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CN-121972918-A - Preparation method for improving surface quality of titanium alloy seamless tube

CN121972918ACN 121972918 ACN121972918 ACN 121972918ACN-121972918-A

Abstract

The invention relates to a preparation method for improving the surface quality of a titanium alloy seamless pipe, and belongs to the technical field of metal material processing. The method comprises the following steps of S1, performing surface grain refining pretreatment on a blank, performing surface shot blasting grain refining treatment on a titanium alloy bar, performing low-temperature annealing treatment, S2, preparing a gradient composite lubricating layer and a multilayer composite sleeve, spraying a bottom layer glass lubricant on the surface of the bar, after solidification, sequentially sleeving an inner layer titanium foil sleeve and an outer layer metal sleeve on the surface of the bar, filling a solid lubricant powder layer, welding and sealing, spraying an outer layer glass lubricant on the outer surface of the metal soft sleeve, S3, reducing a lubrication groove by using a biconical die, S4, performing on-line pickling treatment, S5, performing neutral electrolytic polishing, and S6, cleaning and air-drying. The method can obviously improve the surface quality, ensure the purity of the interface and reduce the cost. Solves the technical problems that the existing full-titanium sheath has high cost, and the single-layer glass lubricant is easy to damage and difficult to stably lubricate.

Inventors

  • TANG MIN
  • XIAO QIANG
  • LI XIAOYU
  • CHENG XIAOWEI

Assignees

  • 成都先进金属材料产业技术研究院股份有限公司

Dates

Publication Date
20260505
Application Date
20260331

Claims (10)

  1. 1. The preparation method for improving the surface quality of the titanium alloy seamless tube is characterized by comprising the following steps of: S1, performing surface grain refining pretreatment on a blank, and performing low-temperature annealing treatment after performing surface shot blasting grain refining treatment on a titanium alloy bar; S2, preparing a gradient composite lubricating layer and a multilayer composite sheath, spraying a bottom layer glass lubricant on the surface of the pretreated titanium alloy bar, after the bottom layer lubricant is solidified, sequentially sleeving an inner layer titanium foil sheath and an outer layer metal sheath on the surface of the bar, filling a solid lubricant powder layer between the inner layer sheath and the outer layer sheath, welding and sealing the double-layer composite sheath, and then spraying an outer layer glass lubricant on the outer surface of the metal soft sheath; S3, extruding the variable-diameter lubrication groove by using a double-cone die; s4, carrying out on-line acid washing treatment; s5, neutral electrolytic polishing; S6, cleaning and air-drying.
  2. 2. The method for improving the surface quality of a titanium alloy seamless pipe according to claim 1, wherein in the step S1, a centrifugal shot blasting machine is adopted to perform shot blasting and grain refining treatment on the surface of a bar, high-hardness ceramic shots or glass shots are used as shot media, high-speed bombardment is performed on the outer surface of the bar, the shot diameter is 0.2-0.8mm, the shot strength is 0.2-0.6 mmA, the surface coverage rate is 100% -200%, an ultrafine grain tissue layer with the thickness of 50-150 mu m is formed on the surface layer of the bar, the annealing temperature is 450-550 ℃, the heat preservation time is 30-60min, and air cooling is performed.
  3. 3. The method for improving the surface quality of a titanium alloy seamless pipe according to claim 1, wherein the temperature of the bottom glass lubricant is 800-900 ℃, the spraying thickness is 50-100 μm, the temperature of the outer glass lubricant is 900-1050 ℃, and the spraying thickness is 80-150 μm in the step S2.
  4. 4. The preparation method for improving the surface quality of the titanium alloy seamless pipe is characterized in that the inner titanium foil sheath is TA1 or TA2 pure titanium foil with the thickness of 0.1-0.3mm, the inner titanium foil sheath is tightly attached to the surface of a bar in a spiral winding mode, the outer metal sheath is a low carbon steel or stainless steel thin-wall sleeve with the thickness of 0.5-1.2mm, the thickness of a solid lubricant powder layer filled between the inner and outer titanium foil sheaths is 0.2-0.5mm, the inner titanium foil sheath is sealed by argon arc welding, and the outer metal sheath is sealed by laser welding or plasma welding.
  5. 5. The preparation method for improving the surface quality of the titanium alloy seamless pipe according to claim 1, wherein the raw materials of the bottom layer glass lubricant in the step S2 comprise, by weight, 15-25% of SiO 2 40-50%、CaO 5-10%、MgO 2-5%、Al 2 O 3 3-6%、Na 2 O and 15-25% of binder, and the raw materials of the outer layer glass lubricant comprise, by weight, 10-20% of ：SiO2 45-55%、CaO 8-12%、MgO 3-6%、Al 2 O 3 4-8%、K 2 O 5-10%、B 2 O 3 5-10%、% of binder.
  6. 6. The preparation method for improving the surface quality of the titanium alloy seamless pipe according to claim 1, wherein in the step S3, the titanium alloy bar obtained in the step S2 is heated to 950-1050 ℃, the temperature is kept for 60-120min, then a biconical die with a variable-diameter lubrication groove is adopted for extrusion, the biconical die comprises a first conical surface and a second conical surface, the taper angle of the first conical surface is 30-45 degrees, the taper angle of the second conical surface is 15-25 degrees, a spiral fine oil storage groove is formed in the second conical surface, the section of the oil storage groove is semicircular or trapezoid, the groove depth is 0.1-0.3mm, the groove width is 0.2-0.5mm, the distance between adjacent grooves is 0.5-1.2mm, the spiral angle is 30-60 degrees, the solid lubricant is filled in the oil storage groove, the extrusion ratio is 8-15, and the extrusion speed is 50-100mm/S.
  7. 7. The method for improving the surface quality of a titanium alloy seamless tube according to claim 6, wherein the solid lubricant in the step S3 is a mixture of molybdenum disulfide and graphite, the mass ratio is 1:1-3:1, and 5-10% of cerium oxide is added to the solid lubricant as a high-temperature stabilizer.
  8. 8. The preparation method for improving the surface quality of the titanium alloy seamless pipe, which is disclosed in claim 1, is characterized in that the step S4 immediately carries out on-line spray pickling treatment by utilizing the waste heat of the pipe at 200-300 ℃ after the titanium alloy seamless pipe extruded in the step S3 is ejected, wherein the pickling solution comprises, by weight, 5-10% of citric acid, 3-8% of oxalic acid, 0.5-1.5% of corrosion inhibitor, 0.1-0.5% of surfactant and the balance deionized water, and the spraying pressure is 0.3-0.6MPa and the spraying time is 10-30S.
  9. 9. The preparation method for improving the surface quality of the titanium alloy seamless pipe according to claim 1, which is characterized in that in the step S5, the titanium alloy seamless pipe treated in the step S4 is subjected to neutral electrolytic polishing, wherein electrolyte is neutral salt solution, and the titanium alloy seamless pipe comprises, by weight, 10-15% of sodium chloride, 5-10% of sodium sulfate, 3-6% of sodium citrate and the balance deionized water, wherein the pH value is 6.5-7.5, the electrolytic voltage is 10-20V, the current density is 20-50A/dm < 2 >, and the polishing time is 2-5min.
  10. 10. The preparation method for improving the surface quality of the titanium alloy seamless pipe according to claim 1, wherein in the step S6, the inner surface and the outer surface of the titanium alloy seamless pipe obtained in the step S5 are washed by clean water, then immersed in 2-5% sodium carbonate neutralization solution for treatment for 1-2min, washed by clean water again, and finally rapidly cooled under the protection of nitrogen.

Description

Preparation method for improving surface quality of titanium alloy seamless tube Technical Field The invention relates to a preparation method for improving the surface quality of a titanium alloy seamless pipe, and belongs to the technical field of metal material processing. Background The titanium alloy has the characteristics of low density, high specific strength, excellent corrosion resistance and the like, and is widely applied to the fields of aerospace, petrochemical industry, ocean engineering and the like. Titanium alloy seamless tubes are used as important structural components, and the surface quality of the titanium alloy seamless tubes directly influences the service life and reliability of products. However, the titanium alloy seamless tube has low heat conductivity coefficient (about 6.7W/(m.K)), and the temperature difference between the surface layer and the core part of the blank can reach 200-250 ℃ in the hot extrusion process, so that the strength and plasticity of the surface metal are increased, a hard shell layer is formed, and surface cracks are easy to initiate. Meanwhile, titanium can perform eutectic reaction with a die material at a high temperature of 980-1030 ℃ to generate brittle intermetallic compounds such as TiFe, tiNi and the like, so that surface pollution and die abrasion are caused. In order to improve the forming quality, the prior art adopts a method of combining sheath extrusion with a glass lubricant. The patent CN 119347343A discloses an extrusion forming method of titanium alloy seamless pipe and its product, and adopts steel+copper bimetal sheath to avoid copper pollution, and adopts double cone die extrusion, but has no lubrication. The patent CN 118513635A discloses a coating method for preparing a blank surface coating layer for a large-size titanium alloy pipe, and provides a titanium alloy thin-wall welded pipe sheath, and a glass lubricant is used for assisting in reducing the friction coefficient from 0.8 to 0.1-0.2. However, the prior art still has obvious defects that a single steel/copper sheath is easy to generate an interfacial brittle phase, the cost of the whole titanium sheath is high, the glass lubricant is mostly coated in a single layer, is easy to damage at high temperature, and is difficult to realize stable lubrication in the whole process. And the traditional acid washing and strong acid electrolytic polishing has low efficiency, high waste liquid treatment cost and serious environmental pollution. Therefore, development of a synergistic regulation and control method integrating surface layer tissue modification, composite sheath structure, active lubrication of a die and environment-friendly post-treatment is needed to systematically solve the difficult problem of surface quality control in the titanium alloy hot extrusion process. Disclosure of Invention The invention aims to solve the technical problems that the existing full-titanium sheath is high in cost, and a single-layer glass lubricant is easy to damage and difficult to stably lubricate. The technical scheme adopted for solving the technical problems is that the preparation method for improving the surface quality of the titanium alloy seamless tube comprises the following steps: S1, performing surface grain refining pretreatment on a blank, and performing low-temperature annealing treatment after performing surface shot blasting grain refining treatment on a titanium alloy bar; S2, preparing a gradient composite lubricating layer and a multilayer composite sheath, spraying a bottom layer glass lubricant on the surface of the pretreated titanium alloy bar, after the bottom layer lubricant is solidified, sequentially sleeving an inner layer titanium foil sheath and an outer layer metal sheath on the surface of the bar, filling a solid lubricant powder layer between the inner layer sheath and the outer layer sheath, welding and sealing the double-layer composite sheath, and then spraying an outer layer glass lubricant on the outer surface of the metal soft sheath; S3, extruding the variable-diameter lubrication groove by using a double-cone die; s4, carrying out on-line acid washing treatment; s5, neutral electrolytic polishing; S6, cleaning and air-drying. Further, in the step S1, a centrifugal shot blasting machine is adopted to carry out shot blasting and grain refining treatment on the surface of the bar, high-hardness ceramic shots or glass shots are used as shot mediums, high-speed bombardment is carried out on the outer surface of the bar, the shot diameter is 0.2-0.8mm, the shot strength is 0.2-0.6 mmA, the surface coverage rate is 100-200%, an ultrafine grain tissue layer with the thickness of 50-150 mu m is formed on the surface layer of the bar, the annealing temperature is 450-550 ℃, the heat preservation time is 30-60min, and air cooling is carried out. Further, in the step S2, the tolerance temperature of the bottom layer glass lubricant is 800-900 ℃, the spraying thic