Carbon and Low Alloy Steels

Carbon steel (containing <1.7% C in an iron matrix) are used as low-cost, large volume construction materials in chemical, petrochemical, and power plants, as well as in process vessels, tubing, and other load supporting structures. Widely used in springs, bearings, rods, and wires, carbon steel is also consumed in large amounts as automotive and ship body and part materials. Sometimes it is used as very cheap alternative to cutting tool materials.

Low alloy steels (containing <10% C, Mn, Cr, Ni, Mo, B, V, and Si combined), have better strength and hardness than carbon steels – and even stainless steels if temperature is well under 400º C. Low alloy steels are used as construction materials in chemical, petrochemical, and power plants, as well as in process pressure vessels, tubing, and load supporting structures. They are also used as automotive and low cost aerospace part materials and low cost cutting tools.

One special class of low alloy steels is the chrome-moly (Cr/Mo Steels) steels. These steels contain up from 1-9% Cr and 0.5- 1% Mo. Having good creep resistance and high temperature characteristics, these alloys have found great success in the petrochemical and power generation industry applications. Typical products for these industries include boilers, heaters, heat exchangers, reactors, and hydrocrackers.

Carbon and low alloy scrap are not the most attractive potential scrap market because the content of valuable elements is low, resulting in small differences in value between different grades. The manufacturing program of a steel plant has a great influence on the requirements of scrap composition. Bad scrap quality is most detrimental to the quality of the end product. Please contact our experts to understand how handheld XRF can greatly improve your alloy sorting.

Cu and Sn are normally found only in old scrap, appearing as pure elements or in combination with steel parts. Cr, Ni and Mo cannot be visually detected. The only solution is to analyze the scrap. Both portable XRF analyzers and big stationary laboratory analyzers are used to perform the analysis. However, the production of base steel grades causes fewer problems tolerating higher contents of “tramp” elements . Making special steel grades out of 100% scrap input requires careful scrap preparation.

The penalty limits beyond which the scrap price can be decreased for tramp elements in carbon and low alloy steel scrap are as follows:

 Elements Limit Elements Limit Elements Limit
 Cu 0.5% Sn 0.03% Cr 0.2%
 Ni 0.5% Mo 0.2% Pb 0.002%
 Nb 0.05% W 0.01% As 0.05%