What Is Clad Steel?
Clad Steel is a composite material consisting of a different type of steel overlaid on one side of a base material.
Carbon steel or low-alloy steel is used as the base metal. By joining dissimilar metals, it is possible to achieve functions that are not possible with single metals. In addition to new functions, cost reduction can be achieved by combining expensive metals with inexpensive metals.
Clad steels are manufactured by combining base metal and steel, followed by heating and drawing. Clad Steel manufacturing has been around for a long time, and the technique is also used in Japanese swords and knives.
Uses of Clad Steel
Clad Steel is widely used in the following industries:
1. Critical Equipment
In critical facilities such as chemical plants, materials must be corrosion resistant because they handle high temperatures, high pressures, and corrosive substances. Clad Steel provides corrosion resistance in such environments, enabling safe, long-term operation of facilities.
2. Structural Material for Offshore Plants and Ships
Clad steel is also used as a structural material for offshore plants and ships. Ordinary steel materials are susceptible to corrosion due to salt in seawater and erosion from marine organisms. However, Clad Steel is protected from corrosion by stainless steel on its surface, making it highly durable.
3. Kitchen Knives
Clad steel may be used for kitchen knives. Knives made of Clad Steel use high-hardness carbon steel only for the blade part, and soft stainless steel for the other parts. In addition, the high-hardness portion is limited to a specific area and can be sharpened relatively easily.
Principle of Clad Steel
Clad Steel is made by combining base metal and steel and then heating to bond the dissimilar materials. Heating methods include hot rolling, welding, and explosive crimping.
1. Hot Rolling
Hot rolling is a method of joining dissimilar metals by pressure. By applying pressure, metal atoms penetrate into each other’s material side, making it difficult for them to peel off at the interface. Finally, rolling is used to stretch the Clad Steel to the required thickness.
2. Welding
Welding is a process where the surface layer of the base metal is melted by heat and then the surface layer of the mating material is also melted by heat and bonded together. The method of melting the mating material side should be changed depending on the application and the properties of the mating material.
3. Explosion Crimping
Explosion crimping is a method of joining dissimilar metals instantaneously by utilizing the instantaneous high energy generated when explosive explode. It is used to join metals that cannot be hot rolled or welded. It is used for joining steel and aluminum, and can be applied to materials that are difficult to heat processed.
Types of Clad Steel
There are various types of Clad Steel, depending on the materials to be combined. The following are some examples of Clad Steel types:
1. Nickel Alloy Clad Steel
Clad Steel is made by laminating stainless steel with nickel or nickel alloy. Nickel is resistant to pinholes and corrosion. It is also less expensive to produce than copper or titanium. Main applications are connectors and transport line pipes.
2. Copper Alloy Clad Steel
Clad Steel is stainless steel laminated with copper and copper alloys. It exhibits excellent electrical properties and has a lower density than nickel, leading to weight reduction. Major applications include coaxial cable cores, diode leads, and other products requiring electrical conductivity.
3. Titanium Alloy Clad Steel
Clad Steel is made by laminating titanium and titanium alloys to stainless steel. Like nickel, it has excellent corrosion resistance. It is especially effective in environments where seawater or highly corrosive solutions are handled. Main applications include seawater desalination equipment.
4. Aluminum Clad Steel
Clad Steel is made by laminating steel material to aluminum. Since the specific weight can be reduced to less than half, improved fuel efficiency can be expected in the automotive and other mobility industries through weight reduction. In addition, the amount of aluminum alloy used can be reduced and material costs can be lowered.
Since steel materials are also used as strength, they can be widely used as structural members that require higher mechanical strength than aluminum alloys, which is an advantage. Since both aluminum alloys and steel materials have excellent formability, aluminum-clad steel, which is composed of both materials, can be easily formed and processed.
By bending or pressing the plates after clad joining, even relatively complex shapes can be formed without cracks. Another advantage is that the steel material and aluminum alloy are heated to a high temperature and joined by diffusion, resulting in less formation of a thin, brittle intermediate layer.