Advanced Materials Research Vols. 581-582

Abstract: The joining of austenitic stainless steel (AISI 201) to low carbon steel sheets (CS) was attempted by gas tungsten arc welding (GTAW) with four types of consumables. The studied consumables were ER308L, ER309L, ER316L stainless steel wires, and AWS A5.18 carbon steel wire. The welding parameters – i.e. the current of 90 A and the welding speed of 62 mm.min-1 – were fixed in all welding operations. The microstructure of weld metal produced by stainless steel consumables consisted of delta ferrite in austenite matrix. The delta ferrite in the form of continuous dendrite was observed in weld metals produced by 308L and 309L fillers. The dendrite of delta ferrite was relatively discontinuous in weld metal produced by 316L filler. The microstructure of weld metal produced by carbon steel filler consisted of equiaxed ferrite and pearlite, similar to that of carbon steel. The corrosion behavior of weld metal was investigated by potentiodynamic method. Specimens were tested in 0.35-wt% NaCl solution saturated by laboratory air at 27°C. It was found that the corrosion potential of weld metal produced by carbon steel filler was considerably lower than those of AISI 201 base metal and weld metals welded using stainless steel consumables. Weld metals produced by stainless steel fillers –308L,309L and316L– exhibited the similar corrosion potentials as that of 201 base metal. The pitting potentials of weld metals produced by 309L, 316L fillers were higher than those of 201 base metal and weld metal produced by 308L filler respectively. It was discussed that the increase of Cr content in weld metals by using 309L filler contained with 24.791 wt% of Cr, or the addition of Cr and Mo in weld metals by using 316L filler contained with 21.347 wt% of Cr and 2 wt% of Mo, promoted the pitting corrosion resistance of weld metal to be comparable with that of Fe-17Cr-3Ni (201) base metal. An emission spectroscopy was applied to quantify the amount of elements in weld metals. By considering the contents of Cr and Mo, the pitting resistance equivalent number (PREN) of each weld metal was calculated. The discussion of the corrosion resistance of weld metals related to PREN and microstructure was made in the paper.

Abstract: The corundum-mullite was toughened by in-situ synthesized mullite whiskers and the process parameters influencing the fracture toughness of corundum-mullite, such as sintering temperature, addition amount of AlF₃ and V₂O₅, were optimized by means of response surface method. Corundum-mullite with fracture toughness of 9.44 MPa.m^-1/2 could be obtained under the optimized conditions, i.e. sintering temperature of 1400°C, 4.8 wt.% of AlF₃ and 5.8 wt.% of V₂O₅. The results showed that it was feasible to prepare corundum-mullite toughened by in-situ synthesized mullite whiskers by the optimized parameters. In addition, an accurate model based on response surface method was proposed to predict the experimental results.

Abstract: For the ratio from orthogonal experiment, the phosphating solution which prepared with zinc oxide, phosphate acid, tartaric acid, sodium molybdate, Ma Jif salt, sodium fluoride, phytic acid, chrome alum to do the single factor variable experiments. For the various factors effect on the corrosion resistance of phosphating film to do the in-depth analysis. Preliminary analyse the film formation mechanism via the scan curve of the potential to the time, and determined the best film-forming time.

Abstract: By FEAt method, the tensile processes of single crystal copper with the type I crack at temperature of 293K were simulated, and the effect of different initial crack lengths to crack propagation mechanism was analyzed. The results indicate that the different initial crack lengths have significant effect on crack propagation mechanism. With the increase of crack length, the critical stress of crack propagation was significantly reduced, the dislocation walls were easy to appear, and mesh staggered of the crack branch along the cleavage plane was more pronounced.

Abstract: In order to find the most effective hydrometallurgical method of removing iron, aluminum and calcium from MG-Si, a variety of acid leaching methods were presented. The research results show that the order of capacity of metallic impurity removal is HF, HCl, HNO3 and H2SO4. The most effective hydrometallurgical method is the leaching by mixed acid with hydrofluoric acid and sulfuric acid. Removal efficiency of hydrochloric acid pressure leaching can improved as the pressure increases. Sulfuric acid and nitric acid even using high pressure leaching cannot obtain high impurity removal rate. The leaching by hydrofluoric acid or mixed acid containing hydrofluoric acid and sulfuric acid is very effective on removal of iron and aluminum, but less effective on calcium.

Abstract: In this paper, the crystallization behavior including crystallization temperature, nucleation temperature, microstructure of glass-ceramics and crystal phase composition during preparation of glass-ceramics by melting method from blast furnace(BF) slag of Baotou iron and steel company, quartz sand and other materials was investigated using differential thermal analysis, X-ray diffraction and scanning electron microscopy. The results show that the crystallization peak temperatures of the parent glasses are 962~966°C when the ratio of blast furnace slag changes from 20% to 50%, and uniform, compact grains in the prepared glass-ceramics are obtained, whose diameters are about 0.2-0.5μm. In addition, the major crystalline phases are identified as diopside(Ca(Mg,Al)(Si,Al)2O6）and diopside containing aluminum(Ca(Mg0.5Al0.5)(Al0.5Si1.5O6), and the mechanical properties of glass-ceramics are good, among which the flexural strength is more than 110Mpa. The results have theoretical guidance meaning and practical reference value for realizing industrial production of preparation of glass-ceramics from BF slag of Baotou iron and steel company.

Abstract: Effect of the laying head temperature and controlled cooling process on microstructure and mechanical properties of 72LXA wire rod were investigated．The results show that under the same cooling process，with the raising laying temperature and increasing sorbitizing rate and decreasing proeutectoid ferrite，the steel rod strength is improving，proeutectoid ferrite and sorbitizing rate are the critical impact factors on steel rod properties；indentifying cooling after perlite forming can restrain the dissolve of lamellar cementite；the mechanical properties of whole rod coil are improved by the proper rolling rate and air cooling．The high strength of 1050 MPa of steel rod was obtained，that shows the defined hot rolling process can conform to the steel rod properties requirement．

Abstract: The effect of sodium carbonate concentration on alumina leaching of low A/S ratio clinkers and SiO2 concentration in leached liquor was studied in this paper. The clinker with the Al2O3/SiO2 mass ratio of 1.0 (the molar ratios of CaO/SiO2 and Na2O/Al2O3 are 2.0 and 1.05) was sintered at 1230°C using AR reagents. The alumina leaching rate and SiO2 concentration in leached liquor increase with the increase of sodium carbonate concentration, and the alumina leaching rate reaches its maximum of 96.36% when the sodium carbonate concentration is 15g/L. The results of XRD indicate that sodium carbonate can inhibit the formation of hydrogarnet, and there is almost no formation of hydrogarnet when the sodium carbonate concentration is 15g/L.

Abstract: Through the processing of mineralogical study on a copper ore from Jilin province in China, it found that the copper exist mostly with the form of chalcopyrite, and others exist with the form of copper oxide minerals which with complex ingredient. The copper oxide minerals are due to the altered of the edge of chalcopyrite, and have not formed the independent copper oxide ore. It belongs to unconventional hard-to-beneficiate copper ore. Coarse grinding fineness and bulk floatation was used to recover the copper oxide ore and copper sulfide ore by using amino double phosphoric acid and butylamine dithiophosphate as the collector. This process was similar to the carrier flotation and achieved an effective processing of the copper oxide ore and obtained a high-grade copper concentrate assaying 15.8% with a high recovery of 82.4%.

Abstract: Based on the actual arrangement of secondary cooling nozzle of Slab Caster, the paper determines and analyzes the water volume density distribution of different assembled Arrangement of nozzles. The results demonstrate that the distribution of the nozzles in every area is ideal, and can make the uniformity of the slab temperature relatively. The reality is that the more nozzles included in one row, the better uniformity of water volume density distribution can be got. Both the uniformity of water volume density distribution and the complexity of the pipes’ instruction should be considered in designing the assembled arrangement of nozzles. The uniformity of water volume density distribution will change seriously with unreasonable instruction or unqualified nozzles, that will influence the uniformity of the slab cooling seriously.