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Hui Y.,Shougang Institute of Technology | Hui Y.,Shougang Group | Pan H.,Shougang Institute of Technology | Li W.,Shougang Institute of Technology | And 3 more authors.
Jinshu Xuebao/Acta Metallurgica Sinica | Year: 2017

In the production process of ultra-high strength steel, heating schedule of casting slab is one of primary controlling parameters in hot rolling techniques. Heating temperature and holding time affect the prior austenite grain size and the solution of microalloyed elements directly, which both affect austenite recrystallization, precipitation and mechanical properties. A plenty of researches have been made to get better understanding and controlling the austenite grain size or precipitation behavior during austenitizing process over the past half a century, but it lacks systematic researches. Hence it is very important to confirm a reasonable heating schedule. In this work, the austenite grain coarsening behavior and microalloying carbonitrides dissolving behavior in 1000 MPa grade Nb-Ti microalloyed ultra-high strength steel during isothermal holding at different temperatures were studied by OM, TEM and EDS. The results showed that the precipitates in the slab can be obviously classified into three kinds by their size and shape. The average dimension of the bigger cubic precipitates is over 1 μm, and that of the smaller spherical, ellipsoid or cubic precipitates is below 500 nm or less. EDS results showed that the bigger cu bic precipitates are TiN, and the smaller spherical, ellipsoid or cubic precipitates are mainly composed of Nb, Ti composite precipitates and a bit of TiS or Ti (C, S). With the increasing of holding temperature, increase of the original austenite grain size showed a monotonous increase trend, and the austenite grain grows rapidly when the heating temperature exceeds 1200℃; the amount of precipitates decreased and their size increased, the atomic ratio of Ti/Nb increased gradually, and EDS results showed all the precipitates contain Nb, Ti elements. With the increasing of holding time, the average austenite grain grew up in parabolic law, the amount of small sized spherical and ellipsoid precipitates dissolved gradually, and that of the large sized cubic precipitates increased gradually and their edges become blurred. The effects of heating temperature and holding time on austenite grain size and precipitation behavior were considered synthetically, the heating temperature at 1250℃ by holding 80 min will be more appropriate for the 1000 MPa grade Nb, Ti microalloyed ultra-high strength steel. © All right reserved.

Liang B.,University of Science and Technology Beijing | Song C.,University of Science and Technology Beijing | Zhao R.,University of Science and Technology Beijing | Chang G.,University of Science and Technology Beijing | And 3 more authors.
Chinese Journal of Environmental Engineering | Year: 2013

The slaking and modification of quicklime were studied to investigate the optimal slaking conditions for desulfurization and the optimal ratio of ash from head of sintering machine. Quicklime from certain company was employed as a desulfurizer, while dense semi-dry desulfurization process applicated for sintering flue gas in a certain steel plant was taken as an example. The results show that under the conditions that water to ash ratio is 1.5~1.7, grain size of quicklime is below 200 μm, slaking temperature is approximate 55°C, agitation shaft rotation speed is 15~25 r/min, the optimal conversion rate can be obtained. The optimal modified agent volume can be obtained when ash from head of sintering machine accounts for 5%. Meantime, the operational cost and desulfurization efficiency of the targeted project were analyzed. Utilization of self-produce modified desulfurizer could not only save operational cost such as water and electricity consumption, but also improve desulfurization efficiency, which could provide reliable reference for the long-term stable operation of equipments.

Chen G.-J.,Shougang Institute of Technology | Wu G.,SHOUGANG Group | Liu N.-H.,Shougang Institute of Technology | Ge H.,China Steel Corporation | Yang M.,SHOUQIN Metal Material Ltd Company
Energy Materials 2014, Conference Proceedings | Year: 2014

Great progress of energy conservation in SHOUGANG is made in recent years, but there is still some gap compared with international advanced steel enterprises. To lower steel comprehensive energy consumption and dig its energy-saving potential in SHOUGANG further, method of energy consumption theory analysis is applied in steel comprehensive consumption benchmarking from the factors such as technical flow, process energy consumption and steel ratio coefficient in SHOUGANG three new-built plants such as SHOUQIN, QIANGANG and JINGTANG. Analysis result shows that it is the effective approach to lower steel comprehensive consumption by shortening flow, lowering process energy consumption in iron-making and iron-steel ratio. By benchmarking of process energy consumption in SHOUGANG three new-built plants, it shows that iron-making process energy consumption in QIANGANG is lowest, sinter and steel-making process energy consumption in SHOUQIN is lowest and hot rolling process energy consumption in JINGTANG is lowest, but higher than the advanced Chinese steel enterprises, so some basic measures to lower energy consumption are put forward, and the best optimizing effect of steel energy-saving can be reached by combining and optimizing with single equipment and systemic energy-saving technology on the base of single energy-saving technology applied fully and energy efficiency of single equipment exerted further.

Wang L.,CAS Shenyang Institute of Metal Research | Xie G.,CAS Shenyang Institute of Metal Research | Xiao J.H.,CAS Shenyang Institute of Metal Research | Qiu D.Y.,Shougang Group | And 2 more authors.
Materials Science Forum | Year: 2015

Crack initiation and propagation during creep test in a recrystallization (RX) grain containing directionally solidified (DS) nickel-base superalloy was studied by employing electronic backscattered diffraction (EBSD) technique. Creep samples were locally deformed and then heat treated to get local RX at the center of the gauge length. Creep test was carried out at 980 °C/235. MPa. It was found that during creep test, precipitate free zones (PFZ) were formed along the RX grain boundary and the cracks were initiated and propagated along the interface (a) between PFZ and RX grains, (b) between PFZ and the matrix or (c) within PFZ. It indicated that the crack initiation and the propagation were crystal orientation dependent. © (2015) Trans Tech Publications, Switzerland.

Zhang Z.-S.,University of Science and Technology Beijing | Lian F.,University of Science and Technology Beijing | Liao H.-Q.,Shougang Group | Yang Q.,University of Science and Technology Beijing | Cao W.-B.,University of Science and Technology Beijing
Beijing Keji Daxue Xuebao/Journal of University of Science and Technology Beijing | Year: 2012

High-temperature modification by iron tailings was performed to study its influence on the volume stability and cementitious properties of steel slag. The mineral constituents and microstructure of steel slag after the high-temperature modification were analyzed via X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy dispersive spectrometry (EDS). It is found that the content of f-CaO obviously decreases and the cementitious properties of steel slag improve through the high-temperature modification. Compared with raw steel slag, the mass fraction of f-CaO in steel slag decreases from 4.84% to 1.82% after modification with 20% iron tailings at 1 250°C and the activity index increases up to 5.6% after 28 d. With an increase in the mass fraction of iron tailings from 10% to 30%, silicate mineral phases such as manganolite, akermanite and calcium magnesium pyroxene form in the modified steel slag. The high-temperature modification promotes the decomposition of RO phase, in which FeO transforms to magnetite (Fe3O4) simultaneously.

Yu H.-X.,University of Science and Technology Beijing | Wang X.-H.,University of Science and Technology Beijing | Zhang J.,University of Science and Technology Beijing | Li H.-B.,Shougang Group | Wang W.-J.,University of Science and Technology Beijing
Journal of Iron and Steel Research International | Year: 2011

Alloying structural steel used for mechanical structures has a high requirement for cleanliness because its failures are greatly affected by non-metallic inclusions and total oxygen content in steel. It has been reported by some steelmaking plants to have some problems in controlling total oxygen content and inclusions during alloying structural steel production. For this purpose, cleanliness control in 0. 2C-0. 3Si-0. 6Mn-lCr-0. 2Mo steel was investigated. Firstly, low melting temperature zone (≤1 873 K) of CaO-Al 2O 3-MgO system and formation condition of low melting temperature inclusions were investigated through thermodynamic equilibrium calculation. On this basis, industrial tests were carried out. Through sampling at different stages, transformation of oxide inclusions and change of total oxygen content in steel were studied. The results show that: in order to form CaO-Al 2O 3-MgO system inclusions with low melting temperature, mass percent of A1 2O 3, MgO and CaO in inclusions should be controlled from 37.6% to 70.8%, 0 to 17.4% and 25.5% to 60.6%; For the condition of 1873 K and 0.05% (mass percent) dissolved aluminum in steel, the activities of dissolved oxygen, magnesium and calcium should be controlled as 0. 298 × 10 -4 -2 × 10 -4, 0.1 × 10 -5 -40 × 10 -5 and 0.8 × 10 -8 -180 × 10 -8 respectively. With secondary refining proceeding, average total oxygen content and inclusion amount decrease, the type of most inclusions changes from Al 2 O 3 after tapping to Al 2 O 3-MgO after top slag is formed during ladle furnace refining and finally to CaO-Al 2 O 3-MgO after RH treatment. In the final products, average total oxygen content was 12. 7 × 10 -6 and most inclusions were in spherical shape with size less than 5 μm. © 2011 Central Iron and Steel Research Institute.

Wang Y.-S.,University of Science and Technology Beijing | Wang Y.-S.,Shougang Group | Wu S.-L.,University of Science and Technology Beijing | Zhao Z.-X.,Shougang Group | Pan W.,Shougang Group
Kang T'ieh/Iron and Steel (Peking) | Year: 2010

A low quality ore called MGF was researched for using in sinter process. Firstly, high temperature properties of ore were studied by micro sintering equipment, based on which, sinter pot test was carried out to verify the application of MGF. Results show that the assimilation and liquid phase fluidity of MGF both are high, which can be used as a measure to make up the disadvantage of that ore with high SiO2 and Al2O3 content and bad size composition. At last, through industrial practice, usage of MGF with ratio of 6% is feasible in sintering and blast furnace.

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