No abstract

Defect in surface induction hardening layer at the eccentric axle neck of C38N2 automobile engine crankshaft was investigated. Fracture morphology and microstructure of the defect were analyzed by optical microscope and scanning electron microscope, and compared with the microstructure characteristics in defect-free locations. And the reasons and the technical procedures of the defects were discussed. The results indicated that the surface defect is a quenching crack caused by induction hardening process. The crack propagation is along prior-austenite grain boundaries and is affected by MnS inclusions. Martensite lath in surface hardening layer at position having 45° or 90° with mouldjoint is shorter than that at the defect position. Distribution characteristics of inclusions at different positions have significant difference. Inclusions in the defect position are slender spindle and are distributed nearly vertical the crankshaft surface. Distribution of the inclusions in the 45° position is approximately parallel to the crankshaft surface. And the inclusions in the 90° position are mostly graininess. Distributional difference of the inclusions at the different positions is related to uneven flowing of metal during stamp forging process.

Water stress is an important approach to use water resources efficiently and remit the agricultural water shortage. Hemarthria compressa is one of perennial grasses, a pasture of high quality, which has abundant species resources in China. To explore the response of the growth, yield and water use efficiency(WUE) of Hemarthria compressa under water stress, this study, adapting pot experiment, imposed three water stress degree (LD, MD and SD) treatments and a control treatment on Hemarthria compressa. The data of growth indicators during control period, yield and total water consumption were obtained. The results show a noticeable inhibitory action of water stress on the growth of Hemarthria compressa. Along with the intensifying of water stress, plant height increment, leaf area, total biomass, dry matter of each organ and yield decreased, and the root-shoot ratio increased firstly and inclined to slump finally. Plants under the middle water stress treatment achieved the greatest WUE of 38.25 kg/m3. The first 10d in the water control period was the most sensitive period of the pasture responding to water stress.

According to the demand of oil and gas field development with a small amount of hydrogen sulfide, CT80S sulfur resistance coiled tubing was developed through the raw materials and manufacturing technology. The microstructure, mechanical properties, fatigue life and corrosion resistance of the CT80S sulfur resistant coiled tubing were analyzed. The results showed that the microstructure of CT80S sulfur resistant coiled tubing was consisted of the ferrite and pearlite with the grain size of 12, banded structure of 1.0, and the inclusions was less than 1.0. The strength and hardness of the pipe meet the requirements of API Spec 5ST, and the hardness control was less than 18HRC. The pipe had excellent low cycle fatigue property, the mean fatigue life of Φ31.8 × 3.18mm tube was 1055 cycles when the internal pressure was 34.47MPa and the bending radius was 1219mm. According to NACE TM 0284 and NACE TM 0177 standard, the HIC and SCC performance tests were carried out in same solution. The results show that the developed tubing is insensitive to HIC and the resistance to sulfide stress corrosion is good, under 90%σs stress loading not break.