高钢级管线钢变形抗力模型

利用Gleeble-3500热模拟试验机,对两种不同成分的高钢级管线钢进行单道次压缩实验的塑性变形抗力进行研究。分析了变形温度、变形速率、变形程度对变形抗力的影响,建立一种适合X70、X80高钢级管线钢的变形抗力模型。通过多元非线性进行回归分析,证明模型具有良好的曲线拟合特性。模型成功的应用于轧制生产的现场,计算出的轧制力值误差控制在11%以内。     

Method of testing stabilized stainless steels for resistance to intergranular corrosion

Relationships between the effective chromium and carbon contents and the parameter of resistance (k) are discussed in this paper in relation to their applicability to stabilized steels. The efficiency coefficients of stabilization in Ti-stabilized steels of four types, determined according to the completeness of chemical composition, were the basis for indicating the parameters of the resistance of these steels to intergranular corrosion. The comparison with low carbon steels, two of optimized chemical composition, one stabilized with niobium, reveals sufficient resistance to, and guarantee of this resistance to the intergranular corrosion for the 08Cr18Ni10Ti grade. The method of evaluating the resistance to intergranular attack based on calculating the minimum effective chromium content, the maximum effective carbon content and the resistance parameter k that issues therefrom, is suitable for practical application directly during the making of stainless steels.     

双相不锈复合钢板埋弧自动焊

研究了Ｈ１１／Ｘ２ＣｒＮｉＭｏＮ２２．５双相不锈复合钢板埋弧自动焊工艺，焊接材料的选择及其焊接性。结果表明，复层焊缝的δ铁素体含量在３５％～４５％内，其焊接性优良。过渡层的焊接采用较弱焊接规范和单道焊工艺，以控制较小的稀释率和良好的焊缝成形，防止在与基层焊缝的熔合线附近产生大量马氏体组织和其它硬化相。Ｈ１１／Ｘ２ＣｒＮｉＭｏＮ２２．５双相不锈复合钢板埋弧自动焊焊接接头具有良好的力学性能，复层焊缝具有极为优良的抗晶间腐蚀和应力腐蚀的能力。本研究为煤气工程中汽化炉的制造选定了合适的焊接材料并制定了最佳埋弧自动焊工艺。     

Effect of alloying elements on response of nonoriented electrical steels to stamping operations

A suitable alloying design for improving the punchability of nonoriented electrical steels containing 0.1 % Si was investigated. The appropriate addition of sulfur to steels containing relatively high manganese content is very useful in obtaining good punchability without detrimental effects on magnetic properties.     

Chloride-induced stress corrosion cracking of Duplex stainless steels. Models,test methods and experience

Stress corrosion cracking (SCC) induced by chlorides frequently causes problems in applications where standard austenitic stainless steels are being used. Often this problem can be solved by the use of duplex stainless steels. In this report the mechanisms for SCC have been surveyed, and the cause for the high SCC resistance of duplex stainless steels has been discussed and evaluation of test methods for SCC and how duplex stainless steels respond to them, as well as practical experience of duplex stainless steels. The study shows that no single mechanism can be attributed to the good resistance to SCC of duplex stainless steels. Probably a synergistic effect of electrochemical and/or mechanical effects is responsible for the good performance. Test methods for SCC often give relatively good correspondence with real applications, but ranking is often doubtful, and comparisons of different material types should be made with caution. Numerous cases with SCC on standard austenitic stainless steels have been solved by the use of duplex stainless steels.     

Fundamental principles for choosing steels on the basis of results of wear tests

The development of scientific foundations for the creation of new high-strength steels with high wear resistance and their application is a very important problem of modern engineering. The difficulties of its solution are connected with the absence of methodological foundations for a reliable estimation of the wear resistance. The fundamental scientific principles for control over this characteristic with allowance for the structural changes and the corresponding changes in the mechanical properties of steels have not been developed. The place of this characteristic and its relationship with the structure in the theory of fracture of materials under various loads has not been determined yet. At the same time, the wear resistance is a parameter that can characterize the operational reliability of steels under various conditions. However, the methods for determining the wear resistance should be substantiated experimentally and theoretically. The aim of the present work consisted in choosing steels for parts operating under the conditions of composite loads and abrasive wear. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 28–30, February, 1998.     

Feasibility of electro-slag cast steel for hot-working tools

A study on electro-slag cast steel has been performed to assess the feasibility of its use in hot-working tools in place of traditional forged steels. In this study, some important material properties that are essential for the proper performance of hot-working tool steels have been measured. The properties of the electro-slag cast steel are compared with those of hot-working tool steels currently used in industrial practices. The use of electro-slag cast steel in specific applications has been evaluated and compared with the operational performance of currently used steels in industrial environments. The wear resistance, impact toughness, thermal fatigue resistance, and repair weldability of electro-slag cast steel have been determined. The material properties were found to be comparable to existing hot-working tool steels. The number of effective blows obtained from an industrial application test also confirms that electro-slag cast steel is a feasible material for hot-working tools.     

Corrosion behavior of coated steels and Mn‐ and Co‐alloyed steels for separator materials on the cathode side in molten carbonate fuel cells

The corrosion behavior and the electrical resistivity of the oxide scale that forms on alternative materials for bipolar plates in molten carbonate fuel cells (MCFCs) were investigated. Commercial stainless steels (SS) containing cobalt (Haynes 556) and manganese (Nitronic 30, Nitronic 50, and Nitronic 60) were tested under cathodic MCFC conditions Additionally, 316L SS coated with cobalt by thermal spraying was studied. Oxide‐scale resistivity measurements were coupled with observations of microstructural/compositional changes over time. All tested materials formed multilayered oxide scales. The composition of these phases was the key factor in determining the interfacial electrical resistivity. The high cobalt content of Haynes 556 (18 wt%) did not decrease its electrical resistivity or improve its corrosion resistance. Thus, Co‐containing stainless steels, such as Haynes 556, do not appear to be candidate bipolar plate materials for MCFCs. In contrast, the cobalt coating on 316L SS did lead to improved corrosion resistance. The Nitronic alloys formed Mn‐containing oxide scales, which appear to have a beneficial effect on lowering the resistivity of the oxide scale. The corrosion resistance of these Mn‐containing stainless steels was greater than that of 316L SS, the present bipolar plate material.     

A critical study of stress corrosion cracking testing methods for stainless steels in hot chloride media

The selection of a stress corrosion cracking (SCC) test which procures a reliable classification of stainless steels with regard to their SCC resistance in chloride media requires the choice of a suitable electrolyte in which the passive film is similar to those built in industrial conditions and the choice of a reliable mechanical testing mode. The same classification is obtained by the slow strain rate technique (SSRT) and the constant load technique. It appears that SCC mechanisms are little modified in the two testing modes. The effect of some alloying additions (Mo, Ni, Ti, Cu) to austenitic stainless steels and the behaviour of a duplex austeno-ferritic steel has been examined by these two modes.     

Corrosion behaviour and characteristics of reforming chromized coatings on SS 420 steel in the simulated environment of proton exchange membrane fuel cells

Low-temperature pack chromization is utilized in combination with various activating pretreatment methods, including rolling and electrical discharge machining, to improve the performance of SS 420 stainless steels in the simulated environments of proton exchange membrane fuel cells (PEMFCs). The corrosion resistance and hydrophobicity of chromized steels are enhanced with the pretreatments. The rolled and chromized steel possessing a continuous, uniform, and hydrophobic coating exhibits the best corrosion resistance and stability among all tested specimens. Furthermore, the specimen exhibits the smallest interfacial contact resistance at a compaction pressure of 140 N cm⁻², among all tested specimens.     

Langzeit-Korrosionsuntersuchungen an austenitischen Stählen im Hochdruckteil einer Harnstoffanlage

Longterm corrosion field tests with austenitic steels in the high pressure parts of a urea plant In view of the conditions encountered in urea manufacture, in particular in the high pressure section the corrosion resistance is investigated using various austenitic steels immersed in reaction mixtures typical of urea manufacture. The specimens were placed in an operating plant; different test durations (total 13 000 hours) enable the time dependence of the attack to be assessed. The steels tested were CrNi steels with nitrogen and 17.45?19.8% Cr and 10.3-12% Ni, CrNiMo steels, some of them with Ti and Cu addition and 17% Cr and 20 and 13.8% Ni, respectively. According to the results the corrosion resistance increases with the chromium level while ferrite in particular with longer test durations has a pronounced negative effect. A suitable screening test for corrosion resistance under the conditions of urea manufacture is testing in boiling nitric acid.     

The properties of nanocomposite coatings formed on a steel 20H surface by means of electrospark processing using rod-shaped electrodes of steels 65 G and Sv 08

The phase composition, the sizes of the grains (crystallites), the microstructure and microhardness, and the physical and mechanical properties of the nanocomposite coatings on the 20H steel surface resulting from the electrical processing in a gas medium by compact electrodes made of steels 65G and Sv08 with regard to the processing velocity and their influence on the wear resistance of the composition have been investigated.     

Ion exchange resin fibres for potential measurement in crevice corrosion studies

Fibres of cation and anion exchange resins, regenerated in the Na⁺ and Cl⁻ forms respectively, have been used to monitor corrosion potentials during crevice corrosion of stainless steels. The resin fibre probe has a relatively high electrical resistance but has the significant advantage that it can be produced flush with the crevice wall, thus avoiding the entrainment of additional electrolyte.     

Numerical simulation of spot welding for galvanised sheet steels

Abstract

Galvanised sheet steels are now widely used to be the substrate for body in white (BIW) construction in the automotive industry. Weldability of galvanised sheet steels much worsened compared to spot welding of low carbon steels. The present paper develops a 2D axisymmetric model and employs an incremental coupled thermal–electrical–mechanical analysis to predict the nugget development during resistance spot welding (RSW) of galvanised sheet steels. Temperature dependent contact resistance for faying surfaces was determined to take into account of the influence of zinc coat for spot welding galvanised sheet steels. The effect of dynamic contact radii on temperature distribution was studied and compared with results under constant contact area assumption. The predicted nugget shape and size agreed well with the experimental data. Higher current and longer welding time should be applied for galvanised sheet steels compared to low carbon steel spot welding. The proposed model can be applied to predict weld quality and choose optimal welding conditions for spot welding galvanised sheet steels.     

Einfluß der Elemente Phosphor,Mangan, Chrom,Molybdän und Vanadium auf das Verhalten niedriglegierter Stähle bei Spannungsrißkorrosion

Influence of elements such as phosphorus, manganese, chromium, molybdenum and vanadium on the stress corrosion behaviour of low alloy steels A series of such steels having graduated alloy addition contents were obtained experimentally in an electrical furnace and were tested under permanent tensile loads in calcium nitrate solution after different heat treatments and at different relative loads. The heat treatment has a very pronounced bearing on corrosion susceptibility: overheating produces the highest sensitivity annealing at 750°C the — relatively — highest resistance, while normalizing occupies an intermediate position. P has but little effect on corrosion susceptibility so that its influence can practically be neglected. Mn seems to have generally a beneficial effect while Cr — even in amounts up to 2% — is unable to improve corrosion resistance. In the case of V there is some improvement in some cases only while Mo generally produces increased corrosion resistance. In this connection, a new method for evaluating experimental results has been described, which has been developed for the practice of steel assessment. The experimental results confirm, that a steel may be designated ?resistant”? at a certain load when its useful life under tensile load in alkaline media is 240 hrs. Extension of the test duration does not yield an improvement in evaluation accuracy.     

High temperature air oxidation behaviour of “poor man” high manganese-aluminum steels

The behaviour of austenitic high manganese (19.8%–32.5%)aluminum (7.1%–10.2%) steels in high temperature air has been examined. Tests have been carried out in the 600–900°C temperature range for durations up to 200 h. The steels form a high manganese scale at high oxidation rates; aluminum does not contribute to the formation of this scale. Only a 1.5% silicon bearing steel shows a good oxidation resistance up to 700°C, the oxidation rate being lower because as shown by XPS analyses a silicon-containing scale is formed. The oxidation resistance of these steels is always lower than that of conventional grades of austenitic stainless steels.     

Corrosion behaviour of experimental copper–antimony–molybdenum carbon steels in industrial and marine atmospheres and in a sulphuric acid aqueous solution

Low alloyed carbon steels are used in several applications as in automotive, home appliances and civil industries. Sb-bearing steels have been developed to withstand acid condensation, mainly to exhibit corrosion resistance to sulphuric acid aqueous solutions. This work is aimed at studying the corrosion resistance of three experimental low alloyed carbon steels with additions of copper, antimony and molybdenum using the electrochemical impedance spectroscopy (EIS) in a sulphuric acid aqueous solution, and field tests in industrial and marine atmospheres. The field tests showed the mass loss of antimony–molybdenum carbon steels was higher compared to that of other steels. The alloyed carbon steels with copper and antimony additions showed the highest atmospheric corrosion resistance evaluated by using field tests in industrial and marine environments. The molybdenum-bearing steels showed the highest corrosion resistance in a sulphuric acid solution, measured by using the EIS.     

Electrochemical Evaluation of Corrosion on Borided and Non-borided Steels Immersed in 1 M HCl Solution

In this study the corrosion resistances of AISI 1018 and AISI 304 borided and non-borided steels were estimated using polarization resistance and electrochemical impedance spectroscopy (EIS) techniques. Boriding of the steel samples was conducted using the powder-pack method at 1223 K with 6 h of exposure. Structural examinations of the surfaces of the borided steels showed the presence of a Fe₂B layer with isolated FeB teeth on the AISI 1018 steel, whereas a compact layer of FeB/Fe₂B was formed on the AISI 304 steel. Polarization resistance and EIS of the borided and non-borided steels surfaces were performed in a corrosive solution of 1 M HCl. The EIS data were analyzed during 43 days of exposure to the acid solution. Impedance curves obtained during this period for the borided and non-borided steels were modeled using equivalent electrical circuits. The results of both electrochemical techniques indicated that boride layers formed at the steel surfaces effectively protect the samples from the corrosive effects of HCl. The main corrosion processes observed on the boride layers were pitting and crevice corrosion.     

Effects of solution temperature on localized corrosion of high nickel content stainless steels and nickel in chromated LiBr solution

The potentiodynamic technique has been used to study the general and localized corrosion resistance of high-alloyed stainless steels (UNS N02031 and UNS R20033) and nickel (UNS N02205) at different temperatures (from 25 °C to 80 °C) in a heavy brine Lithium Bromide solution.The engineering question of concern is the compatibility of the LiBr fluid with the structural materials of refrigeration systems which use absorption technology. The results of potentiodynamic polarization studies indicate excellent corrosion resistance for stainless steels in LiBr solution at room temperature and no big differences at temperatures above 50 °C. In the temperature range of 25-80 °C, a linear relationship exists between logarithmic of corrosion rate and reciprocal of absolute temperature (Arrhenius plot). The linear plots showed that the mechanism of the corresponding passivation process is the same for the three investigated alloys, essentially due to the presence of nickel. Tests indicated that stainless steels UNS N02031 and UNS R20033 were the most suitable for use to be used in the construction of absorption units for refrigeration purposes.     

The structural state and wear resistance of chromium steels modified with nitrogen ions

The structure and phase composition of several typical chromium steels subjected to ion-beam treatment with intense beams of nitrogen ions have been studied, and the effect of parameters of the structural state of modified layers on their hardness and wear resistance upon friction without lubricant has been examined as well. The content and size of CrN particles in nitrogen-implanted high-chromium steels has been determined. The formation of fields of elastic interphase deformations has been found in the modified layers of high-chromium steels containing CrN particles, and the factor of the volume misfit Δv/v has been estimated. It has been shown that the ion-beam nitriding substantially enhances the wear resistance of the nitrogen-modified layers of high-chromium steels. It has been concluded that CrN particles block plastic shears in the modified layers, retard the processes of localization of deformation in them, and decelerate the kinetics of nucleation and propagation of microcracks upon friction. It has been established that an increase in the volume fraction of CrN particles present in the modified layers of chromium steels is accompanied by a proportional growth of their wear resistance.