The design of Scissors

- Nov 27, 2017 -

Commonly used tool materials are carbon steel, aluminum alloy steel, coated steel and special materials, currently used most of the 2CR13 stainless steel blades. 1. Carbon steel (High-carbon)

Carbon steel means: carbon content is less than 1.35%, in addition to iron, carbon and limit within the silicon, manganese, phosphorus, sulfur and other impurities, does not contain other alloy elements of steels. The performance of carbon steel depends mainly on the amount of carbonaceous. With the increase of carbon content, the strength and hardness of steel increased, and the ductility, toughness and weldability decreased. Compared with other steel classes, carbon steel is used as the earliest, low cost, wide performance range and maximum dosage. Suitable for the nominal pressure ≤32.0mpa, the temperature is 30-425 ℃ water, steam, air, hydrogen, ammonia, nitrogen and petroleum product and so on medium. Commonly used brands are WC1, WCB, ZG25 and High-quality Steel 20, 25, 30 and Low-alloy structure 16Mn.

Carbon content is divided into Low-carbon steel (0.04%~0.25%), Medium carbon (0.25%~0.6%), high carbon (carbon content is 0.6%~1.35%). Used in the manufacture of knives, measuring tools, molds, etc., generally high carbon steel. 2. Aluminum Alloy Steel

Aluminum-based alloys collectively. The main alloy elements are copper, silicon, magnesium, zinc, manganese, secondary alloying elements are nickel, iron, titanium, chromium, lithium and so on.

⑴. Small density: Aluminum has a density of 2.7 about 1/3 of copper (8.9) or steel (7.8). For the density of small space aircraft, ships, vehicles and other means of transport and building lightweight is very useful, but also can save transportation costs and processing costs, reduce costs, in the industry, construction, civil and other fields of wide application

⑵. Good corrosion Resistance, weatherability: Aluminum and aluminum alloy in the atmosphere can form a hard and dense, with good corrosion resistance of the oxide film, through the anodic oxidation, electrophoretic paint, powder spraying, and other surface treatment, can further improve the corrosion resistance of aluminum;

⑶. Good decorative: aluminum alloy with good plasticity, machinable a variety of specifications, the formation of products, through the surface treatment can produce different properties, different colors of the film layer, with good decorative; ⑷. Good thermal conductivity: aluminum thermal conductivity is very high, in the metal after silver, gold, copper, is 3 times times the iron, Aluminum is 12 times times as heavy as iron, so aluminum is a good material for radiators and heaters.

Aluminum alloy density is low, but the strength is higher, close to or more than high-quality steel, plastic, can be processed into a variety of profiles, with excellent conductivity, thermal conductivity and corrosion resistance, industrial widely used, the use of the second only after the iron.

3. Coating Steel

Coated tool is a new tool material in the past 20 years, it is an important breakthrough in the development of cutting tool, and it is an effective measure to resolve the contradiction between hardness, abrasion resistance and strength and toughness in tool material. The coated tool is obtained by coating a refractory metal compound with high wear resistance, on the base of some tough cemented carbide or high speed steel tool. The commonly used coating materials are tic, tin and $literal. In the early 70, the first coating of carbide substrate on a layer of titanium carbide (Tic), in 1976, Titanium Carbide-alumina dual-coated cemented carbide, in 1981, the emergence of titanium carbide-alumina-cobalt nitride Tri-coated cemented carbide.

On the high speed steel substrate, the tool coating is tin, common physical vapor deposition (PVD method) coating, commonly used in drill bits, taps, milling cutters, hob and other complex tools, coating thickness of several microns, coating hardness of up to 80HRC, equivalent to the hardness of ordinary cemented carbide, durability can be increased 2-5 times. Cemented carbide coating is on the toughness of the cemented carbide substrate, coating a layer of a few microns to more than 10 microns thick high wear-resistant, refractory metal compounds, generally using chemical vapor deposition method (CVD method). The coating thickness of cemented carbide produced by Zhuzhou cemented carbide factory in China can reach 9um, and the surface hardness can reach 2500-4200HV. At present, the industrial developed countries on the coating tool research and promotion of the use of very rapid development, in the leading position in Sweden.

4. Diamond Cutting Tools

Diamond cutters are divided into natural diamond and synthetic diamond tools. Natural diamond has the highest hardness and thermal conductivity in natural material C but because of the high price, processing and welding are very difficult, with the exception of a few special uses (such as watch precision parts, light ornaments and jewelry carving processing). With high technology and

18 Ultra-precision machining is developing rapidly. such as micro-mechanical micro-parts, atomic nuclear reactors and other High-tech fields of various mirrors, missiles or rockets in the navigation gyro, computer hard disk chip, accelerator electronic gun, such as ultra-precision parts processing, single crystal natural diamond can meet the above requirements. In recent years, a variety of chemical mechanisms have been developed to grind diamond tools and to protect the atmosphere brazing diamond technology. Make the natural diamond tool manufacturing process become simpler.

In the the 1950s, the Diamond base diamond was manufactured by using high temperature and high pressure technology to synthesize diamond powder in 70. PCD grains are arranged in an orderly state. It is not directional, so the hardness is even. It has very high hardness and thermal conductivity, low thermal expansion coefficient. High elastic modulus and low friction coefficient, the blade is very sharp. It can process a variety of non-ferrous metals and extremely wear-resistant high-performance non-metallic materials, such as aluminum, copper, magnesium and its alloys, cemented carbide, fiber plasticized materials, metal matrix composites, wood composite materials.

The properties of three kinds of main diamond tool materials, such as--PCD, CVD thick film and synthetic single crystal diamond, are as follows: PCD weldability, mechanical grinding and fracture toughness are the highest, the abrasion resistance and the quality of the edge are centered, and the corrosion resistance is the worst. CVD thick film corrosion resistance is best, mechanical grinding, edge quality and fracture toughness and wear resistance center, poor weldability, synthetic single crystal diamond cutting edge quality, wear resistance and corrosion resistance best, weldability, mechanical grinding and fracture toughness of the worst. 5. Cubic Boron nitride

Cubic boron nitride (CBN) is a pure synthetic material. It is the second superhard material--CBN powder that was synthesized in the the late 1950s by making diamond-like methods. Due to the poor sintering performance of CBN, the cubic boron nitride (polycrystalline cubic boron nitride pcbn) was produced until the 70 's, which is sintered by the CBN powder and a few bonding phases (Co, ni or tin, tic or $literal) at high temperature and pressure. CBN is a dense phase of boron nitride, has high hardness (after diamond) and heat resistance (1300, 1500 degrees), excellent chemical stability (far better than diamond) and thermal conductivity, low friction coefficient.


Some parameters of 2cr13: standard: GB/t 1220-1992 quenching condition with high hardness and good corrosion resistance. Used as turbine blades. Chemical composition:

Carbon c:0.16~0.25 silicon si:≤1.00 Manganese mn:≤1.00 sulfide S: ≤0.030

19 p: ≤0.035 chromium cr:12.00~14.00 ni ni: Allow ≤0.60 mechanical properties:

Tensile strength Σb (MPa): Quenching and tempering, ≥635 condition yield strength σ0.2 (MPa): Quenching tempering, ≥440 elongation rate δ5 (%): Quenching tempering, ≥20 section shrinkage rate of PSI (%): quenching and tempering, ≥50 impact Power AKV (J): Quenching and Tempering, ≥63 hardness: annealing, ≤ 223HB; quenching and tempering, ≥192HB heat treatment Specification and Metallographic organization:

Heat Treatment Specification: 1 annealing, 800~900℃ slow cold or about 750 ℃ fast cold, 2 quenching, 920~980℃ oil cold, 3 tempering, 600~750℃ fast cold. Metallographic structure: The organization characteristic is the martensite body shape.

The above materials can be used for the design of scissors, but the design should be based on mechanical properties, chemical properties, processing performance, economic performance and other factors, the selection of optimal materials.