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Titanium Pipe Important Reason
Titanium Pipe Hydrogen is one of the most harmful elements in titanium, which can reduce the plasticity and toughness of ti and lead to brittle cracking. If the hydrogen content of the parent material or welding material is larger, the dehydrogenation should be done beforehand. Titanium can be combined with oxygen and nitrogen rapidly in 600 Shan, producing titanium dioxide and titanium nitride (hardness is great).Titanium Pipe When heated to more than 800 Shan, titanium dioxide dissolves in the titanium and diffuses into the inner microstructure of the metallic titanium, forming a 0.01 intermediate brittle layer. The higher the temperature, Titanium Pipe the longer the time, the more serious oxidation and nitriding, the plasticity of welded joints will be reduced dramatically.
In addition, titanium is easy to form brittle carbide with carbon, reducing the melting point of plastic and weldable titanium, which is refractory metal and requires high-temperature heat source during welding. Titanium thermal conductivity is low, only half of carbon steel, Titanium Pipe heat is not easy to escape, overheating tendency is serious. When the rigidity of the structure is large, the crack of weak zone can also be caused by the welding tensile stress. In addition titanium contaminated with iron ions become brittle. This is also one of the important reasons that lead to the crack in the weld zone of TI material.
The following measures can be adopted to prevent porosity and crack during titanium welding:
(1) Prepare before welding. The surface quality of weldment and welding wire has a great influence on the mechanical properties of welded joints, Titanium Pipe so it must be strictly cleaned. Iron plate and titanium wire can be used in mechanical cleaning and chemical cleaning two methods.
(a) Mechanical cleaning: For welding quality requirements are not high or acid pickling has difficulty welding, can be grinder, fine sandpaper, carbide scraper or stainless steel wire brush, but it is best to use carbide scraper scraping titanium plate, remove oxide film.
(b) Chemical cleaning: Before welding, test pieces and wire can be pickling, pickling solution can be Hf5 water melts. Rinse with purified water after pickling and apply welding immediately after drying. Or with acetone, ethanol, carbon tetrachloride, methanol and other polished titanium plate groove and its sides (50mm), the surface of the wire, the workpiece fixture and titanium plate contact part. Clean the surface of the weldment and weld within 2 hours.
Correct selection of welding equipment.Titanium Pipe According to welding technical requirements and technical specifications, the specific selection of appropriate welding equipment. For example, the titanium and titanium alloy gold Tungsten Plate Argon arc welding, should be selected with a drop characteristics, high-frequency arc arc welding power supply, and delayed the time of the recurrence of less than 15 seconds, to avoid welding suffered oxidation, pollution.
(2) Correct selection of welding materials.Titanium Pipe Argon purity should not be less than 99.99%, dew point Under-40 Shan, impurities total mass fraction of 0.001%. The back of important components should be protected by argon, and when the pressure in the argon cylinder drops to 0.981MPa, it should be discontinued to prevent the quality of the welded joint. In principle, it should be selected with the same basic metal composition of titanium wire, welding wire to vacuum annealing State supply. Sometimes in order to improve the weld metal plasticity, can also choose the strength than the basic metal slightly lower welding wire.
(3) Grasp the weld groove. In principle, the number of welding floors and welding metals should be minimized. With the increase of the number of welding layers, the cumulative suction of the weld seam increases, so as to affect the performance of welded joints, and because titanium and titanium alloy welding weld pool size is larger, so try to open a single V-type 70 ° IBP ° groove, and do not swing.Titanium Pipe The end of the welding wire shall not be removed from the gas protection range, and the nozzle diameter may be enlarged to enlarge the protection area.
(4) Pay attention to the selection of gas flow protection. The choice of gas flow to achieve a good protection effect, too large flow is not easy to form a stable laminar flow, and increase the cooling speed of the weld, so that the weld surface layer appears more α-phase, resulting in microcracks. When the amount of argon in the towed hood is insufficient, the weld exhibits different oxidation color, Titanium Pipe and the flow of the main nozzle will be disturbed when the flux is too large. The argon flow on the back of the weld can not be too large, otherwise it will affect the gas protection effect of the first layer of the front weld. In short, to control the flow of gas and flow rate, to prevent the occurrence of turbulence, the effect of protection.
(5) Correct selection of welding process parameters. To increase the stay time of deep pool to prevent bubbles escaping, can effectively reduce the porosity. At the same time, using small current, high welding speed welding specifications, the number of welding layer less.
Titanium, widely used in aviation, aerospace, Marine, chemical, medical, sports and other fields, has been hailed as a "space" metal "Marine metal" metal "wisdom", is an important strategic metals, the 21st century is also the national key support one of the new material industry.