Machine-shop swarf from ferrous machining. De-oiled and often briquetted for induction-furnace charging.

ISRI Description and Specification

Iron and steel turnings and borings are machine-shop swarf from turning, boring, milling, drilling, and grinding operations on ferrous workpieces. Cast iron borings (from cylinder boring, brake disc machining, etc.) have high carbon and silicon content consistent with the cast iron base material. Steel turnings (from mild steel, medium-carbon, and alloy steel machining) have lower carbon content and variable alloying depending on the workpiece grade. The material must be free of excessive oil and coolant (which causes environmental and processing issues), free of non-ferrous chips (from mixed-material machining operations where aluminium, copper, or brass components are machined on the same equipment), free of grinding media or abrasive grinding wheel debris, and within moisture content limits. Turnings and borings are typically sold on a clean, dry basis after centrifuging and briquetting or in loose form, with pricing reflecting oil content, iron type, and the ratio of cast iron to steel (which affects chemistry management in the melting furnace).

Processing Methods

Centrifuge de-oiling is the standard first processing step for wet turnings — it removes 85–95% of the entrained cutting fluid, improving metal content yield and reducing furnace emissions. Briquetting of de-oiled turnings into dense, handleable briquettes is increasingly common, as it eliminates the dust and fines problem associated with loose turnings, reduces oxidation loss during furnace charging, and improves material handling logistics significantly. Turnings briquettes produced at sufficient density (typically 4,500–5,000 kg/m³) can be charged directly into induction furnaces with minimal additional processing.

Who Uses Turnings & Borings

Induction furnace melt shops and small EAF operations with briquetted turnings charging capability are the primary consumers. Iron foundries in automotive machining clusters consume cast iron borings (from cylinder block and brake disc machining) directly in their cupola or induction furnace charge mixes. In India, the dense concentration of automotive component machining operations in Pune, Chennai, Gurgaon, and Sanand generates large volumes of both cast iron and steel turnings. Scrap dealers and processing yards near these machining clusters aggregate, centrifuge, and briquette turnings for supply to local melt shops, creating a significant short-cycle domestic scrap economy around machining-intensive automotive manufacturing zones.