Thermodynamics of carbon in liquid manganese and ferromanganese alloys

The thermodynamics of carbon in manganese and ferromanganese melts were studied to predict the refining limit of carbon during the decarburization of molten ferromanganese. The equilibrium carbon content in a Mn-C melt was determined by the C-CO equilibrium in the presence of pure solid MnO at 1673 to 1773 K. The activities of manganese and carbon in the Mn-C melt were then calculated from the experimental results, the equilibrium constant for the reaction, and the Gibbs-Duhem equation integrated by the Belton-Fruehan treatment. The standard free-energy change of carbon dissolution in the manganese melt was determined to be 41,700 — 59.6 T J/g · atom, with the standard state taken as 1 wt pct carbon in solution. The effect of iron on the activity coefficient of carbon in ferromanganese was determined by measuring the carbon solubility in Mn-Fe melts. The first- and second-order interaction parameters between carbon and iron in ferromanganese melts were determined. The activity coefficient of carbon in the ferromanganese alloy melt can be expressed as

Nitrogen solubility in liquid Fe-V and Fe-Cr-Ni-V alloys

Nitrogen solubility in liquid Fe, Fe-V, Fe-Cr-V, Fe-Ni-V and Fe-18 pct Cr-8 pet Ni-V alloys has been measured using the Sieverts’ method for vanadium contents up to 15 wt pct and over the temperature range from 1775 to 2040 K. Nitrogen solution obeyed Sieverts’ law for all alloys investigated. Nitride formation was observed in Fe-13 pet V, Fe-15 pet V and Fe-18 pet Cr-8 pet Ni-10 pet V alloys at lower temperatures. The nitrogen solubility increases with increasing vanadium content and for a given composition decreases with increasing temperature. In Fe-V alloys, the nitrogen solubility at 1 atm N₂ pressure is 0.72 wt pet at 1863 K and 15 pct V. The heat and entropy of solution of nitrogen in Fe-V alloys were determined as functions of vanadium content. The first and second order interaction parameters were determined as functions of temperature as: $$e_N^V = \frac{{ - 463.6}}{T} + 0.148 and e_N^{VV} = \frac{{17.72}}{T} - 0.0069$$ The effects of alloying elements on the activity coefficient of nitrogen were measured in Fe-5 pet and 10 pet Cr-V, Fe-5 pet and 10 pet Ni-V and Fe-18 pet Cr-8 pct Ni-V alloys. In Fe-18 pet Cr-8 pet Ni-10 pet V, the nitrogen solubility at 1 atm N₂ pressure is 0.97 wt pet at 1873 K. The second order cross interaction parameters, e _N ^Cr,V and e _N ^Ni,V , were determined at 1873 K as 0.00129 and ? 0.00038 respectively.     

Nitrogen solubility in complex liquid Fe−Cr−Ni alloys

Measurements of nitrogen solubility were performed in a series of liquid iron-chromium-nickel alloys near the composition of the commercial superalloy INCOLOY^* 800 (I:21 pct Cr, 33 pct Ni, bal. Fe). This work was carried out at 1450 to 1600°C and up to one atmosphere of nitrogen gas pressure. Sieverts' law was obeyed by nitrogen in all the alloys. Changes were observed in the compositions of all the melts studied, mainly due to the chromium loss by volatilization. These changes necessitated nitrogen solubility measurements in a series of alloys immediately surrounding alloy I. The experimental results have been prepared as a regression polynomial equation for the logarithm of nitrogen solubility as a function of temperature and reported weight percentages of chromium and nickel in the alloys. The standard Gibbs free energy of nitrogen solution in a region around alloy I is given as ΓG ^o=−58,700+48.20T Joules/g atom N. At 1600°C, the temperature coefficient of nitrogen solubility in I is −2.65×10⁻⁴ pct N/K. The shape of a portion, of the nitrogen solubility surface for the Fe−Cr−Ni system near to alloy I at 1600°C is defined.     

Nitrogen solubility in liquid Fe-Ta,Fe-Cr-Ta,Fe-Ni-Ta,and Fe-Cr-Ni-Ta alloys

The nitrogen solubility in liquid Fe-Ta, Fe-Cr-Ta, Fe-Ni-Ta, and Fe-18 pet Cr-8 pet Ni-Ta alloys was measured using the Sieverts’ method. The experiments covered the temperature range from 1782 to 2031 K, and tantalum contents from 2.0 to 20.0 wt pct Ta. Nitrogen solution obeyed Sieverts’ law and no nitride precipitation was observed in this concentration range. Tantalum increases the nitrogen solubility and the heat of solution of nitrogen is more negative at higher tantalum contents in these alloys. The excess enthalpy and entropy of solution of nitrogen were determined. The first and second order interaction parameters between nitrogen and tantalum were determined as a function of temperature, e _N ^Ta = -101.7/T + 0.018 and e _N ^TaTa = -3.27/T + 0.0022. The effects of alloying elements on the activity coefficient of nitrogen were measured and the second order cross-interaction parameters between nitrogen and Ta with Cr and Ni were determined at 1873 K as e _N ^CrTa = 0.00052 and e _N ^NiTa = 0.00045.     

Nitrogen solubility and aluminum nitride precipitation in liquid iron alloys containing nickel and aluminum

The solubility of nitrogen in liquid iron-base Fe-Ni-Al alloys has been measured up to the solubility limit for formation of aluminum nitride using the Sieverts’ method. Measurements were conducted over the temperature range from 1843 to 2023 K and aluminum concentration range from 1.5 to 3.0 wt pct Al. The effect of nickel additions was determined at 2, 5 and 10 wt pct Ni. The cross interaction parameter describing the effect of nickel and aluminum on the activity coefficient of nitrogen in iron was determined. The first and second order effects of nickel on the activity coefficient of aluminum also were determined. The solubility product of aluminum nitride increases with increasing aluminum content and increasing temperature. Addition of nickel decreases the solubility products of aluminum nitride in lower aluminum content alloys. However, the effect of the cross interaction terme _Al ^NiAl becomes significant with increasing aluminum content and compensates for the effects of the first and second order nickel-nitrogen and nickelaluminum interaction terms. Therefore the effect of nickel additions show little effect on the solubility products of aluminum nitride in higher aluminum alloys.     

The solubility of nitrogen in liquid manganese

The solubility of nitrogen in liquid manganese, in equilibrium with gas containing vary-ing amounts of nitrogen, has been determined at 1300, 1400, and 1500‡C. At one atm pressure of nitrogen, the solubility is 2.6 wt pct at 1300‡C and decreases to 1.7 wt pct at 1500‡C Dissolution of nitrogen in manganese does not follow Sievert's law. The activity coefficient of nitrogen in manganese increases with increasing nitrogen concentration. At one atm nitrogen pressure, the value of the activity coefficient, relative to the in-finitely dilute solution, is 1.55 between 1300 and 1500‡C.     

The solubility of nitrogen in liquid manganese

The solubility of nitrogen in liquid manganese, in equilibrium with gas containing varying amounts of nitrogen, has been determined at 1300, 1400, and 1500°C. At one atm pressure of nitrogen, the solubility is 2.6 wt pct at 1300°C and decreases to 1.7 wt pct at 1500°C. Dissolution of nitrogen in manganese does not follow Sievert’s law. The activity coefficient of nitrogen in manganese increases with increasing nitrogen concentration. At one atm nitrogen pressure, the value of the activity coefficient, relative to the infinitely dilute solution, is 1.55 between 1300 and 1500°C.     

Nitrogen solubility and nitride formation in austenitic Fe-Ti alloys

The equilibrium nitrogen solubility and nitride formation in austenitic Fe and Fe-Ti alloys were measured in the temperature range from 1273 to 1563 K. Specimens 0.5 mm thick were equilibrated with four different nitrogen-argon gas mixtures containing 1 pct hydrogen. The nitrogen solubility in austenitic iron obeys Sieverts' law. The equilibrium nitrogen content was determined to be log (wt pct N)_γ-Fe, P_{N2=1 atm} = (539 ± 17)/T − (2.00 ± 0.01). The precipitated titanium nitride was identified as cubic TiN, and the solubility product was determined to be log(wt pct Ti) (wt pct N) = −14,400/T + 4.94.     

Nitrogen solubility and aluminum nitride precipitation in liquid iron,Fe-Cr,Fe-Cr-Ni,and Fe-Cr-Ni-Mo alloys

The nitrogen solubility and aluminum nitride formation in liquid Fe-Al, Fe-Cr-Al, Fe-18 pct Cr-8 pct Ni-Al and Fe-18 pct Cr-8 pct Ni-Mo-Al alloys were measured by the Sieverts' method. The temperature range extended from 1823 to 2073 K, and the aluminum contents from 1.01 to 3.85 wt pct Al. Increasing aluminum content increases the nitrogen solubility. The effect of molybdenum additions was determined for 2, 4 and 8 wt pct Mo levels. The first and second order effects of chromium, nickel, molybdenum and aluminum on the activity coefficient of nitrogen in iron were determined. The first and second order effects of chromium, nickel and molybdenum on the activity coefficient of aluminum also were determined. The nitride precipitates were identified as stoichiometric aluminum nitride, AIN, by X-ray diffraction analysis. The lattice spacing was in good agreement with the ASTM standard patterns for AIN in both higher and lower Al content solutions. The solubility product of AIN increases with increasing aluminum concentration and with temperature in liquid iron and the iron alloys studied. However, the magnitudes of the solubility products of AIN in those alloys are different because of the effects of chromium and nickel additions. Additions of molybdenum show little effect on the solubility product of AIN. The standard free energy of formation of AIN in liquid iron is: δG? = -245,990 + 107.59 \T J/g-molAIN, based on the standard state of the infinitely dilute solution in liquid iron for aluminum and nitrogen, referred to a hypothetical one wt pct solution, and on the pure compound for A1N.     

Nitrogen solubility and aluminum nitride precipitation in liquid iron, Fe-Cr, Fe-Cr-Ni, and Fe-Cr-Ni-Mo alloys

The nitrogen solubility and aluminum nitride formation in liquid Fe-Al, Fe-Cr-Al, Fe-18 pct Cr-8 pct Ni-Al and Fe-18 pct Cr-8 pct Ni-Mo-Al alloys were measured by the Sieverts' method. The temperature range extended from 1823 to 2073 K, and the aluminum contents from 1.01 to 3.85 wt pct Al. Increasing aluminum content increases the nitrogen solubility. The effect of molybdenum additions was determined for 2, 4 and 8 wt pct Mo levels. The first and second order effects of chromium, nickel, molybdenum and aluminum on the activity coefficient of nitrogen in iron were determined. The first and second order effects of chromium, nickel and molybdenum on the activity coefficient of aluminum also were determined. The nitride precipitates were identified as stoichiometric aluminum nitride, AIN, by X-ray diffraction analysis. The lattice spacing was in good agreement with the ASTM standard patterns for AIN in both higher and lower Al content solutions. The solubility product of AIN increases with increasing aluminum concentration and with temperature in liquid iron and the iron alloys studied. However, the magnitudes of the solubility products of AIN in those alloys are different because of the effects of chromium and nickel additions. Additions of molybdenum show little effect on the solubility product of AIN. The standard free energy of formation of AIN in liquid iron is: δG‡ = -245,990 + 107.59 \T J/g-molAIN, based on the standard state of the infinitely dilute solution in liquid iron for aluminum and nitrogen, referred to a hypothetical one wt pct solution, and on the pure compound for A1N.     

锰铁中锰和磷的分步测定

锰铁中锰和磷的含量是锰铁分级的主要指标,以往锰铁中锰和磷的含量测定,需要分别采用三价锰滴定法和钼蓝分光光度法,测定过程繁琐,冗长。实验采用一次取样,硝酸-氢氟酸-高氯酸溶解试样,加入过氧化氢将二氧化锰还原为锰(II)的方式制备母液,分别用EDTA滴定法测定锰铁中锰含量,磷铋钼蓝分光光度法测定锰铁中磷含量,建立了对锰铁中锰和磷的分步测定方法。对测定锰的条件进行了优化,结果表明,通过加入三乙醇胺-酒石酸钾钠溶液可掩蔽试液中的铁、铜、铝、钛;采用锰铁标准物质进行试验,结果表明,以甲基百里香酚蓝为指示剂时,测定结果和认定值相吻合,且终点变色是从蓝色变为浅红色,更易观察;加入30mL无水乙醇、25mL 80℃左右的热水可解决指示剂僵化的问题。对磷含量测定中砷和残余硅的干扰消除方法进行了探讨,结果表明,砷的干扰可以通过加入硫代硫酸钠-亚硫酸钠溶液消除,残余硅的干扰可以通过加入酒石酸钾钠溶液消除。按照实验方法测定锰铁试样中锰和磷,锰测定结果的相对标准偏差(n=8)小于0.30%,磷测定结果的相对标准偏差(n=8)小于4.0%。方法应用于锰铁标准物质中锰和磷的测定,锰测定结果的相对误差绝对值小于0.25%,磷测定结果的相对误差绝对值小于4.0%。     

The solubility of the liquid oxysulfide phase in liquid Fe-O-S alloys

The solubility of the liquid oxide phase in liquid Fe-O alloys has been measured for the temperature range of 1378 to 1740 °C. Also the solubility of the liquid oxysulfide phase in liquid Fe-O-S alloys has been determined for the composition range of 0.08 to 0.30 wt pct oxygen and 0 to 0.5 wt pct sulfur. The oxygen content of liquid iron saturated with the liquid oxide phase is log O = ?6358/T + 2.76. The standard free energy for the formation of the oxide phase is: xFe(l) + O(pct) = Fe_xO(l); ΔG° = 242.4 ? 0.0829T + 166,990/T(kJ). The equation for the standard free energy in the temperature range of 1550 to 1650 °C may be written as: ?117.5 + 0.0496T (kJ). The effect of composition on temperature of saturation of liquid Fe-O-S alloys with the oxysulfide phase is:T(K) = ?6358/(log pct O ? 2.76) - (pct S)x [554 + 135.0(log O ? 2.77)]. The relationship applies for the composition range of 0.15 to 0.30 wt pct oxygen and 0.0 to 0.5 wt pct sulfur and temperatures from 1480 to 1680 °C.     

The solubility of hydrogen in liquid binary Al-Li alloys

The solubility of hydrogen in liquid binary aluminum alloys with 1, 2, and 3 wt pct lithium has been determined for the temperature range of 913 to 1073 K and pressure 5.3 × 10⁴ to 10.7 × 10⁴ Pa, using an appropriate version of Sieverts’ method. The results fit the Van’t Hoff isobar and Sieverts’ isotherm and the solubility,S, is given by: Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2113/T/k + 2.568 Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2797/T/k + 3.329 Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2889/T/k + 3.508 whereS° is a standard value of solubility equal to 1 cm³ of diatomic hydrogen measured at 273 K and 101,325 Pa per 100 g of metal, andP° is a standard pressure equal to 101,325 Pa. Added lithium progressively increases the solubility of hydrogen in liquid aluminum, due more to its effect on the entropy of solution of hydrogen, through its influence on the liquid metal structure than to an increase in the solute hydrogen atom binding enthalpy.     

The solubility of hydrogen in liquid binary Al-Li alloys

The solubility of hydrogen in liquid binary aluminum alloys with 1, 2, and 3 wt pct lithium has been determined for the temperature range of 913 to 1073 K and pressure 5.3 × 10⁴ to 10.7 × 10⁴ Pa, using an appropriate version of Sieverts’ method. The results fit the Van’t Hoff isobar and Sieverts’ isotherm and the solubility,S, is given by: Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2113/T/k + 2.568 Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2797/T/k + 3.329 Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2889/T/k + 3.508 whereS° is a standard value of solubility equal to 1 cm³ of diatomic hydrogen measured at 273 K and 101,325 Pa per 100 g of metal, andP° is a standard pressure equal to 101,325 Pa. Added lithium progressively increases the solubility of hydrogen in liquid aluminum, due more to its effect on the entropy of solution of hydrogen, through its influence on the liquid metal structure than to an increase in the solute hydrogen atom binding enthalpy.     

Experimental studies on hydrogen solubility in liquid ternary iron-nickel-chromium alloys

The hydrogen solubilities in liquid ternary iron-nickel-chromium alloys have been experimentally determined by Sieverts’ method. The experimental data have been evaluated with the help of regression analysis (Gauß-Jordan) and using own published empirical equations (polynomials). With the help of experimentally determined hydrogen solubilities and the coefficients of the polynomials, the concentration dependencies of hydrogen solubilities, interaction coefficients, enthalpies and entropies of hydrogen solution have been determined. The hydrogen solubility increases with increasing temperature and with an increase in the nickel and chromium concentration. The results have been represented as isothermal planes. The hydrogen solubilities in liquid ternary iron-nickel-chromium alloys (x_Cr ≤ 50%) have been predicted with the help of “Central Atoms” model, assuming the concentration dependencies of the “model parameter λ” and selecting the value of the coordination number (Z’ = 10) for each of the “reference elements” iron or nickel. The comparison between the experimentally determined and the predicted hydrogen solubilities in iron-nickel-chromium alloys confirms that the prediction of hydrogen solubilities in liquid system iron-nickel-chromium can be qualitatively made over a wide range of alloy concentrations (x_Cr = 50%) with the aid of “Central Atoms” model and with the assumption of concentration dependencies of the “model parameter λ”.     

氢醌滴定法测定锰铁中锰

试验并确定了氢醌滴定法测定锰铁中锰的实验条件。试样经酸溶解后,在磷酸介质中和加热条件下,用高氯酸作氧化剂, N 苯代邻氨基苯甲酸溶液作指示剂,氢醌标准溶液滴定试样中锰。用该方法对锰铁标准物质及实际试样中锰含量进行测定,结果表明：本法的测定结果与认定值或国标方法(GB/T56981-2008)的测定结果相符,测定结果的相对标准偏差小于03%（n=6）,方法也可用于锰矿石中锰含量的测定。     

Solubility of nitrogen in liquid Fe-Cr-Ni alloys containing manganese and molybdenum

The nitrogen solubility in liquid Fe-Cr-Ni alloys containing Mo or Mn was determined by the Sieverts’ method. The first and second order mutual interactions among nitrogen, chromium, nickel, molybdenum, and manganese in iron were determined as a function of temperature. The heat and entropy of solution in these alloys were correlated as functions of the logarithm of the activity coefficient of nitrogen at 1873 K independent of the composition of the alloys. An equation was derived to predict the nitrogen solubility in liquid multicomponent iron alloys for the range from logJn, 1873K = 0 to −1.4 as, log(wt pct N)_T = (-247/T-1.22)-(4780/T-1.51) (logf N, 1873K)- (1760/T-0.91) (logfN,1873K)².     

Solubility of nitrogen in liquid Fe-Cr-Ni alloys containing manganese and molybdenum

The nitrogen solubility in liquid Fe-Cr-Ni alloys containing Mo or Mn was determined by the Sieverts’ method. The first and second order mutual interactions among nitrogen, chromium, nickel, molybdenum, and manganese in iron were determined as a function of temperature. The heat and entropy of solution in these alloys were correlated as functions of the logarithm of the activity coefficient of nitrogen at {dy1873} K independent of the composition of the alloys. An equation was derived to predict the nitrogen solubility in liquid multicomponent iron alloys for the range from logf_N, 1873K = 0 to -1.4 as, log (wt pct N)_T = (-247/T - 1.22) - (4780JT - 1.51) (logf_n, 1873K)-(1760/T -0.91) (logf_N,{dy1873}K )².