Research on rolling process of Titanium rod and titanium alloy rod wire

Titanium alloy is widely used in aerospace technology category of high performance data, its light weight, high strength, good toughness, corrosion resistance is its most significant characteristics. With regard to the manufacture of automobiles, titanium alloy is the only material among many metals that simultaneously has high strength, low density, excellent fatigue resistance and corrosion resistance, and low elastic modulus, so it is very ideal for the manufacture of automobiles. In addition, titanium alloy is also widely used in medical equipment, chemical equipment, military (military TC4 titanium rod, titanium plate) and sports equipment (titanium golf club) material category. Because the processing technology is complex, so the data is expensive, which is the main reason for the high price of products. Titanium alloy and many alloy metals, is also composed of titanium and some useful metal components, to meet the requirements of data performance, but its main composition of titanium accounted for more than 90%. Two alloys commonly used in aerospace technology are Ti6Al4V(6% aluminum, 4% vanadium, 90% titanium) and Ti3Al2.5 V(3% aluminum, 2.5% vanadium, 94.5% titanium).

TC4 titanium alloy has good mechanical properties at room temperature and high temperature. It is widely used in the manufacture of aeronautical structural parts, fans and drums of aeroengines, and has accounted for more than 50% of the total amount of aeronautical titanium alloy. Many load-bearing structural parts of aircraft, especially those with variable cross-section, require titanium rods to have good notched stress-fracture performance. The purpose is to ensure that the parts have strong ability to restrain crack initiation and propagation under high stress concentration, and not to fracture failure. The upper limit of this type TC4 titanium alloy bar specification in the relevant technical standards in China is (; > 220 mm. At present, there is no public report on the preparation process of TC4 titanium alloy bar requiring notched stress fracture performance at home and abroad. It is generally believed that high hydrogen content or poor microstructure uniformity of TC4 titanium alloy will reduce its room temperature notch stress fracture performance (1). In industrial batch production, it is common that the notched stress fracture properties of such bars are not qualified due to improper process.

When the middle lower roller passes the material, the rolling force constantly impacts the middle roller, which makes the anti-loosening device of the inclined wedge fail rapidly and the stable state of the middle roller fixed is destroyed. The adjusted pass will change with the destruction of the stable state of the middle roll, which will affect the stability of the titanium rod size and ultimately affect the quality of the finished product. In rolling process, in order to prevent the bakelite tile structure heat wear and to offer them to pouring cooling water for cooling and lubrication, bakelite Ji cold water tend to spray Sou to roll on the surface, the blank table and drop quickly, especially when rolling of titanium and titanium alloy, because of the titanium and titanium alloy thermal conductivity is bad, bad material inside and outside temperature difference will be bigger, go against the uniform deformation, Rolling accuracy can not be guaranteed; Inclined wedge side fixing method for higher friction resistance and higher electricity consumption when rolling, even if 630kW motor is used, boring car phenomenon often happens and affect production. The size of titanium and titanium alloy bars in 250 mill is stable, the quality of outer surface is improved and the yield of finished products is improved.

According to the current technical standards, 350mmdiameter TC4 titanium alloy bar is provided in the ultra specification range. Under the premise of guaranteeing the mechanical properties unchanged, the ultrasonic inspection level is required to be improved from grade B in GB/T5193 of the original small size bar to Grade A. Therefore, the relevant technology research of preparation of large size TC4 titanium alloy bar with special requirements is carried out. It is prepared by two processes (1) The large size TC4 titanium alloy bar of Xing 350mm can be prepared by using the forging process of p phase zone and upsetting + direct drawing in two phase zone. The structure, properties and flaw detection level can meet the technical requirements of supply.

(2) The same axialized structure of primary A is beneficial to improve the notched stress fracture performance at room temperature, while the short rod-a-phase structure with strong directional consistency decreases the notched stress fracture performance.

The rods with length of 75mm were cut longitudinally on the 50mmTC4 titanium alloy bar forged by two processes, respectively, for ordinary annealing treatment at two temperatures, the annealing system was Ml(720 u x2h/AC) and M2(790t:x2h/AC). The low-fold microstructure of forged bar was observed by naked eye. The metallographic samples were cut horizontally at the 1/2 radius of the forged and annealed rod lining respectively, and their microstructure was observed by 0LMPUS optical microscope. After annealing treatment at 1/2 radius of the bar sample billet along vertical line, mechanical processing into a standard room temperature tensile and gaps in the stress rupture properties of the test sample, using lnStron4507 tensile testing machine and DN2 mechanics performance test was carried out on the sample notch tensile testing machine, observation hole stress fracture microstructure of the specimen gap area. Ultrasonic nondestructive testing of TC4 titanium alloy bars forged by two processes was carried out by USING S0NIC-138VFD ultrasonic flaw detector.