Titanium rod and titanium alloy rod die forging process
Due to the large pressure, the life of the titanium rod is reduced. Therefore, when the closed die forging method is used to forge a titanium rod, closed die forging must strictly limit the volume of the original blank, which complicates the preparation process. Whether closed die forging should be considered from both interest and process feasibility. For open die forging, the burr loss accounts for 15% to 20% of the weight of the blank. Technical waste of the nip part (if it is necessary to leave this part in the forging condition) is 10% of the blank weight. The relative loss of the burr metal is usually with the blank. Increase in weight, some structural asymmetry, large cross-sectional area, and local forgings that are difficult to fill. Burr consumption can be as high as 50%. Although closed die forging has no burr loss, the blank making process is complicated and needs to be added. Multiple transitional slots will undoubtedly increase auxiliary costs.
Then only the final billet for heat treatment and cutting is processed. Forging temperature and deformation degree are the basic factors that determine the microstructure and properties of the alloy. The heat treatment of titanium rods is different from the heat treatment of steels. Die forging is usually used to make the shape and size close to the waste products. It does not play a decisive role in the organization of the alloy. Therefore, the final stage of the titanium rod process specification has a particularly important role. It is necessary to make the total deformation of the blank not less than 30%. The deformation temperature does not exceed the phase transition temperature. In order to make the titanium rod obtain higher strength and plasticity at the same time, the temperature and the degree of deformation should be sought to be as uniform as possible throughout the deformation blank.
After the recrystallization heat treatment, the titanium rods and the uniformity of the properties are inferior to the steel forgings. In the area of intense metal flow, its low magnification is a fuzzy crystal, high-order is an equiaxed fine crystal, and a hard-to-deform area, due to a small amount of deformation or no deformation, its structure is often preserved before deformation. Therefore, in forging some important titanium rod parts (such as compressor disks, blades, etc.), in addition to controlling the deformation temperature below TB and appropriate deformation level, it is very important to control the microstructure of the raw blank, otherwise, Some defects will be inherited in the forgings, and the subsequent heat treatment can not be eliminated, will lead to forging scrap.
In the sharply deformed region where the thermal effect is locally concentrated, when the hammer is forged on a titanium rod forging with a complicated shape. Even if the heating temperature is strictly controlled, the temperature of the metal may still exceed the TB of the alloy. For example, when the cross-sectional area of the titanium rod is forged, the hammer will be excessively heavy, and the temperature in the middle (web area) will be lower due to the effect of thermal deformation. The edge is locally high at about 100°C. In addition, hard-to-deform zones and regions with critical deformation levels are susceptible to formation of coarse-grained structures with relatively low plasticity and endurance during heating after die forging. Therefore, forgings with complex forging shapes on the hammer are often unstable in their mechanical properties. But it will lead to a sharp increase in deformation resistance, reducing the temperature of the forging heating can eliminate the risk of local overheating of the blank. To increase tool wear and power consumption, it is also necessary to use more powerful equipment.
Using multiple tapping methods can also reduce local overheating of the blank. However, it is necessary to increase the number of heating fires when the hammer is forged. To make up for the loss of heat between the blank and the cooler mold. When the requirements for the plasticity and durability strength of the deformed metal are not too high, the forging shape is relatively simple forgings. It is better to use hammer forging. However, the β alloy should not be hammer forged, because multiple heating in the forging process will have a beneficial effect on the mechanical properties. Compared with the forging hammer, the working speed of the press (hydraulic press, etc.) is greatly reduced, and the deformation resistance and deformation thermal effect of the alloy can be reduced. When a titanium rod is die-formed on a hydraulic press, the unit die forging force of the blank is about 30% lower than the forging die of the hammer, which can increase the life of the die. The reduction in thermal effects also reduces the risk of metal overheating and temperature rise beyond TB.
The unit pressure is the same as the forging hammer forging, and the press is used for the forging. Can reduce the billet heating temperature 50100 °C. In this way, the interaction between the heated metal and the cycle gas and the temperature difference between the blank and the mold are also reduced accordingly, thereby improving the uniformity of deformation, the organizational uniformity of the forgings is greatly improved, and the consistency of the mechanical properties is also improved. . Reduce the rate of deformation, the most obvious rate of increase in the rate of shrinkage, the rate of shrinkage is most sensitive to tissue defects caused by overheating.
The friction with the tool is high and the contact surface of the blank cools too quickly. To improve the fluidity of titanium rods and increase die life. The usual practice is to increase the swaging slope and fillet radius and to use lubricants: The flash bridging height on the forging die is higher than steel, and the deformation of the titanium rod is more difficult than steel to flow into the deep and narrow die groove. This is because of the high deformation resistance of titanium. Generally about 2mm. Non-uniform burr grooves of bridge sizes may sometimes be used to limit or accelerate the flow of metal to a portion of the groove. For example, in order to make the groove easy to fill. A rectangular box-shaped forging (as shown in Fig. 12) has thinner front and rear side walls; the left and right side walls are thicker. When the burr groove shown by B-B is used around the box-shaped member, the resistance of the metal flowing into the left and right side walls is small, so that the metal flows to the thinner front and rear side walls to make it difficult to fill up. Later, the front and rear sidewalls still use the burr groove shown in BB, and the left and right sidewalls use the burr groove shown in AA. Due to the wide size of the bridge and the obstruction of the damping groove, the front and rear thin sidewalls are completely filled, and the metal is relatively thin. Use the above burr groove method to save.
To solve the large complex titanium rod precision forging forming provides a feasible method. This method has been widely used in the production of titanium rods. One of the most effective ways to improve the fluidity of the titanium rod and reduce the deformation resistance is to increase the preheating temperature of the mold. Isothermal die forging and hot die forging developed at home and abroad for nearly two decades.