Introduction of 8 kinds of common metal materials and metal surface treatment technology
Eight common metal materials
1. cast iron -- fluidity
Sewer LIDS are such an obscure part of our everyday environment that few people notice them. Cast iron has such a large and wide range of USES, mainly because of its outstanding fluidity, and it is easy to cast into a variety of complex forms. Cast iron is actually the name given to a mixture of elements, including carbon, silicon, and iron. The higher the carbon content, the better the flow characteristics during pouring. Carbon occurs here in the form of graphite and iron carbide.
The presence of graphite in cast iron gives sewer LIDS excellent abrasion resistance. Rust usually appears only on the top layer, so it is usually polished. Nevertheless, there are special measures to prevent rust in the pouring process, that is, a layer of asphalt coating is added on the surface of the casting, and the asphalt penetrates into the fine holes on the surface of the cast iron, so as to play an anti-rust role. The traditional process of producing cast materials for sand molds is now being used by many designers in other newer and more interesting fields.
Material properties: excellent fluidity, low cost, good abrasion resistance, low shrinkage, brittle, high compression strength, good machinability.
Typical use: cast iron has been used for hundreds of years in construction, bridge, engineering parts, home, kitchen appliances and other fields.
2. Stainless steel -- stainless love
Stainless steel is an alloy of chromium, nickel and other metal elements in steel. Its rustless property is derived from the composition of chromium in the alloy. Chromium forms a strong and self-repairing chromium oxide film on the surface of the alloy, which is invisible to the naked eye. The ratio of stainless steel to nickel we usually refer to is 18:10. The term "stainless steel" does not simply refer to one kind of stainless steel, but refers to more than one hundred industrial stainless steels, each of which has good performance in its specific application field.
At the beginning of the 20th century, stainless steel was introduced into the field of product design. Designers developed many new products based on its toughness and corrosion resistance, covering many fields that had never been involved before. The design attempts were revolutionary: for example, the first time a sterilised, reusable device appeared in the medical industry.
Stainless steel is divided into four main types: austenitic, ferritic, ferritic - austenitic (composite), martensite. The stainless steel used in household products is basically austenite.
Material characteristics: health care, anti-corrosion, can be fine surface treatment, high rigidity, through a variety of processing technology molding, difficult to cold processing.
Typical application: austenitic stainless steel is the most suitable coloring material among the common primary color stainless steel, which can get satisfactory color appearance and shape. Austenitic stainless steel is mainly used in decorative building materials, household products, industrial pipes and building structures. Martensitic stainless steel is mainly used for making cutting tools and turbine blades. Ferritic stainless steel has corrosion resistance, mainly used in durable washing machine and boiler parts; Composite stainless steels are often used in corrosive environments because of their superior corrosion resistance.
3. zinc -- 730 pounds in a lifetime
Zinc, silver and blue-gray, is the third most widely used nonferrous metal after aluminum and copper. An average person consumes 331 kilograms of zinc in their lifetime, according to the U.S. minerals service. Zinc has a very low melting point, so it is also an ideal castable material.
Zinc castings are very common in our daily life: door handles under the surface material, faucet, electronic components, zinc has a very high corrosion resistance, this characteristic makes it has another most basic function, that is, as the surface coating material of steel. In addition to these functions, zinc is an alloy of copper to brass. Corrosion resistance isn't just for steel coatings -- it also helps strengthen our immune systems.
Material properties: health care, corrosion resistance, excellent castability, excellent corrosion resistance, high strength, high hardness, cheap raw materials, low melting point, creep resistance, easy to form alloy with other metals, health care, brittle at room temperature, about 100 degrees Celsius ductility.
Typical application: electronic components. Zinc is one of the alloys that form bronze. Zinc is also clean, hygienic and corrosion resistant. Zinc is also used in roofing materials, photo engraving plates, mobile phone antennas and shutter units in cameras.
4 .aluminum (AL) -- modern material
Aluminum, a white, blue-tinged metal, is really the baby metal compared to gold, which is 9, 000 years old. Aluminum was invented and named at the beginning of the 18th century. Unlike other metals, aluminum does not exist in nature as a direct metallic element. Aluminum in this form is also one of the most abundant metals produced on earth.
When the metal aluminum first appeared, it was not immediately applied to people's lives. Later, a batch of new products for its unique functions and characteristics came out gradually, and this high-tech material gradually has an increasingly wide market. Although aluminum has a relatively short history, the production of aluminum products on the market now far exceeds that of other non-ferrous products combined.
Material characteristics: flexible and plastic, easy to make alloy, high strength to weight ratio, excellent corrosion resistance, easy to conduct electricity and heat, recyclable.
Typical USES: vehicle skeleton, aircraft parts, kitchen appliances, packaging, and furniture. Aluminum is also used to reinforce large structures, such as the Cupid statue in London's Piccadilly Circus and the top of the Chrysler building in New York.
5. Magnesium alloy -- ultra-thin aesthetic design
Magnesium is an extremely important non-ferrous metal. It is lighter than aluminum and can well form high-strength alloys with other metals. Magnesium alloys have the advantages of light specific gravity, high specific strength and stiffness, good thermal conductivity, good damping and electromagnetic shielding properties, easy processing and formation, and easy recovery. However, due to the limitations of high price and technology, magnesium and its alloys are only used in a small amount in aviation, aerospace and military industries. Magnesium is now the third largest metal engineering material after steel and aluminum, widely used in aerospace, automotive, electronics, mobile communications, metallurgy and other fields. It can be expected that magnesium will become more important in the future due to the increased production costs of other structural metals.
The proportion of magnesium alloy is 68% of aluminum alloy, 27% of zinc alloy and 23% of steel. It is often used in automobile parts, 3C product shell and building materials. Most ultra-thin laptop and mobile phone casings are made of magnesium alloy. Since the last century, people still have an unerasable love for metal texture and luster. Although plastic products can form the appearance of metal, their luster, hardness, temperature and texture are still different from metal. As a new metal material, magnesium alloy gives people a feeling of high-tech products.
The corrosion resistance of magnesium alloy is 8 times that of carbon steel, 4 times that of aluminum alloy, and more than 10 times that of plastic. The commonly used magnesium alloys are incombustible, especially when used in automobile parts and building materials, which can avoid instantaneous combustion. Magnesium is the eighth most abundant mineral in the earth's crust, and most of its raw material is extracted from seawater, so its resources are stable and abundant.
Material characteristics: lightweight structure, high rigidity and impact resistance, excellent corrosion resistance, good thermal conductivity and electromagnetic shielding, good flammability, poor heat resistance, easy recovery.
Typical applications: widely used in aerospace, automotive, electronics, mobile communications, metallurgy and other fields.
6. copper -- man's partner
Copper is an incredibly versatile metal that has so much to do with our lives. Many of man's early tools and weapons were made of copper. Its Latin name cuprum comes from a place called Cyprus. It's a copper rich island.
Copper plays a very important role in modern society: it is widely used in building structures, as a carrier of electricity, and it has been used for thousands of years by people from different cultures to make body ornaments. The malleable, orange-red metal has followed us from its beginnings as a simple decoder to its later role as a key part in complex modern communications applications. Copper is an excellent conductor of electricity, second only to silver. In terms of the time history of people using metal materials, copper is the second oldest metal used for human being after gold. This is largely because copper is easy to extract and copper is relatively easy to separate from copper.
Material properties: excellent corrosion resistance, excellent thermal conductivity, electrical conductivity, hard, flexible, ductile, polished, unique effect.
Typical applications: wire, engine coil, printing circuit, roofing material, pipe material, heating material, jewelry, cooker. It is also one of the main alloys used to make bronze.
7. Chrome - high finish finish
The most common form of chromium is used in stainless steel as an alloying element to enhance the hardness of stainless steel. Chromium plating processes are generally divided into three types: decorative coating, hard chromium coating and black chromium coating. Chromium plating is widely used in engineering field. Decorative chromium coating is usually used as the top layer of plating on the outside of nickel layer. The coating has delicate polishing effect like mirror surface. As a decorative finishing process, the chrome coating thickness is only 0.006 mm. When considering the use of chromium coating process, it is important to fully consider the dangers of this process. In the last decade, there has been a growing trend to replace hexavalent decorative chromium water with trivalent chromium water, which is highly carcinogenic and considered less toxic.
Material characteristics: very high finish, excellent corrosion resistance, hard and durable, easy to clean, low friction coefficient.
Typical use: decorative chrome plating is a coating material for many automotive components, including door handles and bumpers. In addition, chrome is used in bicycle parts, bathroom faucets, and furniture, kitchen utensils, and tableware. Hard chrome plating is used in more industrial applications, including ram in job control blocks, jet engine components, plastic molds, and shock absorbers. Black chrome is mainly used for musical instrument decoration and solar energy utilization.
8. titanium -- light and strong
Titanium is a very special metal, very light, but also very tough and corrosion resistant, at room temperature to maintain its own color for life. Titanium has a melting point similar to platinum, so it is often used in aerospace and military precision components. Add electrical currents and chemical treatments, and you get different colors. Titanium has excellent resistance to acid and alkali corrosion. Titanium soaked in aqua aqua for several years is still shiny and shining. If you add titanium to stainless steel, add only about one percent, greatly improve the rust resistance.
Titanium has low density, high temperature resistance, corrosion resistance and other excellent characteristics, the density of titanium alloy is half of steel and steel about the same strength; Titanium is resistant to both high and low temperatures. High intensity is maintained over a wide temperature range ranging from -253℃ to 500℃. These advantages are essential for space metals. Titanium alloy is to make rocket engine shell and artificial satellite, spacecraft good material, have "space metal" said. Due to these advantages, titanium has become a prominent rare metal since the 1950s.
Titanium is a pure metal. Because titanium is "pure", no chemical reactions will occur when substances come into contact with it. That is to say, due to its high corrosion resistance and stability, titanium does not affect its essence after long-term contact with people, so it will not cause human allergies. It is the only metal that has no impact on human plant nerves and taste, and is known as "biophilic metal".
Titanium's biggest drawback is that it is difficult to refine. This is mainly because titanium can combine with oxygen, carbon, nitrogen and many other elements at high temperatures. So people used to think of titanium as a "rare metal". In fact, titanium accounts for about 6‰ of the weight of the earth's crust, more than 10 times more than copper, tin, manganese and zinc combined.
Material properties: very high strength, excellent corrosion resistance by weight ratio, difficult to cold work, good weldability, about 40% lighter than steel, 60% heavier than aluminum, low conductivity, low thermal expansion rate, high melting point.
Typical USES: golf clubs, tennis rackets, portable computers, cameras, suitcases, surgical implants, aircraft skeletons, chemical equipment and maritime equipment. Titanium is also used as a white pigment for paper, painting and plastics.
Metal surface treatment process
1. Introduction of surface treatment technology
Using modern physics, chemistry, metal science and heat treatment and other disciplines of technology to change the surface conditions and properties of parts, make it and the heart of the material for optimal combination, in order to meet the predetermined performance requirements of the process method, known as surface treatment technology.
Functions of surface treatment:
Improve the surface corrosion resistance and wear resistance, slow down, eliminate and repair material surface changes and damage;
To obtain a surface with special function for ordinary materials;
Save energy, reduce cost and improve environment.
2. Classification of metal surface treatment technology
It can be divided into four categories: surface modification technology, surface alloying technology, surface conversion membrane technology and surface laminating technology.
One.Surface modification technology
1. Surface hardening
Surface quenching is a heat treatment method that USES rapid heating to harden the surface austenitization without changing the chemical composition and heart structure of steel.
The main methods of surface quenching include flame quenching and induction heating, and common heat sources such as oxyacetylene or oxypropane.
2. Laser surface enhancement
Laser surface hardening is to heat the thin material on the surface of the workpiece to the phase transition temperature or the temperature above the melting point in a very short time, and then cool it in a very short time to harden and strengthen the surface of the workpiece.
Laser surface strengthening can be divided into laser phase change strengthening, laser surface alloying and laser cladding.
Laser surface enhancement has small thermal impact zone, small deformation and easy operation, which is mainly used for locally strengthened parts, such as blanking die, crankshaft, CAM, camshaft, spline shaft, precision instrument guide rail, high-speed steel cutter, gear and internal combustion engine cylinder liner.
3, shot peening
Shot peening is a technique to eject a large number of high-speed projectiles onto the surface of the parts, just like countless small hammers hitting the metal surface to make the surface and sub-surface of the parts undergo a certain plastic deformation and realize the strengthening.
Improve the mechanical strength, wear resistance, fatigue resistance and corrosion resistance of parts;
Used for surface extinction and peeling;
Eliminate the residual stress of casting, forging and welding.
Rolling is at room temperature with hard roller or roller pressure on the rotating surface of the workpiece, and move along the direction of the bus, make the workpiece surface plastic deformation, hardening, in order to obtain accurate, clean and enhanced surface or specific pattern of surface treatment technology.
Application: cylinder, cone, plane and other parts with simple shape.
Wire-drawing refers to the surface treatment method of forcing the metal through the mold under the action of external force, the metal cross-sectional area is compressed, and the required cross-sectional area shape and size is obtained, which is called metal wire-drawing technology.
Draw silk can need according to adornment, make straight grain, random grain, corrugative wait for a few kinds with whirl grain.
Polishing is a finishing method to modify the surface of parts, which can only get a smooth surface, but cannot improve or even maintain the original machining accuracy. The Ra value after polishing can reach 1.6~0.008 micron depending on the pre-processing condition.
Generally divided into mechanical polishing and chemical polishing.
TWO.Surface alloying technology
Chemical surface heat treatment
The typical process of surface alloying technology is chemical surface heat treatment. It is a heat treatment process that places the workpiece in a specific medium for heating and heat preservation, and makes the active atoms in the medium penetrate into the surface of the workpiece, thus changing the chemical composition and organization of the surface of the workpiece, and then changing its performance.
Compared with surface quenching, chemical surface heat treatment not only changes the surface structure of steel, but also changes its chemical composition. According to the different elements of infiltration, chemical heat treatment can be divided into carburizing, nitriding, multi-element co-infiltration, infiltration of other elements and so on. The chemical heat treatment process includes three basic processes: decomposition, absorption and diffusion.
The two main ways of chemical surface heat treatment are carburizing and nitriding.
Three.Surface conversion membrane technology
1. Blackening and phosphating
A process in which steel or steel parts are heated to the right temperature in air-steam or chemicals to form a blue or black oxide film on the surface. Also become blue.
The process by which the workpiece (steel or aluminum or zinc) is immersed in phosphating solution (some acid phosphate-based solution) and deposited on the surface to form a crystalline phosphate-conversion film insoluble in water is called phosphating.
Mainly refers to the anodic oxidation of aluminum and aluminum alloy. Anodizing is to immerse aluminum or aluminum alloy parts in acidic electrolyte, act as an anode under the action of external current, and form an anti-corrosion oxidation film layer firmly bound to the substrate on the surface of the parts. This layer of oxidation film has protective, decorative, insulating, wear resistance and other special characteristics.
Pretreatment such as polishing, deoiling and cleaning should be carried out before anodizing, followed by washing, coloring and sealing.
Application: it is often used for the protection and treatment of some special parts of automobiles and airplanes, as well as the decorative treatment of handicrafts and daily hardware products.
Four, surface coating technology
1. Thermal spraying
Thermal spraying is to heat metal or non-metallic materials melting, by compressed gas continuous blowing to the surface of the product, forming a solid coating with the substrate, from the surface of the product to obtain the required physical and chemical properties.
Thermal spraying technology can improve the wear resistance, corrosion resistance, heat resistance and insulation of materials.
Applications: aerospace, atomic energy, electronics and other cutting-edge technologies, including almost all fields.
2. Vacuum plating
vacuum plating refers to the surface treatment process of depositing various metal and non-metallic films on the metal surface by distillation or sputtering under vacuum conditions.
A very thin surface coating can be obtained by vacuum plating.
Principle of vacuum sputtering
According to different processes, vacuum plating can be divided into vacuum evaporation, vacuum sputtering, vacuum ion plating.
Electroplating is an electrochemical and REDOX process. Take nickel plating as an example: the metal parts are immersed in the solution of metal salt (NiSO4) as the cathode, and the metal nickel plate as the anode. After the dc power is connected, the metal nickel plating layer will be deposited on the parts.
Electroplating methods are divided into ordinary electroplating and special electroplating.
Vapor deposition technology refers to a new type of deposition technology in which vapor materials containing sedimentary elements are deposited on the surface of materials to form thin films by physical or chemical means.
According to the principle of deposition process, vapor deposition technology can be divided into physical vapor deposition (PVD) and chemical vapor deposition (CVD).
Physical vapor deposition (PVD)
Physical vapor deposition (PVD) refers to the technology of depositing a thin film on the surface of a material by means of vaporizing the material into atoms, molecules or ionizing into ions by means of physical methods under vacuum conditions.
Physical deposition techniques mainly include vacuum evaporation, sputtering and ion deposition.
Physical vapor deposition has a wide range of suitable matrix materials and membrane materials. Simple technology, material saving, no pollution; The obtained film has the advantages of strong adhesion, uniform thickness, compactness and few pinholes.
Widely used in mechanical, aerospace, electronics, optics and light industry and other fields to prepare wear resistant, corrosion resistant, heat resistant, conductive, insulating, optical, magnetic, piezoelectric, smooth, superconducting and other thin films.
Chemical vapor deposition (CVD)
Chemical vapor deposition (CVD) refers to the method by which metal or compound films are formed on the surface of matrix by the interaction of mixed gas and substrate at a certain temperature.
Because of its good abrasion resistance, corrosion resistance, heat resistance and special properties such as electricity and optics, CVD film has been widely used in mechanical manufacturing, aerospace, transportation, coal chemical industry and other industrial fields.
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