eHow Difference Between Hot- & Cold-Rolled Steel

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Hot rolled and cold rolled steel differ in three major aspects: rolling temperature, thickness and physical properties. Coil or sheet steel is initially hot reduced from slabs, either to a finished product or to produce strip steel for further processing. Cold rolled steel begins with a hot rolled strip product that, through the rolling process, is further reduced in thickness, a process that also changes the physical properties (primarily the crystalline structure) of the product.

      Rolling Temperatures
   1. Hot-rolling requires temperatures of 1,652 degrees to 2,012 degrees Fahrenheit (900 to 1,100 degrees Celsius), while cold-rolled steel is rolled at room temperature.

      Steel coming off the finishing stand at the hot mill is cooled by water spray and coiled at temperatures of 932 degrees Fahrenheit (500 degrees Celsius) and 1,400 degrees Fahrenheit (760 degrees Celsius). The hot-rolled steel is then cooled to room temperature. Once at ambient temperature, the steel can be cold reduced or cold rolled.

      Product Thicknesses:
   2. Coiling steel
      Lathe Turning Stainless Steel image by Stana from Fotolia.com
      Coiling steel
      Typically, hot rolling begins with a standard 10-inch (250 mm) thick slab, either directly from a continuous caster or reheated to the desired temperature. The steel moves through a series of mill stands that reduce the slab to a hot roll strip with thicknesses ranging from 0.071 inches (1.80 mm) to 0.350 inches (8.89 mm).

      Cold rolling through a second series of mills further reduces the hot rolled steel to a cold rolled product with a thickness range from .0126 inches (.32 mm) to .157 inches (3.99 mm).
      Physical Properties
   3. Ball bearings are used to test steel hardness.
      steel balls image by Igor Shootov from Fotolia.com
      Ball bearings are used to test steel hardness.
      Steel's physical structure varies by product; heating and cooling change the molecular structure of the metal. Steel coming off the hot mill will be softer and more ductile than material further processed through a cold mill.

      Ductility, measured by elongation testing, determines the amount of material deformation that occurs before the material fractures. Elongation (in 2 inches) for hot rolled is from 39 to 43 percent, while cold rolled ranges from 40 to 46 percent.
      Other Differences
   4. Because it is softer, hot rolled steel forms easily, while cold rolled has superior drawing quality. Cold rolled's tighter tolerances make it a better choice for highly engineered end uses.
      The blue-gray oxide that forms the finish on hot rolled is unsuitable for painting without further processing and surface preparation, while cold rolled's smooth gray finish is ready to paint.

      Each product can be produced with a variety of chemical and physical characteristics to meet specific applications.
      Applications
   5. Automobile body constructed of both hot- and cold-rolled steel
      car image by Tammy Mobley from Fotolia.com
      Automobile body constructed of both hot- and cold-rolled steel
      Hot-rolled steel is used in construction, industrial machinery, and shipbuilding as well as for unexposed automotive and appliance parts such as frames, brackets, wheels and clutch plates. Hot-rolled steel is a suitable product where thickness, strength and formability are important.

      Cold-rolled applications include refrigerators, stoves, washers, dryers and small appliances as well as a wide variety of exposed automotive parts. Cold-rolled applications often require tight tolerances and a smooth, paintable surface.

A Simple Safety Culture: a Little Goes a Long Way to Reduce Costs

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There is a difference between "unsafe" and "hazardous." The nature of work in the sheet metal and HVAC industry is inherently hazardous (tools and equipment, working from heights, chemicals, etc.) but it is only as unsafe as the employers and employees allow it to be.

What is the "culture" of safety at your company? Do you have a 100 percent mandatory eye protection policy? Or do your workers wear eye protection on a "hit or miss" basis? When an employee reminds a fellow employee to wear his safety glasses, is that considered negative feedback? Or does the fellow employee appreciate the concern being put forward?

The idea of establishing a safety culture versus simply following a safety program is not a new concept, although it appears that forming a company safety culture is recent trend. A very simple definition of a "safety culture" is described by Sue and Tom Cox in "The Structure of Employee Attitudes To Safety - A European Example."

"A safety culture is a term often used to describe the way in which safety is managed in the workplace, and often reflects the attitudes, beliefs, perceptions and values that employees share in relation to safety."

Don't let a safety culture for your business get distracted by behavioral safety studies and complicated measurements. A safety culture can simply be established by management taking the attitude and belief that safety is a priority and working with employees to perceive and value safety at that same priority level.

As a result, every employee, including management, then takes the responsibility to ensure that safety remains a focus in daily operations. Moving toward a positive safety culture is not an "overnight" occurrence. It often takes many months, maybe several years, to promote safety at a very high level. But companies who have made a safety culture part of the business have seen many benefits including reduced workers compensation costs, higher employee productivity, and other positive outcomes.

For more information on safety cultures and how to improve your company safety and health efforts, go to the SMACNA safety web page.

Metals and Commodities Prices

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Click HERE or Full Article: Metalprices.com Free LME and Comex price charts and tables in USD/LB for aluminum, antimony, chrome, cobalt, columbium, copper, germanium, gold, iron, lead, moly, nickelalloy, palladium, platinum, silver, tantalum, tin, titanium, tungsten, vanadium and zinc. American Metals Market (AMM) International daily news service covering the metals industries, with up-to-date prices of 1,400 industrial materials. Covers mining to production, distribution to manufacturing and reuse. Includes events, analysis and online marketplace. Subscription service with some free resources. London Metal Exchange (LME) Prices Get daily prices and stocks as well as historical prices and charts directly from the LME. The LME is the international standard for metal commodity pricing of copper, aluminum, zinc, lead, tin, nickel, silver and aluminum alloy. World Carbon Steel Prices & Forecasts Global steel prices from MEPS, the leader in steel price data. Monthly price chart of hot rolled coil, hot rolled plate, cold rolled coil, HD galv. coil, electro zinc, coil wire, rod (mesh), medium sections & beams, rebar and merchant bar.