International comparison of impurities mixing and accumulation in steel scrap

Abstract

The accumulation of impurities in the recycling of steel impacts the quality of secondary steel. Understanding impurity levels is crucial in the context of the proliferation of circular economy policies, expected high recycling rates, and growth of scrap consumption. By assuming the accumulation of impurities to be equal worldwide, the understanding of the extent and variation of the mixing and accumulation was limited in previous studies, and the factors influencing those variations were not considered. This is a first cross-national comparison of impurity accumulation in recycled steel. In this study, the copper, tin, nickel, chromium, and molybdenum content was analyzed in over 500 samples of electric arc furnace rebars from China, Japan, Vietnam, Ukraine, and the Netherlands (representing northwestern Europe) with an optical emission spectrometer. The impurity content in rebars represents the content of impurities accumulated in steel scrap in the countries studied. The measured content of impurities was then used to determine the factors influencing the accumulation of those impurities. It was revealed that the recycling technology, the presence of a market for recovered metals, the quality of the material input, steelmaking practices, and the management of byproducts derived from a legislative or economic context played a role in the impurities content. By communicating on scrap chemical content, the collaboration between the recycling and steel industries could be enhanced in terms of matching the demand and supply and facilitating an increase in the scrap share in steelmaking.

The Materials Science behind Sustainable Metals and Alloys

“…Especially elements such as copper, nickel, chromium, molybdenum and tin can accumulate to high fractions in old scrap and affect casting, hot and cold cracking, and corrosion if not removed or diluted. 76,403,412 Copper and tin are both potentially harmful tramp elements that can enter the steel scrap streams through the growing use of these element in electrified vehicles, in solderings, and generally through the increasing electrification of many products and processes, Figure 101 and Figure 102.…”

“…Particularly old scrap has varying composition and can frequently contain harmful tramp elements. Especially elements such as copper, nickel, chromium, molybdenum and tin can accumulate to high fractions in old scrap and affect casting, hot and cold cracking, and corrosion if not removed or diluted. ,, …”

Appraising the value of compositional information and its implications to scrap-based production of steel

“…Moreover, Matino et al (2017) found that using a large quantity of low quality scrap (i.e., scrap with a high impurity content) can even affect the energy and environmental impact of the process. Therefore, more information can be mutually beneficial for scrap dealers and steelmakers (Panasiuk et al 2022) and helps in increasing the amount of scrap that will be acceptable for production. The compositional information is an important feature of the physical materials that needs to flow at a high level between actors for a well-functioning circular economy (Nordic Innovation 2021).…”

Mapping the global flows of steel scraps: an alloy elements recovery perspective

“…Practically, steel is not always used in its pure form, but is frequently alloyed with other elements in order to enhance its performance (Ohno et al 2015, Tan et al 2021, such as increased strength, high corrosion resistance, light weight, longer life spans, and better recyclability. For instance, zinc (Zn), aluminum (Al), and tin (Sn) are added as coating elements to enhance the corrosion resistance of steel (Panasiuk et al 2022). Other alloy elements (AEs) include manganese (Mn), chromium (Cr), nickel (Ni), molybdenum (Mo), vanadium(V), etc (Nakajima et al 2013).…”