BT9 titanium rod surface treatment and technical processing methods
BT9 titanium rod surface treatment
BT9 titanium alloy rod surface treatment technology is mainly to improve the function of titanium surface to meet the special requirements of the material. According to the appearance treatment process, it is divided into the following categories:
1. Surface purification
Mainly to improve the cleanliness of titanium and titanium alloy surfaces and reduce impurities;
2. Corrosion-resistant surface treatment
Mainly to improve the corrosion resistance of titanium and titanium alloy surfaces. Mainly there are mandatory requirements for chemical titanium application industries, such as titanium pipes, titanium containers, etc.;
3. Wear-resistant surface treatment
Mainly improves the wear resistance of titanium and titanium alloy surfaces;
4.Special surface treatment
Mainly focusing on the surface color of titanium and titanium alloys to meet certain special needs of customers.
BT9 titanium alloy rod technology processing
BT9 is an αβ type heat-strength titanium alloy with good comprehensive properties. By utilizing thermal deformation and heat treatment in the αβ zone, the maximum long-term operating temperature of BT9 alloy can reach 500°C. It is a high-temperature titanium alloy widely used in my country's aviation field. It is mainly used to manufacture aero-engine compressor discs, blades, drums and other parts, and can also be used to manufacture aircraft structural parts. The alloy also has good thermal processing technology and can produce titanium rods, titanium forgings, medical titanium rods, etc.
The inherent quality of BT9 titanium alloy products will directly affect the reliability of aero engines and aircraft. Currently, Baoji Titanium Factory routinely uses ultrasonic flaw detection when inspecting the internal quality of BT9 titanium alloy products. However, ultrasonic flaw detection has certain limitations in detecting defects. In actual production, ultrasonic flaw detection of a certain batch of BT9 titanium alloy rods found no abnormalities. However, upon low-power inspection, a bright white patch was discovered in the center of the rod. The researchers used metallographic detection and energy spectrum analysis to analyze the reasons for the formation of white bright blocks, which will have a certain guiding role in the later production of titanium alloy products.
The material used in the test is a Φ750mm steel ingot that has been melted three times using vacuum consumables. After two upsetting and two drawing sessions in the β phase region, a Φ230mm bar was obtained through one upsetting and multiple fire drawings in the αβ phase region. The rods undergo two annealing heat treatments according to standard requirements. The polishing rod was inspected using ultrasonic testing and no abnormalities were found. When the rod was sampled for low-magnification inspection, bright silver spots were found on the low-magnification sample. When the same position of the bar is continuously sampled and inspected at low magnification, white bright spots still exist in the same part, indicating that the white bright spots are continuity defects. In order to analyze the causes of the white glossy blocks, samples of the white glossy blocks were prepared, and metallographic examination and trace component analysis were carried out using metallographic microscopes, scanning electron microscopes and energy spectrometers respectively; at the same time, low-magnification samples with white shiny blocks were On the machine, samples were taken from and near the white bright block to perform a room temperature tensile test to analyze the effect of the white bright block on the room temperature tensile properties of the titanium rod. The results show:
(1) Through high-power inspection, it was found that the α phase content in the white bright block was significantly lower than the β phase content, and there was no obvious boundary between the white bright block and the matrix. Therefore, it can be determined that the white bright patches are caused by component segregation. Further energy spectrum analysis found that the contents of Al, Mo, Zr, and Si alloy elements in the white bright blocks were significantly lower than the matrix content, while the Ti content was significantly higher than the matrix content. Therefore, it can be determined that the white bright blocks are caused by the segregation of Al, Mo, Zr, and Si alloy elements. It is titanium-rich segregation and is a metallurgical defect.
(2) Combined with the phenomenon that segregation has a certain depth, it can be determined that segregation is caused by uneven mixing. Since the vacuum consumptive melting process is regional melting, melting and solidification occur at the same time, and the melting homogenization effect is relatively poor. Therefore, if the raw materials are mixed unevenly, the composition of the smelted steel ingot may be uneven and segregate.
