高耐候结构用Q355GNH钢的开发与性能研究

通过对高耐候钢产品的性能要求分析,本试验钢在成分设计上以Cu、P为基,添加少量Cr、Ni,并制定相应的轧制及卷取工艺而成功开发了355强度级别的高耐候结构用钢.对该试验钢的各项性能进行检测,同时根据其成分设计进行了耐腐蚀性能预测,并利用实验室加速腐蚀试验方法对Q355GNH试验钢及Q345B对比钢的腐蚀速率以及其锈层构...     

Corrosion-resistant coating for GTE compressor parts made of steels with low tempering temperatures

The corrosion resistance of an Ni–Co–Cr–Al–Si–Y + SPh (SPh is silicophosphate impregnation) alloy coating on 30Kh13, 38Kh2MYuA, VKS5, and VKS7 structural steels with low tempering temperatures has been studied. The steel–coating compositions have been tested to determine the accelerated cyclic corrosion resistance, the corrosion resistance under tropic climate chamber conditions and in salt fog, the stress corrosion resistance, and the corrosion resistance in an industrial atmosphere. The heat stability of coated samples is studied, metallographic studies of the samples before and after the tests are performed, and the influence of the coating on the strength characteristics of the structural steels is studied.     

Development and application of nitrogen-alloyed austenitic stainless steels in Baosteel

In recent years,nitrogen-alloyed stainless steels have been a research hotspot in the field of stainless steel product and technology. Nitrogen-alloyed austenitic stainless steels developed by Baosteel and their applications are introduced. These steels are nitrogen-controlled products 304 N and 316 LN,nitrogen containing economical products BN series and high-nitrogen stainless steel( HNS) series. The results show that the presence of nitrogen can significantly improve the strength and corrosion resistance of steel produced. By nitrogen alloying,economical austenitic stainless steels w ith considerably less nickel than 304 can be obtained; the corrosion resistances of these steels are almost the same as 304. Furthermore,by a scientific approach of nitrogen alloying,high-nitrogen steel of0. 8% nitrogen content is fabricated under the non-pressurized conditions,and the pitting potential of this steel is 1. 0 V. At present,nitrogen-alloyed steels developed by Baosteel are w idely utilized in the manufacture of cryogenic storage containers,transportation containers,and many household w ares.     

Direct Resistance Heating of steel bars

Testing the Direct Resistance Heating (DRH) of steels as a new technique for use in industrial furnaces. Study of the behaviour of steel bars heated by this technique under different conditions and of their properties and corrosion characteristics.     

Fatigue crack propagation in weathering weldable steel KT 315 Si

Complex loading conditions are typical for structural materials, especially for steels. Fatigue crack propagation measurements during bend loading were carried out with different load ratios on a newly developed weathering steel KT 315 Si. This steel indicates an improved corrosion resistance in comparison with the weathering steel KT 315. Scanning electron microscopy of the fracture surfaces and quantitative microstructure analysis by means of light microscopy were applied to elucidate relations between microstructure and mechanical properties. An important result of the investigation is that the steel KT 315 Si reveals a lowered mean stress sensitivity of the fatigue threshold value ΔK_th in comparison with that of other ferritic-pearlitic steels of the same strength level.     

Study on the Corrosion Resistance of Multiphase TRIP Steels

Multiphase TRIP (Transformation Induced Plasticity) steels are known to combine higher strength with higher ductility.In this paper,the corrosion resistance of this steel has been has been investigated by accelerated corrosion tests,such as wet/dry cyclic corrosion and the weight loss in laboratory.The morphologies of their rust layers were observed by using scanning electron microscopy,and the corrosion performance of these steels was discussed by analyzing the protective mechanism.The results show that the corrosion rate of steel A is significantly greater than that of steels B and C in wet/dry cyclic corrosion and weight loss tests.The corrosion performance of conventional C-Mn-Si TRIP steel is deteriorated in both NaHSO 3 and 3.5 wt.% NaCl aqueous solutions.And superior corrosion performance is exhibited for TRIP steel with low alloying contents due to its high thermodynamic stability.The enhancement of corrosion performance of TRIP steel is attributed to the additions of alloying elements,such as Al,Cu,Cr,Mo,Ni,etc.The alloying elements increase the compactness of rust layers,so electrochemical characteristic of TRIP steel is improved.     

Effect of Carbon Content on Mechanical Properties and Weather Resistance of High Performance Bridge Steels

The influence of carbon content on the mechanical properties of high yield strength bridge steel has been in-vestigated. The results show that the excellent mechanical properties and corrosion resistance are obtained for the steel with carbon content of 0.03%-0.05% (mass percent). According to the results, a new weathering bridge steel plate with carbon content of 0.045% (mass percent)has been developed. The appropriate controlled cooling process should be taken due to the results of CCT (continuous cooling transformation)and TTT (time-temperature-transformation)to ensure both microstructure and mechanical properties. CCT curve of the newly developed steel shows that when accelerated cooling speed is higher than 5℃/s, the intermediate transformation products can be formed. The TTT curve displays that the intermediate transformation temperature ranges from 600 to 530℃. Yield strength of the newly developed steels reaches 500 MPa, and their elongation and toughness are excellent.     

Quench and Partitioning Steel: A New AHSS Concept for Automotive Anti‐Intrusion Applications

A new type of high strength, high toughness, martensitic steel, based on a newly proposed Quench and Partitioning (Q&P) process, is presented. This high strength martensitic grade is produced by the controlled low temperature partitioning of carbon from as‐quenched martensite laths to retained inter‐lath austenite under conditions where both low temperature transition carbide formation and cementite precipitation are suppressed. The contribution focuses on both the current understanding of the fundamental processes involved and includes a discussion of the technical feasibility of large‐scale industrial production of these steels as sheet products. The Q&P process, which is carried out on steels with a lean composition, should be implemented easily on some current industrial continuous annealing and galvanizing lines. In addition, martensitic Q&P sheet steel is characterized by very favourable combinations of strength, ductility and toughness, which are particularly relevant for high strength anti‐intrusion automotive parts.     

Thermal treatment improving creep properties of nitrogen-added Mod.9Cr-1Mo steels

Generation IV reactors are being developed to produce a reliable energy safely and with an economic benefit, because nuclear energy is being seriously considered to meet the increasing demand for a world-wide energy supply without environmental effects. Ferritic/martensitic steels are attracting attention as candidate materials for the Gen-IV reactors due to their high strength and thermal conductivity, low thermal expansion, and good resistance to corrosion. In recent years, new ferritic/martensitic steels have been developed for ultra supercritical fossil power plants through advanced technologies for steel fabrication. The microstructural stability of these materials for the pressure vessel, cladding and core structure of the VHTR and SFR is very important. Nitrogen is a precipitation hardening element, and the thermal stability of nitrides is superior to that of carbides. So the formation of nitrides may improve the thermal stability of the microstructure and eventually increase the creep rupture strength of high Cr steels. The effect of nitrogen on the creep rupture strength and microstructure evolution of nitrogen-added Mod.9Cr-1Mo steels has been studied. Creep testing was carried out at 873 and 923 K under constant load conditions. The optimum controlled Cr₂X precipitates were developed by special heat treatment, and they were not dissolved after a creep deformation. These fine and stable Cr₂X precipitates contributed to the increase of the creep rupture strength. The prior austenite grain size and martensite lath width were decreased by the resultant stable nitrides.     

Hot corrosion of Fe-10Cr-18Ni-5Mn-5Al-Si-N steels in molten sulfate deposits

The effect of Na₂SO₄ coating on the corrosion behaviour of 5 steel alloys as well as two commercial alloys - type 304 stainless steel and Inconel 690 - were tested in air at 900 °C under atmospheric pressure. Corroded samples were analysed by XRD, SEM and EDX. A newly developed alloy (No. 5) having the composition Fe-10.4Cr-15.43Ni-5.52Mn-5.52AI-1.5Si showed almost comparable corrosion resistance with Inconel 690. Stainless steel 304 failed catastrophically. Other newly developed alloys (no. 1-4) showed intermediate resistance. The results have been interpreted in the light of the nature of scales formed and on the premise that Na₂SO₄ decomposes to give S^2- ions which delay the formation of an internal protective film.     

Hydrogen Uptake Enhancement and Accelerated Hydrogen Re-embrittlement of Cd-plated AISI 4340 Steel Bolts Coupled with IN718 Nuts

Hydrogen re-embrittlement on anodically coated high strength steels could be of great concern because the uptake of hydrogen from the corrosion process can cause component failure. A scratched Cd-coated AISI 4340 steel membrane has been coupled with different materials reproducing crevice conditions, and the hydrogen uptake has been measured using a modified Devanathan?CStachurski permeation apparatus. Experimental tests proved that, in presence of a crevice, metals nobler than cadmium strongly enhance local hydrogen reduction on exposed steel areas, thus possibly favoring brittle failure of high strength steel components during service. Therefore, the coupling of uncoated nuts made of noble passive alloys (like Inconel) to Cd-plated AISI 4340 steel bolts should be avoided.     

Effect of Micro-Area pH Value on Formation of Different Rust Phases of Weathering Steel in Initial Corrosion Period

The formation of protective rust layer of atmospheric corrosion resistance was discussed for weathering steel.The rust layers of experimental steels were made by using an accelerating industrial atmospheric corrosion test of dry-wet cyclic immersion.Furthermore XRD were used to measure and analyze the rust layers.The initial corrosion processes below thin water film were observed and the changes of micro-area pH value were measured.The results are as follows:The corrosion processes of P-RE weathering steel are obviously different from those of carbon steel.The surface of P-RE weathering steel rapidly forms α-FeOOH and the micro-area pH value is above 5.4 during the initial corrosion period.While the component of the rust layer for the carbon steel is mainly Fe3O4 and the micro-area pH value is below 3.8.     

Recent developments in stainless steels:austenitic,ferritic,duplex

A review is given concerning some of the recent industrial developments of stainless steels. In austenitic stainless steels,two different directions of alloy development are noticeable:low nickel austenitic stainless steels and high nitrogen stainless steels.In these two cases the aims are different,particularly in terms of strength,but the philosophy of alloy development and the scientific approaches are very similar and they all revolve about the role of nitrogen as an alloying element and how this affects strength,ductility and corrosion resistance. There is now a broad and useful basis of information as to how nitrogen affects solid solution hardening,grain boundary hardening and work hardening and how to make use of these effects in developing materials required by the world market. In the field of corrosion resistance,ferritic,duplex and austenitic stainless steels compete with each other and now there is a growing body of information concerning the relative corrosion resistance based on laboratory data. However,for practical applications and for alloy selection,more than just laboratory data are needed,and thus,the first results are presented here of a many years comparison of the corrosion resistance of 24 commercial stainless steels exposed to corrosion in outdoors marine atmosphere.Hope is expressed to involve in the near future even more steels from a wider range of manufacturers in such corrosion studies.This might help consumers in appropriate alloy selection.It might also help steel makers in developing appropriate stainless steel grades.     

Thixocasting Steel Hand Tools using Al2O3‐coated Steel and Molybdenum Dies

Forging is state‐of‐the‐art for producing hand tools on an industrial scale. Due to high demands on the stiffness and the fracture toughness, high‐strength forging steels are used to provide cavity‐free components with high mechanical load capacity. Moreover, forging is a cost‐effective mass production process but, in spite of all its advantages, it has its limitations, e.g. in the freedom of designs. However, because of the extreme thermal loading (particularly with regard to permanent moulds) and the frequently unavoidable casting defects, hand tools are not cast. By means of thixocasting steel, technical difficulties can be reduced and new options are provided which allow the manufacturing of components with much higher complexity than that using forging. Through near‐net shape production, manufacturing steps and costs can be reduced. Furthermore, steels, which are difficult to forge but nonetheless have high potential for specific applications (such as high strength or corrosion resistant steels), can also be processed. In cooperation with industrial partners, X39CrMo17 stainless steel size 17 combination spanners were thixocast. Forming dies were designed and optimized by simulation, the hot forming X38CrMoV5 tool steel as well as the molybdenum alloy TZM were selected as the tool alloys. The dies were treated by a plasma nitriding process and subsequently coated with crystalline Al₂O₃ protective coatings by plasma‐enhanced chemical vapor deposition (PECVD). During the experiments, combination spanners were successfully cast in the semi‐solid state. Cast parts were heat‐treated to enhance the components' toughness, which was subsequently measured by Charpy impact and tensile tests.     

Corrosion Behaviour of New Railway Axle Steels

Corrosion behaviour of two newly developed axle steels (MS3 and MS6) is critically analysed and compared with that of the conventional railway axle steel with respect to the rust formed on the surface and microstructure of the steels. The microstructure of all three steels is ferrite–pearlite. Immersion, salt-fog exposure and dynamic polarisation tests in 3.5 wt% NaCl solution are carried out. New steels have much better mechanical properties and comparable corrosion resistance in immersion and dynamic polarisation test and much better corrosion resistance in salt-fog exposure test than that of the conventional axle steel.     

Hydrogen Embrittlement of Automotive Advanced High-Strength Steels

Advanced high-strength steels (AHSS) have a better combination between strength and ductility than conventional HSS, and higher crash resistances are obtained in concomitance with weight reduction of car structural components. These steels have been developed in the last few decades, and their use is rapidly increasing. Notwithstanding, some of their important features have to be still understood and studied in order to completely characterize their service behavior. In particular, the high mechanical resistance of AHSS makes hydrogen-related problems a great concern for this steel grade. This article investigates the hydrogen embrittlement (HE) of four AHSS steels. The behavior of one transformation induced plasticity (TRIP), two martensitic with different strength levels, and one hot-stamping steels has been studied using slow strain rate tensile (SSRT) tests on electrochemically hydrogenated notched samples. The embrittlement susceptibility of these AHSS steels has been correlated mainly to their strength level and to their microstructural features. Finally, the hydrogen critical concentrations for HE, established by SSRT tests, have been compared to hydrogen contents absorbed during the painting process of a body in white (BIW) structure, experimentally determined during a real cycle in an industrial plant.     

New Microalloyed Steels for Forgings

Microalloyed steels for forging applications have been newly developed in order to increase strength and toughness properties which thereby give the possibility for light weight constructions.The properties of these steels are set up by a controlled cooling directly from the forging heat without an additional heat treatment.This aim can be achieved on the one hand by a further development of precipitation hardening ferritic pearlitic steels (AFP-steel) due to an extended use of microalloying elements (AFP-M steel) and on the other hand by microalloyed steels which employ a bainitic microstructure (HDB steel).To adjust the targeted microstructure the temperature control has to be assured down to approx.500℃ for the AFP-M steels and down to approx.300℃ for the HDB steels.     

High corrosion resistance 21%Cr-0.4%Cu ferritic stainless steel contributing to resource conservation

With prices for metal resources such as nickel and molybdenum soaring,there is a heightened sense of crisis concerning resource scarcity.While Type304,the most common stainless steel,offers excellent corrosion resistance,its price is affected significantly by the cost of nickel because of its 8%nickel content.The stainless steel that has the same corrosion resistance as that of Type304 and does not contain nickel and molybdenum has been required.JFE Steel Corporation has developed a new 21%Cr-0.4%Cu stainless steel,the world’s first ferritic stainless steel,which offers equivalent corrosion resistance to Type304 while containing absolutely no nickel or molybdenum,two rare metals.The newly developed steel contains 21%chromium with the addition of 0.4% copper.The development of the steel is based on a new discovery that the passive films of stainless steels could be strengthened by the synergy effect of high chromium content and copper addition.Copper addition enriches the chromium content in passive films after field exposure.Newly developed 21%Cr-0.4%Cu stainless steel is adopted for many applications as a substitution for Type304,including commercial kitchenware,building materials and industrial machinery.The steel is expected to be a new standard of a ferritic stainless steel as a substitution for Type304.     

Corrosion Resistance on High Strength Bainitic Steel and 09CuPCrNi After Wet-Dry Cyclic Conditions

The accelerated wet-dry cyclic corrosion tests have been carried out of a high strength bainitic steel and 09CuPCrNi. The results indicated that the corrosion resistance of 09CuPCrNi was better than that of the bainitic steel based on the mass loss measurements. The morphology and composition of the rusting products have been investigated in order to realize the mechanism of rust formation on the two steels. The rust scale on both steels was composed of a dense inner layer and a loose outer layer. The inner layer grew thicker and denser as the test proceeding. Both of inner and outer layers were mainly composed of magnetite (Fe3O4) and maghemite (γ-Fe2O3) with a small amount of lepidocrocite (γ-FeOOH) and akaganeite (β-FeOOH). The rust phase of γ-Fe2O3 was detected in a higher amount of the inner layer, resulting in a much denser inner layer. The inner rust layer of 09CuPCrNi being denser and thicker than that of the high strength bainitic steel was attributed to the alloying elements such as copper, chromium and phosphorus enriched in it. The protective inner rust layer plays an important role in the corrosion resistance of the steel.     

转向节用贝氏体型非调质钢的高周疲劳性能

 利用旋转弯曲疲劳试验方法对比研究了新开发的两种转向节用贝氏体型非调质钢的高周疲劳性能。结果表明, 两种不同碳含量的贝氏体型非调质钢具有细小均匀的贝氏体铁素体+M-A岛组成的粒状贝氏体组织;两者具有相当的强度水平和疲劳性能,但其疲劳性能低于同等强度水平的调质钢。与锻态相比,正火处理后,试验料的抗拉强度和疲劳强度均有一定程度的降低,但屈强比和疲劳极限比明显提高。对疲劳断口的分析表明,试验料的疲劳裂纹均起源于表面基体,疲劳裂纹以准解理机制扩展。裂纹扩展速率试验表明,含碳量较低的试验料的疲劳裂纹扩展速率da/dN明显低于含碳量较高的试验料。