JP2001276997A - Mig welding wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a MIG welding wire made of pure titanium which hardly brings buckling and jamming and which can keep favorable feeding propertry of the wire and has no fear of breakage in the wire drawing process of cold drawing process for an industrial pure titan raw material and deterioration of coiling property in the coiling process of the wire. SOLUTION: While keeping a sufficient mechanical strength that the tensile strength σ of an industrial pure titan wire is 600-1,000 MPa, the wire is prevented from jamming and buckling when it is fed. As the arithmetical mean roughness Ra of the wire surface is 1.0 νm or smaller, the friction between the wire surface and the inside face of the electrode tip is reduced and hence, the wire can be smoothly fed and the fear that jamming or buckling arises is further reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MIG welding wire made of industrial pure titanium.

[0002]

2. Description of the Related Art Titanium and its alloys are activated at a temperature of 500 ° C. or higher, and when they absorb oxygen, nitrogen and hydrogen, they generate pores and become brittle, so that special consideration must be given to their joining. Therefore, conventionally, TIG welding (tungsten inert gas arc) has been used to join a pure titanium or titanium alloy base material.
welding) is adopted. In the TIG welding, for example, as shown in FIG. 3A, an arc AR is generated between the tungsten electrode 101 and a pure titanium or titanium alloy base material WP in an inert gas IG atmosphere such as argon or helium. This is a non-consumable electrode welding method in which the tip of an industrial pure titanium filler material (welding wire) 104 is fed into the arc AR through the feed roller 102 and the wire guide 103 for welding. 105 is an inert gas IG from the tip opening
Gas nozzle (torch) for injecting gas, 106 is the torch 1
A support fixed to 05 and holding the tungsten electrode 101, WM is a weld metal, and MP is a molten pool. In such TIG welding, the arc length and the welding speed can be automatically adjusted to be constant, respectively. By maintaining the arc length at a constant value, the arc is stabilized, and the bead finish is improved.

As a welding method capable of further improving the efficiency, MIG welding (metallic inert gas arc welding)
ding) is known. MIG welding, for example,
As shown in (b), an electrode wire 201 made of industrial pure titanium in an inert gas IG atmosphere such as argon or helium.
An arc AR is generated between the electrode wire 201 and the base material WP made of pure titanium or titanium alloy, and as the electrode wire 201 is melted, the feed roller 202 feeds the distal end of the electrode wire 201 into the arc AR and welds. This is a consumable electrode welding method. A gas nozzle (torch) 205 is provided with a flexible conduit tube 204 at the base end side and ejects an inert gas from the tip. A gas nozzle 206 is fixed to the torch 205 to hold the electrode wire 201 and supply current to the electrode wire 201. The electrode tip (contact tip), WM is a weld metal, and MP is a molten pool. According to the MIG welding, the penetration is deepened due to the improvement of the melting energy and the occurrence of poor welding is suppressed, while the efficiency is improved.
There is an advantage that the tip of the torch 205 is small and welding in a narrow place becomes easy.

[0004]

On the other hand, MIG
In the welding, when the strength of the electrode wire 201 (hereinafter, also referred to simply as a MIG welding wire, also simply referred to as a wire) is not sufficient, or when the friction between the surface of the wire 201 and the inner surface of the electrode tip 206 is large, the feeding of the wire 201 is poor. Become,
The wire 201 may be clogged or buckled.

An object of the present invention is to prevent buckling or clogging during MIG welding, maintain good wire feedability, and perform a wire drawing process by cold drawing of pure titanium material for industrial use. An object of the present invention is to provide a pure titanium MIG welding wire that is less likely to be broken and less likely to deteriorate winding property in a wire winding process.

[0006]

In order to solve the above-mentioned problems, the MIG welding wire of the present invention is
The tensile strength σ of industrial pure titanium wire is 600 to 1000
MPa, and the arithmetic mean roughness Ra of the surface of the wire is 1.0 μm or less.

That is, a sufficient mechanical strength such that the tensile strength σ of the industrial pure titanium wire is 600 to 1000 MPa is secured to prevent clogging and buckling during wire feeding. Further, since the arithmetic average roughness Ra of the wire surface is 1.0 μm or less, the friction between the wire surface and the inner surface of the electrode tip is reduced, the wire is smoothly fed, and the wire is clogged or buckled. The fear is even smaller.

[0008] In this case, if the tensile strength σ is less than 600 MPa, the mechanical strength of the wire becomes insufficient, and buckling may occur during wire feeding. On the other hand, when the tensile strength σ is 10
If it exceeds 00 MPa, the rigidity of the wire becomes too large and the ductility is reduced, so that there is a risk of breakage during cold drawing of the pure titanium industrial material. Further, there is a possibility that the wire cannot be wound in the wire winding step or a predetermined winding shape cannot be imparted to the wire.

If the arithmetic average roughness Ra exceeds 1.0 μm, the friction between the wire surface and the inner surface of the electrode chip becomes uneven, causing a fluctuation in the wire feeding speed, and a power supply failure due to chip wear. And may cause the arc to become unstable.

[0010] The tensile strength σ of the wire is determined by the working rate (cross-sectional reduction rate) r at the time of cold drawing of an industrial pure titanium material.
Alternatively, it has a correlation with the hardness at the surface or cross section of the wire (micro Vickers hardness HmV as an example). For example, when the working ratio r at the time of cold drawing of an industrial pure titanium material is 40 to 80%, the tensile strength σ of the wire is
Corresponds to 600 to 1000 MPa. Therefore, the processing rate r can be used as an index of the wire strength together with or instead of the tensile strength σ of the wire.

Further, as for the surface roughness of the wire, a maximum height Ry or a ten-point average roughness Rz can be used together with or instead of the arithmetic average roughness Ra. At this time, when the arithmetic average roughness Ra is 1.0 μm or less, the maximum height Ry is 15 μm or less, and the ten-point average roughness Rz is 1
0 μm or less is desirable.

Next, in order to facilitate handling as a wire, the wire diameter d of the wire is desirably 2 mm or less. When the wire diameter d exceeds 2 mm, the wire becomes difficult to bend, and the feeding property may be impaired. Note that the lower limit of the wire diameter d is set to about 0.6 mm as a limit at which the electrode tip can hold the wire.

Furthermore, in order to secure the feeding property while maintaining the current supply to the electrode tip, when the reference wire diameter of the wire is d0, the dimensional tolerance d0-d of the wire diameter d of the wire is 0 ≦ ( d0-
d) It is desirable that ≦ 0.03 mm. (D0-d) <0mm
In such a case, the wire feeding may be hindered and buckling may occur. When (d0−d)> 0.03 mm,
There is a possibility that current cannot be supplied to the electrode tip.

Regarding welding wires made of pure titanium for industrial use, JIS H3331-1988 and ANSI / AWS
A 5.16-90. These regulations mainly stipulate the chemical composition of the welding wire made of pure titanium for industrial use, the wire diameter of the wire rod, and its tolerance (dimensional tolerance).

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of a method for manufacturing a MIG welding wire according to the present invention will be described. The MIG welding wire made of industrial pure titanium according to the present invention is, for example, a heat treatment step by annealing → a surface treatment step by applying a lubricating film → a wire drawing step by cold drawing → a surface treatment step by pickling →
It is manufactured through a winding process on a wire spool. FIG.
1 schematically shows an example of a manufacturing process of such an industrial pure titanium MIG welding wire.

(1) Heat Treatment Step by Annealing A coil-shaped industrial pure titanium material TM is introduced into the heating furnace 10 maintained in an inert gas atmosphere such as argon or helium, a vacuum atmosphere or an air atmosphere. 800
C. (for example, 700.degree. C.) for 4 to 6 hours (for example, 5 hours). By this heat treatment, the material for industrial pure titanium TM
Since the extensibility is imparted to the steel sheet, cold drawing in a subsequent step is facilitated. In addition, as the material TM for industrial pure titanium,
For example, a titanium wire specified in JIS H4670-1993 can be used. Further, as another industrial pure titanium material TM, a titanium ingot having a purity of 99.4% or more obtained from sponge titanium or the like specified in JIS H2151-1994 or a bar obtained by extracting the same,
A wire or the like may be used.

(2) Lubricating Coating Generation Step (Surface Treatment Step) The annealed industrial pure titanium material TM is immersed in a lubricant tank 20 filled with a lubricant 21 such as a lime solution.
A lubricating film such as lime is formed on the surface. Such a coating has a lubricating action between the drawing die in the subsequent drawing step and improves the drawability.

(3) Wire drawing process by cold drawing process The industrial pure titanium material TM that has gone through the descaling process is supplied to a cold drawing device 30 having a die holder 31 and a drawing die 32 fixed to the die holder 31. be introduced. Specifically, by inserting an industrially pure titanium material TM through a drawing die 32 having a substantially conical cross section so that the outlet side has a smaller diameter than the inlet side, and pulling it from the outlet side at room temperature. Thus, an industrial pure titanium wire rod TW having a cross section substantially the same as the cross sectional shape of the exit of the drawing die 32 is obtained.

In general, it is known that a drawn wire has an increased mechanical strength such as tensile strength, hardness, fatigue strength and the like, and a reduced ductility such as elongation and drawn as the working ratio increases. ing.

(4) Descaling Step by Pickling or Polishing (Surface Treatment Step) The surface of the industrial pure titanium wire rod TW that has undergone the heat treatment step, the film formation step, and the wire drawing step is subjected to oxidation which is an obstacle during welding. A film (scale) is formed. An example of a method of chemically removing the oxide film to smooth the surface is an acid washing method. Here, the pickling tank 40 contains 5 to 10% by weight.
(E.g., 5% by weight) hydrofluoric acid and 30-40% by weight (e.g., 30% by weight) nitric acid, and the temperature is 30-40%.
By filling a hydrofluoric acid-nitric acid-based pickling solution 41 heated to 60 ° C. (for example, 40 ° C.) and immersing the industrial pure titanium material TM in the pickling solution 41 for 1 to 5 minutes (for example, 2 minutes) Clean the surface. Here, a hydrofluoric acid-nitric acid pickling solution 4
Instead of 1, a sulfuric acid-nitric acid pickling solution or a hydrochloric acid-sulfuric acid pickling solution may be used, and the content, temperature and time can be appropriately set.

Incidentally, in order to remove the oxide film and to smooth the surface, there is a method other than the above, in which the surface is mechanically polished using a buff, a belt or the like. Generally, the surface roughness of a wire after scale removal tends to be smaller by a polishing method than by a pickling method. It is considered that in the pickling method, the wire rod surface becomes moderately rough due to the cutting action of the pickling liquid. However, the polishing method is often carried out as a second-step removal method after the first-step scale removal by pickling, which tends to increase the cost. Therefore, it is necessary to select a method of removing scale in consideration of cost and effect.

(5) Winding Step on Wire Spool The industrial pure titanium wire TW that has undergone the above descaling step passes through the straightening section 49 to the wire spool 50 (spool diameter D).
It is wound up to S) and used as a MIG welding wire 301 described later.

An MIG welding apparatus for performing MIG welding of an engine exhaust pipe EP made of, for example, pure titanium or a titanium alloy as a base material using the industrially pure titanium wire TW manufactured as described above as a MIG welding wire. One example of 300 is shown in FIG. In an atmosphere of an inert gas IG such as argon or helium, between an MIG welding wire 301 formed of an industrial pure titanium wire rod TW and an exhaust pipe EP (base material) made of pure titanium or a titanium alloy. An arc AR is generated. As the wire 301 melts, the feed roller 302 causes the wire 30 to move.
1 is fed into the arc AR and welded. 303
Are straightening rollers for straightening the wire 301;
05 is a flexible conduit tube 30 on the proximal end side.
4, a torch for blowing out inert gas from the tip, 3
Reference numeral 06 denotes an electrode tip (contact tip) that holds the wire 301 and supplies a current to the wire 301, WM denotes a weld metal, and MP denotes a molten pool. In addition, in order to perform shielding with an inert gas until the temperature of the welded portion becomes 500 ° C. or less (a temperature at which titanium and its alloy become inactive), an after shield jig 30 covering the rear in the welding direction is used.
7 and a back shield jig 308 that covers the back side of the welded portion.

[0024]

EXAMPLES (Preparation of MIG Welding Wire 301) A total of six types of MIG welding wires 301 for testing were prepared based on the manufacturing process shown in FIG. That is, JIS H46
An industrial pure titanium material TM composed of a 70-1993 titanium wire was placed in a heating furnace 20 maintained in an air atmosphere for 60 hours.
Heating was performed at 0 ° C. for 5 hours to perform annealing. Next, these industrial pure titanium materials TM are immersed in a lime solution or the like,
A lubricating film such as lime was formed on the surface. Then, for these industrial pure titanium materials TM, the reference wire diameter d0
Was changed to a range of 20 to 80% so as to obtain a pure titanium wire TW for industrial use. Further, these industrial pure titanium wires TW were immersed in a hydrofluoric-nitric acid pickling solution 31 to remove scale. At this time, the concentration of the hydrofluoric-nitric acid-based pickling liquid 31 is determined for each wire (5 to 10% by weight of hydrofluoric acid, 30 to 40% by weight of nitric acid), temperature (30 to 60 ° C),
The immersion time (1-5 minutes) was changed. Each of the industrial pure titanium wires TW has a spool diameter Ds of 300.
The wire was wound around a 50 mm wire spool 50.

(Measurement of Dimensional Tolerance and Mechanical / Surface Characteristics) The maximum and minimum values of the wire diameter d (and each of the six types of industrially pure titanium wire TW used as the MIG welding wire 301). The minimum value and the maximum value of the dimensional tolerance d0-d) are measured. Next, the tensile strength σ of each wire TW
Is measured. Further, regarding the surface roughness of each wire TW,
The arithmetic average roughness Ra, the maximum height Ry, and the ten-point average roughness Rz are measured. The cut-off value and the evaluation length in the arithmetic average roughness Ra, and the reference length and the evaluation length in the maximum height Ry and the ten-point average roughness Rz are all JI.
The standard value of SB0601-1994 is used. Table 1 shows a list of the above measurement results.

(Sendability test) Each industrial pure titanium wire T
W (the wire spool 50 around which W was wound) was set in the MIG welding apparatus 300 in FIG. 2, and welding with the MIG welding wire 301 was performed. Specifically, two torches 305 each having a length of 1.5 m and 3 m (represented by a curve distance L in FIG. 2) of the conduit tube 304 are prepared, and each of the torches 305 is subjected to MIG welding under the following conditions. Was performed to evaluate the feedability of the wire 301. The evaluation is
○ if the wire can be welded without any trouble in the wire feed (good feedability), 場合 if the wire buckles at the start of welding
X (unsatisfactory feedability) when wire feeding was not possible. Table 1 shows the test results. <Welding conditions> ・ Welding method: pulse arc bead-on welding ・ Average current: 110 A ・ Voltage: 18 V ・ Welding speed: 60 cm / min ・ Shielding gas: 100% argon

[0027]

[Table 1]

Table 1 shows the following. (A) As a sufficient mechanical strength of the wire TW, a tensile strength σ
Satisfies 600 to 1000 MPa.
If the tensile strength σ is less than 600 MPa, the mechanical strength of the wire TW is insufficient, and there is a strong possibility that buckling occurs during wire feeding (Test Nos. 1-1 and 1-2). On the other hand, if the tensile strength σ exceeds 1000 MPa, the rigidity of the wire TW becomes too large and the ductility is reduced, so that there is a risk of a breakage when the industrial pure titanium material TM is cold drawn.

(B) The tensile strength σ of the wire TW is substantially proportional to the working ratio r in cold drawing, and has a strong correlation. Therefore, the processing rate r is used together with the tensile strength σ of the wire TW or instead of the tensile strength σ of the wire TW,
It can be used as an indicator of wire strength (Test N
o. 1-1 to 4-2).

(C) If the arithmetic mean roughness Ra of the surface of the wire TW is 1.0 μm or less, the friction between the surface of the wire 301 and the inner surface of the electrode tip 306 is reduced, and the wire 301 is smoothly fed. Clogging and buckling of 301 are less likely to occur. The arithmetic average roughness Ra is 1.0 μm.
When the distance exceeds m, the friction between the surface of the wire 301 and the inner surface of the electrode tip 306 becomes uneven, causing a fluctuation in the wire feeding speed. In addition, a power supply failure occurs due to the wear of the tip 306. Or the wire may buckle (Test Nos. 5-1 and 5-
2).

(D) Regarding the surface roughness of the wire TW, the arithmetic average roughness Ra is the maximum height Ry or the ten-point average roughness Rz.
Is almost proportional to and has a strong correlation. Therefore, the maximum height Ry or the ten-point average roughness Rz can be used together with the arithmetic average roughness Ra or instead of the arithmetic average roughness Ra. At this time, the arithmetic average roughness Ra is 1.0 μm
In the following cases, the maximum height Ry is preferably 15 μm or less, and the ten-point average roughness Rz is preferably 10 μm or less (Test No. 5-1 and Test No. 5-1).
5-2).

(E) The dimensional tolerance d0-d of the wire TW is
If (d0-d) <0 mm, the feeding of the wire 301 is hindered and buckling occurs (Test Nos. 6-1 and 6-).
2). If (d0−d)> 0.03 mm, there is a possibility that current cannot be supplied to the electrode tip 306.

The chemical components of each of the MIG welding wires 301 prepared for the test in Table 1 are as follows:
JIS H3331-1988 and ANSI / AWS A
5. All the wire numbers satisfied the rules of 16-90, so the display was omitted. The material TM of the MIG welding wire 301 made of industrial pure titanium was changed to JIS H
This is considered to be because it was composed of a titanium wire specified in 4670-1993.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a manufacturing process of a MIG welding wire according to the present invention.

FIG. 2 is a schematic diagram showing an example of a MIG welding device using the MIG welding wire of the present invention, and a cross-sectional view of the wire.

FIG. 3 is an explanatory view of a general TIG welding method and a MIG welding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Heating furnace 20 Lubricant tank 30 Cold drawing apparatus 40 Pickling tank 50 Wire spool 300 MIG welding apparatus 301 MIG welding wire (wire) 302 Feeding roller 303 Straightening roller 304 Conduit tube 305 Torch 306 Electrode tip 307 After shield Jig 308 Jig for back shield AR Arc EP Exhaust pipe (base material) IG Inert gas TM Industrial pure titanium material TW Industrial pure titanium wire

Claims (3)

[Claims] 1. The tensile strength σ of an industrial pure titanium wire rod is 6
A MIG welding wire that satisfies 00 to 1000 MPa and has an arithmetic average roughness Ra of 1.0 μm or less on the surface of the wire. 2. The MIG welding wire according to claim 1, wherein the wire has a wire diameter d of 2 mm or less. 3. When the reference wire diameter of the wire is d0,
The dimensional tolerance d0-d of the wire diameter d of the wire is 0 ≦ (d0-d)
The wire for MIG welding according to claim 1 or 2, wherein ≤ 0.03 mm.