Finding Value in Pig Iron and Creating Value in Melting
Making iron castings involves two main sub-processes, one that deals with preparation of liquid metal, with the right proportion of alloying elements dissolved into it; and another that converts this liquid back to solid in the shape and size defined by the molds. The cost of making a casting is determined primarily by the metallic content, and it is ironic that much effort is spent on counting the molds and polishing the cast parts – while the melting unit is often denied the attention it deserves.
Tempers go wild discussing delays in pouring the molds and arrows are darted if liquid metal arrives late, driving a reason to stock surplus liquid metal despite wasted energy. When profits dip, there is no denying if the finger points towards energy costs in melting and storing. The stark truth is that any talk about optimization in the process chain remains more on paper than in practice.
It would be futile to dwell on this omnipresent scenario, but it is prudent to economize on melting costs and not in holding or delivery. Melting activities in a foundry remain so remote from the production hub because of the hazards associated with bulk handling of solids and hot liquids. Nevertheless, we shall embrace this task in earnest and explore avenues that would offer quantum benefits not only in energy utilization but also in the quality of castings made.
The engineering world understands an iron foundry as a source for cast products, manufactured by melting ferrous scrap and pig iron with some alloy additions and pouring into sand molds, to produce parts in shapes and sizes as ordered. Common terms like “scrap,” “sand,” and “pig” have for ages been diminishing the status accorded to the end products, which frequently are less sophisticated in appearance or precision than many engineered parts.
However, over recent decades the true potential of cast iron in critical applications has gained some recognition, and innovations in processes and equipment have helped to elevate it to the status it deserves. Foundrymen, with the help researchers and plant/machinery builders, have seized this opportunity and striven to raise cast iron’s quality and consistency to meet ever increasing functional needs. Now, words like “scrap,” “sand,” and “pig”hold the keys to creating value for the user.
Pig iron in the charge make-up for cast iron preparation was often perceived as another metallic input, a shade superior to scrap for meeting chemistry. The demands made on iron castings and the advent of SG iron/ductile iron, as well as compacted graphite iron, have brought in many value propositions and enabled the pig iron of the last century to evolve into a niche product, with a broad portfolio to serve the specific needs of several types and grades of cast irons.
The benefits to foundrymen go beyond mere control of elements to factors that can add value to their manufacturing processes. Typically, cleaner melting with reduced slag generation can reduce energy consumption and improve productivity through shortened cycle times, besides the assurance of quality without iterations. These are just a few details that make pig iron an attractive source of metallic input in charge materials.