Titanium and titanium alloy strip production process
The titanium and titanium alloy by smelting, ingot casting, a flat roll rolling, heat treatment and finishing processes into a rectangular cross-section of a sheet or roll of processing materials.
Melting and ingot Titanium has a high melting point and an energetic chemical property, making it easy to interact with air and refractory materials at high or molten temperatures. Titanium and titanium alloys are generally cast in a water-cooled or liquid-metal-cooled copper crucible in a vacuum or inert gas-protected atmosphere. Titanium ingot production is currently the most widely used vacuum consumable electrode arc furnace melting.
A certain proportion of sponge titanium, return material and alloy elements are mixed uniformly, then pressed into lumps on the hydraulic press (called electrode blocks), and the electrode blocks are welded into electrodes (rods) in the plasma welding method. In the vacuum consumable electrode Electric arc furnace remelting into ingots. In order to ensure uniform ingot composition, the particle size of the added alloying elements, return material and titanium sponge are controlled within a certain range, and three vacua remelting. Industrial scale smelting titanium alloy ingot is generally 3 ~ 6t, large ingots up to 15t. The ingot, which is usually melted with a vacuum consumable electrode arc furnace, is round. In recent years, other methods such as plasma smelting, an electron beam smelting, shell smelting and electroslag smelting have also been adopted to melt titanium alloy ingots and ingots. For example, Japan uses a plasma torch smelting 3t slab weight, directly for the use of the rolled strip.
Forging is the main method of crushing the as-cast crystalline structure, improving material properties and obtaining slabs of a certain size and shape. During the heating process before slab forging, the titanium alloy can easily react strongly with the air to form a scale and gettering layer to reduce the plasticity and other properties of the material. Therefore, induction heating or heating in a hermetically sealed chamber resistance furnace is typically used. When using a flame furnace heating, the furnace should be kept for the micro-oxidizing atmosphere, but also in the ingot coated with a protective layer, or in an inert gas heating. Titanium alloy with low thermal conductivity, heating large section or high alloy ingot billet, in order to prevent thermal stress may cause billet cracking, usually low temperature slow, high temperature rapid heating method. Control of ingot heating and final forging temperature and forging deformation is to obtain high quality titanium slab important guarantee.
Titanium alloy slab is forging generally use a hydraulic press and forging hammer. In order to ensure the subsequent smooth rolling process and ensure the surface quality of the slab, forged slabs and ingots should be machined, stripped of surface cracks and depth of 3 ~ 4mm getter layers.
Rolling Compared with aluminum, copper, steel, titanium alloy strip rolling deformation is characterized by resistance, low plasticity, easy oxidation under high temperature, so the processing more difficult. Rolling includes hot rolling, warm rolling and cold rolling. Hot rolling is an essential process of titanium plate production process. When formulating the fierce rolling technology system of titanium alloy sheet and strip, the influence of grain structure on the mechanical properties should also be considered. In order to decrease the formation of getter and scale during heating, pure titanium and low-alloyed titanium alloys have a lower heating temperature, and the holding time can be shortened as much as possible under heat penetration. However, lowering the temperature causes a definite increase in the deformation resistance at the time of rolling, and at the same time, the plasticity also decreases, which is often not allowable for a highly alloyed titanium alloy. In order to achieve uniform and fine grain structure and plate with good performance, often used in the production of hot rolling, rolling and rolling and other warm-rolled to ensure that the plate strip in the α or α + β phase region has enough Deformation. Therefore, to determine a reasonable system of hot rolled process is of great importance.
Hot rolling of titanium strip can be used with coiler reversible four-roll hot rolling mill, four-roll reversing mill and multi-stand four-roll hot rolling mill. Compared with the hot rolling mill group, the reversing four-roll hot strip mill with coil coiler has the advantages of less investment, small area, and good quality rolled hot-rolled coil with a thickness of 3 ~ 6mm, which is suitable for small batch Multi-species titanium plate production equipment. The general use of hot-rolled production of more than 3mm thick titanium alloy sheet.
Titanium alloy plate thickness less than 2mm usually cold-rolled production. Compared with the hot rolled, cold-rolled sheet with excellent surface quality, high dimensional accuracy, small size tolerance and so on. Cold-rolled strip available tape production, but most of the cold-rolled titanium alloy block production. Cold rolling is usually carried out on four-roll reversing cold rolling mills, and multi-stand tandem cold rolling mills can be used. Strip thickness of less than 0.5mm in the 20-roll mill rolling. To improve product quality. These mills should be computer controlled. In order to obtain different thickness of titanium alloy strip, cold rolling, intermediate annealing and finishing processes can be replicated several times. In the production of high-alloyed titanium alloy strip, it is also possible to carry out warm rolling in the range of 600 to 850 C in order to improve the plasticity of the material and reduce the deformation resistance during rolling.
Annealing The titanium alloy strip is heated to a specified temperature for a sufficient time and then cooled at a suitable rate. Ti alloy strip annealing, including intermediate annealing and finished two. The purpose of the intermediate annealing is to remove work hardening, restore the plasticity and deformation capacity of titanium alloy, in order to facilitate the continued rolling. Finished annealing is to produce a certain degree of organization and performance of the product. For α and α + β type alloys, the annealing can be cooled by holding at the α and α + β phase zone temperature and the slower cooling rate to obtain uniform and fine uncrystallized structure, which ensures the material has good performance. For β-type titanium alloys, the annealing is usually cooled in a faster cooling mode after annealing at a definite temperature range in the β-phase region to ensure that a high-plasticity B-phase grain structure is obtained for subsequent processing and use. Thicker strips can be annealed in air; thinner strips are often annealed under vacuum or inert gas. Numerous types of titanium alloy annealing system shown in Table 3. The mechanical properties of several titanium alloy strips after rolling and annealing are given in table 4.
Finishing including caustic washing, pickling, straightening, cutting, sandblasting and grinding. Titanium alloy plate in the sodium hydroxide melts alkaline washing and pickling in hydrochloric acid aqueous solution, be sure to add an appropriate amount of sodium nitrate and nitric acid as an oxidant to prevent titanium hydrogen absorption. Titanium alloy with high yield strength, low modulus of elasticity and large springback make it difficult to straighten and flatten the steel. Hot straightening and hot leveling or vacuum creep straightening can be utilized. As the titanium alloy sensitive to the gap, the production process produces surface defects such as cracks and inspiratory layer should be promptly removed by grinding and other clean to prevent further deformation during deformation weaknesses. Therefore, the finishing process is very important in the production of titanium alloy sheet and strip, is to assure that the product surface quality, geometry and organizational performance in line with technical standards.
The titanium and titanium alloy by smelting, ingot casting, a flat roll rolling, heat treatment and finishing processes into a rectangular cross-section of a sheet or roll of processing materials.
Melting and ingot Titanium has a high melting point and an energetic chemical property, making it easy to interact with air and refractory materials at high or molten temperatures. Titanium and titanium alloys are generally cast in a water-cooled or liquid-metal-cooled copper crucible in a vacuum or inert gas-protected atmosphere. Titanium ingot production is currently the most widely used vacuum consumable electrode arc furnace melting.
A certain proportion of sponge titanium, return material and alloy elements are mixed uniformly, then pressed into lumps on the hydraulic press (called electrode blocks), and the electrode blocks are welded into electrodes (rods) in the plasma welding method. In the vacuum consumable electrode Electric arc furnace remelting into ingots. In order to ensure uniform ingot composition, the particle size of the added alloying elements, return material and titanium sponge are controlled within a certain range, and three vacua remelting. Industrial scale smelting titanium alloy ingot is generally 3 ~ 6t, large ingots up to 15t. The ingot, which is usually melted with a vacuum consumable electrode arc furnace, is round. In recent years, other methods such as plasma smelting, an electron beam smelting, shell smelting and electroslag smelting have also been adopted to melt titanium alloy ingots and ingots. For example, Japan uses a plasma torch smelting 3t slab weight, directly for the use of the rolled strip.
Forging is the main method of crushing the as-cast crystalline structure, improving material properties and obtaining slabs of a certain size and shape. During the heating process before slab forging, the titanium alloy can easily react strongly with the air to form a scale and gettering layer to reduce the plasticity and other properties of the material. Therefore, induction heating or heating in a hermetically sealed chamber resistance furnace is typically used. When using a flame furnace heating, the furnace should be kept for the micro-oxidizing atmosphere, but also in the ingot coated with a protective layer, or in an inert gas heating. Titanium alloy with low thermal conductivity, heating large section or high alloy ingot billet, in order to prevent thermal stress may cause billet cracking, usually low temperature slow, high temperature rapid heating method. Control of ingot heating and final forging temperature and forging deformation is to obtain high quality titanium slab important guarantee.
Titanium alloy slab is forging generally use a hydraulic press and forging hammer. In order to ensure the subsequent smooth rolling process and ensure the surface quality of the slab, forged slabs and ingots should be machined, stripped of surface cracks and depth of 3 ~ 4mm getter layers.
Rolling Compared with aluminum, copper, steel, titanium alloy strip rolling deformation is characterized by resistance, low plasticity, easy oxidation under high temperature, so the processing more difficult. Rolling includes hot rolling, warm rolling and cold rolling. Hot rolling is an essential process of titanium plate production process. When formulating the fierce rolling technology system of titanium alloy sheet and strip, the influence of grain structure on the mechanical properties should also be considered. In order to decrease the formation of getter and scale during heating, pure titanium and low-alloyed titanium alloys have a lower heating temperature, and the holding time can be shortened as much as possible under heat penetration. However, lowering the temperature causes a definite increase in the deformation resistance at the time of rolling, and at the same time, the plasticity also decreases, which is often not allowable for a highly alloyed titanium alloy. In order to achieve uniform and fine grain structure and plate with good performance, often used in the production of hot rolling, rolling and rolling and other warm-rolled to ensure that the plate strip in the α or α + β phase region has enough Deformation. Therefore, to determine a reasonable system of hot rolled process is of great importance.
Hot rolling of titanium strip can be used with coiler reversible four-roll hot rolling mill, four-roll reversing mill and multi-stand four-roll hot rolling mill. Compared with the hot rolling mill group, the reversing four-roll hot strip mill with coil coiler has the advantages of less investment, small area, and good quality rolled hot-rolled coil with a thickness of 3 ~ 6mm, which is suitable for small batch Multi-species titanium plate production equipment. The general use of hot-rolled production of more than 3mm thick titanium alloy sheet.
Titanium alloy plate thickness less than 2mm usually cold-rolled production. Compared with the hot rolled, cold-rolled sheet with excellent surface quality, high dimensional accuracy, small size tolerance and so on. Cold-rolled strip available tape production, but most of the cold-rolled titanium alloy block production. Cold rolling is usually carried out on four-roll reversing cold rolling mills, and multi-stand tandem cold rolling mills can be used. Strip thickness of less than 0.5mm in the 20-roll mill rolling. To improve product quality. These mills should be computer controlled. In order to obtain different thickness of titanium alloy strip, cold rolling, intermediate annealing and finishing processes can be replicated several times. In the production of high-alloyed titanium alloy strip, it is also possible to carry out warm rolling in the range of 600 to 850 C in order to improve the plasticity of the material and reduce the deformation resistance during rolling.
Annealing The titanium alloy strip is heated to a specified temperature for a sufficient time and then cooled at a suitable rate. Ti alloy strip annealing, including intermediate annealing and finished two. The purpose of the intermediate annealing is to remove work hardening, restore the plasticity and deformation capacity of titanium alloy, in order to facilitate the continued rolling. Finished annealing is to produce a certain degree of organization and performance of the product. For α and α + β type alloys, the annealing can be cooled by holding at the α and α + β phase zone temperature and the slower cooling rate to obtain uniform and fine uncrystallized structure, which ensures the material has good performance. For β-type titanium alloys, the annealing is usually cooled in a faster cooling mode after annealing at a definite temperature range in the β-phase region to ensure that a high-plasticity B-phase grain structure is obtained for subsequent processing and use. Thicker strips can be annealed in air; thinner strips are often annealed under vacuum or inert gas. Numerous types of titanium alloy annealing system shown in Table 3. The mechanical properties of several titanium alloy strips after rolling and annealing are given in table 4.
Finishing including caustic washing, pickling, straightening, cutting, sandblasting and grinding. Titanium alloy plate in the sodium hydroxide melts alkaline washing and pickling in hydrochloric acid aqueous solution, be sure to add an appropriate amount of sodium nitrate and nitric acid as an oxidant to prevent titanium hydrogen absorption. Titanium alloy with high yield strength, low modulus of elasticity and large springback make it difficult to straighten and flatten the steel. Hot straightening and hot leveling or vacuum creep straightening can be utilized. As the titanium alloy sensitive to the gap, the production process produces surface defects such as cracks and inspiratory layer should be promptly removed by grinding and other clean to prevent further deformation during deformation weaknesses. Therefore, the finishing process is very important in the production of titanium alloy sheet and strip, is to assure that the product surface quality, geometry and organizational performance in line with technical standards.
