It is a process that hardens metals by changing their structure, and is often used to process stainless steel. There are many uses for cold rolled stainless steel as a raw material in medical, aerospace, and automotive engineering. To learn more about cold rolled steel, how it's produced, and what it can be used for, read on.
Cold rolled steel, sometimes abbreviated to CRS, is well-known for being an extremely ductile material, and is ideal for applications where precision is necessary. It is used in many applications, like household appliances, furniture, lockers, and filing cabinets. In construction applications, CRS is commonly used for building garages, steel sheds, and other industrial buildings.
Cold rolling is a technique used to enhance the strength of steel without using any high temperatures. Mechanical stress is applied in lieu of heat, allowing for the metal's shape to be modified. This process, known as strain hardening, can increase the tensile strength of a steel component by up to 20% and improve its surface finish.
During the cold rolling process, when the metal is put under mechanical stress, it causes a permanent change to the crystalline structure of the metal. In addition to improving its surface finish, cold rolling also improves its dimensional accuracy, which increases its strength and often improves corrosion resistance.
Cold rolled stainless steel coils can be precision manufactured, allowing for production to tight tolerances. This work hardening process of the steel through cold rolling is done to create various levels of temper such as quarter-, half-, and full-hard. The amount of cold work on each depends on the hardness desired, with reduction (up to 50%) increasing yield point while decreasing ductility. As an example, simple bending tasks are possible with quarter-hard. Half-hard allows a 90-degree angle bend, while full hard can be bent at 45 degrees without breaking. This type of metal finds utility in various applications due to its ability to be bent without risk of breakage.
Stainless steel grades that are commonly cold rolled include:
Austenitic Stainless Steel
Ferritic Stainless Steel
Martensitic Stainless Steel
Precipitation Hardening Stainless Steel
The process of cold rolling a metal alloy begins with either sheet metal or strip coil, which are then put through rollers to compress and squeeze it under high pressure just below its ultimate tensile strength. The amount of compression can be adjusted to give the finished piece different mechanical and hardness properties. Cold reduction is used to make the metal thinner by going through multiple tandem rolling mill stands, which have vertical rolls powered by powerful motors that apply extreme compression.
These mills make the hot-rolled, pickled coils thinner. After passing through the rolls, it is increased in strength but is also brittle. Subsequently, to soften the steel and make it easier to work with, annealing at a higher temperature is necessary. This renders the metal more malleable so that it can be bent and formed for use in many applications.
As another method of cold rolling, a reversing mill passes the strip back and forth between mandrels, reducing its thickness each pass until the desired thickness is achieved. Cold rolling can reduce metal thickness by 60 to 80 percent, so it can then be used to produce consumer goods or other products.
In spite of the fact that cold rolling is most commonly used with steel, many alloys and metals can also be cold rolled to alter their crystalline composition. If they are rolled at temperatures below re-crystallization point, permanent defects develop. Consequently, the crystals are less likely to move within the metal structure, which increases the metal's hardness and tensile strength.
As well as stainless steel, titanium, aluminum alloys, and nickel alloys can all be cold rolled. Cold rolling metals such as stainless steel coil increases strength and surface finish, but it decreases ductility. When the metal is annealed, it can be used in many different ways once it has been annealed. The same applies to metal wire that has been cold drawn or rolled.
Deep drawing metal requires that a rolled coil be punched through a hole or die. The punch and die must match in dimensions, but with the latter having some clearance for easier passage of the material. Each draw operation is done individually and causes the diameter to decrease while increasing the part's height or depth. This ensures that re-crystallization occurs as the metal shape is altered. Products formed through this process can range from battery enclosures to implantable medical devices, aerospace components and defense items for aircraft.
Even though extrusion is still a relatively new metalworking technique, it is an important and versatile manufacturing process. Cold extrusion produces a constant cross-section product by forcing a slug of material through a die at room or slightly elevated temperatures. Tin, aluminum alloys, copper, lead, steel, and other metals can be extruded.
A flat metal strip coil is converted into a variety of shapes using metal stamping, another manufacturing process ideal for producing metal products with tight tolerances. There are a number of different metal forming techniques involved in this complex process, including punching, coining, piercing, blanking, and bending.
The process involves passing a long strip of metal (usually coiled steel) through sets of rolls, each performing a portion of the bend, until the desired cross-section profile is achieved.
There are many ways to use cold rolled steel and many industries in which it can be applied. Contact a China metallurgical expert if you would like to learn more about cold rolled metals. They can advise you on the most appropriate alloy, grade, and properties. Having cold worked metals for nearly 100 years, Aofeng Metal Material is proud to serve the nuclear, aerospace, and medical industries.