钢铁钒钛

WATER-MODEL TEST ABOUT MOULD FLOWAGE OPITIMIZATION FOR SLAB CASTER AT PZH STEEL

ZHOU Yi-ping, YANG Su-bo, YAN Xue-mo, DAI Yun-ge, ZHANG Hua-shu, PENG Shu-dong, WU Wei

2002, 23(1): 1-5.

Abstract(39) PDF(2)

Abstract:
Water-model test about mould flowage optimization was taken at PZH Steel slab caster.It was studied that effects of operating conditions such as continuous casting speed, mould width, nozzle structure etc.on mould flowage, level fluctuation, fluid behavior and floation of inclusions.The results are valuable for optimizing mould process parameter and continuous casting operation.

THE PRESENT SITUATION ANALYSIS FOR PRODUCTION CYCLES OF LADLE AT PZH STEEL

LI Li, ZHOU Rui-he, XUE Nian-fu, PEI You-cai, WANG De-kui

2002, 23(1): 6-11.

Abstract(40) PDF(1)

Abstract:
Hot state of ladles and its effects on the molten steel temperature in production cycles were studied at PZH Steel,by combining mathematical modeling with production data statistics.The main factors affecting the hot state of ladles were discovered.

STUDY OF HOT ROLLING TEMPERATURE PARAMETERS FOR MICRO-CARBON STEEL IN LABORATORY

ZHANG Kai-hua, CHANG Jun, LI Jun

2002, 23(1): 12-16.

Abstract(33) PDF(1)

Abstract:
According to the characteristics of micro-carbon steel,simulative test was taken in laboratory under the principle of "high heating temperature,high beginning rolling temperature,high final rolling temperature and low rolling temperature".The effects of heating temperature on the AlN solubility,final rolling temperature on the grain size,coiling temperature on the AlN and cementite carbide precipitation,cooling rate on the grain size were conducted.The hot rolling temperature parameters of micro-carbon steel in laboratory were put forward.

PREPARATION TECHNOLOGY OF V₂O₅ SOL - GEL FROM INDUSTRIAL V₂O₅

YANG Shao-li, XU Chu-shao, CHEN Hou-sheng, LIAO Dai-hua

2002, 23(1): 17-20,25.

Abstract(57) PDF(1)

Abstract:
V₂O₅ Sol - Gel was prepared from industrial V₂O₅ crystal sheet by the inorganic sol - gelmethod. Viscosity variation of V₂O₅ sols was studied. The thermal analysis of V₂O₅ gels and V₂O₅ crys-tals was taken. The research result indicated that suitable technological parameters for preparation ofV₂O₅ sol - gel are: melting temperature of V₂O₅ crystal being 800~900℃, holding time of meltingtemperature being 5 ~ 10 min. The so1 can form gel when the concentration of sols is higher than 22 g/L. The viscosity of sol will increase as prolonging the placed - time, and the viscosity increases morewhen the concentration is higher. The component of V₂O₅ gels keeps stabilization in heating conditions(below 500℃), and phase transformation does not occur.

STUDY OF SLAG PROPERTY FROM Ferro Vanadium

WANG Yong-gang, YANG Feng, ZHANG Jian-hui

2002, 23(1): 21-25.

Abstract(38) PDF(1)

Abstract:
The characteristics of slag from melting high vanadium iron at Panhong was analyzed.The slag property of melting high vanadium iron was discussed.It was studied that effects of slag physico-chemical property on melting process parameter and technical-and-economic indexes.

CONTEMPORARY CONVERTER STEELMAKING TECHNOLOGIES AND DEVELOPMENTAL SUGGESTION TO PANGANG

WEN Yong-cai, YANG Sen-xiang, WANG Sheng, ZHANG Huai

2002, 23(1): 26-31.

Abstract(82) PDF(1)

Abstract:
The development history of converter steelmaking is reviewed.The main advance of steelmaking technology in different times are described.The technologies of contemporary converter steelmaking are introduced in detail.Development of converter technologies at Pangang is proposed in light of the actual conditions.

ROLLING PROCESS DESIGN OF S49 RAIL

CHEN Ya-ping, WANG Yan-zhong, TAO Gong-ming

2002, 23(1): 32-34,55.

Abstract(49) PDF(2)

Abstract:
According the features of rail-beam plant and S49 rail section, the rolling process design of S49 rail is discussed.It is presented how to choose the pass system and determine the parameter of pass system.The rolling mill guides were designed.S49 rail was produced successfully at first test by optimizing design of pass system.

PRECIPITATION AND GRAIN REFINEMENT IN VANADIUM-CONTAINING STEEIS

STANISLAW Zajac

2002, 23(1): 35-48.

Abstract(72) PDF(2)

Abstract:
The present work has concentrated on the roles of vanadium, nitrogen and carbon in controlling the precipitation of V(C,N) in austenite and ferrite and their effects on:(i) grain refinement by promoting the formation of intragranular ferrite, and (ii) precipitalion strengthening by interphase and random precipitation.
The degree of precipitation strengthening of ferrite at a given vanadium content depends on the available quantities of carbon and nitrogen. It is concluded that nitrogen is a very reliable alloying element, increasing the yield strength of V-microalloyed steels by some 6 MPa for every 0.001%N, essentially independent of processing conditions. The role of tarbon in precipitation strengthening is complicated. The present results have shown that the precipitation strengthening of V-microalloyed steels increases significantly with the total C-content, ≈5.5MPa/0.01%C. The explanation is that the metastable equilibrium between ferrite and undercooled austenite greatly increases the solubility of carbon in ferrite, in the times available during transformation, thereby contributing to profuse nucleation of V(C,N) particles. This effect of carbon is particularly significant for medium carbon steels typically used for hot rolled bars and sections.
The experimental results strongly indicate that vanadium can be effectively used not only for precipitation strengthening but also for ferrite grain refinement. It was shown that vanadium contributes to the formation of two types of intragranulary nucleated ferrite; polygonal(idiomorph) ferrite and acicular (sideplate)ferrite. Intragranular polygonal ferrite nucleates on VN particles that grow in austenite during isothermal holding or slow cooling throughout the austenite range. Acicular ferrite microstructure forms in V- microalloyed steels during isothermal transformation at lower temperatures (~450 C). The acicular ferrite microstructure was obtained in V-microalloyed steels containing high, medium or very low nitrogen levels. This suggests that vanadium on its own can promote the formation of the acicular ferrite microstructure.

Vanadium Microalloyed Forging Steels

GEORGE Krauss

2002, 23(1): 49-55.

Abstract(43) PDF(1)

Abstract:
The production processing, microstructure and properties of vanadium microalloyed forging steels with medium-carbon are introduced. The strengthening produced by vanadium enhances the strength of medium-carbon steels. As a result, no further heat treatment is required for vanadium microalloyed forging steels. The increasing of strengths is due to fine vanadium carbonitride particles precipitating in ferrite-pearlite microstructure during cooling after forging. The highest strengths of steels are produced in base microstructrures with large volume fractions of pearlite. As a result, the resistance to cleavage fracture during impact loading is low. There are several available approaches for improving toughness. One approach is to lower the carbon content if lower strength can be tolerated. Another approach is to add titanium as a microalloying element. The third approach is to increasing sulfur content properly.

DEVELOPMENT AND USE OF VANADIUM IN MICROALLOYED REINFORCING BAR-ADVANTAGES OF HIGH-STRENGTH-STEEL

D. Russwurm

2002, 23(1): 56-63.

Abstract(52) PDF(2)

Abstract:
The use of reinforcing steel and its consumption per capita a year in some European countries are introduced. The application conditions of reinforcing steels as structure materials and their advantages as reinforcement used in concrete are also described. The production routs of reinforcing steel and its performance characteristics such as yield strength, ductility, weldability and fatigue etc. are stated in detail. Reinforcing steel using vanadium as microalloying element has advantages and characteristics in many aspects such as economy, metallurgy and so on.

THE EFFECTS OF MICROALLOYING ELEMENTS ON CRACKING DURING CONTINUOUS CASTING

D. N、Crowther

2002, 23(1): 64-80.

Abstract(58) PDF(4)

Abstract:
To ensure the appropriate quality in finished products, it is important that defects in continuously cast products are minimised. As the use of hot charging and thin slab casting coupled with direct rolling becomes more common, it is increasingly important to produce defect-free continuously cast products, as inspection and repair in these situations become more difficult.
Of the many types of defect in continuously cast products, only transverse surface cracking is strongly influenced by the presence of microalloying elements. Nb has a particularly strong detrimental effect, and Nb additions of as low as 0.01% can promote cracking. For V steels with <0.005%N, transverse cracking does not appear to occur, although at high levels of V and N(0.15%V,0.02%N), transverse cracking has been reported.
It is believed that transverse cracks form in the mould, and propagate later in the continuous casting process, particularly during the straightening process. Microalloyed steels can exhibit low ductility over certain temperature ranges, and when the straightening process is carried out in this low ductility region, cracking can occur. In this respect, Nb has a strong effect in deepening the ductility trough, and extending it to higher temperatures. This behaviour is due to the presence of Nb(CN) precipitates, which promote low ductility failures, and retard recrystallisation. The effect of V on hot ductility is much less marked, and only at high levels of V and N does their ductility approach that found in Nb steels. V additions to Nb steels appear to slightly improve hot ductility, by promoting coarser precipitates. The effects of Ti on hot ductility are complex and still not completely understood.
Transverse cracking may be minimised by appropriate selection of steel composition, such as minimising Nb, replacing Nb by V and N combinations, or by making V additions to Nb steels. Machine operating conditions such as secondary cooling strategy are also important in avoiding transverse cracking. By selecting straightening temperatures which are outside the temperature range of low hot ductility, cracking can be reduced.

2002 Vol. 23, No. 1