DISTRIBUTION OF Cu AND ITS EFFECT ON MICROSTRUCTURE OF Cu-BEARING STEEL

In order to investigate the distribution of Cu and its effect on the microstructure of Cu-bearing steel, a series of mild steels containing different contents of Cu are developed by vacuum electric arc furnace. These steels are annealed at 1 260℃, 1 100 ℃ and 1 000℃ respectively for one hour and followed by furnace cooling to room temperature to simulate the heat treatment before the rolling process. The results show that Cu did not obviously segregate in annealed steels. The scanning electron microscope （SEM） observation show that the main microstruetures in Cu-bearing steel are ferrite and pearlite; The volume fraction of pearlite in steel increase with increasing Cu content. The grain size reduces with the decrease of annealing temperature. The results of energy dispersive X-ray analysis （EDXA） suggest that the Cu content in pearlite is higher than that in ferrite, which means that the microstructure-segregatian of Cu exists. However, the cast specimens show that Cu content in MnS and S-rich phase is very high, and Cu changed the distribution of/vinS in steel. In addition, the optimal Cu content in steel between 0.2%-0.4% and the optimal annealing temperature between 1 100-1 200℃are determined by the economical and practical principles.

Influence of copper on quality of hot strips by EAF-CSP process

Electron microscopy and X-ray Energy Dispersive Spectroscopy (XEDS) study on influence of Cu on low carbon hot strips produced by CSP (Compact Strip Production) process has been carried out. The results indicated that copper segregation and enrichment at interfacial layer between oxidized surface and steel matrix is the key factor, which results in microcracks and edge flaws on the strips. The primary considerations to prevent detrimental effects from Cu include controlling copper content in proper level, higher soaking temperature and non-oxidizable atmosphere during soaking. Copper sulfide precipitates with nanometers in size were observed, they may be beneficial to the properties of CSP products, and influence of Cu on quality of CSP hot strips is discussed.

Influence of copper on quality of hot strips by EAF-CSP process

Electron microscopy and X-ray Energy Dispersive Spectroscopy (XEDS) study oninfluence of Cu on low carbon hot strips produced by CSP (Compact Strip Production) process has beencarried out. The results indicated that copper segregation and enrichment at interfacial layerbetween oxidized surface and steel matrix is the key factor, which results in microcracks and edgeflaws on the strips. The primary considerations to prevent detrimental effects from Cu includecontrolling copper content in proper level, higher soaking temperature and non-oxidizable atmosphereduring soaking. Copper sulfide precipitates with nanometers in size were observed, they may bebeneficial to the properties of CSP products, and influence of Cu on quality of CSP hot strips isdiscussed.

Homogenization on solution treatment and its effects on the precipitation-hardening of selective laser melted 17-4PH stainless steel

17-4 precipitation-hardened(PH)stainless steel(SS)exhibits high strength and good corrosion resistance via Cu-precipitation hardening.Unlike conventional wrought 17-4PH SS,Cu segregation andε-Cu pre-cipitates are observed in additively manufactured(AM)17-4PH SS owing to the repeated rapid cooling after heating,which characterizes the AM process.In this study,solution treatment was conducted under various temperatures(1,000,1,050,1,100,and 1,200℃)and durations(1,2,4,and 8 h)to minimize the negative effects of Cu segregation andε-Cu precipitates on precipitation hardening.The mechanical prop-erties and microstructures of each condition for the Cu precipitation behavior were examined.Although theε-Cu precipitates did not disappear after solution treatment,the average diameter of theε-Cu precipi-tates tended to decrease with increasing solution treatment temperature and duration.Therefore,solution treatment at a temperature of 1,200℃ for 8 h was the best,resulting in improved strength compared to the conventional solution treatment at 1,050℃.Solution treatment on at least 1,100℃ is effective in AM.