N. A. Kozyrev

Some Aspects of Oxidation-Reduction Reactions under Carbon-Bearing Flux Welding

The authors have completed thermodynamic calculations of oxidation-reduction processes under submerged arc welding with application of carbon containing additive. The calculations have shown that carbon, due to its high reducing properties under T = 1950 - 2200 K, introduced into the system can significantly decrease the amount of non-metallic inclusions in the weld metal and so improve its mechanical properties.

New carbon-fluorine additives for welding fluxes

The influence of a carbon-fluorine additive in AN-348, AN-60, and AN-67 oxidative flux on the welding of 09Γ2C steel and in OK Flux 10.71 basic aluminate flux on the welding of 10XCHД steel is studied experimentally. The composition of the additive is as follows: 14.01–22.72% Al, 13–22.04% F, 13.16–21.34% C, 8.27–13.4% Na, 0.09–0.14% K, 0.66–1.09% Ca, 26.11–42.35% SiO2, 1.15–1.86% FeO, 0.07–0.12% MnO, 0.001–0.1% MgO, 1.47–2.38% S, and 0.03–0.05% P. The experiments show that the use of carbon as the reducing agent is optimal in terms of preventing the formation of nonmetallic inclusions in the weld seam, since its gaseous compounds CO and CO2 are easily captured and do not introduce nonmetallic inclusions in the weld seam. With 4–6% carbon-fluorine additive in the fluxes, the total oxygen content in the seam falls. When using the proposed additive, the mechanical properties and the impact strength at negative temperatures are improved on account of the lower content of nonmetallic inclusions (oxides) in the weld seam. The carbon concentration in the weld seam remains the same as in the basic steel.

Technological aspects of using a carbon–fluorine-containing addition in submerged-arc welding

Abstract The technological aspects of adding carbon–fluorine-containing additions to AN-348, AN-60 and AN-67 fluxes in welding 09G2S steel are investigated. It is shown that the addition decreases the total oxygen content of the welded joint, lowers the degree of contamination with oxide non-metallic inclusions and the level of gas saturation of the weld metal, and increases the mechanical properties and impact toughness of the welded joints. The carbon concentration of the welded joint remains similar to that of the parent metal.

Carbon-containing additions for welding fluxes

Abstract The reduction properties of carbon with other elements – reduction agents in a liquid metal – oxide melts – gas system and the thermodynamic mobility of reactions – are evaluated. It is shown that the carbon added to the composition has high reduction properties at T = 1950–2200 K and exerts a strong effect on the oxygen content of the system. The results of calculations of the thermodynamic characteristics of the reactions of removal of hydrogen in interaction with metal fluorides are presented. It is shown that the application of the compound Na3AlF6 is more efficient in comparison with fluorite for the removal of oxygen in submerged-arc welding. The technological aspects of the addition of the carbon–fluorine-containing addition to the AN-348, AN-60 and AN-67 fluxes in welding 09G2S steel are examined. It is shown that when using this addition, the total oxygen content of the welded joint decreases, the degree of contamination with oxide non-metallic inclusions is smaller and the level of gas saturation of the weld metal also decreases, the required mechanical properties and impact toughness of the welded joint are higher and the carbon concentration of the welded joints remains on the level of the parent metal.

Production of Welding Fluxes Using Waste Slag Formed in Silicomanganese Smelting

The possibility in principle of using slag, which is formed in the silicon-manganese smelting process, in producing welding fluxes is shown. The composition of and technology used for a new fused flux has been designed. A comparative evaluation of the new flux and the widely used AN-348 type flux was done. It has been proved that the new flux has high strength properties.

Influence of Filler Metals in Welding Wires on the Phase and Chemical Composition of Weld Metal

The influence of filler metals used in welding wires on the phase and chemical composition of the metal, which is surfaced to mining equipment exposed to abrasive wear, has been investigated. Under a laboratory environment, samples of Mo-V-B and Cr-Mn-Mo-V wires were made. The performed experiments have revealed that fillers of the Cr-Mn-Mo-V system used in powder wire show better wear resistance of the weld metal than that of the Mn-Mo-V-B system; the absence of boron, which promotes grain refinement in the Mn-Mo-V-B system, significantly reduces wear resistance; the Mn-Mo-V-B weld metal has a finer structure than the Cr-Mn-Mo-V weld metal.

New production technology for rail steel

In rail production from electrosteel without vac uum treatment at OAO Novokuznetskii Metallur gicheskii Kombinat, various measures to limit the access of hydrogen to the metal were developed, and possible sources of hydrogen were studied [1]. The increase in hydrogen content during treatment in the ladle–furnace unit is found to depend on the quantity of coke powder (coke dust from the dry slaking sys tem) added to correct the carbon content and hence on the carbon content in the steel prior to discharge from the furnace and in the first ladle sample at the ladle–furnace unit (Fig. 1). The character of the dependence is explained by the mass content of car bon in the first ladle test of the metal at the ladle–fur nace unit.

Quality comparison of OAO NKMK and imported rails

Italy (K) 0.78 1.04 0.46 0.023 0.009 0.003 0.090 0.004 0.009 0.97 0.090 0.04 0.0016 0.0036 Russia (G) 0.71 0.83 0.36 0.011 0.006 0.005 0.060 – – 0.79 0.080 0.16 – 0.0120 Russia (S) 0.80 0.79 0.43 0.011 0.006 0.005 0.060 – – 0.56 0.080 0.12 0.0016 0.0130 Russia (F) 0.77 0.89 0.31 0.015 0.007 0.003 0.070 – – 0.10 0.070 0.14 0.0020 0.0120 United States (S) 0.83 0.98 0.26 0.009 0.009 0.002 0.002 0.0014 0.019 0.23 0.080 0.27 – 0.0087 Japan (E) 0.91 0.93 0.29 0.012 0.007 0.002 0.002 0.0010 0.003 0.21 0.010 0.02 0.0009 0.0033 Russia (A) 0.92 0.96 0.32 0.012 0.009 0.003 0.080 – – 0.07 0.060 0.11 0.0028 0.0140 Japan (I) 0.99 0.73 0.53 0.012 0.006 0.002 0.002 0.0010 0.004 0.21 0.010 0.01 0.0020 0.0031 United States (P) 0.96 1.03 0.38 0.011 0.003 0.005 0.003 0.0220 – 0.23 0.090 0.31 – 0.0118 Japan (L) 0.75 0.82 0.67 0.011 0.006 0.002 0.002 0.0010 0.004 0.51 0.010 0.01 0.0007 0.0040 United States (M) 0.83 1.07 0.30 0.016 0.007 0.003 0.003 0.0150 0.020 0.26 0.081 0.28 – 0.0109 Russia (N)** 0.79 0.89 0.32 0.015 0.011 0.035 0.069 – – 0.08 0.070 0.13 0.0020 0.0130 Russia (T)*** 0.75 0.88 0.31 0.015 0.011 0.032 0.041 – – 0.08 0.070 0.13 0.0022 0.0100 Russia (E)*** 0.76 0.88 0.30 0.014 0.010 0.028 0.068 – – 0.08 0.070 0.13 0.0020 0.0120

Quality of the Seam in Welding under Flux by Means of Barium–Strontium Carbonatite

The use of barium–strontium carbonatite in the modification and refining of ferrocarbon alloys is considered. Its use in welding fluxes is proposed. That possibility is analyzed for the example of BSK-2 barium–strontium modifier (Technical Specifications TU 1717-001-75073896–2005) produced by OOO NPK Metalltekhnoprom, with the following composition: 13.0–19.0% BaO, 3.5–7.5% SrO, 17.5–25.5% CaO, 19.8–29.8% SiO2, 0.7–1.1% MgO, 2.5–3.5% K2O, 1.0–2.0% Na2O, 1.5–6.5% Fe2O3, 0–0.4% MnO, 1.9–3.9% Al2O3, 0.7–1.1% TiO2, and 16.0–20.0% CO2. A production technology is proposed for a flux additive containing 70% barium–strontium carbonatite and 30% liquid glass. Several welding-flux compositions based on slag from silicomanganese production are tested. The flux additive is introduced in quantities of 1, 3, and 5%. The specifics of welding under the proposed welding fluxes are determined. The chemical composition of the fluxes, the slag crusts, and the metal in the weld seam are determined by X-ray spectral analysis. The weld seams are studied metallographically. It is possible in principle to use barium–strontium carbonatite as a refining additive to welding fluxes; it also provides a protective atmosphere for the welded metal. By introducing barium–strontium carbonatite, the content of nonmetallic inclusions (nondeforming silicates, point oxides, and brittle silicates) in the weld seam may be reduced, and the desulfurizing properties of the welding fluxes may be enhanced. The introduction of up to 5% barium–strontium carbonatite in welding fluxes based on silicomanganese slag ensures that the metal in the weld seam has ferrite–pearlite structure of Widmanstatten type. The grain size is slightly reduced here: from a score of 4 to 4–5.

Thermodynamic Assessment of the Reduction of WO 3 by Carbon and Silicon

An interesting process in terms of resource conservation is the arc surfacing of worn components by means of powder wire in which the filler contains tungsten oxide WO3 and a reducing agent (carbon and silicon). Thermodynamic assessment of the probability of 21 reactions in standard conditions is based on tabular data for the reagents in the range 1500–3500 K. This range includes the temperatures at the periphery of the arc and in the upper layers of the surfacing bath. The reactions assessed include direct reduction of WO3 by carbon and silicon, indirect reduction of WO3 by carbon, and reaction of tungsten compounds with carbon and silicon to form tungsten carbides and silicides. The possible reaction products considered are W, WC, W2C, WSi2, W5Si3, CO, CO2, SiO, and SiO2. The reduction of the oxide is written for 1 mole of O2, while the reactions of tungsten compounds with carbon and silicon compounds are written for 2/3 mole of tungsten W. The probability of the reactions is estimated in terms of the standard Gibbs energy. In the range 1500–3500 K, the standard states of the reagents are assumed to be as follows: W(so); WO3(so, li), with phase transition at 1745 K; WC(so); W2C(so); C(so); CO(g); CO2(g); WSi2(so, li), with phase transition at 2433 K; W5Si3(so, li), with phase transition at 2623 K; Si(so,li), with phase transition at 1690 K; SiO(g) and SiO2(so, li), with phase transition at 1996 K. To assess the influence of the possible evaporation of tungsten oxide WO3 in the arc (Tb = 1943 K) on the thermodynamic properties, the thermodynamic characteristics of two reactions are considered; the standard state in this temperature range is assumed to be WO3(g). Thermodynamic analysis of the reduction of tungsten oxide WO3 shows that the temperature of the melt and the composition of the powder wire may affect the composition and properties of the layer applied. At high melt temperatures (>2500 K), the formation of tungsten and also tungsten carbides and silicides is likely. These reactions significantly change the composition of the gas phase, but not that of the slag phase in the surfacing bath. Below 1500 K, the most likely processes are the formation of tungsten silicides and tungsten on account of the reduction of WO3 by silicon. In that case, the slag phase becomes more acidic on account of the silicon dioxide SiO2 formed. However, this temperature range is below the melting point of WO3 (1745 K). In the range 1500–2500, numerous competing reduction processes result in the formation of tungsten and also tungsten carbides and silicides in the melt. The reaction of tungsten compounds with carbon and silicon to form carbides and silicides is less likely than reduction processes. Evaporation of tungsten oxide WO3 in the arc increases the thermodynamic probability of reduction; this effect is greatest at low temperatures.