海洋环境用热轧304L不锈钢-A36碳钢复合钢板的腐蚀行为研究

目的探究304L不锈钢和A36碳钢热轧复合钢板中不锈钢覆层、碳钢基体以及不锈钢-碳钢复合界面在海洋大气环境及海水浸没环境中的腐蚀行为与腐蚀机理。方法采用中性盐雾实验和电化学实验模拟了海洋大气环境及海水浸没环境,对304L不锈钢-A36碳钢热轧复合钢板的腐蚀机理进行了全面评估。利用扫描电子显微镜(SEM)和能量色散光谱(EDS)表征复合材料界面的微观结构和局部元素分布,使用X射线衍射仪(XRD)表征了腐蚀产物的成分和化合价。结果在复合界面上存在一个明显的元素过渡区域。2种钢复合界面结合平滑,结合质量良好,轧制对2种钢复合界面处的组织无明显影响。当中性盐雾实验进行到96 h时,复合界面的腐蚀速率开始超越碳钢基体的腐蚀速率。实验结束时,复合界面与碳钢基体的腐蚀失重量分别达到582g/m^(2)和468g/m^(2),复合界面在海洋大气环境中的腐蚀速率为碳钢基体的1.24倍。此外,在复合界面碳钢侧的腐蚀产物中观察到富氯层。在电化学实验中,复合界面显示出了比碳钢基体更小的阻抗,这使复合界面在海水浸没环境中的腐蚀速率为碳钢基体的1.13倍。在复合界面处发现电偶腐蚀效应,加速了A36碳钢侧的腐蚀。开路电位的测试结果表明,复合界面的开路电位与耐蚀性较差的碳钢的开路电位接近,不同不锈钢-碳钢面积比复合界面的开路电位变化较小。结论在不同海洋腐蚀环境中,复合界面的腐蚀速率均大于覆层及基体的腐蚀速率,在海洋大气环境中尤为严重,复合界面碳钢部分的小面积暴露将导致材料的耐腐蚀性严重下降,在实际工程使用中应避免复合界面,尤其是复合界面碳钢部分的直接暴露。

TA2+Q345B轧制复合板覆层腐蚀特性研究

钛/钢轧制复合板因其优异的耐蚀性和结构性能而广泛应用于化工、海事等领域。因复合板轧制工艺需兼顾钛/钢两者特性而与单一材质的传统生产工艺有所差别,且在冶金结合界面处元素互扩散是否对覆层TA2组织及腐蚀性能产生影响待研究。通过组织观察、能谱测试和电化学腐蚀试验,研究了界面元素互扩散对覆层TA2组织及腐蚀性能的影响。结果表明:冶金结合界面处元素的互扩散距离仅为8~10μm,不足以影响整个覆层组织;覆层TA2耐腐蚀膜成膜初期存在反复腐蚀,但随着静置时间延长而逐渐稳定,不再发生腐蚀。

厚板数据中心和智能制造的实践与探索

介绍了业务需求驱动下PIDAS系统的开发过程,系统的架构、功能、特点和初步应用情况,为基于四级计算机控制系统制造业从自动化、信息化向数字化、网络化、智能化转型提供一个实际的案例。系统由信息和通信技术(ICT)与业务技术长期融合的技术团队自主开发;首先突破跨层级多频度异构数据的采集、处理和存储技术,以及基于业务价值取向的数据可视化技术,在单工序上实现应用;然后突破跨工序的跨层级多频度异构数据协同采集、处理和存储技术,以及业务知识化建模与持久化技术,把应用拓展到一条产线;最后突破工厂级数据中心软硬件平台架构技术,初步探索了多系统动态协同智能控制技术,构建了工厂级数据中心并初步实现了智能应用。

轧制过程边部线状缺陷形成机理研究

对边部线状缺陷的产生机理,通过高温压缩和高温拉伸热模拟试验,研究了试验钢种的高温两相区变形抗力的特点。试验结果表明:试验钢种在两相区内的变形抗力不随变形温度的升高而降低,存在明显的拐点现象。两相区内变形抗力的降低引起该温度下金属不均匀变形,从而在钢板边部形成皱褶,最终形成边部线状缺陷。通过调整变形温度避开两相区变形,从而避免边部线状缺陷的形成。

碳钢高温变形两相区流变应力行为预测

部分钢铁材料在两相区高温变形时,流变应力往往不随变形温度升高而降低,而是在两相区内出现流变应力的谷值。为了弄清主要化学成分对两相区内流变应力行为的影响,通过热模拟压缩试验研究不同成分钢铁材料在两相区附近的变形行为,分析变形后的金相组织以及两相区附近流变应力的变化,获得铁素体相变开始温度Ar3和两相区内流变应力的降幅。通过回归拟合得到C、Si和Mn等主要合金元素对铁素体相变开始温度Ar3以及流变应力降幅的影响关系。

Study on the interface of direct hot rolling titanium-clad steel plates

In this study,the interface characteristics of a direct hot rolling titanium-clad steel plate were analyzed, and the mechanism of interface cracking was explored. The detrimental effect from the formation of TiFe ,TiC,and a Si-enriched layer on the bonding strength was clarified, and an industrial-scaled titanium-clad steel plate with shear strength over 200 MPa was produced with a carefully set schedule accordingly. It was found that hot rolling titanium-clad steel plates had a flat interface without obvious cracks. In the rolling process,both Ti and Fe atoms interdiflhsed,but Fe difthsed much faster than Ti. The Fe-diffused area consisted of three regions. After a high temperature heat treatment, the diffusion depth of Fe and Ti elements increased significantly and evident Si segregation and TiFe layers were identified. Thermal cracking initiated in the Si segregation layer and then propagated along the TiFe layer and Fe-diffused layer on the titanium side.

Dynamic Recrystallization Behaviour of Nb-Ti Microalloyed Steels

The dynamic recrystallization （DRX） behavior of Nb-Ti microalloyed steels was investigated by isothermal single compression tests in the temperature range of 900-1 150 ℃ at constant strain rates of 0.1-5 s^-1. DRX was retarded effectively at low temperature due to the onset of dynamic precipitation of Nb and Ti carbonitrides, resulting in higher values of the peak strain. An expression was developed for the activation energy of deformation as a function of the contents of Nb and Ti in solution as well as other alloying elements. A new value of corrective factor was determined and applied to quantify the retardation produced by increase in the amount of Nb and Ti dissolved at the reheating temperature. The ratio of critical strain to peak strain decreases with increasing equivalent Nb content. In addition, the effects of Ti content and deformation conditions on DRX kinetics and steady state grain size were determined. Finally, the kinetics of dynamic precipitation was determined and effect of dynamic precipitation on the onset of DRX was clarified based on the comparison between precipitate pinning force and recrystallization driving force.

Microstructure and properties of S30403+Q345R roll-bonded clad steel plate for pressure vessels

To meet the demand of the domestic pressure vessel industry for roll-bonded clad steel plates, Baosteel has developed an S30403 ＋ Q345R roll-bonded clad steel plate. Comprehensive inspections of the composition, microstructure, and properties are made to systematically evaluate the steel plate in the normalized and normalized ＋ stress relieved states. The results show the cladding interface of the S30403 ＋ Q345R roll-bonded clad steel plate has high shear strength, the base metal has good properties, and the mechanical properties of the steel plate head and tail are uniform. The performance is fully consistent with the technical requirements of the roll-bonded clad steel plate for pressure vessels.

Study on grain refinement of interstitial-free steel during continuous frictional angular extrusion

To explore the application of severe plastic deformation for grain refinement in steel production, a new method called continuous frictional angular extrusion （CFAE） was applied to refine the grain of interstitial-free steel. The deformation was carried out at room temperature and individual sheet specimens were processed in different number of passes. An overall grain size of 200nm was achieved after 8 passes and the proportion of high-angle boundaries to the total boundaries was more than 60%. Through the characterization of high resolution EBSD, X-ray diffraction （XRD） and hardness testing,this paper discussed the evolution of microstructures and textures during deformation and explored the development direction of the method.

Development of a roll-bonded UNS N08825 alloy clad pipeline steel in Baosteel

In this study, a roll-bonded UNS N088225 alloy clad pipeline steel was investigated and developed in Baosteel. Based on the requirements of a number of potential projects, we performed a series of strict evaluations including mechanical and corrosion tests. The results show the mechanical properties and corrosion resistance of this clad steel to be excellent and to meet the requirements of all the design parameters.

Microstructure and mechanical properties of a high strength and high corrosion resistance roll-bonded clad checkered plate

The checkered plate,also known as the floor/pattern plate ,has a raised pattern that provides excellent skid resistance for a wide range of applications. As one of most commonly used products, the carbon steel checkered plate requires a high-cost coating for corrosion resistance. Although the austenitic stainless steel checkered plate meets corrosion resistance requirements ,it does not necessarily provide high overall performance due to its low yield strength, which means greater thickness and weight. Combining the advantages of stainless and carbon structural steel, Baosteel has developed a new roll-bonded clad checkered plate that exhibits high performance in skid resistance, strength, and corrosion resistance. Metallographic analysis shows the cladding interfaces to be very good, with stainless steel filling the whole pattern and a uniform microstructure in the different cladding layers. The yield strength and tensile strength of the product are 470 MPa and 610 MPa, respectively. In addition,the fracture morphology exhibits excellent interfacial bonding properties. We performed external and internal bend tests at room temperature, 180°, and 0.7a without the development of any cracks, which indicates its excellent formability.

FEM study on inflow strain in heavy plate during rolling

Heavy plate rolling processing in every single pass was simulated by the method of FEM. Distribution of the inflow strain on the specified path and related parameters （plate thickness H, pass reduction dH, rolling speed V） in the thickness direction of the plate center were studied. The results show that the plate thickness H and pass reduction dH have significant effects on the inflow strain on the specified path, while the rolling speed presents little effect. The relationships between the strain （PEEQ） and the plate thickness （H）/pass reduction （dH） were also established based on the simulation results.

Mechanical and corrosion properties of N08825 CRA clad pipeline steel

Corrosion-resistant-alloy(CRA)clad steel combines the good mechanical properties of the base material and the excellent corrosion resistance of the cladding material,while also being much more economical than solid CRAs.As gas and oil fields can have high concentrations of H2 S,Cl-,CO2,and other chemicals,the pipes used to transport gas or oil must have high corrosion resistance and good mechanical properties.UNS N08825 nickel-based alloys with their excellent corrosion resistance can be a good cladding material in clad steel.In this paper,UNS N08825+X65 clad steel was produced by two different processes.The thermomechanical and quenching and tempering processes were investigated and their mechanical properties and corrosion resistance were compared.Intergranular corrosion and pitting corrosion tests were conducted and the results were evaluated.A high-pressure and high-temperature gas-field environment was also simulated to test the stress corrosion cracking of the steel.The results show that both clad plates have good mechanical properties and excellent corrosion resistance.The experimental results were compared and the differences between the two processes were identified and discussed.

Preface

Bonding together two or more materials with different properties to obtain a new material with better properties has been a long-standing concept and practice in human history. One example that is relevant all around the world is making a sharp and break-resistant knife with a hard steel edge and tough steel on the back of the blade. Until 1868, the volume of composite steels manufactured was quite small and productivity was low.

Investigation of separation phenomenon in high-toughness X70 thick-walled linepipe steel

Separation is a commonly observed phenomenon during drop weight tear testing in high-toughness linepipe steels. Severe separation is harmful because it may cause fracturing or bursting of pipes. In this study, a quantitative measurement of separation was proposed, and using this new method, a relationship between the separation and microstructure was determined and discussed. The microstructures observed using optical and scanning electron microscopy revealed that the separation was related to the mixed ferfitic and bainitic microstructures, or rather,it was related to the carbon enrichment in bainite.

Transformation of low carbon steel during deformation at γ/α temperature based on online rolling data

Alloying elements, such as silicon and manganese, have a major impact on the phase transformation point of steel. Specifically, manganese is an element for the expansion and stability of the austenite region, while silicon can expand and stabilize the ferrite region. Phase transformation occurs during the hot rolling process for the steel with certain silicon content, which leads to great changes of the deformation resistance, thereby affecting the rolling stability. Consequently, a better understanding of phase transformation in the rolling process will contribute to the enhancement of product quality. In this paper ,the on-line rolling data were processed by means of the inverse calculation method. In this method, the steel deformation resistance with various silicon and manganese contents was obtained and analyzed to determine the deformation behavior of the steel, which can help improve the on-line control model and enhance the steel quality.

Effect of Nb content on strength of Nb micro-alloyed steels

Microstructures and properties of three Nb micro-alloyed steels were studied through hot rolling experiment. The result indicates that the ferrite grain size （dF ） decreases with increasing Nb content （Nb）, and the bainite fraction （fB） increases with increasing Nb content （Nb）. The effect of ferrite grain size （dF） on yield strength （δy） is related to Nb content （Nb）, and the effect of bainite fraction （fB） on yield strength （δy） is unrelated to Nb content （Nb）. Modelling of yield strength （δy） for Nb micro-alloyed steels with high accuracy has been built up with Nb content （Nb） and bainite fraction （fB） taken into account as new parameters, and formulas for ferrite grain size （dF ） and bainite fraction （fB） vs Nb content （Nb） have also been established under the experiment conditions. The research results could provide instructions for industrial productions.

Accuracy improvement of the traditional rolling force and torque model powered by an industrial data platform

The calculation results of the rolling force and torque model based on Orowan's differential equation numerical solution method do not fit with the industrial measurements very well.In particular,a quite large deviation on the torque model was found.On the basis of analyzing the shortcomings of the existing method,an improved rolling force and torque model algorithm aided by the Process Integrated Data Application System platform is proposed.Accordingly,the calculation accuracy of the rolling torque model is improved.The improved models are verified by 1711136 records of a data platform.The improved models are also based on Orowan's differential equation.Two coefficients,namely,friction factor and forward slip,are recognized as the crucial factors to be determined from industrial measurements to improve the accuracy.Therefore,the proposed method is a hybrid method that can be used to deeply understand the rolling process and improve the model's accuracy by combining traditional plastic mechanics and data-driving global optimization algorithms.This paper proposes a new approach to studying theoretical rolling deformation models powered by the industrial data platform.

Cogitation on the digital transformation of the process manufacturing industry triggered by the practices of the PIDAS

Digital transformation is the process of an industry moving to a digital business of continuous growth and improvement with digital technologies.It is an important path for the manufacturing industry to reconstruct and upgrade the existing operation mode to achieve efficiency, effectiveness, and product quality improvement.In this study, we analyze why the successful digital transformation practice is scarcely found in the core business of process manufacturing industries, such as the steel and cement industries.By introducing the development and application of the Process Intelligent Data Application System(PIDAS),which is the digital platform of heavy plates in Baosteel, the concepts, ideas, and development experience of the digital transformation of the process manufacturing are summarized.Moreover, the core issues worthy of attention are pointed out.Finally, a feasible route for the digital transformation of the process manufacturing is proposed.

Texture evolution during semicontinuous equal-channel angular extrusion process of interstitial-free steel

Semicontinuous equal-channel angular extrusion（ SC-ECAE） is a novel severe plastic deformation technique that has been developed to produce ultrafine-grain steels. Instead of external forces being exerted on specimens in the conventional ECAE,driving forces are applied to dies in SC-EACE. The deformation of interstitial-free（ IF） steel w as performed at room temperature,and individual specimens w ere repeatedly processed at various passes. An overall grain size of 0. 55 μm w as achieved after 10 passes. During SC-ECAE,the main textures of IF steel included { 111} ,{ 110} ,{ 112} ,{ 110} ,and { 110} At an early stage,increasing dislocations induce new textures and increase intensity. When the deformation continues,low-angle boundaries are formed betw een dislocation cell bands,w hich cause some dislocation cell bands to change their orientation,and therefore,the intensity of the textures begins to decrease. After more passes,the intensity of textures continues to decrease w ith high-angle boundaries,and the sub-grains in dislocation cell bands continuously increase. The present study reports the evolution of textures during deformation; these w ere examined and characterized using high-resolution electron backscattered diffraction（ EBSD） in a field emission scanning electron microscope. The mechanisms of texture evolution are discussed.