The main purpose and scope of application of the electronic tensile testing machine: this series of material testing machines are widely used in various small cross-section metal wires, dry mortar, waterproof materials, rubber and plastics, insulation materials, textiles, wires and cables, coatings, non-woven fabrics, and paper Test various physical properties such as stretching, tearing, peeling, elongation, etc. for various materials, as well as mechanical properties of other parts. Comply with GB2611-81 “General Standard for Testing Machines”, “Test Methods for Asphalt Waterproof Rolls” GB/T328-89, “Determination of Tensile Properties of Vulcanized Rubber and Mat Plastic Rubber” GB/T528-1998, “Polyvinyl Chloride Waterproof Rolls” “GB12952-2003, “Petroleum Asphalt Fiberglass Tire Felt” GB/T14686-93 and other national standards.
Spring is an elastic element widely used in the mechanical and electronic industries. The spring can produce greater elastic deformation when loaded, converting mechanical work or kinetic energy into deformation energy, and the deformation of the spring disappears and returns to its original shape after unloading. Deformation energy is converted into mechanical work or kinetic energy.
1. The main functions of the spring are:
① Force measurement, such as spring scales and gauge springs;
②Control movement, such as clutch, brake and valve control spring;
③Vibration reduction and buffering, such as buffers, springs of shock absorbers, etc.;
④ Energy storage or energy transmission, such as springs on clocks, meters and automatic control mechanisms.
2. Type of spring:
There are many types of springs, such as compression springs, extension springs, torsion springs and metal wire forming.
3. The name and size relationship of each part of the spring:
(1) Talk about spring wire diameter d: the diameter of the steel wire used to make the spring.
(2) Spring outer diameter D: the maximum outer diameter of the spring.
(3) Spring inner diameter D1: the minimum outer diameter of the spring.
(4) Spring diameter D2: the average diameter of the spring. Their calculation formula is: D2=(D+D1)÷2=D1+d=D-d
(5) t: Except for the support ring, the axial distance between the corresponding points of two adjacent coils of the spring on the pitch diameter becomes the pitch, which is represented by t.
(6) Effective number of turns n: the number of turns that the spring can maintain the same pitch.
(7) Number of support turns n2: In order to make the spring work evenly, to ensure that the end of the axis is vertical, the two ends of the spring are often tightened during manufacturing. The number of tight turns only serves as a support and is called a support ring. Generally there are 1.5T, 2T, 2.5T, and 2T is commonly used.
(8) Total number of turns n1: the sum of effective number of turns and support ring. That is, n1=n+n2.
(9) Free height H0: the height of the spring without external force. Calculated by the following formula: H0=nt+(n2-0.5)d=nt+1.5d (when n2=2)
(10) Spring unfolding length L: The length of steel wire required to wind the spring. L≈n1(ЛD2)2+n2 (compression spring) L=ЛD2n+ hook extension length (tension spring)
(11) Spiral direction: there are left and right rotations. Right-handed is commonly used, and right-handed is generally used if it is not indicated in the drawing.
4. The prescribed drawing method of the spring:
(1) On the view of parallel coil spring lines, the contour lines of each circle are drawn as straight lines.
(2) If the effective number of turns is more than 4 turns, you can only draw 1 to 2 turns at both ends (not including support ring). The middle is connected by a dotted line through the center of the spring wire.
(3) On the drawing, when the direction of rotation of the spring is not specified, the coil spring is drawn as right-handed, and the left-handed spring is also drawn as right-handed, but the word “left” should be marked.
When the hardness of titanium alloy is greater than HB350, cutting is particularly difficult, and when the hardness is less than HB300, it is prone to sticking and cutting is difficult. But the hardness of titanium alloy is only one aspect that is difficult to cut. The key lies in the influence of the combination of chemical, physical and mechanical properties of titanium alloy on its machinability. Titanium alloy has the following cutting characteristics:
(1) Small deformation coefficient: This is a significant feature of titanium alloy cutting processing, and the deformation coefficient is less than or close to 1. The sliding friction distance of chips on the rake face is greatly increased, which accelerates tool wear.
(2) High cutting temperature: Because the thermal conductivity of titanium alloy is very small (only equivalent to 1/5 ~ 1/7 of 45 steel), the contact length between the chip and the rake face is extremely short, and the heat generated during cutting is not easy to transfer It is concentrated in a small area near the cutting area and the cutting edge, and the cutting temperature is very high. Under the same cutting conditions, the cutting temperature can be more than twice as high as when cutting 45 steel.
(3) The cutting force per unit area is large: the main cutting force is about 20% smaller than that during steel cutting. Because the contact length between the chip and the rake face is extremely short, the cutting force per unit contact area is greatly increased, which is likely to cause chipping. At the same time, due to the small modulus of elasticity of titanium alloy, it is prone to bending deformation under the action of radial force during processing, causing vibration, increasing tool wear and affecting the accuracy of parts. Therefore, the process system is required to have better rigidity. Supreme enterprise
(4) Chilling phenomenon is serious: due to the high chemical activity of titanium, it is easy to absorb oxygen and nitrogen in the air to form a hard and brittle skin at high cutting temperature; at the same time, plastic deformation during cutting will also cause surface hardening . Chilling phenomenon not only reduces the fatigue strength of parts, but also aggravates tool wear, which is a very important feature when cutting titanium alloys.
(5) The tool is easy to wear: After the blank is processed by stamping, forging, hot rolling and other methods, a hard and brittle uneven skin is formed, which can easily cause chipping, making the removal of the hard skin the most difficult process in titanium alloy processing. In addition, due to the strong chemical affinity of titanium alloy to tool materials, the tool is prone to bond wear under the conditions of high cutting temperature and high cutting force per unit area. When turning titanium alloy, sometimes the wear of the rake face is even more serious than that of the flank; when the feed rate f<0.1 mm/r, the wear mainly occurs on the flank; when f>0.2 mm/r, the front The blade face will be worn; when using carbide tools for fine turning and semi-finishing turning, the wear of the flank face is more suitable for VBmax<0.4 mm.
Cutting titanium alloy should start from the two aspects of lowering cutting temperature and reducing adhesion. It is suitable to choose tool materials with good red hardness, high bending strength, good thermal conductivity, and poor affinity with titanium alloys. YG cemented carbide is more suitable. Due to the poor heat resistance of high-speed steel, tools made of cemented carbide should be used as much as possible. Commonly used cemented carbide tool materials include YG8, YG3, YG6X, YG6A, 813, 643, YS2T and YD15.
Coated inserts and YT cemented carbide will have a violent affinity with titanium alloys, which will aggravate the bonding and wear of the tool, and are not suitable for cutting titanium alloys; for complex and multi-edge tools, high-vanadium high-speed steel (such as W12Cr4V4Mo ), high-cobalt high-speed steel (such as W2Mo9Cr4VCo8) or aluminum high-speed steel (such as W6Mo5Cr4V2Al, M10Mo4Cr4V3Al) and other tool materials, suitable for making drills, reamers, end mills, broaches, taps and other tools for cutting titanium alloys.
Using diamond and cubic boron nitride as tools for cutting titanium alloys can achieve significant results. For example, the cutting speed can reach 200 m/min under the condition of emulsion cooling with natural diamond tools; if the cutting fluid is not used, the allowable cutting speed is only 100 m/min at the same amount of wear.
In the process of cutting titanium alloy, the matters that should be paid attention to are:
(1) Due to the small modulus of elasticity of titanium alloy, the clamping deformation and force deformation of the workpiece during processing will reduce the processing accuracy of the workpiece; the clamping force should not be too large when the workpiece is installed, and auxiliary support can be added when necessary.
(2) If a cutting fluid containing chlorine is used, it will decompose and release hydrogen at high temperatures during the cutting process, which will be absorbed by titanium and cause hydrogen embrittlement; it may also cause high-temperature stress corrosion cracking of titanium alloys.
(3) The chloride in the cutting fluid may also decompose or volatilize toxic gas during use. Safety protection measures should be taken during use, otherwise it should not be used; after cutting, the parts should be thoroughly cleaned with a chlorine-free cleaning agent in time to remove chlorine residues Things.
(4) It is forbidden to use lead or zinc-based alloy tools and fixtures to contact titanium alloys, and copper, tin, cadmium and their alloys are also prohibited.
(5) All tools, fixtures or other devices in contact with the titanium alloy must be clean; the cleaned titanium alloy parts must be protected from grease or fingerprint contamination, otherwise it may cause salt (sodium chloride) stress corrosion in the future.
(6) Under normal circumstances, there is no risk of ignition when cutting titanium alloys. Only in micro-cutting, the small chips cut off will ignite and burn. In order to avoid fire, in addition to pouring a large amount of cutting fluid, it is also necessary to prevent the accumulation of chips on the machine tool. The tool should be replaced immediately after being blunt, or the cutting speed should be reduced, and the feed rate should be increased to increase the chip thickness. In case of fire, fire extinguishing equipment such as talcum powder, limestone powder, dry sand should be used to extinguish the fire. Carbon tetrachloride and carbon dioxide fire extinguishers are strictly prohibited, and watering is prohibited, because water can accelerate the combustion and even cause hydrogen explosion.
Titanium alloy features:
Titanium has a relatively low density of 4.5g/cm3, which is only 60% of iron. It is usually called light metal with aluminum and magnesium, and its corresponding titanium alloys, aluminum alloys, and magnesium alloys are called light alloys. Many countries in the world have recognized the importance of titanium alloy materials, and have successively conducted research and development on titanium alloy materials, and have been practically applied. Titanium is an important structural metal developed in the 1950s. Titanium alloys are widely used in various fields because of their high specific strength, good corrosion resistance, high heat resistance, and easy welding. High strength and easy welding are beneficial to the manufacture of golf club heads.
The first practical titanium alloy was Ti-6Al (aluminum)-4V (alum) alloy successfully developed by the United States in 1954. Ti-6Al-4V alloy has reached a good level in terms of heat resistance, strength, plasticity, toughness, formability, weldability, corrosion resistance and biocompatibility. The amount of Ti-6Al-4V alloy used has accounted for 75-85% of all titanium alloys. Many other alloys can be regarded as modifications of Ti-6Al-4V alloy. At present, there are hundreds of titanium alloys developed in the world, and there are 20 to 30 kinds of the most famous alloys, for example, Ti-6Al-4V, Ti-5Al-2.5Sn, Ti-2Al-2.5Zr, Ti -32Mo, Ti-Mo-Ni, Ti-Pd, Ti-811, Ti-6242, Ti-1023, Ti-10-5-3, Ti-1100, BT9, BT20, IMI829, IMI834, etc.; for ball The rods are 10-2-3, SP700, 15-3-3-3 (commonly referred to as β titanium), 22-4, DAT51.
The improvement effect of cryogenic treatment technology is to penetrate the inside of the treated part (the overall effect), which is not limited to the surface, so when the cutting tool is re-grinded and reused, the modification effect of the workpiece will not be invalid; it will not cause the shape and size of the workpiece. Change, and have the effect of enhancing the size stability and reducing the quenching stress; the process system is simple, the power consumption is low, and the shape and size of the workpiece are not limited, and the operation is simple; there is no environmental pollution, and it is a completely environmentally friendly technology
The application of cryogenic modification technology is gradually being recognized and developed by the business community. The experimental results and results obtained so far show that cryogenic modification technology can be applied in the following aspects: 1. High-speed steel cutting tools and cutting tools , The improvement of the life of measuring tools; 2. The improvement of the life of cemented carbide cutting tools and cutting tools; 3. The improvement of the life of carbide drills and drilling tools; 4. The improvement of the performance of diamond products, such as the thermal stability of synthetic diamonds Progress, the performance of artificial diamond mining drill bits, diamond Φ105mm saw blades, etc.; 5. The top hammer function of the diamond hot press is improved; 6. The size of the assembly parts of precision machinery is not disordered; 7. The function of carbon fiber yarn is improved; 8 , The service life of oil nozzles, springs, gears and bearings is improved; 9. The service life of hot work molds and cold work molds in the machinery manufacturing industry is improved. Cryogenic treatment technology is a new technology that has emerged in recent years to improve the performance of metal workpieces. The so-called cryogenic treatment is to use liquid nitrogen (-196℃) as the cooling medium to inherit the cooling process of the quenched metal material, reaching a temperature far below room temperature, and promoting the retained austenite present after conventional heat treatment Further transformation, thereby improving the performance of metal materials.
. Cryogenic treatment can significantly improve the wear resistance, toughness and size stability of metal workpieces, and double the service life of the workpieces.
The emergence of cryogenic treatment technology has aroused a high degree of attention from the scientific research community and the industry. It has been used in cutting tools, measuring tools, molds and precision parts abroad, such as oil pump nozzles, turbine shafts, rollers, valves, and gears. , Modification of springs and other workpieces.