Mechanical properties of commercially pure aluminium subjected to repetitive bending and straightening process

The feasibility of using the Repetitive Bending and Straightening (RBS) process to improve the mechanical properties of commercial purity aluminium has been investigated. RBS was carried out by bending with a U-bending die of 10 mm radius followed by straightening between flat dies. The ultimate tensile strength (UTS) and yield strength (YS) slightly increased with increasing number of passes. The maximum UTS of 84 MPa and YS of 68 MPa were obtained after four passes and % elongation to failure decreased from 46% to 35% after four passes. The RBS processed Al showed poor improvement in mechanical properties as compared to other SPD processes. Repetitive bending and straightening process is therefore not an effective process to introduce fine grained structures in metals or alloys.     

Data‐Driven Pareto Optimization for Microalloyed Steels Using Genetic Algorithms

A data base was put together for the mechanical properties of microalloyed steels, which contained about 800 entries for ultimate tensile strength (UTS), yield strength (YS), and elongation. Using an evolutionary neural network, based upon a predator–prey genetic algorithms of bi‐objective type, this information was used to construct data‐driven models for UTS, YS, and elongation. The optimum Pareto tradeoffs between these properties were obtained using a multi‐objective genetic algorithm. The results led to some hitherto unexplored steel compositions with optimum properties. Some such steels were actually cast and the experimentally observed property values were found to be well in accord with the predicted results.     

Effect of Intercritical Annealing Parameters on Dual Phase Behavior of Commercial Low-Alloyed Steels

 It is known that dual phase (DP) heat treatments and alloying elements have a strong effect on martensitic transformations and mechanical properties. In the present work, the effects of some intercritical annealing parameters (heating rate, soaking temperature, soaking time, and quench media) on the microstructure and mechanical properties of cold rolled DP steel were studied. The microstructure of specimens quenched after each annealing stage, was analyzed using optical microscopy. The tensile properties, determined for specimens submitted to complete annealing cycles, are influenced by the volume fractions of multi phases (originated from martensite, bainite and retained austenite), which depend on annealing processing parameters. The results obtained showed that the yield strength (YS) and the ultimate tensile strength (UTS) increase with the increasing intercritical temperature and cooling rate. This can be explained by higher martensite volume ratio with the increased volume fraction of austenite formed at the higher temperatures and cooling rates. The experimental data also showed that, for the annealing cycles carried out, higher UTS values than ~ 800 MPa could be obtained with the S3 steel grade.     

Mechanical properties of ultra-high-strength steels at elevated temperatures

ABSTRACT

This paper presents an experimental study on the mechanical properties of ultra-high-strength steels at elevated temperatures. Tensile tests were carried out at 300–600°C on Docol 1200M and Docol 1400M steel samples. The results indicate that as the temperature increases Young’s Modulus, yield strength (YS) and ultimate tensile strength (UTS) display a decrease. YS/UTS ratios at 300°C are lower than those at room temperature, they make peaks at 400 and 500°C for Docol 1400M and Docol 1200M, respectively, and then decrease again beyond those temperatures. While total elongation continuously increases, uniform elongation slightly decreases with increasing temperature. Present carbides in tempered matrix continue to grow and new carbides are observed at the grain boundaries. Considering all roll forming parameters, 300°C seems the most convenient temperature for warm forming. In this sense, the warm roll forming has a potential for forming complex-shaped parts by reconciling strength with formability.     

Solution Treatment Effects on Microstructure and Mechanical Properties of Al-(1 to 13 pct)Si-Mg Cast Alloys

The effects of solution treatment time and Si content and morphology on microstructures and mechanical properties of heat-treated Al-Si-Mg cast alloys were investigated systematically. Five alloys, with Si levels ranging from 1 to 13 pct, were tested in as-cast, T4, and T61 conditions. The eutectic Si was both unmodified and Sr-modified. Results show that the microstructures are affected significantly by alloy composition, eutectic Si morphology, and solution treatment time. Si content has significant effects on ultimate tensile strength (UTS), yield strength (YS), and elongation as well as a strong influence on solution treatment response. In T61 treatment with different solutionizing times, UTS and YS reach their maximum values in ~1 hour of solutionizing followed by a decrease, then a slight increase, and finally, a plateau close to the maximum level. Elongation of alloys with a high Si content, 7 pct and 13 pct, increases rapidly at solutionizing times of 1 to 2 hours then varies in a wide range, showing improvements in the 4 to 10 hours range. The data indicate that a solution treatment time of ~1 hour is sufficient to achieve maximum strength. The changes in mechanical properties were correlated to changes in microstructure evolution—Mg-Si precipitation, Si particle fragmentation, and microstructure homogenization. Empirical models uniquely relating Si content to UTS and YS are given for T61 heat-treated alloys.     

Nanostructured Ti Consolidated via Spark Plasma Sintering

Cryomilled nanocrystalline commercially pure (CP)-Ti powders were spark plasma sintered (SPS) using different process parameters (heating rate, temperature, pressure, and dwell time) to study densification, microstructure, and mechanical behavior. The results were rationalized on the basis of the relevant literature and experimental results, and they reveal a strong dependence on SPS parameters. An interesting finding was that the measured high ductility was accompanied by a moderate strength (yield strength [YS] = 770 MPa, ultimate tensile strength [UTS] = 840 MPa with ~27 pct elongation to failure). The combinations of microstructure and mechanical response were attributed to the multistep processing at different temperature ranges as well as to the presence of interstitial solutes.     

Aging Effects on Heat Treatment Response and Mechanical Properties of Al-(1 to 13 pct)Si-Mg Cast Alloys

The effects of solution treatment time and Si content and morphology on microstructures and mechanical properties of heat-treated Al-Si-Mg cast alloys were investigated systematically. Five alloys, with Si levels ranging from 1 to 13 pct, were tested in as-cast, T4, and T61 conditions. The eutectic Si was both unmodified and Sr-modified. Results show that the microstructures are affected significantly by alloy composition, eutectic Si morphology, and solution treatment time. Si content has significant effects on ultimate tensile strength (UTS), yield strength (YS), and elongation as well as a strong influence on solution treatment response. In T61 treatment with different solutionizing times, UTS and YS reach their maximum values in ~1 hour of solutionizing followed by a decrease, then a slight increase, and finally, a plateau close to the maximum level. Elongation of alloys with a high Si content, 7 pct and 13 pct, increases rapidly at solutionizing times of 1 to 2 hours then varies in a wide range, showing improvements in the 4 to 10 hours range. The data indicate that a solution treatment time of ~1 hour is sufficient to achieve maximum strength. The changes in mechanical properties were correlated to changes in microstructure evolution—Mg-Si precipitation, Si particle fragmentation, and microstructure homogenization. Empirical models uniquely relating Si content to UTS and YS are given for T61 heat-treated alloys.     

稀土元素Sm对Mg-Zn-Y合金组织结构和力学性能的影响

制备了Mg-6Zn-1.5Y-0.8Zr-xSm(x=0,1,2,3)系列合金,研究了稀土元素Sm对Mg-6Zn-1.5Y-0.8Zr合金组织结构和力学性能的影响.通过金相显微镜、扫描电镜、EDS、XRD等观察和分析了合金的微观形貌和组织结构,测量了合金抗拉强度、屈服强度和伸长率等力学性能.结果表明:合金中添加稀土元素Sm后晶粒有了明显的细化,随着Sm元素含量的增加,晶粒细化效果更为明显;通过XRD分析,添加Sm元素后,合金中并没有出现新的含Sm的物相,通过扫描电镜和EDS分析表明,合金中加入的Sm置换了部分Y,形成了Mg3( SmY)2 Zn3,Mg3( SmY) Zn6的相结构,Sm元素对Y的置换主要出现在Mg3( SmY) Zn6结构当中,在Mg3 (SmY) Zn6相结构出现较少;力学性能测试结果表明,随着Sm含量增多,合金晶粒细化,细晶强化作用明显,合金屈服强度逐渐增大,而抗拉强度和伸长率在Sm含量为2％时达到最大,比未添加Sm元素时提高约15％以上.     

Effect of nano-SiC content on mechanical properties of SiC/2014Al composites fabricated by powder metallurgy combined with hot extrusion

Nano-SiC particulates (n-SiC_p) reinforced 2014Al matrix composites with different reinforcement volume fractions (0, 0.25, 0.5 and 1?vol.-%) were fabricated by powder metallurgy combined with hot extrusion. The effect of volume fraction of n-SiC_p on mechanical properties of composites was studied at both ambient and elevated temperatures. The increase of n-SiC_p content led to an increase in yield strength (YS) and ultimate tensile strength (UTS) and a slight decrease in elongation which is much better than the composites reinforced with micro-SiC_p. The 0.5?vol.-% n-SiC_p/2014Al composite observed the highest YS and UTS of ～378 and ～573?MPa at room temperature and of ～303 and ～409?MPa at 473?K. The enhancement of the properties is suggested to be induced by uniformly dispersed and well-bonded n-SiC_p reinforcements as well as the age-hardening effect of the more and finer precipitates.     

Optimising annealing process on hot dip galvanising line based on robust predictive models adjusted with genetic algorithms

Abstract

This paper describes the process for optimising the annealing cycle on a hot dip galvanising line based on a combination of the techniques of artificial intelligence and genetic algorithms for creating two types of regression models. The first model can predict the furnace operating temperature for each coil and is trained to learn from the experience of the plant operators when the process has been correctly adjusted in ‘manual mode’ and from the control system when it has been properly operated in ‘automatic mode’. Once the scheduling has been optimised, and using the two predictive models, a computer simulation is made of the galvanising process in order to optimise the target settings when there are sudden transitions in the steel strip. This substantially improves the thermal treatment, as these sudden transitions may occur when there are two welded coils differing in size and type of steel, whereby a drastic change in strip specifications leads to irregular thermal treatments that may affect the steel’s coating or properties in that part of the coil.     

人工神经网络在热轧宽厚板力学性能预测中的应用

建立了神经网络预测热轧管线钢力学性能的网络模型，在此基础上，利用神经网络对热轧管线钢力学性能进行了预测，并将预测结果与生产数据进行了比较，同时，还利用神经网络对生产工艺参数进行了优化，计算结果表明，神经网络预测值与实测值之间接相对误差可以控制在11.6%以内，这对现场进行力学性能预测和工艺参数优化具有较强的现实意义。     

Effect of Welding and Post-weld Heat Treatment on Tensile Properties of Nimonic 263 at Room and Elevated Temperatures

Nimonic 263 has been developed for the improved ductility in welded assemblies and is a candidate material for gas turbine combustor and transition pieces along with its good weldability and mechanical properties at room and elevated temperatures. In this study, the tensile behavior of an as-welded Nimonic 263 specimen at room temperature and 1053 K (780 °C) was examined in conjunction with microstructural evolution during welding and postweld heat treatment (PWHT). With the welding and the PWHT, the yield strength (YS), ultimate tensile strength (UTS), and tensile elongation of Nimonic 263 varied in a complex manner. It was observed that the PWHT of resolutionization at 1423 K (1150 °C) for 2 hours gave the highest YS and UTS values, whereas the tensile elongation was the lowest, at both testing temperatures. With increasing resolutionization time, the YS and UTS tended to decrease along with the increase in tensile ductility. The tensile behaviors of as-welded Nimonic 263 specimens was affected by several factors, including grain size, residual stress, possible microsegregation of γ′ forming elements, a tendency for interdendritic or intergranular fracture and a morphological change in both M₂₃C₆ and MC type carbides, depending on the testing temperature and the PWHT. The complex changes in tensile properties of Nimonic 263 with welding and PWHT at room temperature and 1053 K (780 °C) were discussed based on the micrographic and fractographic observations.     

Effect of thermal cycling on the mechanical properties of 350-grade maraging steel

The effects of retained austenite produced by thermal cycling on the mechanical properties of a precipitation-hardened 350-grade commercial maraging steel were examined. The presence of retained austenite caused decreases in the yield strength (YS) and ultimate tensile strength (UTS) and effected a significant increase in the tensile ductility. Increased impact toughness was also produced by this treatment. The mechanical stability of retained austenite was evaluated by tension and impact tests at subambient temperatures. A deformation-induced transformation of the austenite was manifested as load drops on the load-elongation plots at subzero temperatures. This transformation imparts excellent low-temperature ductility to the material. A wide range of strength, ductility, and toughness can be obtained by subjecting the steel to thermal cycling before the precipitation-hardening treatment.     

Mechanical Properties of a Ni–Cr–Mo Steel Subjected to Room Temperature Carburizing Using Surface Mechano-Chemical Carburizing Treatment (SMCT)

Surface mechano-chemical carburizing treatment (SMCT) is a modified version of surface mechanical attrition treatment and it is one of the cutting-edge technologies for producing hard nano-crystalline surface in metallic materials. In the present study, a case carburized surface layer is achieved in 1.75 Ni–Cr–Mo steel at room temperature using SMCT. Activated charcoal powder is continuously fed during the process so as to achieve the carbon diffusion into the surface layer. The SMCT process has been carried out for different periods say 15, 30, 45 and 60 min respectively. The microstructure and surface chemical composition is investigated by using TEM and XRF analysis. The mechanical properties such as yield strength (YS), ultimate tensile strength (UTS), fracture toughness and surface hardness of SMCT samples have been investigated using universal testing machine, Plain strain fracture toughness test and Microvickers hardness test respectively. The surface carbon content has been found to increase linearly and grain size reduces continuously with processing time. A 60 min SMCT samples reveal 0.8% C and about 10 nm grains over the surface. The SMCT samples show significant improvement in mechanical properties. The surface hardness increases from 180 HV_0.1 to ~ 878 HV_0.1 by 60 min of treatment. About 55% increment in the YS and 30% increment in UTS is achieved by 60 min of SMCT. It is also interesting to note that the fracture toughness of the samples enhances from 24 to 47 MPa \( \sqrt m \) after 60 min of SMCT.     

冷却工艺对超低碳贝氏体钢强韧性影响的研究

研究了一种含有Cu、Ni、Mo、Nb、B等元素的超低碳贝氏体钢,以搞清楚其在不同的热机械处理 弛豫-析出-控制相变技术 回火工艺(TMCP RPC T)条件下组织和强韧性能的变化规律.实验室研究和工业试制表明,随着工艺制度的不同,钢的显微组织表现为粒状贝氏体和板条贝氏体的比例、形态、尺寸不同;在一定的冷却速度下,轧态钢的屈服强度、抗拉强度和屈强比随终冷温度的降低呈现上升趋势;回火后钢的屈强比较热轧态有所提高.试验条件下,回火温度对Nb析出数量的影响不明显,加热时Nb的固溶程度对该钢的最终组织有明显影响;采用TMCP RPC、TMCP RPC T工艺路线,通过调整工艺参数,能够获得不同性能组合的钢板,实现高性能钢种的柔性化设计.     

Effect of thermomechanical treatment on structure and mechanical properties of Mo-bearing dual phase steel

The effects of hot rolling of a dual phase steel in the (α + γ) range on microstructure and mechanical properties was investigated by using two thermomechanical (TMT) routes. The first consisted of heating A_c3, soaking, cooling to deformation temperature in the (α + γ) range. The second comprises heating to deformation temperature in the (α + γ) range, followed by rolling and quenching. Parameters varied were temperature (with the first route) and extent of deformation (with the second). The microstructures were characterised by optical and transmission electron microscopy. The results indicate a distinct difference in the final structure and properties due to the two different TMT routes. The first TMT route resulted in a greater amount of ferrite, finer lath width of martensite, finer ferrite grain size and increased density of dislocations. The strength properties decreased, the YS/UTS ratio decreased and ductility increased with the increase in the extent and temperature of deformation. However, TMT route 2 resulted in an increase in the amount of martensite, finer ferrite grain size, decrease in the martensite lath width and increased dislocation density. The strength properties increased, YS/UTS ratio increased and ductility decreased with increase in the extent and temperature of deformation.     

Steel annealing furnace robust neural network model

Abstract

In this day and age, galvanised coated steel is an essential product in several key manufacturing sectors because of its anticorrosive properties. The increase in demand has led managers to improve the different phases in their production chains. Among the efforts needed to accomplish this task, process modelling can be identified as the one with the most powerful outputs in spite of its non-trivial development. In many fields, such as industrial modelling, multilayer feedforward neural networks are often proposed as universal function approximators. These supervised neural networks are commonly trained by the traditional, back-propagation learning format, which minimises the mean squared error (mse) of the training data. However, in the presence of corrupted or extremely deviated samples (outliers), this training scheme may produce incorrect models, and it is well known that industrial data sets frequently contain outliers. The process modelled is a steel coil annealing furnace in a galvanising line, which shares characteristics with most of the furnaces used in galvanised lines all over the world. This paper reports the effectiveness of robust learning algorithms compared to the classical mse-based learning algorithm for the modelling of a real industry process. From this model an adequate line velocity (the velocity set point) for a coil, depending on its characteristics and the furnace condition to receive this coil (temperature set points), can be obtained. With this set point generation model the operator could set strategies to manage the line, i.e. set the order of the coil to be treated or preview the line's speed conditions for the transitory situations.     

Controlling Properties of HSLA Line Pipe Steels for Oil and Gas Applications

DANIELI has recently implemented its Coil Quality Estimator (DANIELI-CQETM) system to the Hot Strip Mill of United Metallurgical Company (OMK) at Vyksa,Russia.This system is developed for the purpose of real time assessment and control of mechanical properties for hot rolled coils.Mechanical properties such as strength,toughness,ductility and hardness are predicted over the entire length of a strip while it is processed.The property estimation is based on the final microstructure as predicted from a group of interconnected physically based metallurgical models,supplemented by Artificial Neural Network.The CQE system is used for prediction and control of properties of HSLA line pipe grades steel and other grades.The system performance,is judged by accuracy and reliability of prediction,has been compared with the physical material testing data from the plant.The results are found to be excellent.CQE is found useful for generation of test certificate of coil,quality assurance,process control,product development,and customer claim assessment.It is used for resource optimization for production,and other operational improvements such as reduction of downgrades.The present paper shares the results of CQE performance for prediction of HSLA line pipe grade steels.     

Prediction of aluminium concentration in molten zinc pot of continuous hot dip galvanising line

Abstract

The strict control of aluminium concentration in a galvanising pot is extremely important to meet the high surface quality of galvanised steels that has been demanded by the industry. The present study proposes a mathematical model for the prediction of aluminium concentration in a galvanising pot of a continuous hot dip galvanising line. It is assumed that aluminium in the molten zinc pot is consumed as coating layer, dross, and inhibition layer. The quantities of aluminium consumed as dross and inhibition layer in the molten zinc pot are evaluated using the results of physical model experiments available in the literature. The operation conditions of the continuous hot dip galvanising line are online collected and then used as input data for the model. It is found that dross is a main source of the preferential consumption of aluminium in the molten zinc pot. The predicted pot aluminium concentration follows the trend of experimentally measured values rather well during both galvanising and galvannealing operations.