Introduction to Common Metal Materials and Surface Treatment Processes

Today, we will comprehensively introduce the characteristics and uses of eight common metal materials to everyone. It is very practical, and remember to collect it after reading it!
Eight Common Metal Materials
1. Cast iron - fluidity
As an inconspicuous part of our daily living environment, sewer covers are rarely noticed by people. The reason why cast iron has such a large and wide range of uses is mainly due to its excellent fluidity and its easy casting into various complex forms. Cast iron is actually the name for a mixture of multiple elements, including carbon, silicon, and iron. The higher the carbon content, the better its flow characteristics during the pouring process. Carbon appears here in two forms: graphite and iron carbide.
The presence of graphite in cast iron endows sewer covers with excellent wear resistance. Rust usually only appears on the surface, so it is usually polished. However, there are still special measures to prevent rust during the pouring process, which is to apply a layer of asphalt coating on the surface of the casting. The asphalt seeps into the fine holes on the surface of the cast iron, thereby playing a rust prevention role. The traditional process of producing sand mold casting materials has now been applied by many designers to other newer and more interesting fields.
Material characteristics: excellent fluidity, low cost, good wear resistance, low solidification shrinkage, brittleness, high compressive strength, and good machinability.
Typical use: Cast iron has a history of application for hundreds of years, involving fields such as architecture, bridges, engineering components, home furnishings, and kitchen utensils.
2 Stainless Steel - Love Without Rust
Stainless steel is an alloy made by incorporating chromium, nickel, and other metallic elements into steel. Its non rusting characteristic comes from the composition of chromium in the alloy. Chromium forms a strong and self-healing chromium oxide film on the surface of the alloy, which is invisible to the naked eye. The ratio of stainless steel to nickel that we usually refer to is generally 18:10. The term "stainless steel" refers not only to a single type of stainless steel, but also to over a hundred industrial stainless steels, each of which has excellent 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 based on its toughness and corrosion resistance, involving many fields that had never been explored before. This series of design attempts is very revolutionary. For example, devices that can be reused after disinfection have first appeared in the medical industry.
Stainless steel is divided into four main types: austenite, ferrite, ferrite austenite (composite), and martensite. The stainless steel used in household products is mostly austenitic.
Material characteristics: Health care, corrosion resistance, fine surface treatment, high rigidity, can be formed through various processing techniques, and is difficult to perform cold processing.
Typical use: Among commonly used primary color stainless steels, austenitic stainless steel is the most suitable coloring material, which can achieve satisfactory color appearance and shape. Austenitic stainless steel is mainly used in decorative building materials, household products, industrial pipelines, and building structures; Martensitic stainless steel is mainly used for making cutting tools and turbine blades; Ferritic stainless steel has anti-corrosion properties and is mainly used in durable washing machines and boiler components; Composite stainless steel has stronger corrosion resistance, so it is often used in corrosive environments.
3 Zinc -730 pounds in a lifetime
Zinc, with a silver glow and a hint of blue gray, is the third most widely used non-ferrous metal after aluminum and copper. A statistics from the United States Bureau of Mines shows that an average person consumes a total of 331 kilograms of zinc in their lifetime. Zinc has a very low melting point, so it is also an ideal casting material.
Zinc based castings are very common in our daily lives: materials such as door handles, watches, faucets, electronic components, etc. below the surface layer. Zinc has extremely high anti-corrosion properties, which gives it another basic function, which is to serve as a surface coating material for steel. In addition to the above functions, zinc is also an alloy material used to synthesize brass together with copper. Its corrosion resistance is not only applied to steel surface coatings - it also helps to enhance our human immune system.
Material characteristics: hygiene, corrosion resistance, excellent castability, excellent corrosion resistance, high strength, high hardness, cheap raw materials, low melting point, creep resistance, easy to form alloys with other metals, with health benefits, fragile at room temperature, and ductility at around 100 degrees Celsius.
Typical use: Electronic product components. Zinc is one of the alloy materials used to form bronze. Zinc also has characteristics of cleanliness, hygiene, and corrosion resistance. In addition, zinc is also used in roof materials, photo engraving plates, mobile phone antennas, and shutter devices in cameras.
4 Aluminum (Al) - Modern Materials
Compared to gold, which has a history of 9000 years of use, aluminum, a white metal with a slight blue light, can only be considered a baby among metal materials. Aluminum was introduced and named in the early 18th century. Unlike other metallic elements, aluminum does not exist in nature as a direct metallic element, but is extracted from bauxite containing 50% alumina (also known as bauxite). Aluminum, which exists in minerals in this form, is also one of the most abundant metallic elements on Earth.
When aluminum, a metal, first appeared, it was not immediately applied to people's lives. Later, a batch of new products targeting its unique functions and characteristics gradually emerged, and this high-tech material also gradually gained a wider market. Although the application history of aluminum is relatively short, the production of aluminum products on the market now far exceeds the sum of other non-ferrous metal products.
Material characteristics: flexible and malleable, easy to make alloys, high strength to weight ratio, excellent corrosion resistance, easy to conduct electricity and heat, recyclable.
Typical uses: vehicle skeleton, aircraft components, kitchen utensils, packaging, and furniture. Aluminum is also often used to reinforce large building structures, such as the statue of God of Love on Piccadilly Square in London and the top of the Chrysler Motor Building in New York, all of which have been reinforced with aluminum materials.
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 advantages such as light density, high specific strength and stiffness, good thermal conductivity, good damping and electromagnetic shielding performance, easy processing and molding, and easy recycling. However, for a long time, due to high prices and technological limitations, magnesium and magnesium alloys have only been used in small quantities in aviation, aerospace, and military industries, and are therefore known as "noble metals". Magnesium is currently the third largest metal engineering material after steel and aluminum, and is widely used in aerospace, automotive, electronics, mobile communication, metallurgy and other fields. It can be expected that due to the increase in production costs of other structural metals, the importance of magnesium metal will become even greater in the future.
Magnesium alloy accounts for 68% of aluminum alloy, 27% of zinc alloy, and 23% of steel. It is commonly used in automotive parts, 3C product casings, building materials, etc. Most ultra-thin laptops and mobile phone casings are made of magnesium alloy.
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. The commonly used magnesium alloy has non flammability, especially when used in automotive components and building materials, which can avoid instantaneous combustion. Most of the magnesium raw materials are 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 non flammability, poor heat resistance, and easy recycling.
Typical applications: Widely used in aerospace, automotive, electronics, mobile communication, metallurgy and other fields.
6 Copper - Human Companion
Copper is simply an incredible versatile metal that is so closely related to our lives. Many early tools and weapons of humanity were made of copper. Its Latin name "cuprum" originated from a place called Cyprus, which is an island with abundant copper resources. People use the abbreviation Cu for the island's name to name this metal material, so copper has its current code name.
Copper plays a very important role in modern society: it is widely used in building structures as a carrier for transmitting electricity. In addition, for thousands of years, it has been used as a raw material for making body decorations by people from different cultural backgrounds. From simple decoding and transmission to playing a crucial role in complex modern communication applications, this ductile and orange colored metal has accompanied our development and progress all the way. Copper is an excellent conductor, with conductivity second only to silver. In terms of the time history of people using metal materials, copper is the oldest metal used by humans, second only to gold. This is largely due to the ease of copper mining, and the fact that the copper industry is relatively easy to separate from copper.
Material characteristics: excellent corrosion resistance, excellent thermal conductivity, conductivity, hardness, flexibility, ductility, unique effect after polishing.
Typical applications: wires, engine coils, printed circuits, roofing materials, piping materials, heating materials, jewelry, cookware. It is also one of the main alloy components for making bronze.
7 Chromium - High gloss post-treatment
The most common form of chromium is used as an alloying element in stainless steel to enhance its hardness. Chromium plating processes are usually divided into three types: decorative coatings, hard chromium coatings, and black chromium coatings. Chromium plating is widely used in the engineering field, and decorative chromium plating is usually applied as the topmost layer outside the nickel layer. The plating has a delicate and mirror like polishing effect. As a decorative post-treatment process, the thickness of the chromium coating is only 0.006 millimeters. When planning to use the chromium plating process, it is important to fully consider the hazards of this process. The trend of hexavalent decorative chromium water being replaced by trivalent chromium water is becoming increasingly apparent, as the former has strong carcinogenicity, while the latter is considered relatively less toxic.
Material characteristics: very high smoothness, excellent anti-corrosion performance, hard and durable, easy to clean, and low friction coefficient.
Typical use: Decorative chrome plating is a coating material for many automotive components, including door handles and bumpers. In addition, chromium is also used for bicycle parts, bathroom faucets, furniture, kitchen utensils, tableware, and more. Hard chrome plating is more commonly 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 instrument decoration and solar energy utilization.
8 Titanium - Lightweight and sturdy
Titanium is a very special metal, with a very lightweight texture, but also very tough and corrosion-resistant, maintaining its color tone for life at room temperature. The melting point of titanium is not much different from that of platinum, so it is commonly used in precision components in aerospace and military industries. After adding current and chemical treatment, different colors will be produced. Titanium has excellent acid and alkali corrosion resistance. After soaking in aqua regia for several years, titanium still shines brightly and shines brightly. If titanium is added to stainless steel, adding only about 1% can greatly improve its rust resistance.
Titanium has excellent characteristics such as low density, high temperature resistance, and corrosion resistance. Titanium alloys have a density half that of steel and a strength similar to that of steel; Titanium is resistant to both high and low temperatures. It can maintain high strength within a wide temperature range of -253 ℃ to 500 ℃. These advantages are essential for space metals. Titanium alloy is a good material for making rocket engine shells, artificial satellites, and spacecraft, and is known as "space metal".
Titanium is a pure metal, and precisely because of its purity, substances do not undergo chemical reactions when in contact with it. That is to say, due to its high corrosion resistance and stability, titanium does not affect its essence even after long-term contact with humans, so it will not cause allergies in humans. It is the only metal that has no effect on human autonomic nervous system and taste, and is known as a "biophilic metal".
The biggest drawback of titanium is that it is difficult to extract. This is mainly because titanium can combine with oxygen, carbon, nitrogen, and many other elements at high temperatures.
Material characteristics: very high strength, excellent corrosion resistance compared to weight, difficult to cold work, good weldability, approximately 40% lighter than steel and 60% heavier than aluminum, low conductivity, low thermal expansion rate, and high melting point.
Typical uses: golf clubs, tennis rackets, portable computers, cameras, luggage, surgical implants, aircraft skeletons, chemical equipment, 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 techniques to change the surface condition and properties of parts, optimize their combination with core materials, and achieve predetermined performance requirements is called surface treatment process.
The function of surface treatment:
(1) Improve surface corrosion resistance and wear resistance, slow down, eliminate and repair material surface changes and damage;
(2) Enable ordinary materials to obtain surfaces with special functions;
(3) Save energy, reduce costs, and improve the environment.
2. Classification of metal surface treatment processes

It can be divided into four categories: surface modification technology, surface alloying technology, surface conversion film 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 austenitize the surface without changing the chemical composition and core structure of the steel, and then quenches it to strengthen the surface of the parts.
The main methods of surface quenching include flame quenching and induction heating, and commonly used heat sources include flames such as oxyacetylene or oxypropane.
2. Laser surface strengthening
Laser surface strengthening is the process of using a focused laser beam to shoot at the surface of a workpiece, heating 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 period of time, and then cooling it in a very short period of time to harden and strengthen the surface of the workpiece.

Laser surface strengthening can be divided into laser phase transformation strengthening treatment, laser surface alloying treatment, and laser cladding treatment.

Laser surface strengthening has a small heat affected zone, small deformation, and convenient operation. It is mainly used for locally strengthened parts, such as punching dies, crankshafts, camshafts, camshafts, spline shafts, precision instrument guides, high-speed steel cutting tools, gears, and internal combustion engine cylinder liners.
3. Shot peening
Shot peening strengthening is a technology that sprays a large number of high-speed moving projectiles onto the surface of a part, like countless small hammers hitting the metal surface, causing certain plastic deformation of the surface and subsurface layers of the part to achieve strengthening.

Function:
(1) Improve the mechanical strength, wear resistance, fatigue resistance, and corrosion resistance of parts;
(2) Used for surface extinction and descaling;
(3) Eliminate residual stresses in castings, forgings, and welded parts.
4. Rolling
Rolling is a surface treatment process that uses a hard roller or roller to apply pressure to a rotating workpiece surface at room temperature and move along the direction of the generatrix, causing plastic deformation and hardening of the workpiece surface, in order to obtain an accurate, smooth, and reinforced surface or specific pattern.

Application: Parts with relatively simple shapes such as cylindrical surfaces, conical surfaces, and flat surfaces.
5. Wire drawing
Wire drawing refers to the surface treatment method in which metal is forced through a mold under external forces, compressing the cross-sectional area of the metal and obtaining the required shape and size of the cross-sectional area.

Drawing can be made into several types according to decorative needs, including straight lines, irregular lines, ripples, and spiral lines.
6. Polishing
Polishing is a finishing method that modifies the surface of a part. Generally, it can only obtain a smooth surface and cannot improve or even maintain the original machining accuracy. Depending on the pre processing condition, the Ra value after polishing can reach 1.6~0.008 μ M.

It is generally divided into mechanical polishing and chemical polishing.

 

2, 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 insulation, allowing active atoms in the medium to penetrate into the surface of the workpiece, thereby changing the chemical composition and structure of the surface of the workpiece, and thereby 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 infiltrated, chemical heat treatment can be divided into carburization, nitridation, multicomponent co infiltration, infiltration of other elements, etc. The chemical heat treatment process includes three basic processes: decomposition, absorption, and diffusion.
The two main methods of chemical surface heat treatment are carburization and nitriding.

 

3, Surface conversion film technology
1. Blackening and phosphating
Blackening:
The process of heating steel or steel components in air water vapor or chemical agents to an appropriate temperature to form a layer of blue or black oxide film on their surface. Also known as turning blue.
Phosphatization:
The process in which a workpiece (steel, aluminum, zinc parts) is immersed in a phosphating solution (a solution mainly composed of acidic phosphates) and deposited on the surface to form a crystalline phosphate conversion film that is insoluble in water is called phosphating.
2. Anodization
Mainly refers to the anodizing of aluminum and aluminum alloys. Anodizing is the process of immersing aluminum or aluminum alloy parts in an acidic electrolyte and using it as an anode under the action of an external current to form a corrosion-resistant oxide film layer firmly bonded to the substrate on the surface of the parts. This oxide film has special characteristics such as protection, decoration, insulation, and wear resistance.

Before anodizing, pre-treatment such as polishing, degreasing, and cleaning should be carried out, followed by rinsing, coloring, and sealing.
Application: Commonly used for protective treatment of certain special components of automobiles and airplanes, as well as decorative treatment of handicrafts and daily hardware products.

 

4, Surface coating technology
1. Thermal spraying
Thermal spraying is the process of heating and melting metal or non-metallic materials, continuously blowing compressed gas onto the surface of the workpiece to form a coating that firmly adheres to the substrate, and obtaining the required physical and chemical properties from the surface of the workpiece.

The use of thermal spraying technology can improve the wear resistance, corrosion resistance, heat resistance, and insulation properties of materials.
Applications: Almost all fields, including cutting-edge technologies such as aerospace, atomic energy, and electronics.
2. Vacuum plating
Vacuum plating is a surface treatment process in which various metal and non-metal thin films are deposited on a metal surface under vacuum conditions through distillation or sputtering.
By vacuum plating, a very thin surface coating can be obtained, which has the advantages of fast speed, good adhesion, and low pollution.

Principle of Vacuum Sputtering Plating
According to different processes, vacuum plating can be divided into vacuum evaporation plating, vacuum sputtering plating, and vacuum ion plating.
3. Electroplating

Electroplating is an electrochemical and redox process. Taking nickel plating as an example: immerse the metal workpiece in a solution of metal salt (NiSO4) as the cathode, and the metal nickel plate as the anode. After connecting the DC power supply, a metal nickel plating layer will be deposited on the workpiece.
The electroplating methods are divided into ordinary electroplating and special electroplating.

Electroplating is an electrochemical and redox process. Taking nickel plating as an example: immerse the metal workpiece in a solution of metal salt (NiSO4) as the cathode, and the metal nickel plate as the anode. After connecting the DC power supply, a metal nickel plating layer will be deposited on the workpiece.
The electroplating methods are divided into ordinary electroplating and special electroplating.