The results of impact tests carried out at - 30 °C on cast alloyed GX8CrNi12, GX5CrNi18-9 and GX5CrNiMo19-11-2 steel grades are reported. It has been shown that at - 30 °C, the addition of 1 % Ni to ...cast GX8CrNi12 steel does not provide the required impact strength of 35 J/cm2. In contrast, other tested materials containing 8 ÷ 9 % Ni can easily reach exceeding 50 J/cm2. Numerous non-metallic inclusions present in the microstructure of cast GX5CrNi-Mo19-11-2 steel resulting from, among others, the miscalculated refining process were found to be one of the main causes of reduced impact strength as compared to the cast GX5CrNi18-9 steel.
The corrosion–abrasion wear resistance of 6% chromium martensitic cast steel containing 0.35–0.95% carbon was investigated in three kinds of sand slurries with pH values of 5, 7 and 10, respectively. ...The corrosion rate of the martensitic cast steel in the solutions with the same pH values was also measured and related with its corrosion–abrasion wear behavior. It is shown that the corrosion–abrasion wear resistance of the steel increased with increase in its carbon content. However, the corrosion process of the corrosive solution could influence the abrasion wear rate of this steel considerably.
In order to produce various stainless steel castings, a new ceramic mold making process based on full mold EPS patterns has been developed. In this method, a ceramic shell approximately 10 mm in ...thickness is created by applying a coating to EPS pattern, which is then heated in a furnace in order to gasify the EPS pattern and harden the ceramic shell coating. Unlike the Replicast process, the ceramic shell thus formed requires neither a vacuum nor back up sand for the pouring, and being pre-heated, is not subject to thermal stress. The strength of the ceramic shell at high temperatures is very important since support sand is not used. A trace of the x-ray diffraction measurements revealed that the cristobalite peak occurs at 21.9°. When the ratio of fused silica is increased, the cristobalite intensity rises significantly and the post-cooling bending strength decreases. It is thought that because fused silica transforms into cristobalite, a large thermal contraction occurs during the cooling period owing to the decrease in bending strength, and as a result, many fine cracks are generated throughout the ceramic material. The results suggest that the most suitable refractory material for the ceramic mold is a 1 : 1 mixture of zircon and fused silica. On this basis, pre-heated ceramic molds have been used without back-up sand to produce various stainless steel castings.
A typical hot concentrated alkaline corrosion environment exists in alumina metallurgical industry, so that steel materials with outstanding alkaline corrosion resistance are strongly demanded for ...its processing equipment. In this paper, the corrosion resistance of two kinds of martensitic cast steels containing chromium in static 303g/L NaOH alkaline solution at 85℃ was studied through polarization and potential-time curves, corrosion weight loss and corrosion morphology analysis. Experimental results showed that protection effect by passive film of cast steel containing Cr was temporary. The low carbon steel without Cr content also exhibited chemical passivity in the same solution. The corrosion mode of the tested Cr-containing cast steel was composed of active dissolving corrosion and caustic embrittlement cracking. Dissolving corrosion was the primary mechanism for the induced weight loss, while severe caustic embrittlement cracking was secondary. With the increase of chromium content in the cast steel, the tendency of the caustic embrittlement cracking decreased, while the active dissolving corrosion increased.
The strength, ductility, and microstructure of seismic austenitic cast steels are discussed in terms of elongation, proof stress, and strain hardening.
Through fiber reinforcement, authors have greatly enhanced the patented mold layer and prevented problems associated with F.M. method. By burning off the fiber reinforced coating therefore making it ...possible to pre-remove the coated mold prior to actual casting operation in addition to removal of blowholes in the carbon steel and rough skin due to modular graphite. Greatest advantage of FM method is the convenience if the mold making operation can be done by FM method, many problems as mentioned are resolved. One method is in advance burning off the EPS within the mold and by providing the necessary oxygen into the mold cavity, these researchers have investigated the full removal of the EPS in such manner. By introducing heat resistant short fibers in the coating, as a result the coating displayed sufficient strength during the combustion and cool down that meets the molding criteria requirements. The F-process as referred to in this paper discusses fiber reinforced coating being burned, cooled down without collapsing and in this paper a 500 X 1000 X 80 mm3 EPS is uniformly coated all over except the bottom side. A graph shows relationship between various fiber lengths and maximum bending moment. For the non-fiber molded part this was 0.34 N vs. 2.70 N that was obtained by reinforcement using SiC. The effects of fiber strength begins at 1~3 mm long fibers and reaches maximum at 6~10 mm long fibers. Subsequently the FM and F processes are illustrated and compared. It was found that for 300 kg casting part the allowable resistant glass reinforcement was sufficient. In reality complete combustion of molding was hard in this trial and many tar-like multi-layer materials and sooth did remain. Couple of tree-like models were made to compare FM and F methods and carbon steel (0.22%C) which were molded. Upon analysis of C contents the problem of carburization of EPS in FM method was reduced.
