged in the pre-expansion die sleeve, the pipe blank to be expanded is arranged in a cavity surrounded by the pre-expansion modules, the outer wall of the pipe blank to be expanded is attached to the minimum diameter of the cavity, and the pre-expansion die sleeve is a circular sleeve consisting of a semicircular upper die sleeve and a semicircular lower die sleeve; ② Heating the pre-bulging tool to 800-900 ℃, then introducing inert gas through an air inlet pipe at a pressure increasing rate of 0.01-0.02 MPa/min, and increasing the pressure to the pressure at the beginning of bulging When the tube blank starts to deform, the pressure is continuously increased until the minimum pressure for ensuring that the round angle is full is reached And at a pressure of Maintaining the pressure, and cooling to room temperature to obtain a pre-bulging piece; The said process Calculated from equation (1): (1) in the formula, The pressure is expressed as MPa when bulging starts, t 0 is the total thickness of the multi-layer tube blank structure in the first step, the unit is mm, and R is the radius of the outer wall of the outermost layer tube blank of the multi-layer tube blank structure in the first step, and the unit is mm; the yield stress of the super-elastic nickel-titanium-based shape memory alloy in a real stress-strain curve with the tool heating temperature and the strain rate of <0.05s -1 is expressed in MPa; The said process Calculated from equation (2): (2) in the formula, In order to ensure the minimum pressure of the fillets when the fillets are full, the unit is MPa, t min is the minimum wall thickness of the designed super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe, the unit is mm, and r min is the radius of the minimum fillets in a cavity surrounded by a plurality of pre-bulging modules, and the unit is mm; The real stress of the super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe is designed correspondingly in a real stress strain curve of the super-elastic nickel-titanium-based shape memory alloy at the tool heating temperature and the strain rate of <0.05s -1 , and the unit is MPa.
9. The method for forming the super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe according to claim 1, wherein the gas-solid composite bulging in the third step is specifically performed according to the following steps: ① The pre-bulging piece is arranged in a gas-solid composite bulging tool, the gas-solid composite bulging tool consists of a composite bulging upper die sleeve, a composite bulging lower die base plate and a composite bulging inner die, the composite bulging lower die sleeve is a conical sleeve formed by 4-piece composite bulging lower die sleeve blocks and is arranged on the composite bulging lower die base plate in a sliding manner, the composite bulging inner die consists of a plurality of composite bulging modules along the axial direction and the circumferential direction, adjacent modules in the axial direction are connected by compression springs to form a module group, a gap of 5 mm-20 mm is arranged between the adjacent module groups in the circumferential direction, the composite bulging inner die is arranged in the composite bulging lower die sleeve, the pre-bulging piece is arranged in a cavity surrounded by the composite bulging inner die, the outer wall of a trough of the pre-bulging piece is attached to the inner wall of the minimum diameter of the cavity, and the inner surface of the composite bulging upper die sleeve is a conical surface and is matched with the outer conical surface of the composite bulging lower die sleeve; ② Heating the gas-solid compound bulging tool to 800-900 ℃, then introducing inert gas through an air inlet pipe at a pressure increasing rate of 0.01-0.02 MPa/min, and increasing the pressure to the pressure at the beginning of bulging When the pressure is higher than the pressure, the pressure is raised to Pressing down the composite bulging upper die sleeve at a speed of 5-8 mm/min, driving the die block groups to move radially towards the center until adjacent die block groups are attached, and then continuing to boost until the minimum pressure for ensuring full fillet is reached And at a pressure of And maintaining the pressure, and cooling to room temperature to obtain the bulging corrugated pipe.
10. The method for forming a multilayer corrugated tube of a super-elastic nickel-titanium-based shape memory alloy according to claim 8 or 9, wherein the axial heights of the peaks and the valleys of the pre-expanded member are h 1 and h 2 respectively, the designed multilayer corrugated tube of the super-elastic nickel-titanium-based shape memory alloy has the axial heights of the peaks and the valleys of h 01 and h 02 respectively, and h 1 -h 01 =5mm~10mm,h 2 -h 02 = 5mm to 15mm, when the thickness of the multilayer corrugated tube of the super-elastic nickel-titanium-based shape memory alloy is less than or equal to 2mm, the strain is less than or equal to 50% at a tool heating temperature and a strain rate of <0.05s -1 , and the pressure is Maintaining pressure for 10-20 min, and when the thickness of the designed super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe is more than 2mm, the strain is more than 50% under the conditions of the fixture heating temperature and the strain rate of <0.05s -1 , and the pressure is the following pressure And maintaining the pressure for 30-60 min.

Description

Forming method of super-elastic nickel-titanium-based shape memory alloy multilayer corrugated pipe Technical Field The invention belongs to the technical field of metal corrugated pipes. Background In fluid conveying pipeline systems and high-end dynamic sealing devices (such as rotating shafts and reciprocating rod seals), flexible corrugated pipes are core components for realizing sealing, displacement compensation, vibration reduction and noise reduction, and the performance of the flexible corrugated pipes directly determines the reliability and service life of the system in the fields of aerospace, petrochemical industry and the like. Although the traditional stainless steel corrugated pipe is widely applied, the traditional stainless steel corrugated pipe is easy to fail due to fatigue cracks under the high-frequency cyclic load and large-deformation working condition, and the limited elastic deformation capacity of the traditional stainless steel corrugated pipe is more difficult to meet the severe requirements of dynamic seal on long service life and large compensation amount. Nickel-titanium based shape memory alloys with superelastic properties provide a new approach to solving this bottleneck. The material can bear up to 8% of recoverable strain, can provide stable restoring force, and can theoretically and remarkably improve the sealing performance, fatigue life, compensation capability and vibration reduction performance of the corrugated pipe. In addition, each layer of the multi-layer bellows is very thin with the total thickness unchanged. The flexibility of a material is generally inversely related to its thickness, i.e., the thinner the material, the more likely it is for elastic bending deformation to occur. Therefore, when the multilayer corrugated pipe bears displacement (axial direction, transverse direction and angular direction), the required force is smaller, the overall flexibility is better, and larger compensation quantity can be realized than that of a single-layer corrugated pipe with the same thickness. This is critical for applications where space is limited and large deformation compensation is required. In combination with the above advantages of the multi-layer structural design, there is a need to propose a multi-layer bellows made of super-elastic nitinol material as a solution to the above problems. However, this solution faces serious manufacturing challenges. The nickel-titanium-based shape memory alloy is extremely sensitive to heat and mechanical processing, and the traditional forming process has serious uneven wall thickness, cracking and layering defect caused by uncooled deformation among various tube blanks due to large deformation degree, or has poor weld joint performance when adopting a welding process, so that the nickel-titanium-based shape memory alloy becomes a fatigue weak point under dynamic load, and early failure is caused. Disclosure of Invention The invention aims to solve the problems that the prior traditional multi-layer corrugated pipe forming process can cause serious uneven wall thickness, cracking and layering defect among pipe blanks due to uncooled deformation due to large deformation degree, or can cause poor performance of a welding line area of the nickel-titanium-based shape memory alloy and cause early failure when a welding process is adopted, and further provides a forming method of the super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe. A method for forming a super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated pipe is carried out according to the following steps: 1. Preparing a multi-layer tube blank structure: nesting a plurality of super-elastic nickel-titanium-based shape memory alloy tube blanks to obtain a multi-layer tube blank structure, and calculating the inner diameter size of the innermost tube blank in the multi-layer tube blank structure according to the minimum inner diameter size of the innermost tube in the designed super-elastic nickel-titanium-based shape memory alloy multi-layer corrugated tube; 2. Preparation before forming: Respectively welding a super-elastic nickel-titanium-based shape memory alloy circular plate at two ends of the multilayer tube blank structure to obtain an end-sealed multilayer tube blank structure, perforating the upper end of the end-sealed multilayer tube blank structure and communicating the upper end with an air inlet tube joint by adopting a welding method to obtain a tube blank to be expanded; 3. Shaping: and pre-bulging is carried out on the pipe blank to be bulged, then gas-solid compound bulging is carried out, the corrugated pipe after bulging is obtained, and the super-elastic nickel-titanium-based shape memory alloy circular plate and a section of wave crest adjacent to the super-elastic nickel-titanium-based shape memory alloy circular plate at the two ends of the corrugated pipe after bulging are removed, so that the