Fe2MoO4 as a Precursor Material for Mo Alloying in Steel (Part II): Up‐Scaling Test

The Mo yield when using three different alloying mixtures (MoO₃ +C; MoO₃ +C + FeO_x; and MoO₃+ C + CaO) was tested both in laboratory experiments (16 g and 0.5 kg scale) and industrial trials (3 ton scale). The alloying is based on in‐situ formation of compounds of Mo in the mixtures from molybdenite concentrate with industrial grade Fe₂O₃. Thermogravimetry (TGA) and X‐ray diffraction (XRD) analyses were performed to identify the reduction steps and final products of the alloying mixtures. At least two steps of mass change were discovered during the reduction of all tested mixtures by carbon. The Mo yield for MoO₃ + C mixture is 93% which was confirmed by both laboratory and industrial experiments. The Mo yield for MoO₃ + C + CaO mixture is around 92% during 16 g scale laboratory and 3 ton scale industrial tests. The best results were obtained in the case of the mixture which contained FeO_x, MoO₃ and C, resulting in the Mo yield up to 98% at all the experiment scale levels. It was found that the combination of both lower evaporation and fast reduction by carbon of the mixture along with further dissolution in steel are necessary to provide high Mo yield during steel alloying. The calculated mass balance of 3 ton trial heats showed that only a small part of initial Mo amount (8–13 ppm) has gone into slag.     

Synthesis and Characterization of Fe2MoO4 as a Precursor Material for Mo Alloying in Steel

Iron molybdate (Fe₂MoO₄) has been studied as a new potential precursor for Mo additions in high alloy steel processing. Fe₂MoO₄ was synthesized by high temperature reactions between MoO₃, FeO_x and carbon by holding the mixture first for 23 hours at 873 K and then for 16 hours at 1373 K. The Fe₂MoO₄ syntheses were carried out with pure reagents as well as commercial grade materials supplied by steel industry. A thermodynamic analysis of the stabilities of the various phases in the Fe‐Mo‐O‐C quaternary was carried out. The synthesis processes, leading to the Fe₂MoO₄ formation from the precursors and further reduction by carbon were studied with the aid of thermogravimetric analysis (TGA), high‐temperature X‐ray diffraction (HT‐XRD) and evolved gas analysis by gas chromatography (GC). The maximum temperature in the case of all the experiments was 1373 K. It was found that the reactions between the precursor components start already above 873 K. The precursor mixture from commercial grade materials offers an economically advantageous process route with high Mo yield in steel.     

Silicothermic self-reducing MoO3 briquettes for direct alloying of Mo in molten steel

Abstract

The use of molybdenum trioxide (MoO₃), which is cheap and relatively abundant MoO₃ has been evaluated as a potential alternative to expensive FeMo as a steel alloying method. Pure MoO₃ volatilises very significantly above its melting point (1068 K) and results in a poor alloy yield when added to steel. The volatilisation of MoO₃ in FeSi–MoO₃, MoO₃–CaO and MoO₃–MgO mixtures have been investigated by TG-DTA. Self-reducing experiments of industrial MoO₃ mixed with FeSi, CaO and CaF₂ have been performed in an electric resistance furnace. The results show that the volatilisation of industrial MoO₃ can be effectively inhibited when adding CaO and FeSi and addition of CaF₂ helps form a low melting point slag and results in good separation of metal and slag, The Mo quickly dissolves in the molten steel with 95% recovery.     

Study of High Temperature Deformation and Recrystallization in W9Mo3Cr4V Steel

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Analysis of High Temperature Deformed Structure and Dynamic Precipitation in W9Mo3Cr4V Steel

In recent years,high temperature deformationand recrystallization have been commonly studied incarbon and low alloy steels[1— 6] .Ref. [3]and Ref.[6 ]have investigated the behavior of hightemperature deformation and recrystallization inhigh speed steels. Using TEM and SEM,variousdeformed structures and sub- structures,dynamicrecrystallized nuclei and dynamic precipitation inW9Mo3Cr4 V steel were studied.1　 Experimental Procedure1.1　 Sample preparation　　 The material used is a commer…     

ICP-MS法测定钢铁中痕量镁和钙含量

建立了电感耦合等离子体质谱法测定钢铁中痕量镁和钙元素含量的分析方法。在优化的仪器工作条件下,采用内标法与加入校正法相结合,在补偿基体效应的同时．提高了测定结果的稳定性。该方法加标回收率为90．0％～110．0％,相对标准偏差小于10．0％．该方法准确、快速,满足冶金行业对钢铁中痕量镁和钙元素的测试需要。     

Study on Transformation of CaO-Al₂O₃-SiO₂-MgO System Inclusions in ZG06Cr13Ni4Mo Stainless Steel

This paper aims at generally studying on the inclusions of ZGG06Cr13Ni4Mo ultra-low carbon stainless steel used for large scale hydraulic turbine sets. On the basis of analysis the industrial test samples, thermodynamic software FactSage is used to study inclusions transformation process in CaO-SiO2-Al2O3-MgO system while stainless steel is been smelting. The results illustrate the inclusions melting points and plasticity variation law. The reasonable inclusions plasticity controlling area is found out in low melting point. The melting point is up to 1280℃ While MgO weight concentration is 10% in CaO-SiO2-Al2O3-MgO system, SiO2, Al2O3 and CaO in inclusions are in weight concentration range of 50-70%, 10-20% and 10-40%, respectively. For purpose of gaining low melting point inclusions, silicon alumina radio in deoxidant should be controlled between 2-5 for ultra-low carbon stainless steel refining in industry.     

在电解二氧化锰生产中去除硫酸锰溶液中As、Sb、Mo等离子的方法

用于碱性锌锰干电池正极活性材料的电解二氧化锰，其化学成分中的As、Sb、Mo杂质含量为0.000 0005％(0．5ppm)以下。因此，必须在电解二氧化锰的制备电解液——硫酸锰溶液阶段，去除溶液中的大量有害杂质。对于溶液中的As、Sb、Mo来说，应达到0．00000003％(0.03ppm)左右，方能保证电解电沉积的EMD中，达到0．0000005％(0．5ppm)以下。