Application of Rare Metal and Cemented Carbide Water Cutting Technology in Titanium Cutting Process Shu Chuntao (Changsha Nonferrous Metallurgy Design and Research Institute Co., Ltd., Changsha 410011, China) The difference in titanium cutting and analysis of two different cutting methods The influence of chemical composition, mechanical properties and machinability of titanium materials provides a basis for the promotion and application of water cutting technology.
1 Introduction Titanium and titanium alloys have been widely used in smelting projects such as nickel, cobalt, zinc and copper in nonferrous metallurgy industry due to their low density (about 4.470MPa), high specific strength and good corrosion resistance. The corrosion-resistant reactor of the non-ferrous smelter and its internal agitator are made of titanium material in whole or in part. However, titanium is chemically active and stable at room temperature in the atmosphere. It forms a dense protective film by parabolic law below 200300C. It is heated to about 250C to start hydrogen absorption. Above 400C, it has oxygen, hydrogen and nitrogen. High chemical activity; rapid oxidation, nitriding and hydrogen absorption when the temperature reaches 600C; and carbonization above about 1 000C. Therefore, during the titanium cutting process, the temperature control directly affects the physical and chemical properties of the titanium material.
Titanium cutting and cutting methods include: flame cutting, metal band saw cutting, grinding wheel saw cutting, shearing machine shearing, laser cutting, plasma cutting and water cutting. Since titanium is rapidly oxidized, nitrided, and hydrogen absorbing at 600 C, the cutting of titanium material is generally not suitable for flame cutting.
The shearing machine cuts the titanium plate easily and is not easy to straighten and flatten. The metal band saw and the grinding wheel saw blade are mostly used for the cutting of the titanium rod pipe. Therefore, the cutting of the titanium plate is mostly performed by cutting, laser, plasma and water cutting. Due to the limitations of existing laser technology, most laser cutting equipment cannot cut metal sheets with a thickness greater than 12 mm. At the same time, the laser cutting equipment has invested a lot, which also limits the promotion of the equipment to a large extent. Therefore, the titanium sheet with a thickness of less than 12 mm is first considered to be directly sheared by a shearing machine, and for a titanium sheet having a thickness of more than 12 mm. Most of the domestic use plasma cutting. Since plasma cutting is a kind of melt cutting method, the cutting process causes a large amount of hydrogen absorption and carbonization in the heat affected zone of the titanium material, so that the physical and chemical properties of the titanium material are malignant. The water cutting technology is a cold processing method, which has the characteristics of low workpiece temperature, no heat affected zone and thermal deformation during cutting, and has been rapidly developed in titanium cutting processing. This article will introduce water cutting technology Corresponding author: Shu Chun Tao (1966-), senior engineer, is mainly engaged in metallurgical equipment design, E-mail: intraoperative application characteristics of the titanium cutting, and compared with plasma cutting, water Provide the basis for the promotion and application of cutting technology.
2 Water cutting technology Water cutting technology is a new cold cutting process developed in the 1970s. In 1971, the Wateret (W) cutting machine was introduced in the United States and successfully cut a variety of non-metallic soft materials. In 1983, Abrasive Wateret (AW) cutting technology was first introduced into the practical stage in the United States to cut a variety of metallic or non-metallic, plastic or brittle materials. Since the day of its birth, water-cutting technology has received much attention and has developed rapidly. It has become the development direction of the 21st century cutting field with many characteristics.
2.1 Working principle Water cutting is to press ordinary water to 400MPa or higher, and spray it through a very small nozzle to produce a water jet with a flow velocity of about three times the speed of sound (1000m/s). The jet is cut. Abrasive jet cutting is the mixing of abrasive particles into a water jet, forming an abrasive jet through a mixing tube, and cutting with an abrasive jet under cold conditions.
2.2 Technical Features The main features of water cutting technology are as follows: 1) Wide cutting range, capable of cutting all kinds of non-metallic materials, and cutting various hard, brittle and tough materials, such as titanium alloy, enamel, glass, Composite materials, etc. (2) The cutting precision is high, the cutting surface is smooth, there is no heat affected zone and delamination phenomenon, so generally no post-order finishing is required, which reduces the processing cost; since the slit is narrow, the material utilization rate is improved. (3) High production efficiency, the water cutting system can be equipped with multiple nozzles for cutting, the workpiece is directly cut into a specified size, the intermediate process and auxiliary time are eliminated, and the production efficiency is improved. (4) Good adaptability, cutting can be started from any point on the workpiece, in any direction; it can process parts that are difficult to process by conventional processes; it is easy to combine CNC technology to realize multi-variety and small batch production of complex shape parts. (5) The operating environment is clean and safe. It is dust-free, tasteless, non-toxic, non-sparking, low vibration and low noise during cutting. It is especially suitable for harsh working environment and dangerous environment with explosion-proof requirements. 2.3 Titanium water cutting process Water cutting technology is not ideal because it does not cause heat-affected zone during the cutting process, and it does not cause material changes. Therefore, it is ideal for titanium and titanium alloys which are susceptible to high temperature and deteriorate the material. Cutting method. Titanium cutting generally adopts abrasive-type high-pressure water jet cutting method. Table 1 is an example of the process parameters of cutting titanium material by high-pressure water jet. From the data in Table 1, the water cutting speed is fast, the precision is high, the slit width is narrow, only 2.3mm, which improves the utilization rate of the material; the cutting quality is good, the cutting surface roughness is only 2040m; the processing workpiece has less burr and the burr height <0.1mm. Table 1 Water cutting process parameters of titanium material 1 plate thickness / mm slit width / mm cutting surface roughness / Mm burr height / mm abrasive consumption / (kg.m abrasive hole diameter / mm t spray pressure 245MPa The spray water volume is 6L min-1, the abrasive is 4 silica sand, the nozzle and the workpiece are spaced 1.0mm. 3 Water cutting and plasma cutting technology difference Water cutting is cold cutting, no heat deformation, good cutting surface quality, no secondary processing (if It is easy to implement when needed.) Plasma cutting has obvious thermal effects, low precision, and it is not easy to perform secondary processing on the cutting surface.
3.1 Cutting speed and precision The water cutting technology (WP402 water jet cutting machine) and plasma cutting technology (CNCTMC CNC precision plasma cutting machine) are used to cut the TA2 titanium plate with a thickness of 20mm. The cutting speed and precision of the two cutting technologies are as follows. Table 2 shows. It can be seen from the data in Table 2 that although the cutting speed of water cutting is less than that of plasma cutting, the accuracy of water cutting is higher than that of plasma cutting, which will be beneficial to the improvement of subsequent processing quality.
Table 2 Titanium cutting speed and precision using different cutting techniques Cutting technology Thickness Cutting speed Straight cutting precision Repeating cutting precision Cutting edge vertical hole W= 16mm) Cutting precision Surface roughness and a water cutting Plasma cutting not forming 3.2 cutting The morphology of the sample cut by the mass water cutter is shown in (a) and (b). It can be seen from the figure that the incision is neat and flat and has no heat affected zone and deformation. The upper and lower dimensional error of the round hole with d=16mm is 0.1mm, and the dimensional accuracy of the cut sample is up to IT11. The morphology of the sample cut by the plasma cutter is shown in (c) and 1 (d). It can be seen from the figure that the slit is rough and carbonization is severe, and the slag is melted above the slit. The upper width is narrower and the workpiece corner is collapsed, and the through hole of d<25 mm cannot be cut.
3.3 Changes in the chemical composition of the titanium material before and after cutting were taken from the edge of the water-cut and plasma-cut titanium TA2 samples for 3 minutes for chemical composition analysis. Table 3 Table 3 shows the chemical composition of the titanium material before and after the titanium material is cut. After the plasma cutting process, the chemical composition of the titanium material before and after the TA2 cutting is performed. It can be seen from the data in Table 3 that the chemical composition of the titanium material after cutting by water is extremely small, and the physical and chemical properties can be basically kept unchanged; while the chemical composition of the titanium material after plasma cutting is large, the physical and chemical properties will also be changed. It changes accordingly. 3.4 Machinability The processing properties of titanium before and after cutting are shown in Table 4. The watch is made of titanium material TA2 for water cutting and plasma cutting, and compares the secondary processing properties of titanium material before and after cutting. It is found that the water-cut titanium material has the processing property and the original state; the plasma-cut titanium material contains high hardness hydrogen due to the cutting surface. , oxides and carbides are difficult to perform secondary processing.
It can be seen from Table 4 that the processing performance of titanium after water cutting does not occur substantially. Table 4: Processing properties before and after TA2 cutting of titanium material. Secondary processing material state Hardness cutting index Hot workability Cold workability Welding property Deformation resistance Deformation energy Original state (700 C annealing, air cooling) After water cutting, 10 after plasma cutting processing means good processing performance, â–³ means processing performance, X means poor processing performance; cutting index is TA2 factory state (annealing) is 100; processing condition: tool material min- Cutting depth 2mm, feed amount 0. r-, wet cutting; life judgment standard: VB changes, and the processing performance of titanium after plasma cutting becomes worse, the hardness increases, and the cutting index decreases.
4 Conclusion Titanium water cutting and cutting processing is carried out under normal temperature and cold conditions. The whole blanking process has no effect on the physical and chemical properties of titanium. This method effectively avoids changes in hydrogen absorption, oxygen absorption, nitrogen uptake, and carbonation in the heat affected zone of the titanium material caused by the plasma cutting high temperature melting process.
Titanium workpiece processed by water cutting and cutting, the cut is neat and straight, and the perpendicularity of the trimming edge is <.5> The water cutting technology has no heat affected zone and deformation, no secondary processing, no toxic gas and dust, and can be cut. Processing any material with a thickness of 1200mm. If the secondary processing factor is considered, the cutting time of the water-cut parts is not longer than that of the plasma cutting, and the material can be tightly discharged, the waste is reduced, and the utilization rate and productivity of the material are fully improved.
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