Ship Plate Steel Research Articles

Effect on cleanliness of molten steel with different refining slag systems for low alloy ship plate

To study the effect of refining slag on the compositions of molten steel and inclusions, the reaction between ship plate steel and different slag systems (slag A-CaO/Al2O3: 1.0, SiO2: 5 mass-% and slag B-CaO/Al2O3: 1.5, SiO2: 9 mass-%) was investigated by laboratory-scale high-temperature equilibrium experiments. Results showed that the desulphurisation capacity of the two slags was very similar, and the average sulphur content for both was 0.002 mass-% in steel, but the deoxidation capacity of slag B was slightly higher than slag A. The amount of inclusions <5 μm was more in steel balanced with slag B than in that balanced with slag A. To generate inclusions smaller than 5 μm, and spherical liquid CaO–MgO–Al2O3–SiO2 inclusions, and to decrease the T[O] (total oxygen) content in steel, refining slag composition should be: CaO/Al2O3 ∼ 1.5, and SiO2 ∼ 9 mass-%. Slag system optimisation can reduce or even eliminate calcium treatment during production. T[O] content in the slab could be controlled to 15–21 ppm, with typical micro-inclusions of ≤10 μm, and CaO–Al2O3–MgO and CaO–Al2O3–CaS systems in molten steel.

Measurement and Control Methods of 3-D NC Press Machines for Forming Springback of Ship Steel Plates

Measurement and Control Methods of 3-D NC Press Machines for Forming Springback of Ship Steel Plates

Optimizing Detection Parameters of Magnetic Barkhausen Noise Using Heat Affected Zone in Welded Ship Steel Plate

Magnetic Barkhausen noise measurements on a welded marine steel plate were performed in a line that passes through the weld bead and extends to the base metal from both sides of the weld. The heat affected zone was characterized by a pattern in the peak height as a function of distance from the weld bead. Barkhausen noise profile analysis by extracting relevant parameters like peak position, profile area and profile half width was also performed. The result showed a clear variation in MBN profile parameters in a way similar to that of the profile peak height. It could be concluded that MBN profile parameters superimposed as a function of measurement distance from the weld bead may provide an accurate determination of the affected material near the weld bead. The variation in MBN profile parameters was enhanced by microstructural and mechanical changes along the measurement line. This experiment demonstrates that the Barkhausen noise profile parameters could be used to track various manufacturing and maintenance processes of steel instead of using a single parameter like the root mean square (rms) to eliminate the variability of results and narrow the tolerance of acceptance criterion.

The Influence of the Induced Ferrite and Precipitates of Ti-bearing Steel on the Ductility of Continuous Casting Slab

AbstractIn order to investigate the loss of the ductility of Ti-bearing ship plate steel under 1000 °C, where the ductility begins to reduce rapidly, so the hot ductility of Ti-bearing ship plate steel has been obtained using the Gleeble 1500 thermal-mechanical simulator and also the studies about the effect of grain boundary ferrite films and precipitates containing Ti on the ductility has been carried out. The result showed that the TiN particles precipitating at 950 °C with a larger size and smaller volume fraction cannot effectively suppress the occurrence of recrystallization and the ductility still retains at a high level, although R.A. value presents a certain degree of decline compared with 1000 °C. A large number of smaller Ti(C,N) particles precipitate at 900 °C and can induce the formation of a very small amount of fine grain boundary ferrite, which deteriorates the adhesion strength of the grain boundary, so the R.A. value rapidly reduces to less than 50%. When the temperature falls to close Ae3 (827 °C), the amount of the grain boundary ferrite films increase due to the ferrite phase transformation, but the ferrite film thickness becomes more uneven at the same time, which results in the increase of strain concentration and plays a leading role in causing the decrease of ductility, so the R.A. value has been kept less than 40% as the temperature cooling to 800 °C from 850 °C. When the temperature further decreases, the ductility starts to recover due to the increase of average ferrite film thickness to a greater degree which greatly reduces the strain concentration of the grain boundary.

Effect of Normalizing on Microstructure and Mechanical Properties of EH36 Alloy

Normalizing is a kind of heat treatments, which have lower cost and higher efficiency. Through this process, the ship plate steel’s microstructure and performance can be promoted evidently. This article studies the effect of normalizing temperature on the microstructure and performance of controlled rolling and controlled cooling (TMCP) EH36 ship plate steel with the thickness of 15mm ,by mechanical properties text and optical microscopy. The results show that the comprehensive property of TMCP ship plate steel can be enhanced remarkably,although it’s hardness could be decrease,the plasticity of it can be improved obviously,especially the low temperature impact property. With the increasing of normalizing temperature,the grain grows,the impact property is decreased.

Effect of Subcritical Quenching on Microstructure and Mechanical Properties of EH36 Alloy

Subcritical quenching is a kind of heat treatments, which have good strength and higher Plastic toughness. Through this process, the ship plate steels microstructure and performance can be promoted evidently. This article studies the effect of subcritical quenching temperature on the microstructure and performance of controlled rolling and controlled cooling (TMCP) EH36 ship plate steel with the thickness of 15mm,by mechanical properties text and optical microscopy. The results show that the comprehensive property of TMCP ship plate steel can be enhanced remarkably, its hardness and plasticity could be improved obviously,especially the low temperature impact property. With the increasing of quenching temperature,the grain grows,the impact property is decreased.

Effect of Heat Treatment on Microstructure and Mechanical Properties of EH36 Alloy

The appropriate heat treatment process may obviously enhance the material mechanics performance, lengthens the service life of the machine parts , reduces the exploitation conditions of the material . This article uses mechanical properties test and the optical microscope research quenching and tempering comprehensive heat treatment craft is 15mm controls to thickness controlled rolling and controlled cooling (TMCP) condition tissue and the properties of the EH36 level ship plate steel influence. The result indicated that, after the heat treatment the TMCP condition ship plate steel overall performance has enhances greatly, although has the drop slightly in the intensity, but its plasticity, the low temperature impact performance all has the distinct improvement in particular.

Influence of Inactivation Treatment of Ship's Ballast Water on Corrosion Resistance of Ship Steel Plate

The effect of seawater after ultraviolet inactivation on corrosion of a shipbuilding steel plate was investigated by means of natural corrosion potential experiments and immersion corrosion test. The effects of natural seawater and treated seawater after ultraviolet inactivation on corrosion of the selected steel plate samples were compared with each other. The results showed that there was no obvious change in the chemical composition of treated seawater compared with natural seawater. The corrosion potential slightly increased by 10 mV, whereas the corrosion rate rose significantly by 20%. The experiments verified the naturally formed biofilm in the natural seawater for the inhibition of corrosion on the shipbuilding steel plate. The possible influences of ballast water treatment on biofilm by ultraviolet and electrolysis inactivation under the condition of practical usage were also investigated. And it was found that ballast water treatment methods with no continuous disinfection could protect original tank biofilm structure, reducing the intensity of tank corrosion.

Influence of Direct Lamellarizing and Tempering on Microstructure and Properties of F550 Ship Plate Steel

The effects of quenching at 820 °C 850 °C 940 °C and tempering at 600 °C on microstructure and properties of F550 ship plate steel were studied by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and other experimental methods. The results show that the highest value of the impact energy at-80 °C is 240 J when the steel is quenched at 850 °C and tempered at 600 °C. A full graumber of martensite-austenite (M-A) constituents which distribute in the shape of point-liner or gather among the grains, is larger compared with lamellarizing and tempering. Although the strength of the steel is higher, the value of the impact energy at-80 °C is lower and unstable. After intercritical quenching, the presence of minor ferrite and austenite grains refined could also be helpful to improve the low temperature toughness. Because polygonal ferrite (QF) is small and distributes uniformly between bainitic ferrite lathes acting as beneficial barriers to cleavage crack propagation.

Study on the Toughening Mechanism of Joint of EH40 Ship Plate Steel with High Heat Input Submerged Arc Welding

The EH40 ship plate steel is welded with submerged arc welding process,and the microstructure and mechanical property of welded joint are analyzed.The results show that the main microstructures of weld metal are acicular ferrite,a few proeutectoid ferrite and small area of M-A.Acicular ferrite dividing the original austenitic grain,effective grain size of weld metal is 3.2 μm.Large angle grain boundaries account for 78.6% of the grain boundaries in the analysis area of weld metal,and large angle grain boundaries mainly distribute between 50 degree and 60 degree,which are good for the impact toughness of weld metal.Few evenly distributed M-A with small size is not harmful to the toughness of weld metal.The microstructures of the coarse grained heat affected zone(CGHAZ) consist bainite,acicular ferrite and proeutectoid ferrite.The toughness in the CGHAZ is improved for the existing high melting point granule precipitated phases(TiO,Al2O3,MgO,TiN),which prohibit the growing of grain and promote the formation of acicular ferrite.The results of mechanical property show that good property joint is obtained,which is consistent with the results of microstructures.

Thermodynamic Parameters Analysis of MgS Superfine Inclusion in Grain Boundary

Activity coefficients and concentrations of dissolved magnesium and sulfur in grain boundary are two essential parts for the calculation of the Gibbs free energy of MgS superfine inclusion in grain boundary. Activity coefficients of dissolved magnesium and sulfur in grain boundary are gained first by the use of Miedema Model and Free Volume Theory. Concentrations of dissolved magnesium and sulfur in grain boundary of Fe-matrix are gained by Mclean’s equation. At last the Gibbs free energy of MgS in grain boundary is -14.048KJ/mol in E-class ship plate steel at T=1363K. By comparing the values of the Gibbs free energy of MgS in grain boundary and that in grain interior, a conclusion can be come to that MgS superfine inclusions may form in grain boundary instead of in grain interior.

Microhardness characterisation in developing high strength, high toughness and superior ballistic resistance low carbon Ni steel

To develop new steels that exceed the ballistic resistance, strength and toughness of current naval ship steel plates, we designed optimally quenching–lamellarising–tempering treated low carbon 10%Ni steel plates. These plates displayed exceptional properties in all aspects; when compared to the widely used HSLA-100 steel plates, they showed superior toughness and an improvement of over 15% in strength and 20 mm fragment simulation projectile ballistic limit V50. A preliminary vibrating sample magnetometer study on the effect of quenching–lamellarising–tempering process and dynamic deformation on the microstructure evolution of the 10%Ni steel during ballistic impact was valuable to our understanding of the steel. The data led us to conclude that dynamic deformation during ballistic perforation induced an austenite to martensite phase transformation, which improves the global dynamic plasticity and ballistic resistance of the steel target. This mechanism, similar to the transformation induced plasticity effect, can be appropriately named ballistic induced plasticity. Characteristics of the microhardness maps of the sectioned craters created by ballistics are consistent with ballistic induced plasticity.

Continuous Cooling Transformation Behavior of D460 Ship Plate Steel

Through the thermal mechanical simulation experiment，combined with the metallographic analysis and microhardness test on the Nb-Ti micro-alloyed steel for the austenitic continuous cooling process. The results shows that: with the increasing of the cooling rate, the phase transformation starting and ending temperature decrease and the ferrite content was decreased at room temperature. In less than 5°C/s low cooling speed region, with the increasing of the cooling rate, the grain size of tested steel obviously increases; In more than 17°C/s high cooling speed region, the grain size and vickers hardness of tested steel change and tends to be smoothly.

Heating Path Generation and Simulation for Ship Plate Steel

To lay the foundation of the automation for line heating forming, a method for heating path generation and simulation for ship plate steel base on STL mode was proposed in this paper. The line heating path was generated by slicing the STL model of the steel plate using a series of planes, and the models of the heating equipment of ship plate steel were build, and the heating process of ship plate steel can be simulated by inputting the models of the heating equipment into the simulation system that was built by using VC++ and OpenGL. The case study shows that the method can primely solve the inconvenient of manual heating and the whole heating process can be observed by the simulation so that the heating process can be made a reasonable monitoring, and the heating path generation and simulation software are runs stably and reliably.

Optimal control of secondary cooling for medium thickness slab continuous casting

A software to simulate the solidification, heat transfer and water flowrate distribution in slab continuous casting was developed by establishing a mathematical model for the heat transfer and solidification in medium thickness slab casting. This model was validated by pin shooting and surface temperature measurement experiments. A reasonable target surface control temperature was found by testing the high temperature mechanical properties of Nb bearing ship plate steel, and then the water flowrate of each loop of the secondary cooling zone was determined by the software. The influence of uneven secondary cooling in the slab width direction on the quality of the slab was also investigated, which provided data for the optimisation of the secondary cooling of the slab caster. On the basis of the above research, an optimisation scheme for a secondary cooling system was proposed. Experimental results showed that the quality of the slab was significantly improved after optimisation. The centreline macrosegregation was reduced, and the ratio of equiaxed grains was increased by 3·18%. In addition, the transverse cracking of the slab was almost eliminated.

Improvement of MIC Behavior of Ship Plate Steel with LaCl&lt;sub&gt;3&lt;/sub&gt;-Zn Epoxy Coating

The MIC behavior of the ship plate steel specimen with LaCl3-Zn epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated in this paper. The variation of corrosion potential over time of different specimens in SRB solution show that the corrosion potential of the specimen with LaCl3-Zn epoxy coating was obviously higher than the Zn-epoxy coating, suggesting that the LaCl3-Zn epoxy coating may offer better protection. The variations of lgflg |Z|=4.5 and fh with time show that the property of anti-infiltration and corrosion resistance of LaCl3-Zn coating is much better than the ones of Zn-epoxy coating. Results also show that more sulfides and corrosion products of LaCl3-Zn epoxy coating were produced which increased the shielding property of the coating. The experimental results of XRD and SEM are in good agreement with the ones of Ecorr, and EIS, etc. They all show that the LaCl3-Zn epoxy coating exhibits more favorable corrosion resistance property than the Zn-epoxy coating. It is obvious that coating the ship plate steel with LaCl3-Zn epoxy is an effective and promising method against the attack of SRB in marine environment.

Experimental Research on Effect of Hot Works on Mechanical Performance of Ship Steel Plate

Hot works is an important method for fairing the ship steel plate to improve the quality of shipbuilding, while the mechanical performance of the ship steel plate may be affected during the fairing process, which could result to some safe problems on the structural strength. DH32 high-strength ship steel plate, which is a kind of widely used material in shipbuilding industry, is taken as an object of the present experimental study. Some main parameters of the plate’s mechanical property through hot-works treatment for different times are investigated systematically. Through analyzing the variation of the mechanical properties, some conclusions are drawn and some useful suggestions put forward.

SIMULATION OF THERMAL BEHAVIOR DURING STEEL SOLIDIFICATION IN SLAB CONTINUOUS CASTING MOLD II. Model Verification and Results Analysis

Based on the thermal-mechanical coupling finite element model described in PartⅠof present work,the thermal behavior of one high strength ship plate steel solidifying in slab continuous casting mold was simulated with the practical continuous casting conditions of a steel plant,and the availability of the model was verified by in-plant measurement temperature.With this model,the thickness distributions and thermal behavior of air gap,mold flux(including liquid flux and solidified flux),and the variation characteristics of heat flux and surface temperature,as well as the influence of casting speed,mold taper,and mold flux properties on thermal behavior of the steel solidifying in mold were investigated.

Transferability of the Gurson Damage Model Parameters with Charpy and Tensile Tests with Different Constrain Level

Little work has been published concerning the transferability of Gurson’s ductile damage model parameters in specimens tested at different strain rates and in the rolling direction of a Grade A ship plate steel. In order to investigate the transferability of the damage model parameters of Gurson’s model, tensile specimens with different constraint level and impact Charpy specimens were simulated to investigate the effect of the strain rate on the damage model parameters of Gurson model. The simulations were performed with the finite element program ABAQUS Explicit [1]. ABAQUS Explicit is ideally suited for the solution of complex nonlinear dynamic and quasi–static problems [2], especially those involving impact and other highly discontinuous events. ABAQUS Explicit supports not only stress–displacement analyses but also fully coupled transient dynamic temperature, displacement, acoustic and coupled acoustic–structural analyses. This makes the program very suitable for modelling fracture initiation and propagation. In ABAQUS Explicit, the element deletion technique is provided, so the damaged or dead elements are removed from the analysis once the failure criterion is locally reached. This simulates crack growth through the microstructure. It was found that the variation of the strain rate affects slightly the value of the damage model parameters of Gurson model.

Experimental Study on High Power Laser Welding of Ship Steel Plate

This article puts forward adopting the fast-flow axis high power CO2 laser to weld the ship steel plate and mainly studies the influences of technical parameters to the seam. This article also analyzes and tests the welded products which are in the conditions of laser power of 8 kW, welding speed of 1m/min and focus position below 3mm of the workpiece. The results indicate that the distortion of laser welding is small, the ratio of depth and width are bigger than 2:1, and the structure is compact and has no deficiency and presents tiny martensite and few remnants austenite. Laser welding of ship steel plate can realize shaping double sides up one time with single side welding by choosing reasonable welding technical parameters. Therefore, the laser welding ship steel plate technique possesses high practical values.