Recycling Chips of Stainless Steel Using a Full Factorial Design

Abstract

The aim of this study was to provide an experimental investigation on the novel method for recycling chips of duplex stainless steel, with the addition of vanadium carbide, in order to produce metal/carbide composites from a high-energy mechanical milling process. Powders of duplex stainless steel with the addition of vanadium carbide were prepared by high-energy mechanical ball milling utilizing a planetary ball mill. For this proposal, experiments following a full factorial design with two replicates were planned, performed, and then analyzed. The four factors investigated in this study were rotation speed, milling time, powder to ball weight ratio and carbide percentage. For each factor, the experiments were conducted into two levels so that the internal behavior among them could be statistically estimated: 250 to 350 rpm for rotation speed, 10 to 50 h for milling time, 10:1 to 22:1 for powder to ball weight ratio, and 0 to 3% carbide percentage. In order to measure and characterize particle size, we utilized the analysis of particle size and a scanning electron microscopy. The results showed with the addition of carbide in the milling process cause an average of reduction in particle size when compared with the material without carbide added. All the four factors investigated in this study presented significant influence on the milling process of duplex stainless steel chips and the reduction of particle size. The statistical analysis showed that the addition of carbide in the process is the most influential factor, followed by the milling time, rotation speed and powder to ball weight ratio. Significant interaction effects among these factors were also identified.

Recent Advancements in Material Waste Recycling: Conventional, Direct Conversion, and Additive Manufacturing Techniques

“…Metal chips can be recycled by turning them into powders by using processes like milling, gas atomization, and electrolytic decomposition. A high-end ball milling process using vanadium carbides has been studied by Mendonça et al [281][282][283] for recycling stainless steel chips (Figure 26).…”

Producing Metal Powder from Machining Chips Using Ball Milling Process: A Review

“…Powder composites with a metal matrix are also possible to be made from metal chips. Some writers addressed this issue in the manufacture of duplex stainless steel composite powder by adding vanadium carbide (VC) particles and increasing the milling duration [ 168 ]. This study also demonstrated that increasing the reinforcing concentration results in a decrease in average particle size.…”

From Machining Chips to Raw Material for Powder Metallurgy—A Review

“…The metal chips used for recycling can involve industrial residues [ 9 ] or as machined fresh type [ 10 ], resulting from operations such as turning [ 11 , 12 ], roughing and finishing [ 13 ] obtained by low speed machining [ 14 , 15 ] or a high speed process [ 13 ]. Materials studied so far involve aluminum alloys, stainless steel, tool steel, titanium alloy, tin alloy and nickel alloy, with different initial sizes.…”

“…Metal chips were applied also for producing metal matrix powder composites. Taking into account the milling time, increase in particle size by extending milling time caused by cold welding, some authors overcame that shortcoming in the production of a duplex stainless steel composite powder mixed with vanadium carbide (VC) particles [ 15 ]. This study also presented that: the increase in the reinforcement concentration results in the reduction of average particle size.…”