PRODUCT CATEGORIES

Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

Titanium alloy vacuum heat treatment improves part performance

Since titanium and its alloys have outstanding advantages such as high specific strength, good heat resistance, and excellent corrosion resistance, they have been widely used in the industrial, chemical, and medical care industries since they were officially used as structural materials in 1952. Application prospects.

Alloying of titanium

Adding alloying elements titanium alloy to titanium can significantly increase the strength of pure titanium. Different alloying elements have different effects on the strengthening effect, allotropic transition temperature and phase stability of titanium. Some elements have a greater solid solubility in a-Ti, forming an α solid solution and increasing the allotropic transition temperature of titanium. Such elements are called a-stable elements, such as Al, C, N, O, and B. etc.: Some elements have a high solid concentration in β-Ti, forming a β solid solution and lowering the allotropic transition temperature of titanium. These elements are called stable elements, such as Fe, Mo, Mg, Mn, V, etc. ; There are also some elements that have a large solid concentration in the α-Ti and β-Ti phases and have little effect on the allotropic transition temperature of titanium. These elements are called neutral elements, such as Sn, Zr, etc.

Among the above three types of alloy elements, α-stable elements and neutral elements mainly solid-solution strengthen α-Ti. Among them, the Al element has the strongest effect, which reduces the density of the alloy, increases the specific strength, and improves the heat resistance of the alloy. properties and recrystallization temperature. β-stabilizing elements also have a solid solution strengthening effect on α-Ti. By adjusting the alloy composition, the composition of α and β phases can be changed to control the properties of titanium alloys. This type of element is indispensable in titanium alloys that can be strengthened by heat treatment.

Processing titanium alloys to improve part performance

The machining center can process multiple parts at the same time to improve production efficiency. Improve the processing accuracy of parts and achieve good product consistency. The machining center has a tool compensation function to obtain the processing accuracy of the machine tool itself. It has wide adaptability and great flexibility, such as arc processing, chamfering and transition filleting of this part, which can realize multiple functions in one machine. The machining center can perform a series of processing such as milling, drilling, boring, and tapping. Accurate cost calculations can be performed and production progress can be controlled. No special fixtures are required, saving a lot of costs and shortening the production cycle. Greatly reduces the labor intensity of workers. It can be used with UG and other processing software for multi-axis processing.

Vacuum heat treatment of titanium alloy

(1) Vacuum annealing

Annealing is the most commonly used heat treatment process for titanium alloys. There are mainly stress relief annealing, recrystallization annealing and double annealing. The purpose of stress relief annealing is to eliminate the internal stress after processing or welding of titanium alloy parts. The annealing temperature is generally 450~650℃, holding for 1~4h, and air cooling. The purpose of recrystallization annealing is to eliminate work hardening, restore plasticity, and obtain a stable structure. The general temperature is 750~800℃, keep warm for 1~3h, and air cool. Double annealing is to improve the plasticity of the two-phase alloy and improve the structural stability. The first annealing temperature is higher than or close to the end temperature of recrystallization, so that recrystallization can fully proceed without causing grain growth. The second annealing heating temperature is slightly lower, but the holding time is longer, so that the β phase can fully decompose and aggregate, thereby Ensure stable usage status organization and performance.

(2)Vacuum hardening

The phase transformation of titanium alloy during the vacuum hardening process is more complicated than that of aluminum alloy and steel. Due to the different alloy composition, vacuum hardening temperature and cooling method, the stable phases generated are different, and the structure morphology and distribution after the phase transformation are also different.

The purpose of hardening and aging is to improve the strength and hardness of titanium alloys. When alpha titanium alloys and alpha + beta titanium alloys containing less beta stabilizing elements are hardened from the beta phase region, diffusion-free martensitic transformation beta → a’ occurs. a’ is a supersaturated solid solution of β stabilizing element in α-Ti. α’ martensite has the same crystal structure as α, with a close-packed hexagonal lattice. α’ has low hardness and good plasticity. It is an unbalanced structure. It decomposes into a mixture of α phase and β phase during heating and aging, and the strength and hardness increase.

For α+3 titanium alloys, the quenching temperature is generally selected in the upper range of the α+β two-phase region, but does not reach the β single-phase region, to prevent the grains from becoming coarse, resulting in a decrease in the plastic toughness of the alloy. For β-titanium alloys, the quenching heating temperature is generally selected near the critical temperature. If the heating temperature is too low, the β-phase solid solution alloy elements are not sufficient, there are many original α-phases, and the strength of the alloy after aging is low; if the heating temperature is too high, then The coarse grains lead to a reduction in the strength and toughness of the alloy after aging. Generally, the quenching temperature is 760~950℃, holding for 5~60min, and cooling in water.

(3) Limitation of time

The quenching heating temperature determines the composition and quantity of the metastable β phase, while the aging temperature and time directly control the morphology, quantity, size and distribution of the α phase precipitation. The aging temperature of titanium alloys is generally between 450 and 550°C, and the aging time depends on the alloy type, ranging from a few hours to dozens of hours.