At present, in mechanical manufacturing, due to the rapid upgrading of products, there are also higher requirements for the selection of parts. Especially in the manufacturing of aerospace, large power stations and ships, some difficult to process materials, such as high-temperature alloys, titanium alloys, heat-resistant stainless steel, composite materials, have been widely used, among which the efficient processing of high-temperature alloy materials, which are widely used and commonly used, has attracted more attention.

High-temperature alloys are generally divided into three categories, namely, iron-based superalloys, nickel-based superalloys and cobalt-based superalloys. In terms of the degree of difficulty, the processing of nickel-based superalloys should be more typical and representative.

The main reasons for the difficult machining of superalloys can be summarized into four aspects: first, the high temperature strength of materials and the high tendency of work hardening. Generally, the unit cutting force of nickel-based superalloys is 50% higher than that of medium-carbon alloy steels; After machining, the work hardening and residual stress of the surface layer of the workpiece are large, and the hardening degree can reach 200%~500%; Second, the thermal conductivity is poor, its thermal conductivity is about 1/5~1/2 of 45 steel, so the cutting temperature is high; Third, it has a strong tendency to bond to the tool, and it is very easy to produce chip build-up when machining the superalloy, which makes the cutting unstable, thus affecting the quality of the machined surface; Fourth, the content of strengthening elements is high. A large number of hard points such as metal carbides and intermetallic compounds with strong abrasiveness are formed in the alloy, which has a strong scratch effect on the knife.

The blanking of superalloy is the first process in mechanical manufacturing. The traditional blanking process is generally to cut the bar or the parts with different sections by using the circular bimetallic band saw blade on the horizontal band saw machine (ordinary alloy tool steel and high-speed steel band saw blades cannot be used for the blanking of superalloy). High-performance high-speed steel bimetallic band saw blade (the blade material is used to cut refractory superalloy, its cutting efficiency is low, and its life is very short. Take cutting a 130mm diameter nickel-based superalloy bar as an example (material is GH4169), using M42 bimetallic saw blade generally takes about 8 to 10 hours to cut a piece, and the life of a saw blade can only be one piece, Later, we selected a high-quality super-hard bimetallic band saw blade (brand M51), and used it to cut and process high-temperature alloy bars of the same specification and material. The result is that the cutting efficiency and service life of the tool are slightly improved, but the increase is only between 15% and 20% (the hardness of the cutting edge of the saw blade is 67~69HRC). We believe that using this material and type of band saw blade to process high-temperature alloy can not meet the production requirements, For this reason, we selected the carbide band saw blade with high hardness after comparison of various schemes. After test and practical application, it is true that the carbide band saw blade has achieved obvious results in the cutting and processing of superalloy, meeting the requirements of the production schedule.

The design and selection of cemented carbide band saw blades have different materials and structures. In practice, we found that not any kind of cemented carbide band saw blade can achieve good results in the cutting and processing of superalloy. Only when the selection is reasonable and the use is appropriate can the ideal results be obtained. For this reason, we have selected and compared the structure, tooth form, material and reasonable selection of cutting parameters of the band saw blade, as follows: Fig. 1 2/3 Structure of variable pitch band saw blade Fig. 1. The carbide band saw blade with cutter structure generally adopts the inlay welding structure. The carbide band saw blade tip has the advantages of high hardness, high wear resistance and high fatigue resistance, but its main disadvantages are brittleness, low strength and impact resistance. When cutting superalloys, the selection of tool structure should not only consider the characteristics of materials, but also the main selection principle should be based on the difficulty of machining of superalloys, the shape of the workpiece to be machined and the main requirements for machining (such as cutting to improve the sawing efficiency or to improve the service life) to determine whether the structure of the band saw blade should be coarse or fine teeth, equal or variable pitch. Through the comparison of test application (especially according to the comparison results of its final sawing and blanking data), we believe that the structure of the band saw blade for cutting superalloy is better to select the carbide band saw blade with coarse teeth and variable tooth pitch. The reason is that when cutting superalloy (especially nickel-based superalloy), the chip adhesion is very strong, the chip is not easy to be discharged smoothly, and the time and time of chip accumulation is easy to make the blade collapse The wear of the rear face of the tool is intensified. The selection of coarse teeth not only increases the strength of the tool edge, but also increases the chip space, facilitating the selection of larger feed speed to improve the cutting efficiency; The use of variable tooth pitch can reduce the cutting noise and vibration, and make the cutting more stable, which is conducive to the improvement of tool durability. See Fig. 1 for the structural diagram of variable pitch band saw blade.

2. Selection of cutter tooth form The tooth form of band saw blade commonly used include standard tooth, hook tooth and ladder tooth. See the figure for the type

A. The cutting front angle of the standard tooth is g=0 °, the tooth surface is perpendicular to the matrix, and the tooth groove is deep and narrow.

B. The cutting front angle of hook tooth is g=5 °~10 °, and the tooth groove is deep and wide.

C. The cutting front angle of ladder tooth is g=10 °~15 °, and the back angle is a=6 °~8 °. The cutter tooth has high strength and is suitable for strong cutting.

For the processing of superalloy materials, in addition to the selection of high-strength cemented carbide materials, the selection of tooth profile is also very important. The ladder tooth has sufficient strength and is not easy to collapse when cutting. Due to the large front angle, the resistance is also smaller than the standard straight tooth. It is also proved by practice that the cutting effect of the ladder tooth is better than the other two tooth profiles.

3. The determination of tool material grades is applicable to the cutting of high-temperature alloy materials. There are two main types of cemented carbide grades, namely, M and K in the ISO standard (currently recommended as S). From the results of sawing comparative test, the two types of tool grades have little difference in cutting efficiency, but in sawing service life, The band saw blade equivalent to M15-M30 is 15%~20% higher than the band saw blade equivalent to M15-M30 (processing high-temperature alloy of the same specification and grade).

4. Reasonable selection of cutting parameters The reasonable selection of cutting parameters plays a vital role in the blanking of superalloy. Reasonable cutting parameters can ensure the normal blanking of the workpiece, ensure the significant improvement of cutting efficiency and service life, and also reduce the harsh noise caused by the adhesion and friction of cutting chips between the tool and the workpiece during blanking, According to the test and application results of various nickel-base superalloy grades that we cut (considering the efficiency and service life), the reasonable cutting amount is selected as follows: the cutting linear speed is 15~the feed speed (material removal rate) is 6~the above cutting amount, which is the result of our long-term test and application, and has certain economy. Through the above four aspects of work, the carbide band saw blade has been used to process superalloy, and obvious economic results have been achieved in Harbin Turbine Plant. Through the comparison of the test and application of multiple data results, the cutting efficiency of the carbide band saw blade used now can be increased by 5 to 8 times compared with the original bimetal band saw blade used to process high-temperature alloy, such as the size of the workpiece is 140 × 245 GH4169 nickel-base superalloy, originally used M42 bimetallic saw blade for blanking, and the next piece of material takes about 6-8 hours. Now, the selected carbide band saw blade is used to process the superalloy, and the blanking time of one piece of workpiece is only about 1 hour. At the same time, the more prominent is the improvement of tool life. When processing the superalloy blanks of the above brands and specifications, the original M42 bimetallic saw blade can only be used for one piece of saw blade, However, currently used carbide band saw blades can generally cut 20 to 24 pieces per band saw blade (40 to 50 pieces per band saw blade can be cut if the cutting amount is reasonably selected and properly operated), although the price of the current carbide band saw blade is about 5 times higher than that of the bimetal saw blade, but in terms of cost performance and comprehensive economic benefits (especially through the comparison of the above typical examples), It is very cost-effective to use carbide band saw blade to process superalloy, which achieves and realizes the purpose of low cost, long service life and high efficiency processing.

The use of carbide band saw blade uses carbide band saw blade to cut and cut superalloy materials. Although it is an efficient and ideal technological means, if it is not used properly, the teeth of the band saw blade will wear sharply and even cause the saw band fracture. This will not only fail to achieve the expected results, but also cause large losses. Therefore, it is very important to use the carbide band saw blade correctly. There should be strict requirements for the use of band saw blades, and the specific requirements are mainly in the following three aspects: 1. Requirements for machine tools: a. The sawing machine has good rigidity and certain accuracy, which can meet the requirements of stable machining of carbide band saw blades; B. Select sawing machines with different power and specifications according to the size of workpiece diameter (cutting area); C. The machine tool is equipped with good chip removal, cooling and saw blade guide device.

2. Requirements for operation and use: a. The workpiece clamp must be firm. After clamping, check whether the clamping point (face) is at the middle and upper part of the workpiece to ensure the stability during processing; B. Running-in of band saw blade: the new band saw blade must be running-in before normal cutting to avoid premature tooth damage. The tooth tip can have normal wear only after the running-in process. Without running-in, the tooth tip will be damaged prematurely. The feed rate during running-in is 20%~30% of the normal feed rate of belt speed.

C. Selection of tension: excessive tension will cause saw band fracture; Insufficient tension will damage the saw band or cause cutting skew. When using carbide band saw, the tension must be adjusted to 2200~2500kg/㎡.

D. Cooling and chip washing during cutting: When cutting superalloy materials with carbide band saw, in order to reduce cutting temperature, reduce cutting resistance and extend the service life of the band saw, the water agent extreme pressure cutting fluid must be continuously poured during sawing. At the same time, the chips generated from sawing should be cleaned synchronously with iron brush.

2. Reasonable selection of cutting parameters For the blanking of superalloy blank, whether the cutting parameters are reasonable will directly ensure the normal sawing process, and the reasonable cutting parameters will also obtain higher cutting efficiency and tool life. Due to the poor cutting performance of superalloy materials, the cutting parameters are much lower than other alloy steel materials, which has been proved by practice, It is reasonable to use the cutting amount recommended by the above examples. If the feed rate (material removal rate) is too low, the wear of the rear face of the tool will increase. If the cutting speed and feed rate are increased, the cutting force will also increase, and the chip removal slot will be blocked, thus leading to edge collapse and tool life reduction