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 the rolling process for thin HSLA heavy plates

Analyzed and studied the characters of high strength low alloy steel which contain Mo,Cr,Nb and Ni.etc.Following actual rolling,combining the feature of rolling mode,and exploiting the equipment advantage of 5 m Heavy Plate Mill,optimized the material design,heating temperature and rolling method, stabilized rolling process of thin alloyed steel,the quality index was advanced.

Effect of Zr-deoxidation on microstructure and mechanical behavior of microalloyed heavy plates with low impurity content

The significance of different deoxidation practises on the ductility and impact toughness of next generation of microalloyed heavy plates was elucidated to explore the best deoxidation practice in obtaining required mechanical properties,which was judged by the combined effects of composition,size and number density of inclusions on the ductility of the experimental high-strength low alloy steel.The impurity contents,i.e.,total O+N+S contents,of 82×10^(-6)(Al-killed)and 118×10^(-6)(Zr-killed)have been induced to characterize both the steels.Ductility was characterized using tensile and Charpy V-notch testing.The number,size and composition of the inclusions were characterized using a field emission scanning electron microscope with an energy dispersive spectrometer.In the Al-killed steel,the inclusion structure consisted of titanium nitrides,stringer calcium aluminates and elongated manganese sulfides,whereas in the Zr-killed steel,the inclusion structure consisted of mainly fine spherical oxide inclusions with sulphide shells.The impurity content did not have a significant effect on the number density of inclusions,as with higher and lower impurity content,the number of inclusions was 83.7 and 78.8 mm^(-2),respectively.However,the size distribution of the inclusions,especially the coarse inclusions with their longest length greater than 8μm,differsmuch from each other.The number density of coarse inclusions differs from 0.8 to 1.1 mm^(-2) with processing,and in Al-killed steel,55.5% of the coarse inclusions were titanium nitrides or manganese sulfides,whereas in Zr-killed steel,only 22.5% of the coarse inclusions were titanium nitrides and manganese sulfides.Coarse titanium nitrides were especially detrimental to the impact toughness.The number density of them should be below 0.33 mm-2 in order to guarantee the best possible toughness in the steel in question.The average crystallographic grain size detected by electron backscattered diffraction of Zr-killed steel(4.28±2.70μm)was smaller than that of Al-killed steel(6.00±4.80μm).As a result from the grain refinement and sulphide shape control,Zr-killed steel exhibited superior impact toughness(223±70 J)at -80℃ as compared with Al-killed steel(153±68 J).Thus,Zr-killed steel was observed to provide good performance in terms of mechanical properties as compared with Al-killed steel.

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.

Industrial practice of clad-rolling in heavy steel plate production

In this paper,a brief introduction on clad-rolling heavy steel plates of 90 mm and 140 mm thick is presented.The steel plates were hot rolled by 265mm slabs that are cladded by double 135mm continuous casting slabs of Q235 steel.After hot rolling,interface of the cladding slabs completely disappeared, revealing uniform grains similar to the rest of the materials.Ultrasonic tests were carried out on both steel plates,demonstrating excellent results.Through thickness tensile tests were also implemented on both steel plates,resulting in perfect mechanical properties complying with specific standards.The result proves that a minimum reduction rate of 1.89 is available in producing 140 mm thick steel plate with excellent through thickness properties.

Review of the last three years since the commissioning of Baosteel's 5m heavy plate plant and future outlook

Baosteel＇ s 5m heavy plate plant was successfully tested on March 1,2005. Since then,the Heavy Plate Plant of Baosteel （hereinafter referred to as ＂the plant＂ ） has been encouraging its employees to study and trace the advanced heavy plate technologies, trying to find out the rules of heavy plate production and its quality control. The plant has gradually mastered this modem heavy plate plant and ensured that Baosteel＇ s production of heavy plates grew year by year,with 1.41 Mt product put in storage in 2007. The plant has focused on developing new technologies and products, meanwhile enhancing its capacity. It has produced a series of plate products, which can be used in manufacturing ship hulls ,pipelines ,bridges ,buildings ,boilers and pressure vessels.

Numerical simulation research of dimension variation in heavy plate during quenching and tempering process

The dimension variation of B610E steel during the quenching and tempering process was simulated by ABAQUS,the coefficient of heat transfer during quenching was verified by the buried thermocouple test and the trend of the dimension variation during the quenching process was also calculated by ABAQUS. It was shown by the comparison of simulated results and industrially measured results that only the simulation of thickness and width variation was accurate, while length variation needed further simulation. Besides, the dimension variation trend was identical with the measured results.

Development of high strength heavy plate A517Q for offshore platform rack

This paper introduces the research and development of high strength A517Q developed by Baosteel for platform rack,with micro-alloying adding suitable quenching and tempering process,trial thickness of 127 - 178 mm high-strength A517Q.The trial plate crossing thickness has a uniform mechanical properties, yield strength greater than 700 MPa,tensile strength than 790 MPa,the Charpy impact than 90 J at -40℃, aging impact than 69 J,has high strength and excellent low temperature impact toughness,While the plate has excellent resistance to crack tearing ability of low-temperature,NDT is less than -45℃.The Developing heavy plates had been used for manufacturing racks of 200-foot jack-up offshore platform,the performance meeting the requirements of the ABS,CCS classification societies.

Quantitative analysis of microstructure based on machine learning and its application in product research and development

The material's microstructure is the output of the material composition and production process;simultaneously, it is the key factor in the material's performance and plays an important role in the material development cycle.The digital features of microstructures that can be recognized by a computer are obtained through the quantitative description of the material's microstructure, and a mathematical model is used to associate them with the composition, process, and properties.Combining the evolution mechanism of microstructure features can help quickly to predict microstructure properties, which can be used to optimize the composition and process, accelerate product development iteration, and solve the long cycle problem of traditional research and development mode while lowering the high cost of high-frequency trial production.This paper introduces the development and application of the combination of image knowledge, computer knowledge, and expert experience in the quantification of microstructures and the practical cases of recent studies of the Mask-Regions with Convolutional Neural Network Features(RCNN) method combined with machine learning in the digital research and development of heavy plates in Baosteel, and prospects the potential application of the quantification of microstructures of materials.

FRICTIONAL CONTACT MULTIPOLE-BEM AND 3-D ANALYSIS OF SCREWPAIRS

The 3-D traction field in the pressure screw-pair of a 3 500 heavy and mediumplate mill press down system is successfully calculated by applying the 3-D frictional contactmultipole-BEM and the corresponding program that has been developed. The computing results show themedium diameter orientation is unreliable, especially under the interference of an outer forcecouple. Under such working conditions, the circumferential traction distribution on the screw teethis extremely uneven, which is the main reason for the destruction and short life time ofscrew-pairs. When utilizing the same precision (the relative tolerance is 10X10^(-5)), themultipole-BEM uses almost the same CPU time as used by the FEM, but the needed computer memory sizeis only one eightieth of that needed by the FEM (10 MB vs. 800 MB). The multipole-BEM is well suitedfor computing large-scale engineering problems.

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.

Electroslag remelting technologies and equipment—modern achievements and trends of development

More than 50 years have passed since the ESR commercialization.Main steps of the ESR technology and appropriate equipment,developing until now,will be outlined.The trends in development of ESR technology and equipment will be also discussed.A special attention will be paid to such applications as ESR of slab ingots for soknown "z-steel" manufacturing,hollow ingots and bimetal steel production.

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.

Cost reduction of alloying element in high strength steel plate by optimization of controlled cooling technology

Controlled cooling technology is getting more and more attention with the development of thermal-mechanical control process. In the past decade, achieving the given finish cooling temperature was the sole goal for the technology. However ,with the research and development of new steels such as super high strength steel, researchers have in recent years realized the determinate effects that different cooling paths have on the finish cooling temperature and paid more attention to the control of the cooling rate. This paper focuses on not only the optimization of the controlled cooling system with high precision and fast cooling rate, but also the research and development of the high strength steel plate with reduced alloying component.

Optimized shearing strategy for heavy plate based on contour recognition

The shearing line is the key to improve the quality and efficiency of heavy plates.A model of contour recognition and intelligent shearing strategy for the heavy plate was proposed.Firstly,multi-array binocular vision linear cameras were used to complete the image acquisition.Secondly,the total length of the steel plate after cooling was predicted by back propagation neural network algorithm according to the contour data.Finally,using the scanning line and a new camber description method,the shearing strategy including head/tail irregular shape length and rough dividing strategy was calculated.The practical application shows that the model and strategy can effectively solve the problems existing in the shearing process and can effectively improve the yield of steel plates.The maximum error of detection width,length,camber,and the length of the irregular deformation area at the head/tail of the plate are all less than 5 mm.The correlation coefficient of the length prediction model based on the back propagation neural network is very high.The reverse ratio result of edge cutting failure using the proposed rough dividing strategy is 1/401=0.2%,which is 2%higher than that by human.

Broadside Compensation Rolling Model for Plan View Pattern Control in Wide and Heavy Plate Rolling Process

On the basis of a 5 m plate mill, a 3D rigid-plastic finite element （FE） model was developed to investigate changes of plate plan view patterns during hot rolling process. By analyzing the simulation results of conventional rolling processes, it was found that the plate plan view pattern was closely related to broadside rolling ratio. Then, the prediction models for plate plan view patterns were formulated by nonlinear regressive analysis of the simulation results and modified for high accuracy. Based on these models, the broadside compensation rolling method perform- ing at the last pass of broadside rolling phase was designed to decrease plate end crops. Comparing the plate plan view patterns with and without broadside compensation roiling, reduced plate end crops indicate that the broadside compensation roiling model is effective for plate plan view pattern control.

Hot Deformation Behavior of a Novel Ni-Cr-Mo-B Ultra-heavy Plate Steel by Hot Compression Test

Hot deformation behavior of a novel Ni-Cr-Mo-B heavy plate steel was studied by hot compression tests,which were conducted on a Gleeble-3800thermo-mechanical simulator corresponding to the temperature range of850-1 150℃ with the strain rates of 0.01-10s-1 and the true strain of 0.8.The results suggest that the majority of flow curves exhibit a typical dynamic recrystallization（DRX）behavior with an apparent single peak stress followed by agradual fall towards a steady-state stress.Important characteristic parameters of flow behavior as critical stress/strain for initiation of DRX and peak and steady-state stress/strain were derived from curves of strain hardening rate versus stress and stress versus strain,respectively.Material constants of the investigated steel were determined based on Arrhenius-type constitutive equation,and then the peak stress was predicted by the equation with the hot deformation activation energy of 379 139J/mol,and the predicted values agree well with the experimental values.Furthermore,the effect of Zener-Hollomon parameter on the characteristic points of flow curves was studied using the power law relation,and the ratio of critical stress and strain to peak stress and strain were found to be 0.91and0.46,respectively.

Continuous Casting of Demanding HSLA Steel Grades for Heavy Plate Application

Continuous casting has evolved as the most important production process in the steel industry.Today it counts for about 95% of the world’s steel production.Parallel to its rising significance,the process technologies have been enhanced in yield,productivity and-in particular quality of semi-finished products has been improved close to the realm of possibility.Further optimizing the product quality beyond the present status has to put the whole manufacturing route from hot metal and/or steel melting through refining to continuous casting under integrated control.Prerequisite for the production of HSLA steel grades of the highest standard are clean steel,internal soundness and defect-free slab surfaces.In this context a brief look is cast on the recent trend of process technology in casting "thick slabs" for extra-heavy plate production.

Study on Magnetic Field Distribution in Electromagnetic Ingot Casting Mold for Extra Heavy Plate

The dual-frequency electromagnetic ingot casting(DFEMIC)method with copper water-cooled ingot mold for extra heavy plate was developed.Electromagnetic field distribution in ingot mold was measured through the teslameter,the shielding effect of the copper ingot mold was judged,it is less than 37.7%of magnetic flux density when there is no ingot mold.The average shielding the magnetic field proportion of copper ingot mold reduced to 54.9%after loading '「' type the magnetic yoke and adjusting its distribution.Improving electromagnetic power can increase the magnetic field strength. Using the slit combination ingot mold could help increasing magnetic flux density in ingot mold.Steel structure outside ingot mold also have interference on magnetic field distribution in ingot mold,Therefore,it is important to paid more attention to electromagnetic shielding and the uniform symmetry of system structure.

Development of A Series NV-F Grade Extra High Strength Plate Steels for Offshore Structure and Shipbuilding

Systematic research on developing a series of extra high strength steel plates for shipbuilding via thermomechanical control process (TMCP) is introduced.A microalloyed low carbon-equivalent SiMnCrNiCu steel was used to develop F460 steel.Ultra low carbon Cu-Ni containing steels were used to develop NV-F550,NV-F620 and NV-F690 steel plates.The effect of TMCP parameters on microstructure and properties was investigated by test-scale plant trials.Industrial production trials were conducted to verify the validity of the laboratory studies on the F460 steel.Heavy plates in 45-60 mm thickness met Det Norske Veritas NV-F460 specification.The effect of heat-input on the mechanical properties of the coarse-grained-heat-affect-zone (CGHAZ) of the advanced heavy plates was studied.