Cast austenite stainless steels (CASS) are widely used in the primary circuit piping of pressurized water nuclear reactors for their excellent mechanical behavior, corrosion resistance and good weldability. But, cast austenite stainless steels have a tendency of thermal aging embrittlement after long term service at mid-temperature (280-320℃). The latest research results were summarized, mainly including the phase transformation rules and its influence factors during long-term thermal aging, the nano hardness, tensile, impact and fatigue behavior of CASS after long-term thermal aging.

Magnetizing reduction followed by magnetic separation is one of the most effective unit operations in the treatment of refractory iron ores. Physical and chemical properties of magnetite by magnetic roasting-magnetic separation which was named artificial magnetite were different from natural magnetite. Reverse flotation results show that flotation performance has great difference between artificial magnetite and natural magnetite, X-ray diffraction and microscope testing technology were adopted to analysis flotation performance of artificial magnetite by observing change in mineral composition and phase in magnetic roasting process. Silicon of raw ore existed in the form of detrital quartz and siliceous mudstone, while silicon of roasting ore existed in the form of silica quartz, and part of the quartz was coated with iron ore, more widely spread than raw ore, incomplete crystal structure is emerged. Mineral phase composition is changed and inhomogeneity is enhanced in internal ore structure after roasting, iron mainly existed in magnetite and maghemite, peak of laihunite and iron silicate appeared in roasting ore; there were laihunite, quartz in magnetic separation concentrate of roasting ore, quartz, and in natural magnetite silicon existed in the form of quartz; part of quartz still existed in reverse flotation concentrate, part of laihunite and iron silicate entered the reverse flotation concentrate.

The hot compression test of high nitrogen martensitic stainless steel was carried out using Gleeble-3800 thermal-mechanical simulator within temperature range of 1040-1120℃ and strain rate range of 1-20s-1. Combining with true stress-true strain curve and microstructure after hot deformation, the influences of deformation parameters on the hot deformation behavior and evolution law of carbon nitrides of high nitrogen martensitic stainless bearing steel were studied. The results indicate that the true stress-strain curves of the material are dynamic recrystallization type under the present deformation conditions. It is also observed that, as strain increases, the average size of carbides decreases gradually and the number of carbides increases. Based on the equation for hot deformation, the deformation activation energy (Q) of 410. 7kJ/mol was obtained at a strain of 0. 6. The flow stress equation including strain and the constitutive equation of Zener-Hollomon parameter for high nitrogen martensitic stainless steel were established.

The progress of dry operating mechanical vacuum pumps in use for steel degassing was introduced by comparing with steam ejectors. The results show that the dry mechanical vacuum pump has obvious advantages in the degassing quality as well as the reliability of pump and of associated dust removal system and gas cooling system. Standardized vacuum pump operation can make the manufacturing cost relatively low, whereas standardized pre-assembled modular build-up permits further cost saving during erection and start-up. The most modern vacuum pump is compact, and energy and water saving.

In the processing of blast furnace, hanging in lump zone is a common problem, which has great influence on smooth operation and high production. Meanwhile, pressure drop of lump zone can directly inflect the possibility of hanging in the lump zone. Therefore, in order to make calculated value consist with the practice of BF, a new mathematic model was built. The relationship among high pressure operation, burden permeability and smooth operation was investigated, which was based on actual production of blast furnace of Qian Steel. The calculating results are in accord with the results of measuring in actual processing. Meanwhile, effective range of changes of burden′s diameter and voidage for pressure drop of lump zoon becomes smaller and smaller as the increasing of top pressure. The model can be ported to operate the hanging problems, and used to predict the change trend of lump zone′s pressure drop with the variety of top pressure and blast volume, which can give the reference data for operator in the process of dealing with the problem of hanging.

The mechanical and thermal fatigue properties of high manganese SDH3-Mod hot working die steel were investigated and influence of manganese on the microstructure were also studied by transmission electron microscopy (TEM). The results reveal that the retained austenite exists as thin film between the lath martensite which improves toughness and slows fatigue cracks propagation. Meanwhile, the coarsening of carbides is efficiently inhibited and softening of steels is sufficiently delayed which improves the resistance of tempering and thermal fatigue because of the addition of manganese. Consequently, SDH3-Mod shows a more significant improvement on the mechanical properties than H13.

Lean duplex stainless steel was a kind of high-property new stainless steel with low cost, bearing nitrogen and ferrite-austenite dual-phase structure. Replacement of nickel by nitrogen can both decrease the cost and improve the mechanical property and corrosion resistance. The history of lean duplex stainless steel was introduced. Especially, the effects of composition and heat treatment on the phase transformation mechanical property and corrosion resistance of different grades were discussed and compared with those of 304 and 316. Meantime, the progress in weldability and welding techniques was analyzed. The grades S32101, S32003 and S32202 had been widely used in nuclear power, bridge, architecture and heat-exchanger, replacing traditional austenite stainless steels AISI 304 and 316. It was concluded that development of lean duplex stainless steel had became one of the trends in future due to its higher strength and corrosion resistance and low content of expensive elements Ni and Mo.

Cathodic charging, notch tension and hydrogen thermal desorption analysis test was used to study the delayed fracture behaviors of high strength steel 42CrMoVNb at different tempering temperatures, which were also compared with commercial structural steel 42CrMo. The results show that the delayed fracture resistance of experimenting steels increases with increasing tempering temperature. Since the tensile strength of 42CrMoVNb steel is higher than that of 42CrMo steel at same tempering temperature, the delayed fracture resistance of the former is lower than that of the latter. And in the high strength (more than 1250MPa), the delayed fracture resistance of 42CrMoVNb steel is evidently better than that of 42CrMo steel. This is because there is fine dispersed (V,X)C carbide precipitated in 42CrMoVNb steel when it is tempered at 550-650℃, which is regarded as a strong hydrogen trap and improve the delayed fracture resistance of the steel.