When smelting with 18.5% MgO slag the furnace runs smoothly with stablehearth temperature. The desulphurizing power of high-MgO slag is comparativelylower. To raise the total basidity ((CaO+MgO)/(SiO_2)) is required. This thesis aims at analyzing the cause of higher coke consumption. Theore-tical calculation shows, if dolomite is used directly as furnace charge, the totalamount of CO_2 (per ton pig) carried into the furnace is raised by 15%, thuscausing an increase of % direct reduction and consequently an increase of cokeconsumption. Dolomite ought to be used as sinter charge.

A total of more than 150 experimental heats was tested, and the results pointout that in order to improve the properties of side-blown Bessemer steel, thefollowing facts should be considered: 1) Normal temperature mechanical test results of side-blown basic Bessemersteel are higher than the lower limits enumerated for group A, steels in the Stan-dard Specifications of the Ministry of Metallurgy. However, due to the highernitrogen content, averaging about 0.008%, such steel is obviously nonfavorable ascompared with acid Bessemer as well as basic open-hearth steels with respect tosuch properties as strain-aging, blue-brittleness and sub-zero behaviors. The pre-vious usage of chemical specifications of open-hearth steel to side-blown basicbessemer steel is evidently impractical, as the influence of nitrogen content in thelatter is unduly neglected. In the present paper, a suggestion is made for modi-fying the chemical specification of basic Bessemer steel. 2) Nitrogen and non-metallic inclusions noticeably affect the properties of steel.When the depth of blowing is kept unchanged, content of nitrogen and non-metallic inclusion depend, to a large extend, upon the amount of residuel carbonat the end point of blowing. The present paper further suggests that in the future,the practice of blowing to too low a carbon content with subsequent recarburizingin the laddle should be avoided.

Under controlled hot working conditions, the specimens of killed and rimminglow carbon steels having different grain size and microstructure have been prepar-ed and subjected to strain-aging tests. In order to find out the effects of strainingand aging, impact, tensile, compression and hardness tests have been employed. The results show that it is possible to improve the properties of low carbonsteel against straining and aging by controlling the hot working conditions andthat the grain size and microstructure of killed steel may vary within fairly widelimits and yet its impact values after strain-aging may still remain within the re-quired standard; whereas strict control of the grain size and microstructure is ne-cessary in order to produce rimming steel of required impact value after strain-aging. It has been found that the impact and tensile test results show more promi-nently the effects of straining and aging; while the compression and hardness testresults are less consistent and do not yield so clear an information. Straining and aging is the combined effect of cold working and aging. Thecontribution of each of these two factors to the total effect of strain-aging varieswith the microstructure of steel.

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In the past eight years the carbide phases present in various alloy steels havebeen studied by a combination of electrolytic extraction, microchemical analysis,X-ray identification, and electron microscopic examination methods, and themain findings are presented here under the following headings: 1. Carbides of transition metals. 2. Iron carbides precipitated during tempering. 3. The partition of alloying elements between cementite and ferrite. 4. The precipitation of alloy carbides and secondary hardening. 5. Carbides in tungsten-chromium tool steels.