Analysis and prevention of cracking during strip casting of AISI 304 stainless steel
- PDF / 460,711 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 91 Downloads / 358 Views
I. INTRODUCTION
RECENTLY, intensive studies have been undertaken on a strip-casting process of austenitic stainless steels to produce thin strips, in order to develop a new technology with lower production costs. In this process, only 10 to 70 pct cold rolling is applied, with complete omission of hot rolling.[1–4] Several companies have already finished constructing plant facilities for commercialization, and new products are currently under commission.[5] Since solidification proceeds much faster in strip casting than in conventional continuous casting, there are many advantages such as refinement of the solidified structure, reduction of microsegregation, and expansion of the solubility limit. Strip casting also lowers the production cost by cutting the labor and energy costs and is an environmentally conscious strip production process. However, it is imperative that the quality of the surface and interior of the final strip-cast products meet the quality level of hot-rolled products produced by continuous casting, because the rolling ratio available after strip casting is limited. Among the quality problems posed by strip casting, the occurrence of solidification cracks on the surface of cast strips is the most critical one. It has been reported that solidification cracking is caused by hot brittleness, inhomogeneous roll cooling, variances in the solidified shell thickness due to heat-transfer barriers, and melt fluctuation in the meniscus region, where contact between the melt and rolls starts.[6,7] The solidification cracking occurring during continuous casting is interpreted by associating the deformation due to thermal stress and transformation stress with the DONG-KYUN CHOO and HEE-KYUNG MOON, Senior Research Engineers, and TAEWOOK KANG, General Manager, are with the Strip Casting Project Team, Research Institute of Industrial Science and Technology, Pohang, 790-600 Korea. SUNGHAK LEE, Professor, Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang, 790-784 Korea, is jointly appointed to the Materials Science and Engineering Department, Pohang University of Technology. Manuscript submitted November 10, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS A
brittle-temperature region.[8,9] It mainly occurs in the region between the melting point and 1200 ⬚C, which corresponds to the first brittle region among the three divided regions in the cooling period from the melting point.[10] It also arises from the distribution of a low-melting-point liquid phase between dendrites, caused by interdendritic segregation.[8] Since it readily arises under small strains when penetration of the liquid phase is not allowed due to an insufficient gap between dendrites, it is generally observed that the solidification cracks initiate and propagate between dendrites. Many studies on the solidification cracking in an AISI 304 stainless steel (a representative austenitic steel) have also been made in the areas of welding and conventional continuous casting.[11,12] Very few studies have been
Data Loading...
