Metal is oftentimes manipulated after being smelted from raw ore to improve its strength, durability, ductility or other physical properties. While most of these metalworking processes involve the use of heat, others do not. Cold working, for example, is a group of metalworking processes that’s designed to improve the physical properties of metal at or near room temperature. What is cold-worked metal exactly, and how does it differ from other metalworking processes?
Overview of Cold-Worked Metal
The term “cold-worked metal” refers to any metal workpiece that’s been physically manipulated below its respective recrystallization temperature. All metals have a specific temperature at which they develop new grains. Known as a recrystallization temperature, it occurs at hot temperatures. Steel, for instance, has a recrystallization temperature of about 750 to 1,300 degrees Fahrenheit. Cold working simply involves reshaping a metal workpiece below this temperature, with most cold-working processes occurring at or near room temperature.
The 4 Main Cold-Working Techniques
There are four main cold-working techniques that companies use to manipulate metal workpieces at or near room temperature: squeezing, drawing, shearing and bending. Each technique involves a different approach. Squeezing, for instance, involves compressing a metal workpiece between two or more rollers, whereas shearing involves cutting a metal workpiece with a straight cutting blade. Regardless, all four techniques allow companies to manipulate the shape and/or size of a metal workpiece while keeping the workpiece at or near room temperature.
Cold-Worked vs Hot-Worked Metal
Metal can be classified as either cold worked or hot worked, depending on the temperature at which it was manipulated. If a metal workpiece is manipulated at or near room temperature, it’s considered cold worked. If it’s manipulated at a temperature above the metal’s recrystallization point, on the other hand, it’s considered hot worked.
Advantages of Cold-Worked Metal
Cold-worked metal is often preferred because of the advantages it offers over hot-worked metal. While hot-working processes can change the size and shape of metal workpieces, it comes at the cost of strength. Exposure to heat typically makes metal workpieces weaker. As a result, cold-working processes are used in applications requiring a strong finished product.
Not only does it offer increased strength, but cold working is also easier to perform. Without the need for heat, companies can perform cold-working processes more quickly than hot-working processes. Therefore, cold-worked metal typically costs less to produce than its hot-worked counterpart.
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FAQs
If a metal workpiece is manipulated at or near room temperature, it's considered cold worked. If it's manipulated at a temperature above the metal's recrystallization point, on the other hand, it's considered hot worked.
What is the cold working process of metal? ›
In metallurgy, cold forming or cold working is any metalworking process in which metal is shaped below its recrystallization temperature, usually at the ambient temperature. Such processes are contrasted with hot working techniques like hot rolling, forging, welding, etc.
What does cold work cause metals to _____? ›
In cold working, process metals are plastically deformed below their recrystallization temperature.
What happens when you cold work steel? ›
The process of cold working involves the strengthening of steel material by physically manipulating the material below the recrystallization temperature. The recrystallization temperature is defined as the temperature at which new defect-free crystalline grains replace the original ones present in the material.
Can all metals be cold worked? ›
It is simply not possible to cold work some types of metals. These include alloy steels that are not ductile at room temperature, carbon steel, and titanium grade 5. Some metals that can be cold worked, such as copper, may also become brittle after cold working.
How does cold working work? ›
When a metal is bent or shaped, dislocations are generated and move. As the number of dislocations in the crystal increases, they will get tangled or pinned and will not be able to move. This will strengthen the metal, making it harder to deform. This process is known as cold working.
What is the meaning of cold working? ›
Definition of 'cold working'
Cold working is a process in which metal is shaped at a fairly low temperature. This increases the metal's yield strength but makes it less ductile. The strength and hardness of steel can be increased by cold working, but that will also make it less ductile.
What metals Cannot be cold worked? ›
Zinc, tin and lead have recrystallization temperatures below room temperature. This means that these metals cannot be cold worked at room temperature since they crystallize spontaneously, reforming a strain free structure.
What are the advantages of cold working metal? ›
Advantages of Cold Working
Metals remain unheated throughout the process. Superior surface finish is attainable as there is no oxidation during cold metalworking. Enhanced strength and hardness of the metal are achieved. Cold working imparts increased strength and hardness to the metal.
Is cold steel stronger? ›
In terms of physical characteristics, cold rolled steels are typically harder and stronger than standard hot rolled steels. As the metal is shaped at the lower temperatures, the steel's hardness, resistance against tension breaking, and resistance against deformation are all increased due to work hardening.
The cold rolling process also makes the steel stronger and less pliable, which is useful in appliance manufacturing. The downside of its superior strength is that there are limited options available for shape customization. Cold rolled steel uses finishes during the process, so it may have a slick or oily surface.
What happens to metal when it gets too cold? ›
Cold makes metal more brittle. One of the issues with the “Titanic” was the steel used to make and rivet in in place was not well suited to cold temperatures and fractured more easily in icy water. Extreme cold, like as cold as liquid gases, will greatly increase the conductivity of metals as their resistance drops.
How does cold working affect metal conductivity? ›
Other side effects of cold working are the changes in electric conductivity as well as ferromagnetic properties. Electric conductivity can be negatively influenced, while ferromagnetic properties can improve. For instance, permanent magnetization can occur in steel, such as tool steel.
What does heat and cold do to metal? ›
Metal expands and contracts with hot and cold conditions, respectively, as a result of the effects of temperature on their molecular activity. Thermal expansion occurs when the temperature rises, and in the field, can cause the metal to visibly increase in length, width, and surface area.
What metals are used in cold forming? ›
Cold forming is a simple process that produces metal components at low temperatures without removing any material. Materials that can be cold formed include, but are not limited to: carbon steels, brass, lead, stainless steel, copper, alloy steels, aluminium, bronze, nickel alloys and precious metals.
