低温下不锈钢焊接件的抗冲击性能

以304L和316L型奥氏体和2505型双相不锈钢焊接件为对象,采用屏蔽金属弧焊与点焊方式,进行低温示波冲击试验研究,温度范围从室温至-196℃。结果表明,随试验温度的降低,304L与316L型奥氏体不锈钢焊件的冲击能量略有减小,而其相应焊条的冲击能量有很大减小。随着双相不锈钢焊件与焊条从韧性向脆性的转变,其冲击能量减小了至少5%。从试件的断裂面可看出,奥氏体不锈钢焊件与焊条呈现韧性断裂形态,出现宽深式、窄深式、浅式凹陷;而双相不锈钢焊件与焊条呈现脆性断裂形态,出现大、小延展层断面。依据荷载-时间曲线,说明奥氏体与双相不锈钢的韧性与脆性断裂性能。从控制不锈钢低温下变形机理的主要参数:堆垛层错能,应变诱发马氏体相变及铁素体相变这些方面,探讨两种不锈钢性能的差异。     

Strength and ductility of corner materials in cold-formed stainless steel sections

The cold work from the manufacturing process of cold-formed steel members can enhance the strength but reduce the ductility of materials. Due to a high cost of stainless steels, it is desirable to utilize this enhanced strength and avoid the early fracture in cold-formed stainless steel members. The paper is concerned with the prediction of the enhanced stress–strain behaviour and reduced ductility of corner materials in cold-formed stainless steel sections. The enhanced strength of corner materials has been traditionally determined using empirical models. However, most of these empirical models are only able to predict the enhanced 0.2% proof strength, but are neither capable of predicting the enhanced ultimate strength nor able to determine the reduced ductility. This paper first presents a modified weighted-average method for predicting the post-ultimate stress–strain behaviour and the fracture strain for stainless steels. An advanced numerical approach is next presented for predicting the full-range stress–strain behaviour of corner materials in cold-formed stainless steel sections, in which the modified weighted-average method is incorporated. The accuracy of this approach is demonstrated by comparing its predictions with test results. The proposed approach is generally applicable to cold-worked materials for predicting their enhanced strength, reduced ductility and full-range stress–strain behaviour. The proposed method and numerical results can explain why and how the ultimate strength of cold-formed steels can be increased and how the post-ultimate stress–strain behaviour can be utilized through cold working.     

Ferritic stainless steels in structural applications

Ferritic stainless steels are low cost, price-stable, corrosion-resistant materials. Although widely used in the automotive and domestic appliance sectors, structural applications are scarce owing to a dearth of performance data and design guidance. The characteristics of ferritics make them appropriate for structures requiring strong and moderately durable structural elements with attractive metallic surface finishes. The present paper provides an overview of the structural behaviour of ferritic stainless steels, including a summary of the findings of a recent European project (SAFSS) on ferritics. Laboratory experiments have been completed including material tests as well as structural member tests, both at ambient and elevated temperatures. The experimental data is supplemented by numerical analysis in order to study a wide range of parameters. The findings of this work have enabled design guidance to be proposed, as discussed herein.     

Einsatz des nichtrostenden Duplex‐Stahls 1.4362 als preisgünstige Alternative im Bauwesen

Use of duplex stainless steel 1.4362 as reasonable alternative in civil engineering applications. Due to drastically increased prices for raw materials in a lot of cases the standard austenitic stainless steels often used in civil engineering are no longer competitive. The duplex stainless steel 1.4362 represent a low cost alternative but it has not yet an official national technical approval. By means of exposure tests as well electrochemical investigations the corrosion behaviour of this type of steel should be clarified in slightly acid, chloride‐containing environments as they often occur in practical applications. The results show that the low cost steel 1.4362 could be used as alternative materials for civil engineering applications where up to now austenitc stainless steels as e.g. 1.4404 or 1.4571 were applied.     

Discussion on the use of stainless steel in constructions in view of sustainability

Recent years have seen an increase in the use of stainless steel in buildings, mainly owing to its corrosion properties and therefore long service life. Among stainless steels, ferritic and lean duplex grades are characterized by low nickel content resulting in a more cost-stable and economic material compared to austenitic stainless steels. These grades have comparable (or even higher) strength than carbon steel and good corrosion resistance at lower cost. That is why, lately, they have been more often used in structural components. In this paper, attention is first paid to the advantages associated with the use of stainless steel in recent construction projects in view of sustainability. Second, life cycle analysis and the background of the new European standard EN 15804 are introduced, including module D, which allows credits to be taken now for the eventual reuse or recycling of material in the future, at the end-of-life stage. Life cycle inventories of stainless steel products (cold-rolled coils and quarto plate) are presented. Depending on the fraction of material recovered at the end of the lifespan, two potential impacts (Primary Energy Demand and Global Warming Potential) are presented for four grades: 1.4301 (AISI 304) and 1.4401 (AISI 316) austenitic grades, 1.4016 (AISI 430) ferritic grade and 1.4462 (AISI 2205) duplex grade. The influence of module D is underlined.     

Stainless steel in construction: A review of research, applications, challenges and opportunities

Stainless steel has unique properties which can be taken advantage of in a wide variety of applications in the construction industry. This paper reviews how research activities over the last 20 years have impacted the use of stainless steel in construction. Significant technological advances in materials processing have led to the development of duplex stainless steels with excellent mechanical properties; important progress has also been made in the improvement of surface finishes for architectural applications Structural research programmes across the world have laid the ground for the development of national and international specifications, codes and standards spanning both the design, fabrication and erection processes. Recommendations are made on research activities aimed at overcoming obstacles to the wider use of stainless steel in construction. New opportunities for stainless steel arising from the shift towards sustainable development are reviewed, including its use in nuclear containment structures, thin-walled cladding and composite floor systems.     

Corrosion performance of welded stainless steels reinforcements in simulated pore solutions

This study analyses the effect of welding in corrugated bars of two austenitic stainless steels (new, low-nickel AISI 204Cu and traditional 304 types) and a duplex stainless steel (SAF 2205 type). Welds have been carried out using shielded metal arc. The effect of the welding on the corrosion behaviour has been studied using anodic polarization curves and double loop electrochemical potentiokinetic reactivation curves. Oxides formed during welding reduce the corrosion resistance of stainless steels. The surface of the reinforcements has been cleaned using pickling and sand-blasting to test their efficiency. Pickling does not completely remove oxides. Sand-blasting removes them, but forms aeration cells and deforms the surface. The efficiency of the cleaning method to assure the passivity of the reinforcements depends on the composition of the welded stainless steel and the characteristics of the environment.     

Effect of welding on local mechanical properties of stainless steels for concrete structures using universal hardness tests

This study analyses the effect of welding on mechanical properties of ribbed bars of two cold-deformed austenitic stainless steels (new, low-nickel AISI 204Cu and traditional 304L types) and two duplex stainless steels (SAF 2205 type, cold and hot-worked). Welds have been carried out using shielded metal arc welding. The effect of welding on local mechanical properties has been studied using a universal hardness equipment, measuring universal and Vickers hardness, elastic and plastic energies and Young modulus. Measured values are correlated with the microstructure of base materials and heat-affected zone. Results show that heat during welding promotes recrystallisation of the microstructure, effect that depends on the degree of deformation. These phenomena can be easily studied with universal hardness. Results suggest that hot-worked 2205 duplex stainless steel can be welded in construction without meaningful modification of its properties. Cold-deformed grades will comply ductility requirements of Eurocode 2 after welding, although reductions of yield strength can be found in 2205 and 304.     

304/304L和316/316L奥氏体不锈钢焊接性能的对比与分析

对比了304/304L和316/316L奥氏体不锈钢钢材的化学成分和力学性能,通过氩弧焊、药芯气保焊和埋弧焊三种焊接工艺比较了两者的焊接材料、焊接参数、组织结构、焊缝力学性能。     

Investigation on Ultimate Strength of STS304L Stainless Steel Welded Connection with Base Metal Fracture Using Finite Element Analysis

Many studies on the application of stainless steels as structural materials in buildings and infra-structures have been performed thanks to superior characteristics of corrosion resistance, fire resistance and aesthetic appeal. Experimental investigation to estimate the ultimate strength and fracture mode of the fillet-welded connections of cold-formed austenitic stainless steel (STS304L) with better intergranular corrosion resistance than that of austenitic stainless steel, STS304 commonly used has carried out by authors. Specimens were fabricated to fail by base metal fracture not weld metal fracture with main variables of weld lengths according to loading direction. All specimens showed a block shear fracture mode. In this paper, finite element analysis model was developed to predict the ultimate behaviors of welded connection and its validity was verified through the comparison with test results. Since the block shear behavior of welded connection due to stress triaxiality and shear-lag effects is different from that of bolted connection, stress and strain distributions in the critical path of tensile and shear fracture section were investigated. Test and analysis strengths were compared with those by current design specifications such as AISC, EC3 and existing researcher’s proposed equations. In addition, through parametric analysis with extended variables, the conditions of end distance and longitudinal weld length for block shear fracture and tensile fracture were suggested.     

Structural uses of stainless steel — buildings and civil engineering

Stainless steels have not traditionally been widely used as structural materials in building and civil engineering. Where the steels have been used for this purpose there has been some other imperative driving the design, usually corrosion resistance or architectural requirements rather than the inherent structural properties of the steel. The primary reason for this low use in structural applications is usually the perceived and actual cost of stainless steel as a material. Developments over the last 10 years, both in available materials and attitudes to durability, are now offering a new opportunity for stainless steels to be considered as primary structural materials.     

Testing and numerical modelling of lean duplex stainless steel hollow section columns

Stainless steels are employed in a wide range of structural applications. The austenitic grades, particularly EN 1.4301 and EN 1.4401, and their low-carbon variants EN 1.4307 and EN 1.4404, are the most commonly used within construction, and these typically contain around 8%–11% nickel. The nickel represents a large portion of the total material cost and thus high nickel prices and price volatility have a strong bearing on both the cost and price stability of stainless steel. While austenitic stainless steel remains the most favourable material choice in many applications, greater emphasis is now being placed on the development of alternative grades with lower nickel content. In this study, the material behaviour and compressive structural response of a lean duplex stainless steel (EN 1.4162), which contains approximately 1.5% nickel, are examined. A total of eight stub column tests and twelve long column tests on lean duplex stainless steel square (SHS) and rectangular hollow sections (RHS) are reported. Precise measurements of material and geometric properties of the test specimens were also made, including the assessment of local and global geometric imperfections. The experimental studies were supplemented by finite element analysis, and parametric studies were performed to generate results over a wider range of cross-sectional and member slenderness. Both the experimental and numerical results were used to assess the applicability of the Eurocode 3: Part 1-4 provisions regarding the Class 3 slenderness limit and effective width formula for internal elements in compression and the column buckling curve for hollow sections to lean duplex structural components. Comparisons between the structural performance of lean duplex stainless steel and that of other more commonly used stainless steel grades are also presented, showing lean duplex stainless steel to be an attractive choice for structural applications.     

Simplified design approach for cold-formed stainless steel compression members subjected to flexural buckling

The design criteria of stainless steel compression member are more complicated than those of carbon steels due to the nonlinear stress strain behavior of the material. In general, the tangent modulus theory is used for the design of cold-formed stainless steel columns. The modified Ramberg–Osgood equation given in the ASCE Standard can be used to determine the tangent modulus at specified level of stresses. However, it is often tedious and time-consuming to determine the column buckling stress because several iterations are usually needed in the calculation. This paper presents new formulations to simplify the determination of flexural buckling stress without iterative process. Taylor series expansion theory is utilized in the study for numerical approximations. The proposed design formulas are presented herein and can be alternatively used to calculate the flexural buckling stress for austenitic type of cold-formed stainless steel columns. It is shown that the column strengths determined by using the proposed design formulas have good agreement with those calculated by using the ASCE Standard Specification. A design example is also included in the paper for cold-formed stainless steel column designed by using the ASCE Standard equations and the proposed design formulas.     

Effect of strain hardening on the buckling of structural members and design codes recommendations

Some aspects of buckling behaviour of structural elements made of nonlinear materials with strain hardening, for which the stress–strain law has no yield plateau (stainless steels, aluminium alloys and others) are discussed. Considering compressed bars and plates made of materials with linear and nonlinear strain hardening, on the basis of tangent modulus theory and the deformation theory, we show that there exists a “threshold” value of the hardening factor below which the hardening does not influence the limit load. But if the hardening factor exceeds the threshold value then the hardening significantly increases the limit load and this increasing is not properly accounted for in some worldwide design codes.     

不锈钢焊接工字形截面残余应力分布试验研究

通过焊接加工10个不锈钢工字形截面试件（选材包括奥氏体型S30408和双相型S22253两种），采用分割法将试件截面切分成条带，量测释放的残余应变，计算得出截面的残余应力大小与分布形态。结果表明：试件截面的残余拉应力峰值低于材料的名义屈服强度，对于奥氏体型S30408和双相型S22253两种不锈钢试件的截面残余拉应力峰值分别约为其名义屈服强度的80%和60%。基于试验结果对现有简化分布模型的评估表明其应用的局限性，提出可以较准确描述不锈钢焊接工字形截面残余应力分布的建议简化模型，结合现有的其他试验数据，对建议简化分布模型的适用范围进行了验证和推广，可以为不锈钢结构构件的稳定性研究和设计提供参考。     

Bearing capacity of non-linear metallic spiders used in point supported glass facades

Experimental and numerical investigations on bearing capacity of non-linear metallic spiders used in glass facades were presented. The non-linear metallic materials adopted in this study included two aluminum alloys (ZL105-T1 and ZL111-T6) and one austenitic stainless steel (AISI 302). A total of 21 spider specimens including three types of configurations were tested. Numerical simulation of the tests was conducted by virtue of sophisticated finite element (FE) models built up with ANSYS software. The test and FE predicted results were used to develop new design proposals for the spiders. Evaluation of the proposed design formulae revealed that a comparatively large safety margin would be appropriate in consideration of brittle glass panels. Finally, safety assessment of the spiders was conducted based upon a practical engineering application-the exhibition greenhouse in Beijing Botanical Garden.     

Numerical study of the cyclic load behavior of AISI 316L stainless steel shear links for seismic fuse device

This paper presents the results of nonlinear finite element analyses conducted on stainless steel shear links. Stainless steels are attractive materials for seismic fuse device especially for corrosion-aware environment such as coastal regions because they are highly corrosion resistant, have good ductility and toughness properties in combination with low maintenance requirements. This paper discusses the promising use of AISI 316L stainless steel for shear links as seismic fuse devices. Hysteresis behaviors of four stainless steel shear link specimens under reversed cyclic loading were examined to assess their ultimate strength, plastic rotation and failure modes. The nonlinear finite element analysis results show that shear links made of AISI 316L stainless steel exhibit a high level of ductility. However, it is also found that because of large over-strength ratio associated with its strain hardening process, mixed shear and flexural failure modes were observed in stainless steel shear links compared with conventional steel shear links with the same length ratio. This raises the issue that proper design requirements such as length ratio, element compactness and stiffener spacing need to be determined to ensure the full development of the overall plastic rotation of the stainless steel shear links.     

热轧和焊接不锈钢结构构件的强度计算

目前世界上还没有国家制订关于热轧和焊接不锈钢结构的设计规范。随着不锈钢构件在建筑结构中的运用 ,以及它们表现出与普通碳素钢和低合金钢构件不同的力学性能 ,必须考虑专门的设计方法。在南非兰德大学铬钢研究组对热轧和焊接不锈钢构件研究的基础上 ,提出了用于热轧和焊接不锈钢结构构件强度预估的理论计算公式 ,供参考     

不锈钢节点板连接件数值分析

尽管不锈钢和碳素钢的力学性能有本质区别,然而,现行规范规定不锈钢连接设计时仍基本遵循碳素钢的设计准则,仅在此基础上稍作修改。对于常见的角钢单肢与加固板连接的情况,EN1993-1-4以及SCI/欧盟不锈钢设计手册对不锈钢的设计规定,直接采用了EN1993-1-8对碳素钢净截面承载力的设计规定,且未作任何修改。对单肢与加固板采用单排螺栓连接的L型不锈钢的净截面承载力进行了研究。建立奥氏体不锈钢的数值模型,并利用现有的试验结果对其进行了验证。这些模型随后用于进行参数研究。最后,基于研究结果对L型不锈钢净截面承载力的设计方程进行了修正,并通过统计分析验证了该方程可靠性。     

Experimental and numerical studies of lean duplex stainless steel beams

Stainless steel is well suited to a range of engineering applications owing to its durability and favourable mechanical properties. The most widely used grades of stainless steel are from the austenitic family and typically contain around 18% chromium and 8%-11% nickel — these grades have a relatively high initial material cost, due, in part, to their high nickel content, and a nominal yield strength (in the annealed condition) of around 220 N/mm². A new, low nickel grade of stainless steel (UNS 32101/EN 1.4162), commonly referred to as ‘lean duplex’, has been developed, that offers over two times the strength of the familiar austenitic grades and at approximately half the initial cost — this lean duplex stainless steel appears well suited to load-bearing applications in construction. This paper reports material and 3-point bending tests on lean duplex stainless steel hollow sections. The 3-point bending tests were replicated by finite element (FE) analysis and, upon validation of the numerical models, parametric studies were conducted to assess the effect of key parameters such as cross-section aspect ratio, cross-section slenderness and moment gradient on the strength and deformation capacity of lean duplex stainless steel beams. Based on both the experimental and numerical results, appropriate slenderness limits and design rules, suitable for incorporation into structural stainless steel design standards, have been proposed.