Table of Content

05 February 2014, Volume 30 Issue 1

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Study on trial production of nitrogen microalloyed reinforced bar

2014, 30(1):  1-5.  doi:

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The study on trial production of HRB400E using the new technique of nitrogen microalloying had been carried out. It was found that the
billet had a thermoplastic brittle zone within the temperature range between 750 and 850 ℃. By controlling the continuous casting process,
cast billet of highquality had been successfully produced. The final rebar had high tensile strength and suitable yield ratio as well as stable
aging performance, and metallurgical structure showed that it consisted of ferrite and pearlite. Further analysis revealed that the improvement
in the strength of newlydeveloped Nmicroalloyed rebar was mainly due to the precipitation of secondaryphase particles with diameter
from 5 to 30 nm. This new technique of nitrogen microalloying could save the usage of vanadium element by approximately 40 % to 60 %.
It made the cost of steel per ton decrease 4060 yuan and created obvious economic profits through adopting the production technology.

Research and development of 25C2Ni4MoV steel for heavy fan main shaft

宋平;翟晓峰;潘宏涛

2014, 30(1):  6-9.  doi:

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For the strictly requirements on UT and no adopting the ESR production process，the smelting control difficulties of this steel grad had been analysis, and accordingly the key control points had been made. And the use of double vacuum process to produce 25Cr2Ni4MoV fan shaft steel had been also determined finally. The final steel product quality after testing had fully met the standard requirements on the chemical composition, mechanical properties, ultrasonic testing, and can completely replace the ESR steel.

生产实践

Metallurgical effects of 120 t converter with less slag refining for decarburization and keep phosphorus

2014, 30(1):  10-12.  doi:

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According to the characteristics of lowcarbon lowsulphur highphosphorus silicon steel, the process of deep desulfurization molten iron
less slag smelting and decarbonization phosphorus conservation was used on 120 t converter in Ma’anshan Iron & Steel Company Ltd. The
converter end point reached w(S)≤0.006 %, w(P)≥0.050 %, and the hit ratio of C-T was improved. The end molten steel oxygen activity was stability about 593×10-6. Blowing loss and splash were down, and molten steel yield was increased by 1.5 %. The mass of lime and other bulk material was controlled below 33.7kg/t, and the remarkable economic benefits were achieved.

Investigation of nonmetallic inclusions in titaniumkilled steel by a three stages deoxidization technology

2014, 30(1):  13-16.  doi:

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By thermodynamics calculation and increasing oxygen content with Fe2O3 addition and deoxidization with titanium addition
for three times, the morphology, dimensions and distribution of nonmetallic inclusions and microstructure of steel in titaniumkilled steel
were investigated. The results showed that, increasing oxygen and deoxidation process three times, and controlling the oxygen content in steel
greater than 0.001 %, oxygen and titanium can generate the titaniumcontaining oxide. Thermodynamic analysis proved that the
titanium oxide was Ti2O3. After adding titanium in the steel the mass fraction of oxygen was about 0.002 %, and the number of titanium oxide below 2 μm increased and the number of titanium oxide between 2 μm to 3 μm changed little in the final sample. These
inclusions could induce the precipitation of acicular ferrite through refine the organization.

Optimization and improvement of 300 t converter skimming process in masteel

2014, 30(1):  17-20.  doi:

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To reduce the slag outflow during converter’s taping，improve the quality of liquid steel, and increase the yield of alloy elements，the original pneumatic slagstopping process for 300 t converter was optimized by applying the skimming dart combined with the pneumatic slagstopping technology in No.4 SteelMaking and Rolling Plant General of Ma’anshan Iron and Steel Co., Ltd. Through the skimming dart technology, the successful slagstopping reached to 98 %, the quantity of slag outflow during taping was reduced by more than 30 %, and the average mass fraction of rephosphorization could be controlled under 0.003 %. Meanwhile, the yield of liquid steel was increased, the effect of slagsplashing and subsequent refining was improved. As a result, better economic benifits were gained.

Elimination of 65 steel wire rod tensile rate of the production practice

2014, 30(1):  21-23,2.  doi:

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This paper introduced the quality objection of cupcone fracture existed in 65 high carbon hard wire rod which was produced by Fujian Sanming Iron and Steel(Group) Co., Ltd. Minguang after July 2012. The reasons of quality objection were analyzed, and it was found that the main reason were alternate segregation position holes and center. Therefore, the process of the converter steelmaking, refining and continuous casting was optimized based on above analysis. The superheat of liquid steel and casting speed were the primary adjustment. Through the exploration and market feedback of the product quality, the measures were proved to be effective. The fracture phenomenon of 65 high carbon hard wire rod was eliminated, and the rate of dissent and claim of customers was correspondingly decreased.

Investigation on decarburization process in 180 t RH degasser

2014, 30(1):  24-28.  doi:

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Investigation on decarburization process in 180 t RH of Shasteel had been conducted, and the effect of initial condition of liquid steel,
vacuum pressure,liftgas flowrate and oxygen blowing time on decarburization process had been explored. The experimental results indicated
that there were three stages during the decarburization process: the decarburization rate constant was very low at the first and third stage, and the second stage was the major decarburization period with the largest decarburization rate constant. By decreasing the initial w(C)/w(O) ratio and the product of w(C)·w(O), the duration of the first stage would be shortened and the decarburization rate constant of the second stage would be increased. The decarburization rate constant would be increased when increasing the exhausting rate constant. If the time to reach the lowest pressure in chamber was less, the carbon content at decarburization end was lower. Blowing oxygen after mid period and increasing the liftgas flowrate from 113 m3 to 150 m3 after decarburization treatment for 7 minutes had no influence on decarburization process.

Investigation on nitrogen controlling techniques in IF steel

2014, 30(1):  29-33.  doi:

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According to the practices of No.3 Steelmaking Work Area of General Steelmaking Plant of Ansteel, the effect of relevant factors on controlling nitrogen content in BOF, refining and continuous casting processes was studied, and nitrogen control technology of low nitrogen steel had been analyzed. The results indicated that increment of nitrogen mainly occurred during tapping process. By increasing hot metal ratio, controlling slag returning to dry, reducing reblowing times and time and feeding iron ore, the mass fraction of nitrogen could be reduced obviously to less than 12×10-6. Optimization of RH operation could improve the effect of advanced nitrogen removal. Shielded casting practice could control increment of nitrogen within 5×10-6.

试验研究

Experimental study on production of boron microalloying medium carbon steel

2014, 30(1):  34-37,5.  doi:

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Mechanics characteristic and the mechanism of boron microalloying were revealed through the development and research of boron microalloyed medium carbon steel production process in Lianyuan Iron & Steel Co. converter→continuous casting process. The results showed that trace amounts of boron made grain coarsening behavior obviously, significantly reduced the yield strength of steel. It was not necessary to design special mold powder for boron microalloyed medium carbon steel, because boron had little effect on mold powder. The stable yielding rate of boron could be obtained through controlling Δw（N）<10×10-6, using ferromanganese, ferrosilicon to deoxidize, adding ferrotitanium at 3 minutes before calcium treatment, feeding boron line at 1 minutes before the calcium treatment in the process of refining, and the average yield was 78.8 %. First Ⅲ brittleness temperature region of medium carbon steel A36LB was among 700-900 ℃, the emergence of corner crack could be avoided through reducing of slab edge water and total water amount.

Analysis of EAF melting technology with large proportion of direct reduction iron

2014, 30(1):  38-40,4.  doi:

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The technology characteristic of EAF melting with large proportion of direct reduction iron were analyzed in one steelmaking plant in Middle East. And the real production indicated that EAF melting with large proportion of direct reduction iron should adopt large hot heel, continuous charging at top, 100 % direct reduction iron continuous melting, melting with foamed slag, bath stirring, which were benefit for organization and liquid steel quality.

Research and application of new modifying technologyfor sulphur removal on liquid desulphurizing slag in hot metal

2014, 30(1):  41-45.  doi:

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Because the liquid desulphurizing slag was difficult to skim, there was a high resulphurization in BOF during hot metal desulphurization using magnesium. To solve above problems, a new modifying technology of sulphur removal was put forward according improving reaction dynamic conditions between modifiers and liquid slags. The effect and influencing factors of original and new technologies were studied by hydraulic model experiment. The experiment results showed that: comparing with traditional technology, new modifying technology had excellent dynamic condition; the reaction area and the number of reaction modifiers were increased significantly. Furthermore, the industrial practice indicated that: the resulphurization in BOF from liquid desulphurizing slag decreased remarkably after new technology used which ensured the stable production of high valueadded low sulfur steel.

Desulphurization analysis of slag with high basicity and prediction model for sulfur distribution ratio

2014, 30(1):  46-50.  doi:

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To investigate the desulphurizing ability of slag with high basicity and high Mannesmann index for pipeline steel, industrial experiments had been carried out. The results showed that in the situation of a higher refining slag basicity and Mannesmann index than the recommended value, the addition of fluorites made the slag have a better fluidity, lower melting temperature and preferable desulphurizing ability. A comparatively accurate model for forecasting LS of pipeline steel was established by modifying the value calculated by KTH model. The ratio of that absolute error which was range of ±5 % reached 85 %.

Experiment research and thermodynamics analysis on calcium treatment of pipeline steel L360QS

2014, 30(1):  51-54,5.  doi:

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Thermodynamics analysis on calcium treatment process of pipeline steel L360QS was investigated by activity interaction coefficient and Bjorkvall method, and then calcium treatment experiment was also carried out. Thermodynamics analysis result shows that, when aluminum content in liquid steel is 0.045 %, w（Ca） and w（S） in molten steel should be respectively controlled about 0.003 321 % and below 0.002 563 % if we want to generate 12CaO&#8226;7Al2O3 inclusions and avoid CaS inclusions precipitation; calcium treatment experiment result demonstrates that CaS inclusions quantity increase with the increasement of calcium content in liquid steel, which decrease the inclusions containing spinel. In order to modify both oxide and sulphide inlusions completely, w（S） in molten steel should be controlled about 0.002 %, and w（Ca）should in the range of 0.003 5 %～0.004 0 %, as well as the w（T.Ca）/ w（S） should be above 1.9, Industrial trial results showed that the inclusions were modified, which achieve the desired effect completely.

Study on process of RH desulfurization by powder injection

2014, 30(1):  55-58.  doi:

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The principle of desulfurization by powder injection was analyzed in detail in this paper. Increasing the quantity of desulfurizer in liquid steel and prolonging the desulfurizer resistance time in liquid steel were proposed to increase RH desulfurization efficiency. And the work of optimizing RH powder injection lance height and driving gas flow rate in desulfurizing process by commercial tests were carried out. The results show that the optimal RH powder injection lance height was 1.3 m and the best driving gas flow rate in desulfurizing process was 50 m3/h. The optimized RH parameters could meet the requirements of producing and the mass fraction of sulfur in the steel could be controlled to be less than 15&#61645;10-6 steadily.

Research on the surface cleanliness of IF steel slab

2014, 30(1):  59-62.  doi:

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The surface inclusion of IF steel, including head, normal and end slab, was studied by original position analyzer for metal (OPA). The results show that: the distribution of the inclusion content and size in inner arc and outer arc are about the same. The inclusion content order in slabs is head slab > end slab > normal slab, the inclusion content in normal slab is steady. The inclusion content is fluctuated significantly in head and end slabs casted in unsteady state period, which decreases after 5.6 mm of the surface. With the distance from the surface of slab increasing, the average size of inclusion in slabs are smaller and smaller, and the same to the percentage of inclusion bigger than 5 μm.

设计改造

The simulation and transformation design of 250 t converter trunnion ring in No. 3 Steelmaking Plant of WISCO

2014, 30(1):  63-66.  doi:

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The leakage accident of the 250 t converter trunnion ring in No.3 Steelmaking Plant of WISCO was described. The reasons which resulted in the leakage accident were analyzed. A 3-D model of the converter was established to analyze the stress distribution of what by FEM. And finally a transformation design was made. After transformation the leakage accident has been released radically.

Design characteristics and production practices of 100 t EAF

2014, 30(1):  67-70,7.  doi:

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The design concepts and features of 100 t domestic high impedance UHP EAF developed by CERI were introduced. The type of furnace was the conventional AC electric arc furnace with the eccentric bottom tapping style. Ultra high power technology, high impedance, hot metal charging technology, wall multi-cluster lance technology, flue gas waste heat recovery technology and other energy efficient technologies were integrated on the EAF. Production practice showed that the technical indicators of the electric arc furnace were excellent and the cost was the lowest on the condition of 65~75 t hot metal charging.

综 述

Review of control of inclusions in stainless steel

2014, 30(1):  71-78.  doi:

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A review of control of inclusions in stainless steel is made. It is analysed selection of deoxidizer influenced cleanliness of stainless steel. The formation condition of inclusions in Al-killed and Si-killed is pointed out. And the approaches to modify different kinds of inclusions to liquid ones are proposed. Oxide metallurgy in stainless steel gradually attracts more attention. It is hoped that properly controlling inclusions can reduce their harm to steel and improve product capabilities.