Effect of Reduction on Bonding Interface of Hot-rolled Wear-resistant Steel BTW1/Q345R Cladding Plate

Wear-resistant cladding plates consisting of a substrate（Q345 R） and a clad layer（BTW1） were bonded through hot rolling at the temperature of 1 200 ℃ and a rolling speed of 0.5 m/s. The microhardness of the cladding plate was also tested after being heat treated. The microstructure evolution on the interface of BTW1/Q345 R sheets under various reduction rates was investigated with a scanning electron microscope（SEM） and EBSD. It is found that the micro-cracks and oxide films on the interface disappear when the reduction is 80%, whereas the maximum uniform diffusion distance reaches 10 μm. As a result, a wide range of metallurgical bonding layers forms, which indicates an improved combination between the BTW1 and the Q345 R. Additionally, it is discovered that the unbroken oxide films on the interface are composed of Mn, Si or Cr at the reductions of 50% and 65%. The SEM fractography of tensile specimen demonstrates that the BTW1 has significant dimple characteristics and possesses lower-sized dimples with the increment in reduction, suggesting that the toughness and bonding strength of the cladding plates would be improved by the increase of reduction. The results reveal that a high rolling reduction causes the interfacial oxide film broken and further forms a higher-sized composite metallurgical bonding interface. The peak microhardness is achieved near the interface.

Rusting behavior and preventative measures of hot-rolled steel plates for automobile applications

As one of the important categories of hot-rolled products, hot-rolled steel plates for automobile applications generally undergo uniform corrosion or localized corrosion according to different environments of manufacturing, transportation and/or storage of the plates. General corrosion often takes place on the surface of a plate in the exterior part of a package, and only reduces the thickness of the plate and slightly increases the roughness of the surface; however, localized corrosion on the surface of a plate inside the package is likely to result in the formation of pit-like defects on the substrate of the plate, which cannot be removed thoroughly by normal acid pickling or sand blasting, and affects the application of the plate. This research report analyzes the phenomena and characteristics of the rusting behavior of hot- rolled steel plates for automobile applications, and the influencing factors are summaried. The corresponding preventative measures are proposed.

Analysis of High-Cr Cast Iron/Low Carbon Steel Wear-resistant Laminated Composite Plate Prepared by Hot-rolled Symmetrical Billet

This study developed a new technology for preparing high-chromium cast iron(HCCI)/low-carbon steel(LCS)wear-resistant composite plates by hot rolling at a 1050°C and a rolling speed of 0.2 m/s.The effects of different rolling reductions(30%,45%,and 60%)on the microstructure(interface and HCCI layer)and mechanical properties(bonding strength,hardness,and wear resistance)of the composite plate were studied.SEM images showed that when the reduction was increased,no impurities and interlayers were found between the microscopic interfaces after hot rolling,and the bonding interface exhibited a wave-like shape.EDS analysis showed that the Cr element diffusion between two metals after hot rolling was promoted when the reduction was increased,thereby improving the bonding quality under the same rolling temperature and rolling speed.Experiments showed that due to the stress release effect of the LCS of the cladded layer,the macro-slab shape after hot rolling performed well,and the brittle HCCI layer underwent thermoplastic deformation without cracking.Moreover,the increase of rolling reduction improved the bonding quality.As the rolling reduction was increased,the volume fraction of Cr-carbides in the HCCI layer also increased,resulting in an increase of hardness and wear-resistance.

Microstructure and properties of Ti-bearing hot-rolled high-strength steel plates for two-sided enameling

The composition and production technology of the type of hot-rolled steel plate used in two-sided enameling were briefly described. The microstructure and mechanical properties before and after enameling were contrastively investigated,and the precipitates in the samples were analyzed using transmission electron microscope and energy dispersive spectrometer. The results show the ferrite grain size of the steel plate after high-temperature enamel firing to be fine,with a large number of TiC and Ti;C;S;precipitates dispersed throughout the ferrite matrix. After two rounds of enamel firing at a temperature range of 800-890 ℃,its yield strength can still reach342 MPa. The results of a hydrogen permeation test show that the hydrogen storage properties of the steel plate are much better than those of ordinary structural carbon steel. A better bubble structure in the enamel layer can be obtained by this steel plate,with no fish-scale defects on the enameled steel-plate surface.

Bending analysis and control of rolled plate during snake hot rolling

In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element(FE) models were established. Effects of different initial thicknesses, pass reductions, speed ratios and offset distances on the bending value of the plate were analyzed. ‘Quasi smooth plate' and optimum offset distance were defined and quasi smooth plate could be acquired by adjusting offset distance, and then bending control equation was fitted. The results show that bending value of the plate as well as the extent of the increase grows with the increase of pass reduction and decrease of initial thickness; the bending value firstly increases and then keeps steady with the ascending speed ratio; the bending value can be reduced by enlarging the offset distance. The optimum offset distance varies for different rolling parameters and it is augmented with the increase of pass reduction and speed ratio and the decrease of initial thickness. A proper offset distance for different rolling parameters can be calculated by the bending control equation and this equation can be a guidance to acquire a quasi smooth plate. The FEM results agree well with experimental results.

Stream Surface Strip Element Method and Simulation of Three-Dimensional Deformation of Continuous Hot Rolled Strip

A new method,the stream surface strip element method,for simulating the three-dimensional deformation of plate and strip rolling process was proposed.The rolling deformation zone was divided into a number of stream surface(curved surface)strip elements along metal flow traces,and the stream surface strip elements were mapped into the corresponding plane strip elements for analysis and computation.The longitudinal distributions of the lateral displacement and the altitudinal displacement of metal were respectively constructed to be a quartic curve and a quadratic curve,of which the lateral distributions were expressed as the third-power spline function,and the altitudinal distributions were fitted in the quadratic curve.From the flow theory of plastic mechanics,the mathematical models of the three-dimensional deformations and stresses of the deformation zone were constructed.Compared with the streamline strip element method proposed by the first author of this paper,the stream surface strip element method takes into account the uneven distributions of stresses and deformations along altitudinal direction,and realizes the precise three-dimensional analysis and computation.The simulation example of continuous hot rolled strip indicates that the method and the model accord with facts and provide a new reliable engineering-computation method for the three-dimensional mechanics simulation of plate and strip rolling process.

Analysis of strain variation in cross shear zone of plate during snake hot rolling

In order to study the distribution of equivalent and shear strain of aluminum alloy plate during snake hot rolling, several coupled thermo-mechanical finite element models(FEM) are established. Effects of speed ratio and offset distance on strain distribution of the plate are analyzed. The length of cross shear zone is defined to have a better understanding of the deformation characteristic in cross shear zone, which is the essential difference from symmetrical rolling in deformation zone. The results show that the equivalent strain and shear strain of lower part both increase with the increase of speed ratio, while the upper part decreases; the equivalent strain through the whole thickness decreases with ascending offset distance, while the shear strain of lower part increases. The length of cross shear zone quickly increases with ascending speed ratio and slightly decreases with ascending offset distance. The "positive" and "negative" cross shear zones are formed with the increase of speed ratio and offset distance, respectively. The value of the sensitivity coefficient of speed ratio is an order of magnitude bigger than the offset distance. However, the shear strain at center point increases with the ascending speed ratio and offset distance for different mechanism. As speed ratio increases, the asymmetry of the distribution of equivalent is becoming larger and the shear strain is generated in the same direction in cross shear zone. The FEM results agree well with experimental results.

Practice to improve the plate camber during hot rolling by optimizing rolling schedule

Plate camber is one of the most important problems in hot rolling process which not only lead to lower output caused by increasing of crop loss,but also influence on the efficiency of follow-up shear processes,in severe cases damages of side guides or stands also occurred.In terms of reversible four-high hot rolling mills,the main causes of this problem exist in the following areas,reasons of stands,such as the stiffness difference between the drive side and operation side;reasons of slabs,such as the original wedge or the temperature difference along the width direction;reasons of side guides,such as the error of work pieces centerin.In their essence,it can be concluded that the initial deviation of deformation on both sides will increase as the processing,and then the work piece will deviate the center line of the stand,which will form camber defects in the end. The attempt of improving the plate camber was carried out by design the optimized schedules on the bases of theory of the steady rolling conditions during hot rolling process.In presizing and broadsizing sequence,according to the biting conditions and maximum torque restrictions,the rolling reduction of every pass should be as large as possible for the propose of increasing the negative convexity of load-gap through increasing the rolling force. When rolling process goes to finishing stage,it will be impossible to correct rolling centerline in last serval passes because the work pieces will be too long and thin,while considering the bad impact on plate profile which brought by increasing force.Therefore,the main purpose of finishing sequence should be profile control,and slowing down the speed of camber extension as much as possible by gap tilt adjustment automatically. The results show that in hot rolling process,the degree of final camber is impacted by all the three sequences. It is suggested that the control or even eliminating the defect is expectable by a well designed rolling schedule fundamentally.

Influences of Al and Si Powders on Microstructure and Hot Mechanical Properties of Al_2O_3-C Slide Plates

The basic formulation of Al2O3- C slide plates was65%（ in mass,the same hereinafter） white fused corundum particles,25% white fused corundum fines,6% active α-Al2O3 micropowder,4% carbon black and flake graphite, and additional 4% phenolic resin.Based on this formulation,3% Al powder,3% Si powder,and 3% Al ＋ 3% Si powder were used to substitute equivalent white corundum fines to improve the hot mechanical properties of Al2O3- C slide plates. The specimens with dimensions of 140 mm × 25 mm × 25 mm were pressed at 150 MPa,dried at 200 ℃ for 24 h,and hot treated at 1 400 ℃ for 3 h in carbon embedded condition. Then hot modulus of rupture and thermal shock resistance of the specimens were tested and the phase compositions and microstructure were analyzed. The results show that specimen with 3% Al powder has the higher hot modulus of rupture but lower residual modulus of rupture after thermal shock than the specimen with3% Si powder; the specimen with 3% Al ＋ 3% Si powders exhibits the highest hot modulus of rupture and the best thermal shock resistance; the change of mechanical property is closely related with the in-situ formed nonoxides： AlN in the form of bars is formed in specimens with Al powder; fibrous SiC whiskers are formed in specimens with Si powder; in the specimens with both Al and Sipowders,besides AlN and SiC whiskers,hexagonal tabular SiAlON is in-situ synthesized,which interlocks with each other.

建筑结构钢板热轧轧机DBN-PSO振动预报及应用

利用实时监测数据(Real-Time Monitoring Data,RMD)参数分析轧机振动状态,综合运用深度置信网络(Deep Belief Networks,DBN)与粒子群(Particle Swarm Optimization,PSO)算法构建轧机振动仿真模型,实现RMD参数的深度挖掘,并达到轧机振动的预报效果。通过融合处理能够获得非常接近实际振动过程的预测数据,具备优异预测能力。结合现场测试的初始数据预测误差在3.5%范围内,跟轧机振动情况相符。当轧制速率变慢后,振动加速度出现了降低结果;入口张力对轧机的振动加速度具有反向作用;轧机振动加速度相对出口张力表现为正相关特点;以不同宽度的轧件进行测试发现轧机振动加速度保持基本恒定的状态。该研究对提高热轧轧机运行稳定性,对保证建筑结构钢板成形精度具有很好的指导意义,可以拓宽到其它的成形设备优化领域。

Improvement of material properties and cladded flat product productivity with roll-bonding technology

Taking advantage of the progress of roll-bonding technology, the integrity of the material technology, and the development of the production and examination facilities of all the main carbon steels, stainless steels and specialty alloys in Baosteel, the cladded flat new products, which combined both properties of base material and clad material ,have been developed and produced in large quantities. The product categories includes heavy plates with high alloy content and homogeneous distribution in thickness and carbon steel plates cladded with all kinds of stainless steels ,nickel alloys ,and titanium alloys. The double-sided and single-sided cladding hot roiled strips and cold rolled sheets were also commercially produced. Due to the combined properties of both the cladding material and backing material, all products show obvious improvement in properties when compared with solid material. The comparability with the existing production process and equipment laid a very solid foundation for high productivity.

Effect of gradient temperature rolling process on promoting crack healing in Q500 heavy plates

To ensure the quality of heavy plate products as determined by ultrasonic inspection, it is necessary to effectively control defects such as cracks and shrinkage cavities in heavy plates. Generally, some defects such as large size cracks exist due to insufficient deformation in the center of traditionally rolled plates. Compared with the traditional rolling process, gradient temperature rolling(GTR) process can effectively increase deformation inside heavy plates. In this study, the effect of GTR on crack healing was analyzed through a comparison experiment with the uniform temperature rolling(UTR). The results show that the GTR process could increase the plastic strain inside the heavy plate and effectively promote the healing process of the preset cracks. The degrees of crack healing at the center and quarter thickness position of the steel plate via GTR were greater than twice those of the plate via UTR. The GTR process can significantly reduce the internal defects of heavy plates and improve the defect detection level of heavy plate products. Also, The GTR process results in the formation of new crystal grains in the crack region, which is crucial to crack healing.

Study on process of roll bonding stainless and carbon steel under non-vacuum condition

The non-vacuum roll bonding method of nickel plating on the base materials is put forward in accordance with the primary problems existed in the roll bonding of stainless/carbon steel. After nickel plating test on the base materials, the microstructure of nickel cladding is observed by scanning electron microscopy （SEM） at high, and room temperature, and the results show that the nickel cladding on base material can be protected from oxidation in the high temperature. Non-vacuum roll bonding tests of nickel plating on base materials are done by the roll bonding equipment, and the roll bonding plates of stainless/carbon steel are obtained. The microstructure and the elements distribution of non-vacuum roll bonding interface are analyzed by optical microscope （OM） and SEM. The results reflect that the nickel plating layer and the base materials bond well.

低碳海洋平台用钢E40-Z35的研制

通过实验室热模拟实验确定工艺参数,开发了连铸坯生产海洋平台用钢E40-Z35的控轧控冷工艺,并进行了现场工业试制.结果表明:采取低碳(w(C)≈0.08%)微合金化成分设计,利用Ca球化处理MnS夹杂物,以及轧制过程中进行高温慢速大压下,未再结晶区开轧温度为900℃,终轧温度为800℃,终冷温度为640℃左右.热轧后产品的-40℃常规冲击和时效冲击吸收功高于200J,厚度方向断面收缩率高于45%,具有良好的抗层状撕裂性能,满足船级社对海洋平台用钢E40-Z35的要求.

钎焊-热轧复合工艺制备不锈钢/碳钢复合板

针对不锈钢/碳钢复合板爆炸-轧制复合工艺存在的主要问题,提出了钎焊—热轧制备新技术,研究了主要工艺参数对钎焊复合板结合强度的影响,分析了钎焊复合板热轧的结合机理,测试了复合板的主要力学性能。结果表明,采用自制的银基钎料可以实现不锈钢/碳钢有效的钎焊结合,理想的钎焊工艺参数为:钎焊温度755～770℃,钎焊时间2.5～3min。热轧过程中钎料层表现出了良好的塑性,压下率为40%时,轧后钎料层未出现断裂、分层。轧制中钎料层同基体形成的金属键显著提高了不锈钢/钎料界面的结合强度,热轧复合板的抗剪强度达到了342.6MPa。

Fe-Si合金高温氧化动力学分析

通过氧化增重的方法,采用热重分析仪对Si含量为0.3%和0.6%的低碳钢热轧板料在300~1200℃下的增重进行了研究。结果表明温度越高氧化铁皮厚度越大,氧化越严重;在不同氧化温度条件下,氧化增重曲线均呈抛物线型,说明在氧化初期,氧化性气氛与钢基体发生化学反应。随着氧化铁皮的生成,变成以扩散反应为主。含Si量为0.6%的钢比含Si量为0.3%的钢单位面积上的氧化铁皮增重少,这说明Si含量越高,氧化增重越少。同时含Si热轧板料高温加热过程生成的Fe2Si O4液相层能降低钢基体的氧化程度。

热轧中厚板组织-性能预测及软件开发

以热力学和动力学理论为基础,开发了组织性能预测系统,并在首钢中厚板厂实现应用。预测了钢板屈服强度、抗拉强度随工艺及冷却参数的变化,预测结果和实测值吻合较好。随着冷却速率的增加,铁素体体积分数减少,晶粒尺寸变细。同样,成品厚度较大时,铁素体晶粒尺寸较大,铁素体体积分数变化不大。待温厚度为成品厚度的2倍左右,可以使Q235中板获得良好的力学性能。

退火时间对Mg-0.6Zr热轧板材阻尼性能的影响

研究了不同退火时间对Mg-0.6Zr热轧板材阻尼性能的影响。结果表明:350℃×3h的退火工艺使合金发生了完全再结晶,同时退火后的强度和硬度有所下降,而延伸率有所提高。合金在热轧态下的阻尼性能很低,且几乎与应变振幅无关;退火处理后,合金的阻尼性能得到明显提高,且随退火时间的延长而增大,完全再结晶后,阻尼性能几乎不再随退火时间的延长而变化,此时阻尼性能与应变振幅有关,即随应变振幅的提高而不断提高,尤其是在高应变振幅下。Mg-0.6Zr系合金上述阻尼性能的变化可以用Granato-Lücke位错钉扎模型来解释。

退火及热轧对碳钢-不锈钢爆炸焊接复合板性能的影响

通过EDS线扫描分析、SEM检测以及力学性能测定,研究了碳钢-不锈钢爆炸焊接复合板在焊态、退火态以及热轧态的力学性能和微区组织特征,分析了复合板元素过渡区域的特点.结果表明,退火热处理以及热轧处理均降低了复合板的抗拉强度和屈服强度,恢复了复合板的塑性以及韧性.复合板在焊态、退火态以及热轧态时的过渡区域具有不同的显微组织形态.退火后其过渡区域的波状界面结构与焊态基本一致,过渡区域宽度约为5μm左右,而热轧成薄板后的复合板,其过渡区域的波状界面消失,过渡区域宽度变宽,约为20μm.

Nb-B复合高强度集装箱板的组织与性能

为研究Nb-B复合高强度集装箱板的相变规律,研究终轧温度和轧后冷却速度对钢板组织和力学性能的影响规律以及钢板的耐腐蚀性能,利用Gleeble-1500热模拟试验机测定了实验钢的动态CCT曲线,在实验室轧机上进行热轧实验,并采用盐雾腐蚀试验(NSS)和周期侵蚀试验(NaHSO3)检验实验钢的腐蚀性能.结果表明:实验钢动态CCT曲线图中大部分为贝氏体转变区;轧后钢板的屈服强度为505～600 MPa,抗拉强度为720～787 MPa,延伸率在13%～22%,终轧温度和冷却速度对组织和力学性能有重要影响;实验钢在NaHSO3溶液中的腐蚀速率为0.892 g/(m2.h),在NaCl盐雾中的腐蚀速率为1.208 g/(m2.h),耐蚀性能良好.