Qingxue Huang

Interface-correlated Characteristics of Stainless Steel/Carbon Steel Plate Fabricated by AAWIV and Hot Rolling

Stainless steel (SS)/carbon steel (CS) clad plates were generated by means of the all-around weld of interface and vacuuming (AAWIV) followed by hot rolling, wherein AAWIV was utilized for controlling the interface oxidation during hot rolling. The structure near the interface was analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanical properties of SS/CS clad plates were investigated by tensile and shear as well as bend tests. The SS/CS interface is relatively flat and no visible separation appears. Line scanning analysis shows that diffusion of Cr and Ni from SS to CS and C from CS to SS occurred during bonding. Higher dislocation densities are observed in both layers of parent plates adhering to the interface. The SS/CS clad plates reveal higher yield, tensile and shear strengths. Both macroscopic delamination at the interface and fracture of base CS as well as intergranular fracture appearance of flyer plate are observed in the tensile test. The shear specimen fails in a ductile manner and the bend specimen tested shows no visible crack at the interface. Taking both interfacial structure and mechanical properties into account, the SS/CS clad plates exhibit sound bonding by the process of AAWIV and hot rolling.

Simulation of Strip Rolling Using Elastoplastic Contact BEM With Friction

With rollers as elastic bodies and workpieces as elastoplastic bodies, the rolling problem can be viewed as a friction elastic-plastic contact problem. With fewer assumptions in the simulation of strigrolling process, a boundary element method (BEM) for two-dimensional elastoplastic finite strain and finite deformation analysis of contact problems with friction was presented. All the equations for contact problems, which include multi-nonlinearities, were obtained. Incremental and iterative procedures were used to find contact pressure and friction stress. Moreover, initial strain rate algorithm and work-hardening material behavior can be assumed in the plastic analysis. Several examples were presented, and the results of contact pressure and friction stress were in excellent agreement with those of analysis.

Fatigue Damage Mechanism of Oil Film Bearing Sleeve

With the rapid development of the steel industry, to keep pace with the current trend of high speed, continuous, and large-scale production that focuses on automation and high levels of efficiency, many state-owned steel companies are being equipped with oil film bearings. Through long-term on-spot inspection and research on the fatigue failure of oil film bearing, three segments of annulated fatigue breakage were found axially along the inner surface of the bearing sleeve. In order to elucidate the reason for the threesegment annulated damage under rolling load, numerical boundary element method was adopted to analyze the contact behaviors between the sleeve and rollneck. Failure mechanism was discussed in detail, the distributions of contact stress were analyzed, and the service lives of the sleeve for different positions on the inner surface were quantitatively described, which provided an effective means to decrease wear and adhesive damage of the sleeve and to increase the load capacity of oil film bearing and its service life as well.

Modeling of Liquid Level and Bubble Behavior in Vacuum Chamber of RH Process

In the Ruhrstahl-Heraeus (RH) refining process, liquid steel flow pattern in a ladle is controlled by the fluid flow behavior in the vacuum chamber. Potassium chloride solution and NaOH solution saturated with CO2 were respectively used as a tracer to investigate the liquid and gas flow behaviors in the vacuum chamber. Principal component and comparative analysis were made to show the factors controlling mixing and circulation flow rate. The liquid level and bubble behavior in the vacuum chamber greatly affect fluid flow in RH process. Experiments were performed to investigate the effects of liquid steel level, gas flow rate, bubble residence time, and gas injection mode on mixing, decarburization, and void fraction. The results indicate that the mixing process can be divided into three regions: the flow rate-affected zone, the concentration gradient-affected zone, and their combination. The liquid steel level in the vacuum chamber of 300 mm is a critical point in the decarburization transition. For liquid level lower than 300 mm, liquid steel circulation controls decarburization, while for liquid level higher than 300 mm, bubble behavior is the main controlling factor. During the RH process, it is recommended to use the concentrated bubble injection mode for low gas flow rates and the uniform bubble injection mode for high gas flow rates.

Mechanical Properties of New Type Negative Offset Structure During Shearing Process of Heavy Steel Plate

According to the revised Cailikefu’s rolling shear force formula, motion path equation of spatial seven-bar path was built, and a mechanical model, with the new structural feature of negative offset, was thus successfully established for 2 800 mm heavy shear of some iron and steel company. Shear and bar forces of steel plate, before and after the adoption of negative offset structure, were analyzed, as well as horizontal force component of mechanism that influences pure rolling shear and back-wall push force that keeps blade clearance. It was found that the back-wall push force keeps large even at the time that the maximum rolling shear was obtained; meanwhile, back-wall push force is the most approximate to side forces when 60–100 mm of offset was adopted, Both theoretical results and onsite shear quality show that the negative offset plays an important role in ensuring the stability of pure rolling shear and keeping blade clearance constant.

Axial Force Analysis and Roll Contour Configuration of Four-High CVC Mill

In order to analyze the influence of technical parameters on work roll axial force of four-high continuous variable crown (CVC) mill, the deformation analyzing model with top roll system and strip was established based on influence function method. Then a CVC work roll curve designing scheme was proposed and it was carried out on some cold rolling mill considering the requirement of comprehensive work roll axial force minimization. The status of comprehensive work roll axial force is improved considering the rolling schedule that is beneficial to the roller bearing. Corresponding to the newly designed work roll contour, the backup roll end chamfer was designed considering comprehensive performance of interroll stress concentration, comprehensive work roll axial force, and strip shape control ability. The distribution of roll wear with newly designed backup roll contour is more even according to the field application data. The newly established roll configuration scheme is beneficial to four-high CVC mill.

Establishment of Optimal Blade Clearance of Stainless Steel Rolling-Cut Shear and Test of Shearing Force Parameters

The purpose aims to improve the plate shearing section quality and metal yield by means of optimal blade clearance adjustment model of rolling-cut shear and accurate calculation of the maximum shearing force, as well as for the system optimization design, structure optimization design to provide important basis. A 3500 mm rolling shear of a large stainless steel factory was taken as the test object, and the blade clearance under different influence factors of the clearance value and the shearing section were tested. The optimized production accumulated data regression analysis and the rolling shear process of stainless steel shear test. The test results show that the optimal blade clearance adjustment module is a comprehensive function, which include steel plate thickness, material, temperature and shear plate volume. The shear stress at starting stage with the relative penetration depth increases affected by the above factors, and the fracture peak decreases rapidly after being cut into the roll phase constant.

Numerical Simulation Analysis of Influence Factors to Shearing Force of Rolling Shear

The calculation results show that relative cut-in depth at the moment of maximum shearing force decreases with the increase of steel plate thickness; along with blade clearance increasing, shearing force would increase slightly compared with the slide pressure of blade carrier; shearing force increases significantly with the increasing blunt end radius; shearing force displays a bit decrement with the decreasing platen force, while the pressure on slide plate of blade carrier increases substantially; shearing force increases a bit with the increasing shear velocity and decreases when nip angle increases while the horizontal component force of shearing force along the direction of plate width increases rapidly. The above results have important reference and actual using value for studying calculation of mechanical parameters of rolling shear and its structural design.

Analysis of Startup Process and Its Optimization for a Two-Stand Reversible Cold Rolling Mill

Dynamic characteristic analysis of a two-stand reversible cold rolling mill in the startup process was carried out. The delay algorithm of the interstand thickness was proposed. A new method combined with the accelerated secant and the tangent methods was established to solve the simultaneous equations. The thickness and interstand tension transition processes with different static tension establishing processes were analyzed. Both mills were operated under constant rolling force control mode in the above process. The results show that the strip thickness in the rolling gap reduces in the static mill screwdown process. The entry stand runs inversely to establish the static interstand tension. This area becomes an abnormal thickness reduction area of the incoming strip. It results in several abnormal interstand tension increases in the subsequent startup process. The tension increase leads to an impact force on the strip that is the main reason of the strip breakage in the startup process. So the static tension establishing process was optimized, and the interstand tension fluctuation and the strip breakage accidents both reduced significantly. The results are beneficial to the startup process of the two-stand reversible cold rolling mill.

Physical Simulation of Critical Blowing Rate of Slag Entrapment of 80 Tons Ladle

The slag entrapment under different conditions of 80t blowing argon ladle furnace was investigated by physical simulation. The water was used to simulate liquid steel and liquid paraffin was for slag. The processing of slag entrapment under different blowing structures was analyzed and the critical velocity and critical droplets diameter of describing it was obtained. Based on the experiments, the relationship between the interface flow velocity and the critical blowing rate (CBR) was deduced. In the real process, it is suggested that the bottom blowing rate is from 40 L/min to 180L/min when the interface tension is 0.12~1.2 N/m during the soft argon blowing.