RU2796651C1 - Method for manufacturing small-diameter wire from titanium and titanium-based alloys - Google Patents

Abstract

FIELD: metal forming.

SUBSTANCE: invention relates to methods for manufacturing cold-formed wire from titanium and alloys based on it, used in welding, as well as in other industries. The method for manufacturing wire from titanium and alloys based on it includes obtaining a pre-deformed workpiece for drawing followed by drawing cycles with annealing. Drawing is carried out through hard-alloy or diamond dies with an elongation ratio between annealing procedures of not more than 1.50, using mineral or vegetable-based oils as lubricants for drawing. Intermediate annealing is carried out with lubricant residues on the wire surface in an atmosphere of inert gas or nitrogen at temperatures of 650-750°C and holding times of no more than 20 minutes, the thermal decomposition products of lubricants formed during annealing on the wire surface act as an under-lubricating coating in the next cycle drawing, after the end of drawing and reaching the final size, degreasing and etching are performed until the lubricant coating is completely removed from the surface of the wire.

EFFECT: production of wire from titanium and alloys based on it with a high-quality and defect-free surface, with no gas saturation of the metal during processing, with high shape and size accuracy.

1 cl, 3 dwg, 10 tbl, 5 ex

Description

The invention relates to the field of metal forming, in particular to methods for manufacturing cold-formed wire from titanium and alloys based on it, used in welding, as well as in other industries: the manufacture of elements of various designs, medicine.

To date, there are several methods for drawing wire from titanium and alloys based on it. The most common drawing method is drawing through steel, carbide or diamond dies. The advantage of this method is the simplicity and low cost of manufacturing a tool (die). The disadvantage of this method in the processing of titanium and its alloys are the high values of the friction force on the contact surface of the metal with the tool. Friction forces can reach 30% of the total drawing force. High friction forces increase the required force for drawing, degrade the quality of the wire surface, increase tool wear, and reduce productivity. This necessitates the selection of special lubricants and lubrication coatings. To reduce friction forces when drawing titanium and alloys based on it through dies, various lubricants are used, containing components such as graphite, sulfur, molybdenum disulfide, and natural wax. Most often, when drawing titanium and alloys based on it, aquadag is used - an aqueous suspension of graphite (Ermanok M.Z. Drawing non-ferrous metals and alloys: a textbook for vocational schools / Vatrushin L.S. - Moscow: Metallurgy, 1988 - p. 288). The disadvantage of some components of such lubricants, such as graphite, is the difficulty of washing equipment, clothing, and skin from it.

For the effective use of lubricants when drawing titanium and its alloys through dies, pre-lubricating coatings, such as oxide or phosphate films, are required. This necessitates additional operations and equipment for applying such coatings to the wire and their subsequent removal. In addition, due to the high tendency of titanium to stick to the tool, even with the use of special lubricants and pre-lubricating coatings, metal sticking to the working surface of the dies periodically occurs, leading to surface defects: scuffing of the wire and its breaks.

There are several ways close in essence to the claimed technical solution.

One of the analogs is a method for producing wire from β-titanium alloy with high tensile strength and fatigue strength, presented in JPH patent 0261042 (C22F1 / 00; C22F1 / 18, 03/01/1990), which proposes annealing in an oxidizing atmosphere, for example, on air, at temperatures not lower than 600 ° C, but not higher than the temperature of complete polymorphic transformation (the temperature of polymorphic transformation of β-titanium alloys, as a rule, is 700-750 ° C) to create an oxide film on the surface of the wire with a thickness of 0.1 to 3 .0 µm. The disadvantage of this method is the inevitable saturation of the near-surface layer of the wire with oxygen and hydrogen, which occurs during annealing in an oxidizing atmosphere, in parallel with the appearance of an oxide film. The gas-saturated layer on titanium and an alloy based on it has low manufacturability and, during subsequent pressure treatment, causes the initiation of surface defects: stress cracks, tears, breaks, etc.

Another close method for obtaining wire from β-titanium alloy with good dimensional accuracy and surface quality is JPS patent 62149859 (C22F1 / 00; C22F1 / 18; C23C8 / 80, 07/03/1987), in which, in order to prevent metal sticking to the tool during drawing an oxide film is also used as a lubricant coating. At the same time, a two-stage annealing is proposed before finishing drawing. The first stage - in air at temperatures from 400 to 650°C for 1 minute to 1 hour - to create an oxide film on the surface of the wire. The second stage is heating in a vacuum or an inert medium to a polymorphic transformation temperature or higher, holding for 5 to 60 minutes and cooling at a rate of at least 1.8 degrees per minute - to fix a high-temperature β-phase in the material, which has better manufacturability in terms of compared with the low-temperature α-phase during pressure treatment.

The disadvantage is the need for heating in a vacuum or a protective environment with the possibility of accelerated cooling, which is rather difficult to implement on industrial thermal equipment.

Closest to the claimed method is a method for producing high-strength wire from (α + β)-titanium alloy of the martensitic class, presented in patent RU 2460825 (C22F 1/18, B21B 3/00, 10.09.2012). In this method, for the manufacture of wire, it is proposed to use cold drawing with intermediate annealing in an air atmosphere, while after the first drawing stroke, mechanical processing is carried out, and the final heat treatment is carried out in an air atmosphere for 60-180 minutes at a temperature of (0.5-0. 7) Tpp (Tpp - temperature of complete polymorphic transformation) with further cooling to room temperature. The oxide film formed as a result of intermediate annealing in an air atmosphere acts as a lubricant coating during drawing.

The disadvantage of this method is the gas saturation of the near-surface layer of the wire with oxygen and hydrogen, which occurs during oxidative annealing, in parallel with the appearance of an oxide film. This is especially critical for multiple annealing-drawing cycles, as well as for small-diameter wire with a large specific surface area.

The increased content of oxygen and hydrogen in the wire causes an unacceptable decrease in manufacturability - embrittlement, and, as a rule, leads to surface defects: cracks, tears and breaks.

The problem to be solved by the claimed invention is to obtain a wire from titanium and alloys based on it with a high-quality and defect-free surface, with no gas saturation of the metal during processing, with high shape and size accuracy.

The technical result, which provides a solution to the problem, is a method for manufacturing small-diameter wire from titanium and alloys based on it, including obtaining a pre-deformed workpiece for drawing, successively performed drawing cycles with annealing, characterized in that drawing is carried out through hard-alloy or diamond dies with a coefficient value extracts between annealings are not more than 1.50 using mineral or vegetable-based oils as lubricants for drawing, while intermediate annealings are performed with lubricant residues on the metal surface in an inert atmosphere at temperatures from 650-750 ° C and holding times not more than 20 minutes, and the products of thermal decomposition of lubricants formed during annealing on the metal surface act as a lubricant coating in the next drawing cycle. Upon completion of drawing and reaching the final size, degreasing and pickling are performed until the remnants of the lubricant coating are completely removed from the surface of the wire. The absence of gas saturation of the treated metal is achieved by performing intermediate annealings in an inert atmosphere, without air access. High accuracy of the shape and dimensions of the wire is achieved by using carbide or diamond dies. As lubricants, we recommend using mineral or vegetable-based oils, as the cheapest and most affordable.

Implementation of methods for manufacturing wire from titanium and alloys based on it according to the prototype and the claimed method:

Example 1. Production of a wire with a diameter of 0.75 mm alloy VT16 from a wire with a diameter of 1.00 mm according to the prototype

The route for manufacturing the wire is given in Table 1. As the initial workpiece, we used a wire with a diameter of 1.00 mm, made by drawing on cassettes with intermediate vacuum annealing. Drawing was carried out through hard-alloy dies with annealing at sizes 1.00; 0.92; 0.87; 0.80 and 0.75 mm in air. No sticking of metal to the dies during the drawing process was recorded.

Table 1 - Route for manufacturing wire with a diameter of 0.75 mm from alloy VT16 Drawing pass number Diameter up to, mm Diameter after, mm Draw ratio annealing in air atmosphere 630°C - 15 minutes 1 1.00 0.92 1.09 annealing in air atmosphere 630°C - 15 minutes 2 0.92 0.87 1.09 annealing in air atmosphere 630°C - 15 minutes 3 0.87 0.80 1.07 annealing in air atmosphere 630°C - 15 minutes 4 0.80 0.75 1.05 annealing in air atmosphere 450°C - 90 minutes

As a result of metallographic studies, it was found that on the surface of the obtained wire with a diameter of 0.75 mm of the VT16 alloy there is an intermittent, uneven in thickness oxide film up to 32 μm thick, there were surface defects - microcracks (Fig. 1).

To estimate the amount of gas saturation of the wire metal during annealing, an analysis of the content of oxygen and hydrogen was performed at the initial, intermediate and final sizes - table 2.

Table 2 - the content of oxygen and hydrogen in a wire with a diameter of 0.75 mm from the VT16 alloy Size, mm Oxygen, wt.% Hydrogen, wt.% 1.00 0.132 0.010 0.87 0.407 0.102 0.75 0.790 0.128 Requirements OST 1 90013-81 ≤ 0.15 ≤ 0.012

Thus, in the manufacture of wire according to the prototype, an oxide film is formed, surface defects - microcracks, and an unacceptable increase in the content of oxygen and hydrogen in the metal occur.

Example 2. Production of a wire with a diameter of 0.70 mm alloy VT16 from a wire with a diameter of 1.0 mm by the inventive method

The route for manufacturing the wire is given in Table 3. As the initial workpiece, a wire with a diameter of 1.00 mm was used, made by drawing on cassettes with intermediate vacuum annealing. Drawing was carried out through hard-alloy and diamond dies using Vapor lubricant based on mineral oil. All intermediate annealings were performed in an inert atmosphere. Nitrogen was used to create an inert atmosphere. No sticking of metal to the dies during the drawing process was recorded. On the finished size, degreasing and etching of the wire in a nitric-hydrofluoric acid solution was performed with a removal of 20-40 microns to remove the sublubricating layer.

Table 3 - Route for manufacturing wire with a diameter of 0.70 mm from alloy VT16 Drawing pass number Diameter up to, mm Diameter after, mm Draw ratio annealing in nitrogen atmosphere 710°C - 7 minutes 1 1.00 0.96 1.09 annealing in nitrogen atmosphere 710°C - 7 minutes 2 0.96 0.92 1.09 3 0.92 0.89 1.07 annealing in nitrogen atmosphere 710°C - 5 minutes 4 0.89 0.87 1.05 5 0.87 0.84 1.07 annealing in nitrogen atmosphere 710°C - 5 minutes 6 0.84 0.80 1.10 7 0.80 0.76 1.14 annealing in nitrogen atmosphere 710°C - 4 minutes 8 0.76 0.72 1.11 annealing in nitrogen atmosphere 710°C - 4 minutes Etching in size (0.70±0.01) mm with removal of 20-40 µm

As a result of metallographic studies, it was found that on the surface of the wire made by the claimed method, there is no oxide film and surface defects, there are separate risks with a depth of about 10 μm with gentle edges (Fig. 2).

To estimate the amount of gas saturation of the metal of a wire with a diameter of 0.70 mm of the VT16 alloy during annealing, an analysis of the content of oxygen and hydrogen was performed at the initial, intermediate and final sizes - table 4.

Table 4 - the content of oxygen and hydrogen in the wire of 0.70 mm alloy VT16 Size, mm Oxygen, wt.% Hydrogen, wt.% 1.00 0.132 0.009 0.84 0.132 0.008 0.70 0.138 0.010 Requirements OST 1 90013-81 ≤ 0.15 ≤ 0.012

Thus, in the manufacture of wire with a diameter of 0.70 mm alloy VT16 according to the claimed method, a significant increase in the content of oxygen and hydrogen in the finished wire compared to the original workpiece with a diameter of 1.00 mm does not occur. Drawing is possible through carbide or diamond dies using a mineral oil lubricant.

Example 3. Production of a wire with a diameter of 0.60 mm from a wire with a diameter of 1.6 mm of VT6 alloy

The wire manufacturing route is shown in Table 5.

As the initial workpiece, a wire with a diameter of 1.60 mm was used, made by drawing on cassettes with intermediate vacuum annealing. The drawing was carried out through carbide and diamond dies using castor (vegetable) oil based lubricant. All intermediate annealings were performed in a protective atmosphere. Nitrogen was used to create an inert atmosphere. No sticking of metal to the dies during the drawing process was recorded. On the finished size, degreasing and etching of the wire in a nitric-hydrofluoric acid solution with a removal of 40-50 microns was performed to remove grease residues and an under-lubricating layer.

Table 5 - Route for manufacturing wire with a diameter of 0.60 mm from alloy VT6 Drawing pass number Diameter up to, mm Diameter after, mm Draw ratio annealing in nitrogen atmosphere 710°C - 10 minutes 1 1.6 1.47 1.18 annealing in nitrogen atmosphere 710°C - 10 minutes 2 1.47 1.30 1.28 annealing in nitrogen atmosphere 710°C - 8 minutes 3 1.30 1.15 1.28 annealing in nitrogen atmosphere 710°C - 8 minutes 4 1.15 1.04 1.22 annealing in nitrogen atmosphere 710°C - 7 minutes 5 1.04 0.92 1.28 annealing in nitrogen atmosphere 710°C - 7 minutes 6 0.92 0.82 1.26 annealing in nitrogen atmosphere 710°C - 5 minutes 7 0.82 0.72 1.30 annealing in nitrogen atmosphere 710°C - 5 minutes 8 0.72 0.65 1.23 annealing in nitrogen atmosphere 710°C - 4 minutes Etching in size (0.60±0.01) mm with removal of 40-50 µm

As a result of metallographic studies, it was found that there is no oxide film and surface defects in the form of cracks and tears on the wire surface. There are separate longitudinal risks with a depth of not more than 0.01 mm (Fig. 3).

To estimate the amount of gas saturation of the metal of a wire with a diameter of 0.60 mm of the VT6 alloy during annealing, an analysis of the content of oxygen and hydrogen at the initial and final dimensions was performed - table 6.

Table 6 - the content of oxygen and hydrogen in a wire with a diameter of 0.60 mm from the alloy VT6 Size, mm Oxygen, % wt. Hydrogen, % mass 1.60 0.06 0.004 0.60 0.06 0.005 Requirements OST 1 90013-81 ≤ 0.20 ≤ 0.015

Thus, in the manufacture of wire with a diameter of 0.60 mm alloy VT6 according to the claimed method, a significant increase in the content of oxygen and hydrogen in the finished wire compared to the original workpiece with a diameter of 1.60 mm does not occur. Drawing is possible through carbide or diamond dies using a mineral oil lubricant.

Example 4. Production of a wire with a diameter of 0.40 mm from a wire with a diameter of 0.80 mm alloy VT1-00sv

The wire manufacturing route is shown in Table 7.

As the initial workpiece, we used a wire with a diameter of 0.80 mm, made by drawing on cassettes with intermediate annealing in an inert medium. Drawing was carried out through hard-alloy and diamond dies using Vapor grease based on mineral oil. All intermediate annealings were performed in a protective atmosphere. Nitrogen was used to create an inert atmosphere. No sticking of metal to the dies during the drawing process was recorded. On the finished size, degreasing and etching of the wire in a nitric-hydrofluoric acid solution with a removal of 50-60 microns was performed to remove grease residues and an under-lubricating layer.

Table 7 - Route for manufacturing wire with a diameter of 0.40 mm from alloy VT1-00sv Drawing pass number Diameter up to, mm Diameter after, mm Draw ratio annealing in nitrogen atmosphere 650°C - 5 minutes 1 0.80 0.7 1.31 annealing in nitrogen atmosphere 650°C - 5 minutes 2 0.70 0.61 1.32 annealing in nitrogen atmosphere 650°C - 4 minutes 3 0.61 0.56 1.19 annealing in nitrogen atmosphere 650°C - 4 minutes 4 0.56 0.51 1.21 annealing in nitrogen atmosphere 650°C - 3 minutes 5 0.51 0.46 1.23 Etching in size (0.40±0.01) mm with removal of 50-60 µm annealing in vacuum 700°C - 120 minutes

As a result of metallographic studies, it was found that there is no oxide film and surface defects on the wire surface.

To estimate the amount of gas saturation of the metal of a wire with a diameter of 0.40 mm of the VT1-00sv alloy during annealing, an analysis of the content of oxygen and hydrogen at the initial and final dimensions was performed - table 8.

Table 8 - the content of oxygen and hydrogen in a wire with a diameter of 0.40 mm from the alloy VT1-00sv Size, mm Oxygen, % wt. Hydrogen, % mass 0.80 0.08 0.001 0.40 0.08 0.001 Requirements GOST 27265-87 ≤ 0.12 ≤ 0.003

Thus, in the manufacture of wire with a diameter of 0.40 mm alloy VT1-00sv according to the claimed method, there is no increase in the content of oxygen and hydrogen in the finished wire compared to the original workpiece with a diameter of 0.8 mm. Drawing is possible through carbide or diamond dies using a mineral oil lubricant.

Example 5. Production of a wire with a diameter of 0.40 mm from a wire with a diameter of 0.80 mm alloy VT20-1sv

The wire manufacturing route is shown in Table 9.

As the initial workpiece, we used a wire with a diameter of 0.80 mm, made by drawing on cassettes with intermediate annealing in an inert medium. Drawing was carried out through hard-alloy and diamond dies using Vapor grease based on mineral oil. All intermediate annealings were performed in a protective atmosphere. Nitrogen was used to create an inert atmosphere. No sticking of metal to the dies during the drawing process was recorded. On the finished size, degreasing and etching of the wire in a nitric-hydrofluoric acid solution with a removal of 50-60 microns was performed to remove grease residues and an under-lubricating layer.

Table 9 - Route for the manufacture of wire with a diameter of 0.40 mm from the alloy VT20-1sv Drawing pass number Diameter up to, mm Diameter after, mm Draw ratio annealing in nitrogen atmosphere 700°C - 6 minutes 1 0.80 0.7 1.31 annealing in nitrogen atmosphere 700°C - 6 minutes 2 0.70 0.61 1.32 annealing in nitrogen atmosphere 700°C - 5 minutes 3 0.61 0.56 1.19 annealing in nitrogen atmosphere 700°C - 5 minutes 4 0.56 0.51 1.21 annealing in nitrogen atmosphere 700°C - 4 minutes 5 0.51 0.46 1.23 Etching in size (0.40±0.01) mm with removal of 50-60 µm annealing in vacuum 700°C - 120 minutes

As a result of metallographic studies, it was found that there is no oxide film and surface defects on the wire surface.

To estimate the amount of gas saturation of the metal of a wire with a diameter of 0.40 mm of the VT20-1sv alloy during annealing, an analysis of the content of oxygen and hydrogen at the initial and final dimensions was performed - table 10.

Table 10 - the content of oxygen and hydrogen in a wire with a diameter of 0.40 mm from the alloy VT20-1sv Size, mm Oxygen, wt.% Hydrogen, wt.% 0.80 0.07 0.001 0.40 0.07 0.001 Requirements GOST 27265-87 ≤ 0.12 ≤ 0.003

Thus, in the manufacture of wire with a diameter of 0.40 mm alloy VT20-1sv according to the claimed method, the increase in the content of oxygen and hydrogen in the finished wire in comparison with the original workpiece with a diameter of 0.8 mm does not occur. Drawing is possible through carbide or diamond dies using a mineral oil lubricant.

It is allowed to manufacture wire from titanium or other alloys based on it with other diameters and along a different route, but within the framework of the proposed method.

Claims (1)

A method for manufacturing wire from titanium and alloys based on it, including obtaining a pre-deformed workpiece for drawing, sequentially performed drawing cycles with annealing, characterized in that drawing is carried out through carbide or diamond dies with an elongation ratio between annealings of not more than 1.50 using as lubricants for drawing oils on a mineral or vegetable basis, while intermediate annealing is carried out with lubricant residues on the surface of the wire in an atmosphere of inert gas or nitrogen at temperatures of 650 - 750 ° C and holding times of no more than 20 minutes, the products formed during annealing thermal decomposition of lubricants on the wire surface act as a lubricant coating in the next drawing cycle, after drawing is completed and the final size is reached, degreasing and etching are performed until the lubricant coating is completely removed from the wire surface.

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