Titanium equipment manufacturing

When welding titanium materials, two points require special attention: the weld area must be cleaned to prevent contamination, and an inert gas should be used for protection to avoid welding stresses. Generally, inert gas shielded welding is used, as well as plasma welding and electron beam welding (which is not feasible for large pieces in a vacuum chamber). :lol

1 Pre-welding preparation and selection of welding materials: The welding method is selected based on the physical, chemical properties and characteristics of pure titanium; TIG welding is commonly used in practice. The proper selection of welding wire is key to ensuring the quality of welding pure titanium, in order to ensure that the weld has the same strength as the base material. The purity of argon directly affects the hardness and toughness of pure titanium welds, and it also has a significant impact on the occurrence of welding cracks. The argon used for welding pure titanium must be high-purity argon (argon-rich Ar 99.99%), with a dew point below –40°C and a H2O content of less than 0.001 mL/L. 2 Several major welding processes and technical measures (1) Welding equipment and its auxiliary tools: Select an appropriate TIG welder (preferably one with an inverter power supply); the welder should be equipped with a high-frequency or high-voltage arc-starting device. The arc-starting method involving rubbing the electrodes is strictly prohibited during welding. A precise argon flow meter is used to control the gas flow rate. (2) Number of welding passes and its determination: In the welding of medium- and thick-walled titanium components, multi-pass welding should be employed; however, the number of welding passes should be reduced as much as possible, provided that the grain size of the material remains fine and stress levels are low. (3) Determination of welding process parameters: The selection of welding processes for pure titanium requires preventing the formation of coarse-grained structures in the weld due to the heat from the arc, as well as avoiding the development of brittle structures resulting from contamination by the atmosphere during cooling after welding. Therefore, it is crucial to control the welding environment and provide protection in the welding area. (4) Key operational techniques: During welding, it is necessary to regularly check the color of the weld surface; a silver-white color is ideal, with a golden yellow color being the next best option. Otherwise, the welding process parameters and the flow rate of the shielding gas need to be adjusted. 3. Other precautions ① Post-welding treatment and inspection. After welding titanium equipment, the welds and heat-affected zones must be pickled, and then the pickling solution must be removed with clean water. ②Based on the welding properties of titanium, any welding method that can effectively prevent gas contamination during the welding process can be used, such as tungsten inert gas welding, metal inert gas welding, plasma arc welding, etc. However, depending on the conditions at the construction site, tungsten inert gas welding (DC positive polarity) not only ensures welding quality but also allows for welding in various positions under those site conditions. ③The welding wire should be made of a material with the same chemical composition as the base metal, and it must come with a quality certificate (sometimes, to improve plasticity, a welding wire with a lower alloy content than that of the base metal can also be used). It is absolutely not allowed to have any internal or surface defects such as cracks or layers, and it must be thoroughly cleaned before welding. ④For large and medium-sized equipment, argon can be used to protect the weld seam and the inner surface in the vicinity of the seam; the tank should also be filled with gas in advance to remove any air, maintaining a slight positive pressure and a flowing condition before starting welding. ⑤Stability should be maintained during welding to prevent the tungsten electrode from coming into contact with the workpiece or welding wire, which could cause tungsten inclusion. If tungsten inclusion occurs, the defect must be removed before welding can proceed. If multi-layer welding is used, the interlayer temperature should be kept below 200°C, and the temperature when leaving the shielding gas should be kept below 400°C. ⑥Furthermore, when joining the longitudinal and circumferential welds of the equipment, the inner walls must be kept level, with the misalignment amount not exceeding 10% of the wall thickness. It is necessary to strictly control the cooling rate after welding within an appropriate range. In short, during the welding process of titanium equipment on site, several key aspects must be properly controlled: grinding, cleaning, environment, protection, parameters, welding, and post-treatment. Each of these steps is important and essential; as long as the procedures are followed strictly, no quality issues will arise

1. Filling metal: Generally, when welding titanium and titanium alloys, the filling metal has the same nominal composition as the base material. To improve the toughness and plasticity of the joint, filler metals with a strength lower than that of the base material are sometimes used ； The welding wire should be carefully cleaned before welding, to remove the lubricants attached during drawing; it can also be washed with an aqueous solution of hydrofluoric acid and nitric acid to ensure a clean surface. 2. Shielding gas: Argon is generally used; helium is sometimes employed only when welding in deep penetration welding or overhead welding positions – the former to increase penetration, and the latter to improve protection. 3. Pre-welding cleaning: Before welding and brazing, the area to be welded and its surroundings must be carefully cleaned to remove contaminants such as grease and oxide scale, and then dried.

The welding wire and the base material are of the same material; argon shielded welding is used, with both manual TIG welding and automatic TIG welding available. The wire feeding speed, gas flow rate, as well as current and voltage levels are determined first on test pieces. Post-weld treatment and flaw detection are also carried out.

The welding quality of a weld can also be determined by its color; generally, a white color indicates better quality

Was the protective cover homemade? There are still finished products available for purchase

Refer to JB4745-2002 for titanium welded containers