TIG Welding Of TA1 Industrial Pure Titanium

Titanium is a new type of material with many excellent properties, such as low density, high tensile strength, high specific strength, and high enough strength at high temperature, in addition to its excellent corrosion resistance and low-temperature impact properties. With the improvement of smelting technology, titanium production is growing rapidly, has been increasingly used in aviation, military, instrumentation and other important technology and equipment.

1 industrial pure titanium welding characteristics

TA1 industrial pure titanium has many excellent characteristics, but the chemical nature of titanium is active, sensitive to heating, heating to 300 ℃ began to absorb hydrogen, from 400 ℃ began to absorb oxygen, from 600 ℃ began to absorb nitrogen, so there will be some problems in the welding process, so for the manufacture of titanium equipment welding is the key to the

process.

1.1 Welded joints are easy to brittle crack

TA1 industrial pure titanium welding, oxygen, nitrogen, hydrogen, carbon, iron for titanium welding is unfavorable. Oxygen content increases, the weld strength increases, while the plasticity decreased significantly; for improving the tensile strength of the weld, hardness, reduce the plasticity of the weld, nitrogen is more pronounced than oxygen; weld hydrogen content changes in the impact performance of the weld for a significant impact, with the increase in the amount of hydrogen, the impact performance of the weld decreases, and in the weld hydrogen by the high-temperature molten pool to the lower temperature of the heat-affected zone diffusion, the heat-affected zone precipitation of the amount of TH2 increased The amount of TH2 precipitation in the heat-affected zone increases, so that the brittleness of the heat-affected zone increases, and then delayed cracking; carbon and titanium at high temperatures to generate titanium carbide can also reduce the plasticity of the weld, resulting in cracking; titanium mixed with ferrous metals will be contaminated by ferric ions, resulting in weld cracking. So in order to TA1 welded joints performance, in the welding should try to avoid mixing these elements.

1.2 Overheating and performance degradation

Titanium's high melting point, large heat capacity, poor thermal conductivity, so titanium welding, post-welding cooling rate should be kept within a certain range, can not be too fast or too slow, when the cooling rate is fast, high temperature β-phase is easy to turn into an unstable organization α 'phase, the plasticity of the joints is not conducive; and when the cooling rate is slow, the weld and the heat affected zone is prone to produce coarse grains of the organization of the overheating, reduce the Joint performance. So when welding to choose the appropriate welding line energy and appropriate cooling speed, the mechanical properties of the welded joints.

2 TA1 industrial pure titanium welding process

Through the above analysis of the performance of TA1 industrial titanium and welding problems, the development of the corresponding welding process, using tungsten argon arc welding for welding process evaluation test.

2.1 Test material

The base material is 10mm TA1 plate, the size of the material is 125 × 400mm, the wire is φ1.2ERTA1ELI, the base material and the chemical composition and mechanical properties of the welding consumables are shown in Table 1, the protective gas selection of 99.99% argon.

2.2 Bevel type

Bevel type for Y-type, bevel angle of 60 °, blunt edge 2mm, bevel machining.

2.3 Parent material and welding consumables cleanup

Titanium plate must be strictly cleaned before welding to remove surface oxides and other dirt to avoid defects such as porosity when welding. First scrub with acetone, and then put into the pickling solution for about 2-3min, rinse and dry after pickling, weld metal with the same method of cleaning.

2.4 Field Welding of Titanium

2.4.1 Grouping, spot welding requirements. Grouping the wrong side of the amount of not more than 10% of the plate thickness, to avoid the use of strong, position welding is to reduce the welding deformation of one of the main measures, spot welding fixed at both ends of the test plate, the length of about 10 mm. position welding wire used, welding parameters and formal welding the same, in each fixed position welding stop arc, should be delayed off the argon gas.

2.4.3 Welding operation:

(1) Before welding, the gas protection device needs to be fixed to prevent the welding process from falling off; (2) the welding work should be completed continuously, if intermittent, before re-welding, the weld and the base material on both sides must be re-cleaned; (3) the diameter of the welding torch nozzle φ15mm, and the gas flow should be stable. During the welding process, the protection of the protective gas should be checked at any time to prevent it from affecting the welding quality, and the interlayer temperature ≤ 150 ℃; (4) When starting the arc, the welding torch is fed with gas in advance, and when the welding is fed with the wire, the end of the wire should always be under the protection of the Ar gas, and when breaking the arc and welding the seam to close the end of the weld, it is necessary to continue to pass the argon gas to protect the weld until the weld and the heat-affected zone cools down to less than 350 ℃.

2.5 Welding quality inspection

2.5.1 Appearance inspection after welding, the color of the weld is bright silver-white, excellent protection, no porosity cracks and other defects, weld shaping is good. After passing the appearance inspection of welded joints, the x-ray flaw detection is grade I, and the surface is free from defects by coloring inspection.

2.5.2 The performance of welded joints is shown in Table 3.

3 Conclusion

Through the experiment and the actual product welding concluded that, in order to make TA1 industrial pure titanium to obtain good performance of welded joints, need to pay attention to the following three points: (1) welding titanium plate before the base metal and welding consumables to de-oil and decontaminate, to avoid contact with ferrous metals; (2) welding should be the appropriate choice of specifications, as far as possible, with a small amount of weld line energy; (3) welding should be more than 400 ° C weld pool and temperature of weld and the heat-affected zone (including the back of the molten pool) to be properly protected to avoid air pollution, gas protection effect. tA1 industrial pure titanium TIG welding
Titanium is a new type of material, has many excellent properties, such as low density, high tensile strength, high specific strength, high temperature still has a high enough strength, in addition, it also has excellent corrosion resistance and low-temperature impact properties. The article analyzes the performance characteristics of TA1 industrial pure titanium and the problems of welded joints during welding, and develops a reasonable welding process according to its main problems in the welding process to ensure the welding quality.