Cold Rolled Steel
What Is Cold Rolled Steel?
The cold rolling process is a method of shaping steel rod into cold finished bar or wire. The rod is mechanically worked to its final shape by passing through a series of rolling mills at ambient temperature. Compared to other steel processing methods, cold rolled steel properties typically include a smoother, scale-free, finish; less material loss; tight manufacturing tolerances; a higher degree of customization; and up to 50% more tensile strength.
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Cold rolling steel results in a more aesthetically pleasing and superior mechanical finish compared to hot rolled steel. While hot rolling steel at times, may be a less expensive process, it can create more variability in the finished shape or profile; often times coupled with higher minimum order quantities. So while there may be some upfront cost savings, if the rod needs to be machined into a custom shape, hot rolled steel can actually cost more over the lifetime of the project.
Cold rolled steel offers the ability to shape bar or wire with little variability and uniform mechanical properties before it arrives at your facility, which can save you time and money. Custom shapes or profiles can be rolled in the bar or wire with accuracy to +/- 0.001” (+/- 0.025 mm). This process further hardens the steel, increasing tensile strength by up to 50%.
Finally, cold-rolled steel comes with a smooth and visually appealing finish, without the blisters, scale, and scars found on hot rolled steel bar and wire. This makes it the ideal choice in any situation where the steel structure is visible and requires high strength.
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Cold rolled steel offers superior finish quality and mechanical properties relative to cold drawn steel. The process of cold drawing steel involves pushing or pulling the rod through a die to form the steel into its shape. While the process can be less expensive than cold rolling steel (depending on the shape), it may require several iterations, or cold drawing passes, to achieve the desired profile, which increases material handling and processing costs.
In terms of mechanical properties, cold drawn steel does not possess the superior hardness and smooth finish achieved by cold rolling steel. In cold rolling, the high pressure of the rolling mills mechanically works the steel, which causes changes in the mechanical properties including increased tensile strength, hardness and weld-ability, along with decreased ductility as the grain structure is changed.
Cold drawing steel also results in a comparatively rougher surface finish, with less uniformity in the mechanical properties from the rod moving through the die. Cold rolled steel offers the smoothest and most consistent finish of any pre-machined shaping process.
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Cold rolling steel and machining offer more shaping versatility and customizability than hot rolling or cold drawing. Machining steel offers the unique ability to change shape down the length of the bar or wire, which the cold rolling process cannot do. However, it comes at a cost. Machining steel is by far the most expensive cost option and has the highest yield loss of any steel shaping process. If you need a uniform shape down the entire length of the bar or wire, cold rolled steel provides unquestionably better value.
At Charter Wire, we've found many of our customers once thought that machined steel shapes were their only option for complex profiles. They are often relieved to find out that cold rolled steel can accomplish many of these shapes, with the same tight manufacturing tolerances they had relied upon through machining, at a lower cost.
Furthermore, cold rolling steel is the only way to achieve the unparalleled surface finish and hardness that results from mechanically working the steel grain structure as it passes through the rolling mills. Having created over 2,000 unique cold rolled steel shapes since our company was founded in 1936, Charter Wire offers unparalleled expertise in creating custom profiles that meet or exceed the expectations for nearly any application.
If machining is still the best option for your process, cold rolling can still provide benefits. Machinability grades that are initially cold rolled to a pre-shape can offer better tool life, asset utilization, and performance in the machining process for our customers due to the increase in hardness and tensile strength that comes from cold rolling steel.