1、Cast iron

Sewer covers are a humble part of our everyday environment, and few people pay attention to them. The reason why cast iron has such a large number and wide range of applications is mainly due to its excellent fluidity and the feature that it is easy to be cast into various complex shapes. Cast iron is actually the name of a mixture composed of multiple elements, including carbon, silicon and iron. The higher the carbon content, the better the flow characteristics during the casting process. Carbon here appears 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 topmost layer, so it is usually worn off. Despite this, there are still specific measures to prevent rust during the casting process. That is, a layer of asphalt coating is applied to the surface of the casting. The asphalt seeps into the fine pores on the surface of the cast iron, thereby playing a role in rust prevention. The traditional process of producing sand mold casting materials is now being applied by many designers to other newer and more interesting fields.

Material properties: Excellent fluidity, low cost, good wear resistance, low solidification shrinkage rate, very brittle, high compressive strength, and good machinability.

Typical applications: Cast iron has a history of several hundred years of application, covering fields such as construction, Bridges, engineering components, household items, and kitchenware.

2、Stainless steel

Stainless steel is an alloy made by infusing chromium, nickel and some other metal elements into steel. The non-rusting property of it comes from the chromium component 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" does not merely refer to a single type of stainless steel, but rather represents over a hundred types of industrial stainless steel. Each type of stainless steel developed 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. Designers developed many new products based on its toughness and corrosion resistance, covering many areas that had never been explored before. This series of design attempts are all highly revolutionary: for instance, devices that can be reused after disinfection first appeared in the medical industry.

Stainless steel is classified into four main types: austenitic, ferritic, ferritic-austenitic (composite type), and martensitic. The stainless steel used in household items is basically austenitic.

Material properties: Hygienic and health-preserving, anti-corrosion, capable of fine surface treatment, high rigidity, can be formed through various processing techniques, and relatively difficult to cold work.

Typical application: Among the 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 items, 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 components of washing machines and boilers. Composite stainless steel has stronger anti-corrosion performance, so it is often used in corrosive environments.

3、zinc

Zinc, with a silvery luster and a hint of bluish-gray, is the third most widely used non-ferrous metal after aluminium and copper. A statistic from the United States Bureau of Mines shows that an average person consumes a total of 331 kilograms of zinc throughout their lifetime. Zinc has a very low melting point, so it is also a very ideal casting material.

Zinc castings are very common in our daily life: the material beneath the surface of door handles, faucets, electronic components, etc. Zinc has extremely high corrosion resistance, and this property endows it with another most fundamental function, that is, as a surface coating material for steel. In addition to the above-mentioned functions, zinc is also an alloy material used to synthesize brass together with copper. Its corrosion resistance is not only applied to the surface coating of steel - it also helps to enhance our human immune system.

Material properties: Health care, anti-corrosion, excellent castability, outstanding anti-corrosion, high strength, high hardness, low raw material cost, low melting point, creep resistance, easy to form alloys with other metals, health care, brittle at room temperature, ductile at around 100 degrees Celsius.

Typical application: Electronic product components. Zinc is one of the alloy materials used to form bronze. Zinc also has the properties of being clean, hygienic and resistant to corrosion. In addition, zinc is also used in roofing materials, photo engraving discs, mobile phone antennas and shutter devices in cameras.

4、aluminum

Compared with gold, which has a history of 9,000 years of use, aluminium, this slightly bluish white metal, can only be regarded as a baby among metal materials. Aluminium was introduced and named in the early 18th century. Unlike other metallic elements, aluminium does not exist in nature as a direct metallic element, but is extracted from bauxite containing 50% aluminium oxide (also known as alumina). Aluminum, which exists in minerals in this form, is also one of the most abundant metallic elements on our Earth.

When aluminium 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 an increasingly broad market. Although the application history of aluminium is relatively short, the current output of aluminium products on the market has far exceeded the total of other non-ferrous metal products.

Material properties: Flexible and malleable, easy to form alloys, high strength-to-weight ratio, excellent corrosion resistance, good electrical and thermal conductivity, recyclable.

Typical uses: vehicle frames, aircraft components, kitchenware, packaging and furniture. Aluminum is also frequently used to reinforce some large building structures. For instance, the statue of Cupid in Piccadilly Circus in London and the top of the Chrysler Building in New York have all been reinforced with aluminum materials.

5、Magnesium alloy

Magnesium is an extremely important non-ferrous metal. It is lighter than aluminium and can form high-strength alloys with other metals very well. Magnesium alloys have the advantages of light specific gravity, high specific strength and specific stiffness, good thermal and electrical conductivity, excellent damping, shock absorption and electromagnetic shielding performance, easy processing and shaping, and easy recycling. However, for a long time, due to their high prices and technical limitations, magnesium and magnesium alloys have only been used in small quantities in the aviation, aerospace and military industries, and thus have been called "noble metals". Magnesium is now the third most important metal engineering material after steel and aluminium, and is widely used in aerospace, automobiles, electronics, mobile communications, metallurgy and other fields. It can be expected that due to the increase in the production costs of other structural metals, the importance of metallic magnesium will become even greater in the future.

Magnesium alloys have a specific gravity of 68% that of aluminum alloys, 27% of zinc alloys, and 23% of steel. They are often used in automotive parts, 3C product casings, building materials, etc. Most ultra-thin laptop and mobile phone casings are made of magnesium alloy. Since the last century, humans have still had an indelible love for the texture and luster of metals. Although plastic products can form a metal-like appearance, their luster, hardness, temperature and texture still lag behind those of metals. Magnesium alloy, as a new type of metal raw material, gives people a sense of high-tech products.

The corrosion resistance of magnesium alloys is 8 times that of carbon steel, 4 times that of aluminum alloys, and more than 10 times that of plastics. Its anti-corrosion ability is the best among alloys. Commonly used magnesium alloys are non-flammable, especially when used in automotive and motorcycle parts as well as building materials, they can prevent sudden combustion. Magnesium ranks eighth in terms of reserves in the Earth's crust. Most of the magnesium raw materials are extracted from seawater, so its resources are stable and abundant.

Material properties: Lightweight structure, high rigidity and impact resistance, excellent corrosion resistance, good thermal conductivity and electromagnetic shielding, good non-flammability, poor heat resistance, easy to recycle.

Typical applications: Widely used in aerospace, automotive, electronic, mobile communication, metallurgy and other fields.

6、copper

Copper is simply an incredibly versatile metal that is so closely related to our lives. Many of mankind's early tools and weapons were made of copper. Its Latin name "cuprum" originated from a place called Cyprus, an island rich in copper resources. People named this metal material after the abbreviation of the island's name, Cu, and thus copper got its current code.

Copper plays a very important role in modern society: it is widely used in building structures as a carrier for transmitting electricity. Additionally, for thousands of years, it has also been used by people from many different cultural backgrounds as a raw material for making body ornaments. From the initial simple decoding and transmission to its crucial role in complex modern communication applications later on, this malleable, orange-red metal has accompanied our development and progress all along. Copper is an excellent conductor, and its electrical conductivity is second only to that of silver. In terms of the time history of people's utilization of metal materials, copper is the second oldest metal that has been utilized by humans after gold. This is largely because copper mines are easy to extract and the copper industry is relatively easy to separate from copper mines.

Material properties: Excellent corrosion resistance, outstanding thermal and electrical conductivity, hardness, flexibility, ductility, and unique effect after polishing.

Typical uses: wires, engine coils, printed circuits, roofing materials, pipe materials, heating materials, jewelry, cookware. It is also one of the main alloying components for making bronze.

7、chromium

The most common form of chromium is its use as an alloying element in stainless steel to enhance its hardness. Chromium plating processes are generally divided into three types: decorative coatings, hard chromium coatings, and black chromium coatings. Chromium plating is widely used in the engineering field. Decorative chromium plating is usually applied as the outermost layer outside the nickel layer, and the plating has a delicate and fine polishing effect like a mirror. As a decorative post-treatment process, the thickness of the chromium coating is only 0.006 millimeters. When planning to adopt the chromium plating process, it is essential to fully consider the dangers of this process. In the past decade, the trend of hexavalent decorative chromium water being replaced by trivalent chromium water has become increasingly obvious, as the former has very strong carcinogenicity, while the latter is considered to be relatively less toxic.

Material properties: Extremely high smoothness, excellent anti-corrosion performance, hard and durable, easy to clean, and low friction coefficient.

Typical uses: Decorative chromium plating is a coating material for many automotive components, including door handles and buffers, etc. In addition, chromium is also applied to bicycle parts, bathroom faucets, as well as furniture, kitchenware, tableware, etc. Hard chrome plating is more commonly used in industrial fields, including random access memory in operation control blocks, jet engine components, plastic molds, and shock absorbers, etc. Black chrome plating is mainly used for musical instrument decoration and solar energy utilization.

8、titanium

Titanium is a very special metal. It is extremely light in texture, yet very tough and corrosion-resistant. It retains its original color throughout its life at room temperature. The melting point of titanium is not much different from that of platinum, so it is often used in aerospace. Military precision components. After applying electric current and chemical treatment, different colors will be produced. Titanium has excellent resistance to acid and alkali corrosion. Even after being soaked in aqua regia for several years, titanium remains shiny and radiant. If titanium is added to stainless steel by only about one percent, its rust resistance will be greatly enhanced.

Titanium possesses excellent properties such as low density, high-temperature resistance, and corrosion resistance. The density of titanium alloys is half that of steel, while their strength is 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 precisely what space metals possess. Titanium alloys are excellent materials for making rocket engine casings, artificial satellites and spaceships, and are known as "space metals". Because titanium has these advantages, it has become a prominent rare metal since the 1950s.

Titanium is a pure metal. It is precisely because of its "purity" that no chemical reaction occurs when substances come into contact with it. That is to say, due to titanium's high corrosion resistance and stability, it does not affect its nature even after long-term contact with humans, so it will not cause allergic reactions. It is the only metal that has no impact on human autonomic nerves and taste, and is thus called a "biophilic metal" by people.

The biggest drawback of titanium is that it is rather difficult to refine. This is mainly because titanium can combine with oxygen, carbon, nitrogen and many other elements at high temperatures. So people once regarded titanium as a "rare metal". In fact, titanium accounts for about 6‰ of the weight of the earth's crust, which is more than ten times the total of copper, tin, manganese and zinc.

Material properties: extremely high strength, excellent weight-to-weight ratio, good corrosion resistance, difficult to cold work, good weldability, approximately 40% lighter than steel and 60% heavier than aluminum, low electrical conductivity, low thermal expansion rate, high melting point.

Typical uses: golf clubs, tennis rackets, portable computers, cameras, suitcases, surgical implants, aircraft skeletons, chemical tools and maritime equipment, etc. In addition, titanium is also used as a white pigment required for paper, painting and plastic, etc.