There are two types of processed steels that companies can by for many different uses. They are known as hot and cold rolled. Both types of steel look, perform, and behave differently, so which is considered better to use? Allow us to explain the differences between both types of processed steel.
What Is Hot Rolling?
Hot rolling is the process of roll-pressing steel at temperatures of 1,700 degree Fahrenheit or more. 1700 degrees is the minimum in which most forms of steel can be recrystallized. When steel is recrystallized, it is easier to work with and make into the shapes that you want.
The process of hot rolling steel starts with a billet of metal, which is a thick, long sheet. This billet is heated, followed by being flattened into a roll. The billet remains heated as it is sent through a group of rollers to give it an ideal shape. For hot rolling sheet metal, the steel is rolled into coils and then left alone to cool down.
As steel is cooled down, it will slightly shrink. The cooler that steel gets, the harder it becomes to control what shape you want it to be.
What Is Cold Rolling?
Cold rolled steel actually is first hot rolled, but takes it a step further. Once the steel is being cooled at room temperature, it is re-rolled in order to get it to the shape, dimensions, and a finish that is more desirable for the people that would use it.
Cold rolling is actually considered a finishing process rather than a process opposite to hot rolling. Cold rolling also can only apply to sheets of steel that get compressed between a series of rollers. Steel is not "rolled" through these rollers, per se, but rather pulled or drawn through. This is one of a few other ways in which steel can be cold rolled in order to look, feel, and measure more refined.
What Are The Differences Between The Two?
Hot rolled steel is easily noticeable for having a scaly surface. How this happens is that the surface bubbles when it's piping hot, and as it cools, the miniature deformations harden and before permanent. If appearance isn't much of a priority, manufacturers tend to choose hot rolled steel. The heat may also change the shape of steel, so rather than having a perfectly square metal bar, you will end up with a slight trapezoid of a bar.
When comparing the appearances of hot and cold rolled steel, you can compare it to night and day. Cold rolled steel has a flat, smooth finish with deformations that are few and far between. The surface of cold rolled steel also looks shiny and feels slick. Bars of steel that are cold rolled are straight and square, and will have sharper edges compared to hot rolled steel. Cold rolled steel is used in scenarios in which the appearance of the steel is important.
Hot rolled steel is used typically in scenarios where dimensions do not need to be exact, such as for railroad tracks or construction. Contrary to popular belief, its scaly surface does not reinforce the steel in any way.
Compared to hot rolled steel, cold rolled steel is generally harder, stronger, and more resilient. When the metal is shaped when it cools, it is more fortified to withstand tension and deformations, which would be expected with hot rolled steel when used for work. There is a caveat to cold rolled steel, and that is that if you use extra treatments with this steel, is that it can cause stress from inside which can cause it to warp.
Hot rolled steel is often cheaper to buy than cold rolled steel, due to less processing being required. Hot rolled steel can cool naturally at room temperature, which makes it contain zero stress from inside that be caused by quenching; unlike cold rolled steel, which requires more processing following cooling.
Both types of process steels have their uses in the workforce. So ultimately, we cannot say which is better than the other. Due to the cosmetic nature of cold rolled steel, it is much more popular, but you can see the benefits in hot rolled steel as well. Choose the kind that will best serve you and your project(s).
• Is more affordable
• Takes less time to process
• Has rounded edges
• Has a rougher surface
• Is less durable
• Doesn't have a refined shape
• Has a smoother surface
• Is more durable
• Has a refined shape
• Is more costly
• Takes more time to process
• Has sharp edges
• Can warp from stress
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Can you think of other pros and cons for hot and cold rolling? Leave your comments below.