A laser welding method suitable for heterogeneous wire connection of magnesium alloy and medical titanium alloy

Abstract

The present application relates to the field of connection (welding) of heterogeneous materials, and is a laser welding method suitable for connecting magnesium alloy and medical titanium alloy heterogeneous wires. The wire needs to be pre-tightened by a clamp, and the welding process needs to pass through a protective gas to avoid oxidation of the metal. The connection between the two heterogeneous wires is achieved by changing the relevant parameters of the laser. The welded joint is connected together by element diffusion, and the tensile strength of the welded joint can reach 62-74 MPa. The present application uses the method of laser welding, uses the lap joint mode, realizes the welding of heterogeneous material wires, and provides a feasible scheme for solving the problem of degradability of the front end of the vascular stent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of connecting (welding) of dissimilar materials, and particularly relates to a laser welding method suitable for connecting magnesium alloy and medical titanium alloy dissimilar wires. BACKGROUND

[0002] Aortic dissection is caused by a tear in the inner lining of the aortic wall, through which blood enters the middle layer of the aortic wall, forming a dissection hematoma, and gradually extending and peeling off the intima and media of the aorta. At present, the treatment for aortic dissection is mainly endovascular aortic repair, which can effectively reduce the risk of aortic rupture by placing a covered stent at the lesion site to block the primary tear of the dissection and reduce the pressure on the blood vessel wall.

[0003] The medical device used in endovascular aortic repair is usually a covered stent, which is fixed at the lesion site by an anchor device at the front end. Generally, the anchor device is 10-20% larger in diameter than the aorta. After endothelialization, the fixation of the anchor device at the front end of the stent disappears, but the pressure on the inner wall of the blood vessel caused by the larger diameter will cause damage to the intima of the blood vessel, leading to a new tear. Therefore, the development of a covered stent with a degradable anchor device can achieve the degradation of the anchor end after endothelialization of the stent, which can effectively reduce the damage to the inner wall of the blood vessel caused by the front end fixation component and reduce the damage and long-term risk of permanent implantation of the anchor end of the stent to the human blood vessel.

[0004] In clinical practice, the covered stent is usually woven from medical titanium alloy wire. In order to achieve degradation of the anchor end after endothelialization of the stent, a biodegradable metal material can be connected to the front end of the medical titanium alloy wire, which will serve as the anchor end part. Magnesium alloy is selected as the biodegradable metal material because it has excellent biocompatibility and exhibits rapid endothelialization and low thrombogenicity when used as a vascular stent material.

[0005] Compared with traditional methods such as adhesive bonding and mechanical connection, laser welding can provide better corrosion resistance and mechanical strength of the joint. However, due to the large differences in physical, chemical and metallurgical properties between magnesium and titanium, it is difficult to weld magnesium / titanium dissimilar metals. Currently, there is no research on the welding of magnesium / titanium dissimilar metal wires, but only on the welding of magnesium / titanium dissimilar metal plates. Compared with the welding of plate stents, the welding of metal wires has very high tolerance requirements for the overlap gap. When the thickness of the connected material is less than 1 mm, the gap between the connected materials cannot exceed 10% of the thinnest material thickness, otherwise the connection cannot be formed.

[0006] Therefore, in order to develop a covered stent with a degradable anchor device at the front end, a laser welding method suitable for connecting magnesium alloy and medical titanium alloy dissimilar wires is proposed SUMMARY

[0007] The present application aims to provide a laser welding method suitable for the connection of magnesium alloy and medical titanium alloy heterogeneous metal wires.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0009] A laser welding method suitable for the connection of magnesium alloy and medical titanium alloy heterogeneous metal wires, comprising the following steps:

[0010] Step 1: polish the magnesium alloy metal wire with sandpaper to remove the surface oxides, and clean the surface grease with acetone; immerse the medical titanium alloy metal wire in acid to remove the surface oxide layer, and clean the surface grease with acetone.

[0011] Step 2: process a clamp for clamping the metal wire by wire cutting.

[0012] Step 3: the joint of the magnesium alloy metal wire and the titanium alloy metal wire adopts a lap joint form, and the two metal wires are fixed by the clamp. The clamp can adjust the lap joint gap of the two metal wires by applying a clamping force.

[0013] Step 4: use pulse laser and continuous laser simultaneously for welding, the current of the pulse laser is 65-85A, the defocusing amount is 130-180mm, the welding speed is 2.8-3.0m / min, the power is 30-50W, and the frequency is 30-50Hz; the power of the continuous laser is 20-60W, and the pulse laser and the continuous laser are offset by 0.1-0.3mm to one side of the magnesium alloy metal wire.

[0014] Further, high-purity argon is used to protect the welding area during welding, and a diode continuous laser and an Nd:YAG pulse laser are used to weld the two heterogeneous metal wires.

[0015] Further, the chemical composition and mass percentage of the magnesium alloy are Y: 3-4.1%, Re: 3-4%, Zr: 0.3-1%, and the rest is Mg.

[0016] Further, the titanium alloy is a medical titanium alloy, and the chemical composition and mass percentage are Ni: 50-60%, Zr: 0.1-1%, Nb: 0.1-0.5%, and the rest is Ti.

[0017] Further, the wavelength of the continuous laser is 980nm.

[0018] Further, the wavelength of the pulse laser is 1064nm.

[0019] Further, the pulse laser and the continuous laser are simultaneously performed in the welding process.

[0020] The present application has the following advantages: the laser welding is used to realize the welding of two kinds of heterogeneous material wires, and provides a feasible scheme for solving the degradable problem of the front end of a blood vessel stent. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a welding schematic diagram;

[0022] Figure 2 is a clamp schematic diagram;

[0023] Figure 3 is a microstructure of a welding seam;

[0024] Figure 4 is an element distribution at a welding seam.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the technical solutions in the embodiments of the present application will be described below, and it should be noted that the embodiments are only descriptive and do not limit the present application in any way. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present application, but not all the embodiments.

[0027] Embodiment 1

[0028] First, the magnesium alloy wire (Y: 4.05%, Re: 3%, Zr: 0.52%, and the rest is Mg) and the medical titanium alloy wire (Ni: 56.3%, Nb: 0.5%, Zr: 0.47%, and the rest is Ti) are surface cleaned: the magnesium alloy wire is polished with sandpaper to remove the surface oxide, and is cleaned with acetone to remove the surface grease; the medical titanium alloy wire is soaked in acid to remove the surface oxide layer, and is cleaned with acetone to remove the surface grease.

[0029] Then, the clamp for clamping the metal wires is processed by wire cutting. The joint of the magnesium alloy metal wire and the titanium alloy metal wire adopts a lap joint form, and the two metal wires are fixed by the clamp. The pre-tightening force is applied to the metal wires by the clamp, and the welding is performed by using the pulse laser and the continuous laser simultaneously. High-purity argon is used to protect the welding area during the welding process. The two kinds of heterogeneous metal wires are welded by using a diode continuous laser and an Nd:YAG pulse laser. The magnesium alloy metal wire and the medical titanium alloy metal wire with a diameter of 0.5 mm are welded when the current of the pulse laser is 70 A. At the same time, the frequency of the pulse laser is 30 Hz, the power of the continuous laser is 40 W, the power of the pulse laser is 32 W, the welding speed of the pulse laser is 2.8 m / min, the defocusing amount of the pulse laser is 145 mm, and the pulse laser and the continuous laser are offset to the side of the magnesium alloy metal wire by 0.2 mm. The wavelength of the continuous laser is 980 nm, and the wavelength of the pulse laser is 1064 nm. The obtained wire welding material can obtain a heterogeneous alloy joint with a tensile strength of 62.47 MPa (tensile test conditions: room temperature, using a tensile testing machine to test the mechanical properties at a tensile speed of 1 mm / min).

[0030] Example 2

[0031] Firstly, the magnesium alloy metal wire (Y: 4.05%, Re: 3%, Zr: 0.52%, and the rest is Mg) and the medical titanium alloy metal wire (Ni: 56.3%, Nb: 0.5%, Zr: 0.47%, and the rest is Ti) are surface cleaned: the magnesium alloy metal wire is polished with sandpaper to remove the surface oxide, and acetone is used to clean and remove the surface grease; the medical titanium alloy metal wire is soaked in acid to remove the surface oxide layer, and acetone is used to clean and remove the surface grease.

[0032] Then, the clamp for clamping the metal wires is processed by wire cutting. The joint of the magnesium alloy metal wire and the titanium alloy metal wire adopts a lap joint form, and the two metal wires are fixed by the clamp. The pre-tightening force is applied to the metal wires by the clamp, and the welding is performed by using the pulse laser and the continuous laser simultaneously. High-purity argon is used to protect the welding area during the welding process. The two kinds of heterogeneous metal wires are welded by using a diode continuous laser and an Nd:YAG pulse laser. The magnesium alloy metal wire and the medical titanium alloy metal wire with a diameter of 0.5 mm are welded when the frequency of the pulse laser is 40 Hz. At the same time, the current of the pulse laser is 70 A, and the rest of the welding parameters are the same as in Example 1. The obtained wire welding material can obtain a heterogeneous alloy joint with a tensile strength of 68.72 MPa (tensile test conditions are the same as in Example 1)

[0033] Example 3

[0034] First, surface cleaning was performed on the magnesium alloy wire (Y: 4.05%, Re: 3%, Zr: 0.52%, and the rest Mg) and the medical titanium alloy wire (Ni: 56.3%, Nb: 0.5%, Zr: 0.47%, and the rest Ti). The magnesium alloy wire was polished with sandpaper to remove the surface oxide, and was cleaned with acetone to remove the surface grease. The medical titanium alloy wire was immersed in acid to remove the surface oxide layer, and was cleaned with acetone to remove the surface grease.

[0035] Then, a clamp for clamping the metal wires was processed by wire cutting. The joint of the magnesium alloy wire and the titanium alloy wire was in the form of lap joint, and the two metal wires were fixed by the clamp. The clamp was used to apply a pre-tightening force to the metal wires, and the welding was performed by using the simultaneous mode of pulsed laser and continuous laser. During the welding, high-purity argon was used to protect the welding area. The diode continuous laser and the Nd:YAG pulsed laser were used to weld the two kinds of heterogeneous metal wires. The magnesium alloy wire and the medical titanium alloy wire with a diameter of 0.5 mm were welded when the current of the pulsed laser was 75 A. At the same time, the frequency of the pulsed laser was 40 Hz, and the other welding parameters were the same as those in Example 1. The obtained wire-bonding material can be used to obtain a heterogeneous alloy joint with a tensile strength of 72.68 MPa (the tensile test conditions are the same as those in Example 1).

[0036] As shown in Figure 3 , the element distribution is as shown in Figure 4 , and the microstructure is as shown in Figure 4 It can be seen that the two kinds of heterogeneous metals are connected by element diffusion.

[0037] Although the embodiments of the present application have been described above, it should be understood that the above-described embodiments are exemplary and should not be construed as limiting the present application. Those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A laser welding method suitable for connecting magnesium alloy and medical titanium alloy heterogeneous metal wires, characterized in that: The following steps are involved: Step 1: Sand the magnesium alloy wire with sandpaper to remove the surface oxide, and clean it with acetone to remove the surface grease; soak the medical titanium alloy wire in acid to remove the surface oxide layer, and clean it with acetone to remove the surface grease; Step 2: Process the fixture for clamping the wire by wire cutting; Step 3: The magnesium alloy wire and the titanium alloy wire are joined in an overlapping manner, and the two wires are fixed with a clamp; the clamp can adjust the overlapping gap between the two wires by applying a clamping force; Step 4: Pulse laser and continuous laser are used simultaneously for welding. The pulse laser current is 65 ~ 85 A, the defocus distance is 130 ~ 180 mm, the welding speed is 2.8 ~ 3.0 m / min, the power is 30 ~ 50 W, and the frequency is 30 ~ 50 Hz; the continuous laser power is 20 ~ 60 W, and both the pulse laser and the continuous laser are offset by 0.1 ~ 0.3 mm to one side of the magnesium alloy wire.

2. The laser welding method for connecting magnesium alloy and medical titanium alloy heterogeneous metal wire according to claim 1, characterized in that: During the welding process, high-purity argon gas is used to protect the welding area, and diode continuous laser and Nd:YAG pulse laser are used to weld the two heterogeneous metal wires.

3. The laser welding method for connecting magnesium alloy and medical titanium alloy heterogeneous metal wires according to claim 1, characterized in that: The chemical composition and mass percentage of the magnesium alloy are Y: 3 ~ 4.1%, Re: 3 ~ 4%, Zr: 0.3 ~ 1%, and the rest is Mg.

4. The laser welding method for connecting magnesium alloy and medical titanium alloy heterogeneous metal wires according to claim 1, characterized in that: The titanium alloy is a medical titanium alloy, and its chemical composition and mass percentage are Ni: 50-60%, Zr: 0.1-1%, Nb: 0.1-0.5%, and the rest is Ti.

5. The laser welding method for connecting magnesium alloy and medical titanium alloy heterogeneous metal wires according to claim 1, characterized in that: The wavelength of the continuous laser is 980 nm.

6. The laser welding method for connecting magnesium alloy and medical titanium alloy heterogeneous metal wires according to claim 1, characterized in that: The wavelength of the pulse laser is 1064 nm.

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