Classification of Steel Scrap
Steel scrap consists of discarded steel or steel products, generally segregated by composition and size or ‘grade’ suitable for melting. There are three main types of scrap which are used by the steel industry as feed stock.
These are:
(i) Internal Scrap: Also known as revert or home scrap. It refers to the reject metal within the steel plant which gets generated during steel making, steel casting and steel finishing activities within the steel plant.
(ii) Prompt Scrap: Also known as process scrap and it is the waste generated during the product manufacturing by the steel plant’s customers i.e. the manufacturing industries.
(iii) Obsolete Scrap: Consists of that scrap which is recovered from discarded industrial and consumer items i.e. from ships to refrigerators and from construction beams to automobiles.
Due to the large improvements which have taken place in the steel manufacturing, steel casting, steel finishing, and product manufacturing technologies in the recent past, the amount of generation of the first two types of scraps have reduced a lot.
On the other hand with resources of obsolete scrap are increasing as the world is becoming more industrialized and due to larger quantity of discarded consumer durables and worn out industrial equipment.
Another way of classifying steel scrap is to classify it according to the products in which the steel was used before it became scrap. The main steel scrap sources in this sense are automobiles, ships, railroads, construction buildings, machinery, white goods, packaging, electric and electronic equipment, etc.
“GRADE” is a classification of scrap type based upon Institute of Scrap Recycling Industries (ISRI) ferrous scrap classification.
A scrap is considered to be off grade if it fails to meet
- applicable size limitations
- applicable requirements for the type of scrap
- applicable requirement with respect to the scrap quality
Steel scrap is considered to be free of alloys if the residual content of the following elements contained in steel do not occur at levels consistent with the purposeful creation of an alloy steel. Residual level of elements contained within the scrap shall not exceed chromium 0.20 %, nickel 0.45 %, manganese 1.65 % and molybdenum 0.10 %. The combined residuals other than manganese shall not exceed a total of 0.60 %.