A method for preparing a high-strength titanium alloy wire with a bright surface by cold drawing

Abstract

The application belongs to the field of metallurgy and relates to a preparation method of titanium alloy wire, in particular to a bright surface cold drawing preparation method of high-strength titanium alloy wire.The titanium alloy wire is subjected to vacuum heat treatment and surface lubricating treatment, then subjected to multi-group multi-pass bright surface cold drawing process, and finally subjected to surface treatment to obtain titanium alloy wire with target diameter.By controlling pass deformation of 8-20% and heat deformation of 30-50%, the titanium alloy wire is subjected to full-process bright surface cold drawing from φ3.0mm to φ0.2mm, and the drawing speed reaches 15-35m / min.The titanium alloy wire prepared has good metallographic structure, high uniformity, and a yield of more than 80%.For the fine wire from φ0.5mm to φ0.2mm, the bright surface drawing reduces the frequency of the problem that the wire is prone to breakage due to the depression on the surface of the wire caused by the oxide skin on the surface of the wire.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metallurgy, and relates to a preparation method of titanium alloy wire, in particular to a bright surface cold drawing preparation method of high-strength titanium alloy wire. BACKGROUND

[0002] Titanium alloy TC4ELI has excellent comprehensive mechanical properties, corrosion resistance and good biocompatibility, and has a wide range of application scenarios in the fields of aviation, aerospace, shipbuilding, chemical industry, sports equipment and medical industry, and has realized large-scale commercial use. TC4ELI, due to its low impurity content and high strength, is also the main raw material for medical cables. Medical cables are mainly used for fixing and supporting the waist in the medical field, helping patients recover and protecting body parts, and are suitable for the treatment and rehabilitation process of various waist diseases, so medical cables usually require high tensile strength. The cold drawing process of TC4ELI through heat treatment solid solution is also the preferred wire material for medical cables.

[0003] Titanium alloy wire drawing process includes cold drawing, hot drawing and warm drawing, among which cold drawing, i.e. drawing below the recrystallization temperature, is the most commonly used processing method. Roll die drawing and die drawing have high cold drawing efficiency, but roll die drawing has difficulties in drawing wires below φ2.0 mm due to the limitation of die structure; traditional die drawing needs to have an oxide skin as a lubricating carrier, and oxygen increase is inevitable during processing, and finally oxygen needs to be treated, which is complex and high in cost. Oxide skin is produced during hot drawing, and the process of removing the oxide skin needs to be peeled off several times, resulting in low yield and high oxygen content, and there are problems such as slow drawing speed and uncontrollable metallography. Warm drawing is drawing at a temperature of 300-400 DEG C, and its disadvantage is that the drawing resistance of the wire is large during the drawing process, and the strength of the wire after drawing is low. SUMMARY

[0004] The present application provides a bright surface cold drawing preparation method of high-strength titanium alloy wire, which combines the use of pressurized dies and titanium alloy wire surface lubrication treatment to draw the wire in a bright surface state of titanium alloy, form a layer of inorganic salt lubricating film on the surface of the wire, and at the same time of forming the film lubrication interface, use pressurized dies to draw the lubricating film into the compression zone of the die, realize sliding friction on the surface of the wire, and thus achieve the effect of bright surface drawing. The technical problem of low yield and high oxygen content caused by the oxide skin produced during the hot drawing process of titanium alloy wire is solved, the grain is refined, the tensile strength of the wire is improved, and the problems of slow drawing speed and uncontrollable metallography are solved.

[0005] The technical scheme of the present application is as follows:

[0006] A bright surface cold drawing preparation method of high-strength titanium alloy wire, comprising the following steps:

[0007] (1) taking titanium alloy wire material;

[0008] (2) vacuum heat treatment and surface lubrication treatment of the titanium alloy wire material;

[0009] (3) multi-group multi-pass bright surface cold drawing process, vacuum heat treatment and surface lubrication treatment between each group of cold drawing processes;

[0010] the multi-group multi-pass bright surface cold drawing process,

[0011] A, when the target diameter is 1.0-3.0mm, the number of groups is 3-6, the number of passes per group is 2-6, the pass deformation is 8%-20%, and the fire deformation is 30%-50%;

[0012] or B, when the target diameter is 0.2-1.0mm, the number of groups is 3-6, the number of passes per group is 3-7, the pass deformation is 8%-20%, and the fire deformation is 30%-65%;

[0013] (4) after cold drawing to the target diameter, surface treatment is performed to obtain finished wire material.

[0014] Further, the titanium alloy wire material in step (1) has a mass percentage of Al: 5.5-6.3%, V: 3.5-4.2%, Fe≤0.20%, O≤0.10%, C≤0.06%, H<0.01%, N≤0.03%, Si<0.05%, and the balance being Ti.

[0015] Further, in step (3), when the target diameter is 1.0-3.0mm, the diameter of the wire material for drawing process is 1.5-4mm; when the target diameter is 0.2-1.0mm, the diameter of the wire material for drawing process is 0.5-1.5mm; and when the target diameter is 1.0mm, either A or B can be used for drawing process.

[0016] Further, the vacuum heat treatment temperature in steps (2) and (3) is 700-900℃, the holding time is 30-90min, the vacuum degree is 10 -3 -10 -4 Pa; the surface lubrication treatment process is to attach inorganic salt lubricant to the surface of the titanium alloy wire material and dry at 90-150℃.

[0017] Further, the inorganic salt lubricant is obtained by mixing nano-sized montmorillonite K-10 and sodium fatty alcohol polyethyleneglycol ether sulfate according to a mass ratio of 3:1, the adhesion process is that the inorganic salt lubricant is dissolved into a dissolving tank at 90-150℃, and after the dissolution, the titanium alloy wire is passed through or soaked in the inorganic salt lubricant in the dissolving tank, and the titanium alloy wire stays in the inorganic salt lubricant for 20-40s, and the adhesion amount of the inorganic salt lubricant on the titanium alloy wire is 5-10g / m 2 .

[0018] Further, in the multi-group multi-pass bright surface cold drawing process of step (3), when the target diameter is 1.0-3.0mm, the preferred group number is 3-5, the preferred pass number of each group is 2-4, the preferred pass deformation amount is 9%-16%, the single-pass deformation amount gradually decreases, the preferred fire deformation amount is 30%-45%, and the drawing speed is 15-35m / min; when the target diameter is 0.2-1.0mm, the preferred group number is 3-5, the preferred pass number is 4-6, the pass deformation amount of each group is preferably 8%-16%, the single-pass deformation amount is the same, the preferred fire deformation amount is 30%-55%, and the drawing speed is 15-35m / min.

[0019] Further, the surface treatment process of step (4) is:

[0020] A. when the target diameter is 1.0-3.0mm, the wire is subjected to mechanical polishing and cleaning;

[0021] or B. when the target diameter is 0.2-1.0mm, the wire is subjected to electrolytic polishing and cleaning.

[0022] Further, in the electrolytic polishing process, the electrolyte is a 1L solution prepared by adding water to 200ml hydrofluoric acid (mass fraction of 33%) and 500g chromic anhydride (purity of 99.9%), the current density is 0.4-1.0A / cm 2 , the voltage is set to 50-60V, and the polishing speed is 10-30m / min.

[0023] Further, the cleaning process is that the wire is first cleaned in a weak alkaline cleaning solution with a PH of 8.0-9.0, and then ultrasonic cleaned in water.

[0024] When the target diameter is 1.0mm, either the surface treatment process A or B can be used.

[0025] A titanium alloy wire prepared by the preparation method of the present application, characterized in that the wire diameter is 0.2-3mm, and the grain size grade is 10-15.

[0026] Further, the titanium alloy wire φ2.84mm grain size is 10 levels, φ1.0mm grain size is 12 levels, φ0.2mm grain size is 15 levels, and the organization state is α+β two-phase equiaxed structure.

[0027] Advantages and beneficial effects of the present application

[0028] 1. The cold drawing preparation process of the present application can affect the microstructure and mechanical properties of the titanium alloy wire through different pass deformation and fire deformation, and finally obtain the titanium alloy wire with good microstructure and metallurgical phase, and the yield rate is above 80%. The mechanical properties meet the requirements.

[0029] 2. The specific cold drawing preparation process of the present application cooperates with the heat treatment process, so that the drawing speed is 15-35 m / min, and the production efficiency is greatly improved.

[0030] 3. The present application is bright surface drawing, which avoids the problem of low yield rate caused by frequent scaling of oxide skin in the prior art. For φ0.5mm-φ0.2mm thin wire, because of the bright surface drawing, the frequency of the problem that the wire is easy to break due to the depression on the wire surface caused by the treatment of the oxide skin on the wire surface is reduced. At the same time, the problem of increasing oxygen content caused by drawing with oxide skin is solved, which has great practicality in production.

[0031] 4. The cold drawing preparation process of the present application is carried out in the α+β two-phase region. The material is annealed and solid-solved at high temperature to obtain a large proportion of β phase which is easy to deform and draw, and then the grain is broken and refined through cold drawing processing to obtain fine equiaxed structure wire with high tensile strength. After cold drawing with large deformation in multiple passes, the tensile strength of the obtained wire is ≥1350MPa, which is higher than the tensile strength ≥925MPa required in the standard GB / T3623-2007. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Balance phase diagram of TC4 titanium alloy

[0033] Figure 2 Metallographic phase diagram of titanium alloy wire φ2.84mm

[0034] Figure 3 Metallographic phase diagram of titanium alloy wire φ1.0mm

[0035] Figure 4 Metallographic phase diagram of titanium alloy wire φ0.2mm

[0036] Figure 5 Adjacent atoms of titanium alloy wire φ0.2mm with different grain orientations

[0037] Figure 6Figure of bright surface after drawing of titanium alloy wire φ0.2mm DETAILED DESCRIPTION

[0038] The present application is described in detail below with reference to the accompanying drawings and examples

[0039] The cold drawing preparation process of the present application is carried out in the α+β two-phase region, and the material is subjected to high-temperature annealing and solid solution to obtain a large proportion of β phase which is easy to deform and draw, and then the grains are broken and refined by cold drawing to obtain fine equiaxed structure wire. The present application makes full use of the properties of the heat-affected zone of titanium alloy during the heat treatment process in the cold drawing process of titanium alloy wire. After each bright surface cold drawing, the wire is subjected to heat treatment and solid solution. The heat treatment temperature is 700-900℃, the holding time is 30-90min, and the solid solution cooling method is liquid argon cooling to obtain supersaturated solid solution and increase the percentage of β phase, as shown in the figure, which greatly improves the plastic deformation ability of the material. Figure 1

[0040] The die used for cold drawing in the example is a booster die: the booster die is a set of combined die, and a pressure cavity is added in front of the drawing die to increase the adhesion of the lubricating powder and the wire, thereby greatly increasing the lubrication effect of the wire drawing.

[0041] Example 1

[0042] The present example provides a preparation method for bright surface cold drawing of high-strength titanium alloy wire φ1.0mm, and the specific steps are as follows:

[0043] (1) Prepare titanium alloy wire disc material: the chemical composition of the titanium alloy wire disc material treated by the bright surface cold drawing preparation process in the present example is as follows: Al: 6.25%, V: 4.2%, Fe: 0.20%, O: 0.10%, C: 0.06%, N: 0.02%, H: 0.008%, Si: 0.03%, and the balance is Ti; the diameter of the titanium alloy wire disc material is 3.0mm.

[0044] (2) Heat treatment: the titanium alloy wire disc material is subjected to 700℃ sizing and skinning treatment to obtain titanium alloy wire raw material with a diameter of 2.84mm. The sized and skinned titanium alloy wire raw material is loaded into a vacuum annealing furnace, the vacuum degree is 10 - 3 Pa, heated to 700-900℃, specifically 850℃, held for 30-90min, specifically 1h, and quickly cooled to room temperature in liquid argon.

[0045] ​(3) Surface lubrication treatment: after vacuum annealing, the titanium alloy wire surface is polished rough, the nano-sized montmorillonite (K-10) with particle size distribution of 20-60 nm is mixed with fatty alcohol polyethylene glycol ether sodium sulfate (purchased from Hubei Kewode Chemical Industry) at a mass ratio of 3:1, and is dissolved into a dissolving tank with a length of 3 meters and a width of 0.3 meters at 100°C. After dissolving, the titanium alloy wire is passed through (so that the wire passes through the lubricant solution) the dissolving tank, and the wire at any point from entering the lubricant solution to leaving the lubricant solution is 30s (i.e. the residence time is 30s). The lubricant is evenly attached to the surface of the titanium alloy wire to form a lubricating film, and the attachment amount is 5-10 g / m 2 , specifically 8 g / m 2 , and the blast dryer is dried at 100°C to achieve the effect of interfacial lubrication.

[0046] (4) Cold drawing: the titanium alloy wire after surface lubrication is subjected to bright surface cold drawing, and the drawing process is as follows: 4 groups of 4 passes are adopted, the deformation amount of each group of single pass is gradually reduced, and the deformation amounts of the 4 passes are 13.2-13.6%, 12.3-12.6%, 11.2-11.8% and 9.8-10.9% respectively. The cumulative deformation amount of each group, i.e. the deformation amount of each pass, is not more than 42%, and the drawing speed is 15 m / min. After the drawing process of groups 1-3, the titanium alloy wire is subjected to heat treatment and surface lubrication before the drawing of the next group.

[0047] The specific process of heat treatment is as follows: the titanium alloy wire after drawing of the last group is loaded into a vacuum annealing furnace, the vacuum degree is 10 -3 Pa, the temperature is raised to 850°C, the temperature is kept for 1h, and the furnace is quickly discharged and cooled to room temperature in liquid argon.

[0048] The surface lubrication process is as follows: step (3).

[0049] After 4 groups of drawing, the wire is subjected to mechanical polishing to remove surface impurities, is passed through (so that the wire passes through the cleaning solution) a weak alkaline cleaning solution (2% sodium bicarbonate solution) with a pH of 8.3 to remove surface oil stains, and is then cleaned in a pure water ultrasonic water tank to obtain a finished wire with a diameter of φ1.0 mm. The 4 groups of 4 pass drawing process is shown in Tables 1-4.

[0050] Table 1: First group of drawing

[0051]

[0052] Table 2: Second group of drawing

[0053]

[0054]

[0055] Table 3 Third group of drawing

[0056]

[0057] Table 4 Fourth group of drawing

[0058]

[0059] Example 2

[0060] The present example provides a method for preparing a high-strength titanium alloy wire with a diameter of 0.2 mm by bright cold drawing, and the specific steps are as follows:

[0061] Take the φ1.0 mm titanium alloy wire prepared in the above-mentioned example 1, and after heat treatment and surface lubrication, carry out bright surface cold drawing. The heat treatment and surface lubrication process are the same as the heat treatment and surface lubrication process in step (4) of the cold drawing process in example 1, the difference is that the heat treatment temperature is 830℃. Adopt 5 groups of 5 passes drawing, the single pass drawing deformation of each group is approximately the same, the single pass deformation is 9.6-12.8%, the cumulative deformation of each group, i.e. the deformation of each pass, is not more than 50%, the drawing speed is 20m / min, after the drawing process of 1-4 groups, the wire needs to be heat treated and surface lubricated before the next group of drawing, the heat treatment and surface lubrication process are the same as the heat treatment and surface lubrication process in step (4) of the cold drawing process in example 1, the only difference is that the heat treatment temperature is 830℃.

[0062] After 5 groups of drawing, the wire is first electrolytically polished: the electrolyte is 200ml hydrofluoric acid (mass fraction 33%) and 500g chromium anhydride (purity 99.9%) added to 1L solution with water, the current density is 0.8A / cm 2 , the voltage is set to 60V, and the polishing speed is 20m / min; then pass through a weak alkaline cleaning solution (2% mass fraction of sodium bicarbonate solution) with a PH of 8.3 to remove surface oil, and then pass through a pure water ultrasonic water tank for cleaning, finally obtain the finished wire with a diameter of 0.2mm. The 5 groups of 5 pass drawing process is shown in tables 5-9.

[0063] Table 5 First group of drawing

[0064]

[0065] Table 6 Second group of drawing

[0066]

[0067]

[0068] Table 7 Third group of drawing

[0069]

[0070] Table 8 Group 4 Pulling

[0071]

[0072] Table 9 Group 5 Pulling

[0073]

[0074] The titanium alloy wires with diameters of φ1.0 mm and φ0.2 mm prepared in the above embodiments were tested according to the requirements of the wire mechanical property standard GB / T 228.1-2021, and the test results are shown in Table 10.

[0075] Table 10 Mechanical Properties

[0076]

[0077] By comparing the tensile strength with that in standard GB / T3623, the filament in this invention exhibits higher tensile strength. Figures 2-4 The grain size shown in the metallographic images reveals that the titanium alloy disc round material with a diameter of 2.84 mm has a grain size of grade 10, the titanium alloy wire with a diameter of 1.0 mm in Example 1 has a grain size of grade 12, and the titanium alloy wire with a diameter of 0.2 mm in Example 2 has a grain size of grade 15. This is because the titanium alloy wire obtained by the process of this invention has relatively fine grains, and adjacent atoms have different grain orientations, such as... Figure 5 As shown, during plastic deformation, dislocation movement must pass through this common grain boundary, and fine grains have a larger grain boundary area to hinder dislocation movement. Furthermore, when two grains have different orientations, dislocations entering the grain must change their direction of movement; this becomes even more difficult when the orientation difference is large. Therefore, the titanium alloy wire prepared in this invention has high tensile strength. A finished image of the φ0.2mm titanium alloy wire is shown below. Figure 6 It has a glossy surface.

[0078] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for bright surface cold drawing of high strength titanium alloy wire, characterized in that, It comprises the following steps: (1) taking titanium alloy wire raw material; (2) vacuum heat treatment and surface lubrication treatment are carried out on the titanium alloy wire; (3) multi-group multi-pass bright surface cold drawing process is carried out, and vacuum heat treatment and surface lubrication treatment are carried out between each group of cold drawing process; The multi-group multi-pass bright surface cold drawing process is specifically: A, when the target diameter is 1.0-3.0 mm, the drawing process raw material wire diameter is 1.5-4.0 mm, the group number is 3-6, the pass number of each group is 2-6, the pass deformation is 8%-20%, and the fire deformation is 30%-50%; Or B, when the target diameter is 0.2-1.0 mm, the drawing process raw material wire diameter is 0.5-1.5 mm, the group number is 3-6, the pass number of each group is 3-7, the pass deformation is 8%-20%, and the fire deformation is 30%-65%; And when the target diameter is 1.0 mm, either drawing process A or B can be used; (4) after cold drawing to the target diameter, surface treatment is carried out to obtain finished wire.

2. The method of claim 1, wherein: The titanium alloy wire in step (1) has a mass percentage composition of Al: 5.5-6.3%, V: 3.5-4.2%, Fe≤0.20%, O≤0.10%, C≤0.06%, H<0.01%, N≤0.03%, Si<0.05%, and the balance is Ti.

3. The method of claim 1, wherein: The vacuum heat treatment temperature in step (2) and step (3) is 700-900℃, the holding time is 30-90min, and the vacuum degree is 10 -3 ~10 -4 Pa; the surface lubricating treatment process is to attach inorganic salt lubricant on the surface of titanium alloy wire, and dry at 90-150℃.

4. The method of claim 3, wherein: The inorganic salt lubricant is obtained by mixing nano-sized montmorillonite K-10 and sodium fatty alcohol polyethylene glycol ether sulfate according to a mass ratio of 3:1, the adhesion process is that the inorganic salt lubricant is dissolved into a dissolving tank at 90-150 ℃, after dissolving, the titanium alloy wire is passed through or soaked in the inorganic salt lubricant in the dissolving tank, and the titanium alloy wire stays in the inorganic salt lubricant for 20-40 s, and the adhesion amount of the inorganic salt lubricant on the titanium alloy wire is 5-10 g / m 2 .

5. The method of claim 1, wherein: The multi-group multi-pass bright surface cold drawing process in step (3) is as follows: when the target diameter is 1.0-3.0 mm, the preferred group number is 3-5, the preferred pass number of each group is 2-4, the preferred pass deformation is 9%-16%, the single-pass deformation gradually decreases, the preferred fire deformation is 30%-45%, and the drawing speed is 15-35 m / min; when the target diameter is 0.2-1.0 mm, the preferred group number is 3-5, the preferred pass number of each group is 4-6, the preferred pass deformation is 8%-16%, the single-pass deformation is the same, the preferred fire deformation is 30%-55%, and the drawing speed is 15-35 m / min.

6. The method of claim 1, wherein: The surface treatment process in step (4) is: A, when the target diameter is 1.0-3.0 mm, the wire is mechanically polished and cleaned; Or B, when the target diameter is 0.2-1.0 mm, the wire is electrolytically polished and cleaned.

7. The method of claim 6, wherein: The cleaning process is first cleaned in a weak alkaline cleaning solution with a pH of 8.0-9.0, and then ultrasonically cleaned in water; And when the target diameter is 1.0 mm, either surface treatment process A or B can be used.

8. A titanium alloy wire prepared according to the method of claim 1, characterized by: The wire diameter is 0.2-3 mm, and the grain size level is 10-15 levels.

9. The titanium alloy wire of claim 8, wherein: The titanium alloy wire φ2.84 mm has a grain size of 10 levels, φ1.0 mm has a grain size of 12 levels, and φ0.2 mm has a grain size of 15 levels, and the organizational state is α+β two-phase equiaxed structure.

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