RU2694099C1 - Method of producing fine wire from biocompatible tinbtazr alloy - Google Patents

Abstract

FIELD: manufacturing technology.

SUBSTANCE: invention relates to methods for making fine wire from biocompatible TiNbTaZr alloy for cava filters and stents. Possibility of obtaining articles of high strength, plasticity and improved operational characteristics is ensured by that ingots are cast in an electric arc furnace with non-consumable tungsten electrode, homogenising annealing of the melted ingots is carried out in vacuum of 5*10^-5 mm Hg at temperature of 600 °C for 12 hours, rolling is performed on a reversing mill, during which the workpiece is squeezed with reduction of its cross-section to cross-section of 10×10 mm², and increase in length, rotary forging with reduction of workpiece cross-section area under action of tool moving in radial direction at relative rotation of workpiece and tool, thereafter, billet is drawn by means of its gradual multiple drawing through drawing tool for gradual reduction of initial billet cross-section to diameter equal to 0.1 mm.

EFFECT: method involves smelting of billet and its deformation-thermal treatment.

1 cl, 5 dwg

Description

A method of obtaining a superelastic titanium-nickel alloy (JP 58161753, IPC C22F 1/10, publ. 26.09.83 g), including the preliminary hardening of the coarse-grained alloy, subsequent cold deformation by rolling with a degree of deformation of more than 20% and annealing at a temperature of 250-550 ° WITH.

The disadvantages of the method are relatively low degrees of deformation (e less than 100%) and limitations on the degree of grinding of the microstructure, which do not allow to achieve the highest mechanical and functional properties. The presence of nickel in this composition can cause in some patients allergic reactions to medical implants made from it.

A method of obtaining alloys TiNb (Ta and / or Zr) and their processing (RF Patent No. 2485197 IPC C22F 1/18, publ. 06.06.2013). The method of processing the alloy includes hot processing by pressure of an ingot of an alloy based on titanium at an initial temperature of 900-950 ° C and a final temperature of 700-750 ° C, thermomechanical processing by multi-pass cold deformation with a total degree of reduction from 31 to 99%, post-deformation annealing at a temperature of 500 -600 ° C and the final quenching cooling in water. After mechanical pseudoelastic cycling of the resulting billet under conditions of uniaxial stretching to achieve 2% strain for 50-100 cycles and unloading.

The disadvantages of this method include processing in the early stages of pressure, without vacuum. When the alloy is heated more than 400 degrees in a vacuum or inert environment, oxygen absorption by titanium and tantalum is noticed, which negatively affects the fatigue properties of the final product - the wire.

The closest to the proposed invention is a method of producing a wire from an alloy of titanium-niobium-tantalum-zirconium with a shape memory effect. Patent RF 2656626. The method for processing the material includes deformation-thermal treatment of a billet of titanium-niobium-tantalum-zirconium alloy, including homogenizing annealing of the ingot with temperature of 600 ° C in a vacuum environment for 16 hours, rolling an ingot into a plate with further cutting it by the electroerosive method into square bars, rotary forging and drawing to the desired diameter and in 0.28 mm.

The disadvantages of this method include rolling an ingot into a plate with its further cutting. This method requires an additional technological stage of work and, accordingly, equipment for EDM cutting, as well as introduces a reduction in the length of the resulting wire in relation to the proposed method several times.

The objective of the invention is the creation of a method of manufacturing a thin wire from a biocompatible nickel-free alloy for use in medical devices Cava filter and stent.

The technical result is to obtain a single thin biocompatible wire with a diameter of 0.1 mm from an alloy of TiNbTaZr.

The technical result is achieved by the fact that in the method of obtaining a thin wire from a biocompatible TiNbTaZr alloy consisting of melting a billet, deformation-heat treatment of a billet from a titanium-niobium-tantalum-zirconium alloy, combining homogenizing annealing, intensive multi-stage plastic deformation and recrystallization. this formation of titanium and tantalum oxides by carrying out annealing in vacuum of 5 x 10 ^-5 torr, a single wire is obtained from the whole ingot without the need for separation slab TCA on parts as in the prior art, which increases the practicality of the method. According to the invention, the production of wire is carried out in 5 stages. At the first stage, using titanium iodide, zirconium iodide, technically pure niobium and technically pure tantalum as the charge materials, ingot smelting was carried out in an electric arc vacuum furnace with non-consumable tungsten electrode, in the second stage, the ingots were subjected to homogenization annealing in a vacuum 5 * 10 ^-5. mmHg. at a temperature of 600 ° C for 12 hours, the third stage is the rolling process, is that the workpiece is compressed (squeezed), passing into the gap between the rotating rollers, while it decreases in its cross section and increases in length. Rolling occurs on the reversing mill to a section of 10 × 10 mm ² . At the fourth stage, rotational forging, which consists in reducing the cross-sectional area of the workpiece under the influence of a tool moving in the radial direction during relative rotation of the workpiece and tool. At the fifth stage, drawing is carried out, a process characterized by gradual single or multiple pulling of the latter through a special drawing tool designed to gradually reduce the cross section of the original billet to the desired diameter of 0.1 mm (Fig. 5).

To date, the most popular alloy NiTi for the manufacture of medical products such as Stent. However, the constituent nickel is toxic. There are studies of alloys with shape memory effect that do not contain nickel. The alloys TiNbTa and TiNbZr seem promising. An alloy with Zr has a large Young's modulus than is necessary in stents and Kafa-filters, but when added, the Young's Young's modulus enters the required bounds.

The alloy is quite technologically advanced and allows for mechanical processing at room temperature, when removing the work hardening by annealing.

An example of a specific implementation of the invention:

Electric arc remelting

The smelting was carried out in an electric arc vacuum furnace with a non-consumable tungsten electrode LK8 from LEYBOLD-HERAEUS (Germany). The weights were placed in a copper water-cooled mold, after which the working chamber was sealed and evacuated to a pressure of 1 * 10-2 mm. Hg After that, argon was fed into the chamber to a pressure of 2 atm. In the process of the first 2-3 remeltings, a single ingot was obtained, the subsequent remeltings were aimed at obtaining a uniform chemical composition throughout the entire ingot volume. The duration of each melting of one ingot is 1-1.5 minutes. Before the ingot was melted, the getter melted. An ingot of zirconium iodide weighing 15-20 g was used as a getter. Each ingot was melted down 7 times. Further, under these conditions, the obtained ingots are melted into a single ingot weighing 60 g for 2 remeltings. The final ingot had a length of 60-70 mm, a width of 20-25 mm, a height of 10-12 mm.

Figure 1 shows a diagram of a vacuum arc furnace with a non-consumable electrode, where: 1 is a furnace body, 2 is a non-consumable electrode, 3 is an electrode holder, 4 is a crystallizer, 5 is a pallet, 6 is a vacuum seal, 7 is an electrode transfer mechanism, 8 is automatic the electrode displacement controller, 9 — the furnace power source, 10 — the vacuum system, 11 — the current regulator, 12 — the control panel 13 — the movable flow.

Heat treatment.

Smelted ingots were subjected to homogenization annealing in an SSHVZ-1.2,5 / 25-I3 furnace. The ingots were annealed in vacuum 5 * 10 ^-5 mm Hg. at a temperature of 600 ° C for 12 hours

Ingot rolling

The essence of the rolling process is that the workpiece is crimped (compressed), passing into the gap between the rotating rollers, while it decreases in its cross section and increases in length. The shape of the cross section is called a profile.

The rolling process is provided by friction forces between the rotating tool and the workpiece, due to which the workpiece moves in the gap between the rollers, while at the same time deforming. At the moment of capture of the metal from the side of each roll, two forces act on the metal: the normal force N and the tangential friction force T (Fig.).

Figure 2 shows a diagram of the forces acting during rolling: N is the normal force; T - tangential friction force; α - the angle between the normal force and the vertical

Rolling took place on the reverse mill DUO-300. Smelted ingots were deformed in air to a cross section of 10 × 10 mm ² . The blanks were heated in air to a temperature of 600 ° C. Heating was carried out immediately before the deformation in the KYLS 20.18.40 / 10 furnace.

Rotary forging.

Rotational forging - reducing the cross-sectional area of the workpiece under the influence of a tool moving in the radial direction with the relative rotation of the workpiece and the tool.

Figure 3 shows the rotational forging scheme.

Rotational forging of workpieces was successively carried out on radial forging machines В2129.02, В2127.01, В2123.01 (Russia) with a successive change of strikers. Preheating of the blanks in the air just before deformation was carried out in a PTS-2000-40-1200 furnace (Russia).

Drawing.

Wire drawing is a process of metal processing by pressure, characterized by a gradual single or multiple pulling the latter through a special drawing tool designed to gradually reduce the cross section of the original piece. The schematic diagram of the drawing is shown in the figure, where 1 is a die; 2 - wire; Fo is the cross-sectional area at the entrance to the die; Fk is the cross-sectional area at the exit of the die.

Figure 4 shows the drawing pattern.

From a wire diameter of 2 mm to a diameter of 0.4 mm, drawing was performed on a C7328 / ZF machine manufactured by THE NORTHWEST MACHIBE CO.LTD (China). The dragging took place in the air. Aquadag was used as a lubricant.

From a diameter of 2 mm to a diameter of 0.4 mm, drawing was carried out on a UDZWGW 100/8 machine (Germany). Drawing speed 0.7 m / min. From a diameter of 0.4 mm to 0.1 mm, the pitch of the nozzles was 0.02 mm. The dragging took place in the air. Aquadag was used as a lubricant.

Thus, the proposed invention allows to produce a thin wire from an alloy of titanium-niobium-tantalum-zirconium with shape memory effect, as well as to minimize the formation of titanium and tantalum oxides, which provides the material with increased strength, ductility and improved performance characteristics.

Claims (1)

A method for producing a fine wire of a biocompatible alloy TiNbTaZr, comprising smelting the workpiece in the form of an ingot of an alloy of titanium-niobium-tantalum-zirconium, and deformation-thermal processing of the workpiece, comprising homogenizing annealing intensive plastic deformation and recrystallization annealing, characterized in that the smelting of ingots carried out in an electric arc vacuum furnace with a non-consumable tungsten electrode, homogenizing annealing of melted ingots is carried out in a vacuum of 5 * 10 ^-5 mm Hg. at a temperature of 600 ° C for 12 hours, rolling is performed on a reversing mill, during which the workpiece is compressed with a decrease in its cross section to a cross section equal to 10 × 10 mm ² and an increase in length, rotary forging with a decrease in the cross-sectional area of the workpiece under the influence moving in the radial direction of the tool with the relative rotation of the workpiece and the tool, then dragging the workpiece through its gradual multiple pulling through a drawing tool with a phased mind by reducing the cross-section of the original billet to a diameter of 0.1 mm.

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