Cast iron - fluidity
Sewer covers are such an inconspicuous part of our everyday environment that few people pay attention to them. The reason why cast iron has such a large and wide range of uses is mainly due to its excellent fluidity and its ease of casting into various complex shapes. 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 casting. Carbon occurs here in two forms, graphite and iron carbide.
The presence of graphite in cast iron gives sewer covers excellent wear resistance. Rust generally only appears on the outermost layer, so it is usually polished. Even so, there are still special measures to prevent rust during the pouring process, that is, a layer of asphalt coating is added to the surface of the casting, and the asphalt penetrates into the pores on the cast iron surface to prevent rust. The traditional process of producing sand casting materials is now used by many designers in other newer and more interesting fields.
Material properties: excellent fluidity, low cost, good wear resistance, low solidification shrinkage, very brittle, high compressive strength, good machinability.
Typical uses: Cast iron has been used for hundreds of years in fields such as buildings, bridges, engineering components, household and kitchen utensils.
2 stainless steel - stainless love
Stainless steel is an alloy made by incorporating chromium, nickel, and some other metal elements into steel. Its non-rusting feature is derived from the chromium in the alloy. The chromium forms a firm, self-healing chromium oxide film on the surface of the alloy, which is invisible to our naked eyes. The ratio of stainless steel and nickel we usually refer to is generally 18:10. The term "stainless steel" does not simply refer to one kind of stainless steel, but refers to more than one hundred kinds of industrial stainless steels, and each developed stainless steel 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, and designers developed many new products around its toughness and anti-corrosion properties, involving many fields that had never been involved before. This series of design attempts is very revolutionary. For example, for the first time in the medical industry, devices that can be reused after sterilization have appeared.
Stainless steel is divided into four main types: austenitic, ferritic, ferritic-austenitic (composite), martensitic. Stainless steel used in household items is basically austenitic.
Material properties: health care, anti-corrosion, fine surface treatment, high rigidity, can be formed by various processing techniques, and it is difficult to cold process.
Typical use: Among the commonly used primary color stainless steels, austenitic stainless steel is the most suitable coloring material, which can obtain 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 to make knives and turbine blades; ferritic stainless steel is corrosion-resistant and is mainly used in durable washing machines and In boiler parts; composite stainless steel has stronger corrosion resistance, so it is often used in aggressive environments.
3 Zinc - 730 lbs in a lifetime
Zinc, silvery and bluish-gray, is the third most widely used non-ferrous metal after aluminum and copper. A statistic from the U.S. Bureau of Mines shows that an average person consumes a total of 331 kilograms of zinc in his lifetime. Zinc has a very low melting point, so it is also an ideal casting material.
Zinc castings are very common in our daily life: materials under the surface of door handles, faucets, electronic components, etc. Zinc has extremely high corrosion resistance, which makes it have another most basic function, namely As a surface coating material for steel. In addition to the above functions, zinc is also an alloy material that combines with copper to form brass. Its anti-corrosion properties don’t just apply to steel surface coatings – it also helps strengthen our human immune system.
Material properties: health care, anti-corrosion, excellent castability, excellent anti-corrosion, high strength, high hardness, cheap raw materials, low melting point, creep resistance, easy to form alloys with other metals, health care, at room temperature Fragile, ductile at about 100 degrees Celsius.
Typical use: electronic product components. Zinc is one of the alloy materials that form bronze. Zinc also has hygienic and anti-corrosion properties. In addition, zinc is also used in roofing materials, photo engraving discs, mobile phone antennas and shutter devices in cameras.
4 Aluminum (Al) - a modern material
Compared with gold, which has been used for 9,000 years, aluminum, this bluish white metal, can only be regarded as a baby among metal materials. Aluminum came out and was named in the early 18th century. Unlike other metal elements, aluminum does not exist in nature in the form of direct metal elements, but is extracted from bauxite containing 50% alumina (also known as bauxite). Aluminum in this mineral form is also one of the most abundant metallic elements on our planet.
When the metal aluminum first appeared, it was not immediately applied to people's lives. Later, a batch of new products aimed at its unique functions and characteristics gradually came out, and this high-tech material gradually gained a wider and wider market. Although the application history of aluminum is relatively short, the output of aluminum products on the market has far exceeded the sum of other non-ferrous metal products.
Material properties: flexible and plastic, easy to make alloys, high strength-to-weight ratio, excellent corrosion resistance, easy to conduct electricity and heat, and recyclable.
Typical uses: Vehicle skeletons, aircraft parts, kitchen utensils, packaging, and furniture. Aluminum is also often used to strengthen some large building structures, such as the statue of Cupid on Piccadilly Circus in London and the top of the Chrysler Automobile Building in New York, all of which have been reinforced with aluminum.
5 magnesium alloy - ultra-thin aesthetic design
Magnesium is an extremely important non-ferrous metal. It is lighter than aluminum and can form high-strength alloys with other metals. Magnesium alloys have light specific gravity, high specific strength and specific stiffness, good thermal conductivity, and good damping reduction. Shock and electromagnetic shielding performance, easy processing and molding, easy recycling and other advantages. But for a long time, due to the high price and technical limitations, magnesium and magnesium alloys are only used in a small amount in aviation, aerospace and military industries, so they are called "noble metals". Magnesium is now the third largest metal engineering material after steel and aluminum, and is widely used in aerospace, automobiles, electronics, mobile communications, metallurgy and other fields. It can be expected that the importance of magnesium metal will become greater in the future due to the increase in 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 auto parts, 3C product shells, building materials, etc. Most ultra-thin laptop and mobile phone casings are made of magnesium alloys.
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. Its corrosion resistance is the best among alloys. Commonly used magnesium alloys are non-flammable, especially when used in automobile and motorcycle parts and building materials, which can avoid instant combustion. Most of the magnesium raw materials are extracted from seawater, so its resources are stable and sufficient.
Material properties: lightweight structure, high rigidity and impact resistance, excellent corrosion resistance, good thermal conductivity and electromagnetic shielding, good non-flammability, poor heat resistance, and easy recycling.
Typical application: Widely used in aerospace, automobile, electronics, mobile communication, metallurgy and other fields.
6 Bronze - Man's Friend
Copper is an incredibly versatile metal that is so closely related to our lives. Many of humanity's early tools and weapons were made of copper. Its Latin name "cuprum" originated from a place called Cyprus, which is an island rich in copper resources. People used the abbreviation of the island's name Cu to name this metal material, so copper has the current code name.
Copper plays a very important role in modern society: it is used extensively in architectural structures, as a carrier for the transmission of electricity, and has been used by people of many different cultures for thousands of years as a raw material for body decorations . This malleable, orange-red metal has evolved with us, from its simple beginnings in decoding transmissions to its pivotal role in complex modern communications applications. Copper is an excellent conductor, second only to silver in its electrical conductivity. From the perspective of the time history of people using metal materials, copper is the metal that has been used the longest by humans after gold. This is in large part because copper is easy to mine and the copper industry is relatively easy to separate from copper.
Material properties: very good corrosion resistance, excellent thermal conductivity, electrical conductivity, hard, flexible, ductile, unique effect after polishing.
Typical uses: electrical wires, engine coils, printed circuits, roofing materials, plumbing materials, heating materials, jewelry, cooking utensils. It is also one of the main alloying ingredients for making bronze.
7 Chrome - High Finish Finish
The most common form of chromium is used in stainless steel as an alloying element to increase the hardness of stainless steel. Chrome plating processes are generally divided into three types: decorative plating, hard chrome plating, and black chrome plating. Chromium plating is widely used in the engineering field. The decorative chromium plating is usually used as the outermost layer on the outside of the nickel layer. The plating has a delicate and delicate mirror-like polishing effect. As a decorative after-treatment process, the thickness of the chrome plating is only 0.006 mm. When planning to use the chromium plating process, the dangers of this process must be fully considered. The trend of hexavalent decorative chromium water being replaced by trivalent chromium water is becoming more and more obvious, because the former is very carcinogenic, while the latter is considered to be relatively less toxic.
Material properties: very high finish, excellent corrosion resistance, hard and durable, easy to clean, low coefficient of friction.
Typical uses: Decorative chrome plating is the coating material for many automotive components, including door handles and bumpers. In addition, chrome is also used in bicycle parts, bathroom faucets, and furniture, kitchen utensils, tableware, etc. Hard chrome plating is more used in industrial fields, including random access memory in job control blocks, jet engine components, plastic molds, and shock absorbers. Black chrome plating is mainly used for musical instrument decoration and solar energy utilization.
8 titanium - light and strong
Titanium is a very special metal, which is very light in texture, yet very tough and corrosion-resistant, and maintains its own color for life at room temperature. The melting point of titanium is similar to that of platinum, so it is often used in aerospace and military precision components. After adding electric current and chemical treatment, different colors will be produced. Titanium has excellent resistance to acid and alkali corrosion. Titanium soaked in "aqua regia" for several years is still shiny and radiant. If titanium is added to stainless steel, only about one percent is added, which greatly improves the rust resistance.
Titanium has excellent characteristics such as low density, high temperature resistance, and corrosion resistance. The density of titanium alloy is half that of steel and the strength is almost the same as steel; titanium is resistant to high temperature and low temperature. It can maintain high strength in a wide temperature range of -253°C~500°C. These advantages are exactly what space metal must have. Titanium alloys are good materials for making rocket engine casings, artificial satellites, and spacecraft, and are known as "space metals".
Titanium is a pure metal. Because of the "pure" of titanium metal, no chemical reaction will occur when substances come into contact with it. That is to say, because titanium has high corrosion resistance and high stability, it will not affect its essence after long-term contact with people, so it will not cause human allergies. It is the only one that has no effect on human autonomic nerves and taste. Metals are known as "biophilic metals".
The biggest disadvantage of titanium 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.
Material properties: very high strength, excellent corrosion resistance to weight ratio, difficult to cold work, good weldability, about 40% lighter than steel, 60% heavier than aluminum, low electrical conductivity, low thermal expansion rate, high melting point.
Typical uses: golf clubs, tennis rackets, laptops, cameras, luggage, surgical implants, aircraft skeletons, chemical implements, and maritime equipment. In addition, titanium is also used as a white pigment for paper, painting and plastics.
Metal Surface Treatment Process
1. Introduction to surface treatment process
The process of using modern physics, chemistry, metallurgy and heat treatment to change the condition and properties of the surface of the part, so that it can be optimally combined with the core material to achieve the predetermined performance requirements, is called the surface treatment process.
The role of surface treatment:
(1) Improve surface corrosion resistance and wear resistance, slow down, eliminate and repair material surface changes and damage;
(2) Make ordinary materials obtain surfaces with special functions;
(3) Save energy, reduce costs, and improve the environment.
2. Classification of metal surface treatment processes
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It can be divided into 4 categories in total: surface modification technology, surface alloying technology, surface conversion coating technology and surface coating technology.
1. Surface modification technology
1. Surface quenching
Surface quenching refers to a heat treatment method that uses rapid heating to austenize the surface layer and then quenches it to strengthen the surface of the part without changing the chemical composition and core structure of the steel.
The main methods of surface quenching are flame quenching and induction heating. Commonly used heat sources are flames such as oxyacetylene or oxypropane.
2. Laser surface strengthening
Laser surface strengthening is to use a focused laser beam to shoot the surface of the workpiece, heat the extremely thin material on the surface of the workpiece to a temperature above the phase transition temperature or melting point in a very short time, and cool it in a very short time to harden the surface of the workpiece strengthen.
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Laser surface strengthening can be divided into laser phase transformation strengthening treatment, laser surface alloying treatment and laser cladding treatment.
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The heat-affected zone of laser surface strengthening is small, the deformation is small, and the operation is convenient. It is mainly used for locally strengthened parts, such as blanking dies, crankshafts, cams, camshafts, spline shafts, precision instrument guide rails, high-speed steel tools, gears and internal combustion engines. Cylinder liners, etc.
3. Shot peening
Shot peening is a technology that sprays a large number of high-speed projectiles onto the surface of the part, just like countless small hammers hammering the metal surface, so that the surface and subsurface of the part undergo certain plastic deformation to achieve strengthening.
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effect:
(1) Improve the mechanical strength and wear resistance, fatigue resistance and corrosion resistance of parts;
(2) Used for surface matting and descaling;
(3) Eliminate the residual stress of casting, forging and welding parts, etc.
4. Rolling
Rolling is the use of hard rollers or rollers to press on the surface of the rotating workpiece at room temperature and move along the direction of the generatrix to plastically deform and harden the surface of the workpiece to obtain an accurate, smooth and strengthened surface or surface treatment with specific patterns. craft.
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Application: parts with relatively simple shapes such as cylindrical surfaces, conical surfaces, and planes.
5. Drawing
Wire drawing refers to the surface treatment method that makes the metal forcefully pass 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 are obtained, which is called the metal wire drawing process.
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Drawing can be made into straight grain, chaotic grain, corrugated grain and swirl grain according to decoration needs.
Several kinds.
6. Polishing
Polishing is a finishing method for modifying the surface of parts. Generally, only a smooth surface can be obtained, and the original processing accuracy cannot be improved or even maintained. Depending on the pre-processing conditions, the Ra value after polishing can reach 1.6~0.008μm .
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Generally divided into mechanical polishing and chemical polishing.
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2. Surface alloying technology
chemical surface heat treatment
A 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, so that the active atoms in the medium can penetrate into the surface of the workpiece to change the chemical composition and structure of the surface of the workpiece, and then change its performance.
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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 infiltrated, chemical heat treatment can be divided into carburizing, nitriding, multi-component co-infiltrating, infiltrating other elements, etc. The chemical heat treatment process includes three basic processes of decomposition, absorption and diffusion.
The two main methods of chemical surface heat treatment are carburizing and nitriding.
Compared
carburization
Nitriding
Purpose
Improve the surface hardness, wear resistance and fatigue strength of the workpiece, while maintaining good toughness in the core.
Improve the surface hardness, wear resistance and fatigue strength of the workpiece, and improve corrosion resistance.
Timber
Low carbon steel containing 0.1 to 0.25% C. The higher the carbon content, the lower the toughness of the core.
It is medium carbon steel containing Cr, Mo, Al, Ti, V.
common method
Gas carburizing method, solid carburizing method, vacuum carburizing method
Gas nitriding method, ion nitriding method
temperature
900～950℃
500～570℃
surface thickness
Generally 0.5 ~ 2mm
No more than 0.6~0.7mm
use
Widely used in mechanical parts of aircraft, automobiles and tractors, such as gears, shafts, camshafts, etc.
It is used for parts requiring high wear resistance and precision, as well as heat-resistant, wear-resistant and corrosion-resistant parts. Such as the small shaft of the instrument, light-loaded gears and important crankshafts.
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3. Surface conversion coating technology
1. Blackening and phosphating
blackened:
The process of heating steel or steel parts to an appropriate temperature in air-water vapor or chemicals to form a blue or black oxide film on the surface. Also become bluish.
Phosphating:
The process in which the workpiece (steel or aluminum, zinc) is immersed in a phosphating solution (some acid phosphate-based solution), and a layer of water-insoluble crystalline phosphate conversion film is deposited on the surface is called phosphating .
2. Anodizing
Mainly refers to the anodic oxidation of aluminum and aluminum alloy. Anodizing is to immerse aluminum or aluminum alloy parts in an acidic electrolyte, and act as an anode under the action of an external current to form an anti-corrosion oxide film that is firmly combined with the substrate on the surface of the part. This layer of oxide film has special characteristics such as protection, decoration, insulation, and wear resistance.
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Before anodizing, it must undergo pretreatments such as polishing, degreasing, and cleaning, and then it must be processed by rinsing, coloring, and sealing.
Application: It is commonly used in the protective treatment of some special parts of automobiles and aircrafts, as well as the decorative treatment of handicrafts and daily hardware products.
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4. Surface coating technology
1. Thermal spraying
Thermal spraying is the heating and melting of metal or non-metallic materials, and continuous blowing of compressed gas onto the surface of the workpiece to form a coating that is firmly bonded to the substrate and obtain the required physical and chemical properties from the surface of the workpiece.
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The use of thermal spraying technology can improve the wear resistance, corrosion resistance, heat resistance and insulation of materials.
Applications: Almost all fields including aerospace, atomic energy, electronics and other cutting-edge technologies.
2. Vacuum plating
Vacuum plating is a surface treatment process that deposits various metal and non-metal films on the metal surface by distillation or sputtering under vacuum conditions.
A very thin surface coating can be obtained by vacuum plating, and it has the advantages of fast speed, good adhesion, and less pollutants.
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Principle of Vacuum Sputtering Plating
According to different processes, vacuum plating can be divided into vacuum evaporation, vacuum sputtering, and vacuum ion plating.
3. Electroplating
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Electroplating is an electrochemical and redox process. Take nickel plating as an example: the metal part is immersed in a solution of metal salt (NiSO4) as the cathode, and the metal nickel plate is used as the anode. After the DC power supply is turned on, the metal nickel plating layer will be deposited on the part.
Electroplating methods are divided into ordinary electroplating and special electroplating.
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4. Vapor deposition
Vapor deposition technology refers to a new type of coating technology that deposits gas phase substances containing deposition elements on the surface of materials by physical or chemical methods to form thin films.
According to the different principles of the deposition process, vapor deposition techniques can be divided into two categories: physical vapor deposition (PVD) and chemical vapor deposition (CVD).
Physical Vapor Deposition (PVD)
Physical vapor deposition refers to the technology of vaporizing materials into atoms, molecules or ionization into ions by physical methods under vacuum conditions, and depositing a thin film on the surface of materials through the gas phase process.
Physical deposition techniques mainly include three basic methods: vacuum evaporation, sputtering, and ion plating.
Physical vapor deposition has the advantages of a wide range of applicable substrate materials and film materials; simple process, material saving, and no pollution; the obtained film has strong adhesion to the film base, uniform film thickness, compactness, and less pinholes.
It is widely used in the fields of machinery, aerospace, electronics, optics and light industry to prepare wear-resistant, corrosion-resistant, heat-resistant, conductive, insulating, optical, magnetic, piezoelectric, lubricating, superconducting and other thin films.
Chemical Vapor Deposition (CVD)
Chemical vapor deposition refers to a method in which a mixed gas interacts with the surface of a substrate to form a metal or compound film on the surface of the substrate at a certain temperature.
Because chemical vapor deposition film has good wear resistance, corrosion resistance, heat resistance and special properties such as electricity and optics, it has been widely used in machinery manufacturing, aerospace, transportation, coal chemical industry and other industrial fields.
