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What is Cold Rolling?

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  • Written By: T. Briseno
  • Edited By: Jenn Walker
  • Last Modified Date: 26 September 2016
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Cold rolling is a process used in manufacturing and finishing environments to change the thickness, or gauge, of metals or glass. Used mostly in steel mills, cold rolling involves threading flattened steel into a machine that advances the material through a set of rolls. These rolls rotate in opposite directions at a consistent rate of speed, and they are set apart so their width is smaller than the width of the steel sheeting passed through. When the steel goes through the cold mill process, it is pressed into a pre-ordered gauge for further finishing. Often, cold rolling operates in a continuous loop, with multiple sets of rolls working the metal until it reaches a desired thickness or shape.

It is probably most common to imagine steel work as a hot process, with sparks flying and bright orange embers burning around metal. Much of what happens with cold rolling, though, complements the hot rolling process, which is a separate step for reducing the size of steel slabs, sheets, and rods. While hot treatments are most effective for manipulating steel mass, cold rolling refines the metal and works to improve the surface condition. Hot rolling makes the steel malleable, while cold rolling makes it more sturdy.

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What occurs in this metal-on-metal process helps to tighten and strengthen the properties of the steel itself. While the steel thickness decreases, most of the breakdown or variable patches that take place in heat processing are built up, or annealed, by the cold rolling. A similar process occurs with glass manufacturing, though the properties of glass make it less capable of holding up through multiple processes.

Most steel companies have long buildings to accommodate their mills, or machinery. The rolling process can begin with a conveyor belt at one end and a shearing blade at another end. A coil of steel is threaded through the mill, and an operator sets the desired gauge and length of the piece to be cold-rolled. Achieving the right gauge involves calculating the roll widths, operating speed and needed lubricant rate, while meeting the specifications of the order.

When a strip has completed its cycles through the mill, it is cut and moved to another conveyor system where its weight, gauge and identifying details are recorded. Further processing or shipment to the customer follows. Using the cold rolling process allows for the creation of production-ready steel for manufacture in a multitude of automotive, construction and industrial environments.

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TreeMan
Post 4

I have seen raw metal, but the end product always looks much smoother and shinier. Am I right in guessing that the cold rolling process is able to remove some of the surface defects on the metal?

Along the same lines, are there any potential problems that can arise during the cold rolling process? One thing that popped into my mind is if the technicians set the rollers too low for one of the passes. If the metal had to be forced through a space that was too small, it might cause the metal to crack or break somehow. Once the metal roll got thin enough, I would guess shearing might become a problem as well. Does anyone have any thoughts?

JimmyT
Post 3

I am curious about how all of the different materials react to cold rolling and how they are used afterward.

The article mentions being able to use glass, even though it can't be rolled quite as thin. I would assume it starts to crack at a certain point. Would this be the same type of process they use for things like windows, windshield glass, and glass bottles?

It seems like windows and windshields would be easy to make this way. You could roll out the glass to the right thickness and cut the right shape. It also seems like to make glass bottles you could use a sheet of glass and then form the bottle to the right

shape. Is this how they do it, or is there another process for bottles?

In terms of metal, is there any limiting thickness depending on what kind of metal is being rolled? Is this the same process they use to make blanks for other products?

titans62
Post 2

@jcraig - From what I know of metal manufacturing, I believe they do just work the hot metal into blocks to begin. I'm not sure they are that thick, though.

Since I'm sure cold rolling is an extremely energy expensive process, I think it would be in the best interest of the manufacturers to start the metal at the lowest possible thickness. I would think if you started with a 1 inch thick piece of metal it would take several passes through rollers to get down to the thin sheets required for things like car bodies. That is just a guess, though.

I'm curious if anyone who may be more familiar with this knows what amount of extra length

is gained after you put the metal or glass through cold rolling. For example, if you started with a piece of metal that was 10 feet long, after you put it through the rollers, how many feet long would the final roll of compressed metal be at that point?
jcraig
Post 1

What thickness does the original steel coil start at? I am imagining something that is no more than maybe an inch thick at the start, but then my question is how do they get the steel down that that original size?

Do they just have some type of mold or cast that they can make use to form big chunks of metal, and then they take the chunks and put them through several sets of rollers until the sheets of steel are the right thickness?

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