Identify Your Steels by Handheld XRF in Real Time

Stainless steels provide good corrosion resistance in a wide range of environments. Although Ni is almost always added in stainless steels, the elements which provide the corrosion resistance are Cr, Mo, and sometimes Cu. One important property of stainless steels is their ability to hold their corrosion resistance and mechanical strength up to 800º C. By way of comparison at this high temperature, low alloy steel has no strength and corrodes at high rates above 650º C. Please contact our experts to understand how handheld XRF can greatly improve your steel sorting.

Large quantities of stainless steels are used as corrosion and heat resistant construction materials in different process vessels, tubing and turbines used in chemical, petrochemical, pulp and paper, and power plants.  Stainless steels are broken into groups based on their characteristics.

Stainless Steel Groups:

 Group Designation Key Elements Characteristics
 Martensitic Part of 400 series; 410, 420 12-18% Cr; <1% C Excellent strength, Magnetic, Heat-treatable
 Ferritic Part of 400 series 12-18% Cr; <0.2% C Magnetic, Ductility and formability; cold working enhances strength
 Austenitic 200 series; 300 series 17-25% Cr; 8-25% Ni High strength and toughness, non-magnetic, ductile
 Precipitation Hardening (PH) 17-4; 17-7, A286 17% Cr, Ni, Cu Heat treated to achieve final properties by the fabricator
 Duplex 2205, 2207 22% Cr, 5% Ni, Mo Austenite + ferrite, High tensile and yield strength, stress-corrosion resistant

 

Stainless steel production is a very profitable business, based upon a large amount of stainless steel scrap. Without stainless steel scrap, the production of stainless steel in the world would come to a halt.

The portable XRF analyzer has a very quick return of investment. A scrap sorter processing more than100 tons/month can potentially earn the investment back in three months. The money comes from the following sources:

  • There is a shortage of scrap. The one who pays the best price gets the material (but must know what he is buying).
  • Upgrading of scrap: The steel mill pays for the minimum guaranteed concentration. If a stainless steel pile of scrap containing 304 having Ni content between 8- 12% is resorted to two piles, one having 8-10% and the other 10-12% Ni, the last pile is paid for based on 10% Ni, a substantially higher price.
  • Certain tramp elements will result in penalties for the seller. These tramp elements can be determined using a portable XRF analyzer.

The value of stainless comes mainly from its approximately 10% Ni content. Mo content of typically 2 % gives extra value. As an example 1 % Ni in stainless steel scrap corresponds to the coverage of a scrap dealer. Scraps other than stainless scrap used in stainless steel production are Cr-steel scrap, Ni-steel scrap, carbon and low alloy steel scrap, Mn-steel scrap and Ni-alloy scrap.

Elements that cannot be reduced in the metallurgical process are P, V, Cu, W, Nb, Co, Sn, Pb and Ta. In addition, C and S cannot be reduced in foundries. All these elements have to be analyzed. Scrap dealers sort scrap using mainly portable XRF analyzers. Scrap is then analyzed again in the steel factory. A typical stainless steel producer does rough sorting with a portable XRF analyzer and analyzes a statistical sample of every load with a big stationary lab analyzer in the lab.

The penalty limits beyond which the scrap price can be decreased for tramp elements in stainless steel scrap are:  

 Elements Limit Elements Limit Elements Limit
 P 0.04% W 0.1% Sn 0.03%
 V 0.2% Nb 0.1% Pb 0.002%
 Cu 0.5% Co 0.5% Ta 0.2%