Mill roll profile control by means of spray cooling

A 2-dimensional model of a mill roll temperature distribution and radial thermal expansion is presented. The emphasis is on selective axial coolant distribution as a method of controlling strip profile. The Fourier equations describing heat conduction are solved using the method of finite differences. The following effects are considered: (i) The temperature distribution within the roll and strip just prior to entry to the roll bite. (ii) The heat generated in the strip due to deformation. (iii) The heat generated by friction between the strip and the roll. (iv) The temperature distribution of the strip and roll af ter each pass. (v) The heat conducted into the roll when in contact with the strip. (vi) The heat removed from the roll by the coolant, the air and the back-up rolls . The model also takes account of the geometry of the roll. This complexity means that different models for the roll and strip temperature distributions are required. The model evaluates individual heat transfer coefficients along the axis of the roll in order to simulate the effectiveness of each spray zone in removing heat from the roll. A simplified method of evaluating roll thermal cambers, derived from the model, is presented. The model shows good agreement between predicted and measured roll thermal cambers.The model is linked to a strip profile prediction model and used to investigate the effects of changing spray patterns and roll bend on profile. It was found that changing spray pattern has a significant effect on strip profile. It was concluded that: (i) Level spray patterns gave the best shape. (ii) Edge sprays sensitivity is important. (ii) over-cooling outside the strip provides good parabolic shape. ' (iv) A change to exit side, spray levels has a significant effect on strip profile. (v) Exit side sprays only has a tendency of rolling out the middle of the slab (i. e. a flat middle). (vi) All level sprays on the exit side of the roll only produce a distorted profile on the strip. It was also found that for any given change in roll thermal camber, there is a corresponding change in strip profile. The two changes can be related by a linear factor. The value of this factor has been investigated and found to be product and mill dependent

Structure-Properties-Processing Relationships in Metallic Materials

In the current Special Issue of Metals, we present six contributions from academia and industry. Based on their latest research developments, and achievements in their applied research field, the contributors elucidate the effect of temperature during forming operations that were closely analyzed via texture evaluation, present the opportunities that derive from microstructure and process simulation, and show how trace elements may affect critical properties in the performance of metallic materials. Bridging the gap between academia and industry, they provide all the necessary theoretical background through basic and applied research to meet the requirements for industrial application of the new and steadily optimized materials and concepts

Strip tracking measurement and control in hot strip rolling

It is well known that poor strip tracking can lead to reducedproduct quality but also to mill delays. The resultingcosts for internal rejects, customer complaints and yieldlosses have historically been significant. Moreover, the severityof these issues increases dramatically when stripsbecome wider, thinner and harder. Ultimately the rollingprocess becomes completely unstable. Hence, to reducecost of poor quality for the current product mix as well asto enable product development it is vital that strip trackingis improved.Most strip tracking issues arise at the head or the tail ofthe strip. In the rougher mill the main issue is head camber,a shape defect of the bar where the head is curved. Aclear example of this shape is shown in Fig 1. Large headcamber of the transfer bar may result in further problemsdownstream in the finishing mill and should ideally thus beprevented.Another notorious problem closely related to strip trackingis tail pinching in the finishing mill. This is a phenomenonwhere the tail of the strip suddenly moves sideward’s andgets damaged right after it has left the previous stand. AnPoor strip tracking is one of the notorious problems threatening process stability in a hot strip mill. Theseissues often lead to tail pinching and in the worst cases even to cobbles. The main pillars of the strategy setout to tackle these issues for the Hot Strip Mills in IJmuiden are rougher mill camber control and finishing millstrip steering and tail control. For such applications, a camera based measurement system has been developedin-house that is simple, cost-effective and yet both accurate and robust. Moreover, as we show in this paper,the system has proven its merits both as a finishing mill interstand centerline deviation measurement aswell as a rougher mill camber measurement. In the latter application the measurement data can be used forautomatic levelling in the rougher mill. The results of production tests presented in this paper demonstrate thatthe camber measurement in combination with a basic rougher mill tilt set-up model is sufficient to reduce thetransfer bar camber significantly

Centre-line deviation as a measure of camber in steel slabs during unrestricted horizontal rolling

A theoretical analysis of slab motion during camber evolution in unrestricted horizontal rolling is presented. The analysis shows that a linear relationship exists between centre-line deviation (CLD) curvature and outgoing camber, which is a function of ingoing and outgoing slab thickness and ingoing slab camber

Strip tracking in hot strip mills

In the finishing mill, steel strip is rolled from thick slabs through pairs of rollers housed in a continuous train of seven roll stands. As the strip is rolled, unwanted lateral movement, known as strip tracking, can cause the strip to collide with the edge of the mill. Strip tracking control is currently a manual operation, relying on the skill of the operators. When tracking is observed, the stand tilt is adjusted asymmetrically, causing a camber in the strip, steering it towards the centreline. Tracking control can be automated if a reliable measurement of position is available. A vision-based system was developed to measure strip position. Cooling water, steam, high temperatures and electrical noise create a hazardous environment for electronic equipment and hamper image analysis. Hardware was specified to protect all equipment against the environment. A novel image analysis method combining predictive elements, filtering and Bezier curve fitting was created to allow measurements to be made with large amounts of cooling water obscuring the strip edges. The measurement system was designed to integrate with the existing mill systems, using the OPC protocol for communication. The system was created as a development system with only two cameras included, but allowed for additional cameras to be easily added and automatically detected. The results of the system showed that the image analysis techniques were effective, providing an estimated final resolution of 3.5mm/pixel, with measurements ±2mm within 60% confidence. Hardware performance provided good protection of the equipment against the environment but poor quality installation limited overall system performance. A computer model was developed to simulate tracking behaviour in the mill with non-linear variations of strip properties across the strip. The model was not completed to a satisfactory standard capable of producing useful results but the theories described could be developed further.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Strip tracking in hot strip mills

In the finishing mill, steel strip is rolled from thick slabs through pairs of rollers housed in a continuous train of seven roll stands. As the strip is rolled, unwanted lateral movement, known as strip tracking, can cause the strip to collide with the edge of the mill. Strip tracking control is currently a manual operation, relying on the skill of the operators. When tracking is observed, the stand tilt is adjusted asymmetrically, causing a camber in the strip, steering it towards the centreline. Tracking control can be automated if a reliable measurement of position is available. A vision-based system was developed to measure strip position. Cooling water, steam, high temperatures and electrical noise create a hazardous environment for electronic equipment and hamper image analysis. Hardware was specified to protect all equipment against the environment. A novel image analysis method combining predictive elements, filtering and Bezier curve fitting was created to allow measurements to be made with large amounts of cooling water obscuring the strip edges. The measurement system was designed to integrate with the existing mill systems, using the OPC protocol for communication. The system was created as a development system with only two cameras included, but allowed for additional cameras to be easily added and automatically detected. The results of the system showed that the image analysis techniques were effective, providing an estimated final resolution of 3.5mm/pixel, with measurements ±2mm within 60% confidence. Hardware performance provided good protection of the equipment against the environment but poor quality installation limited overall system performance. A computer model was developed to simulate tracking behaviour in the mill with non-linear variations of strip properties across the strip. The model was not completed to a satisfactory standard capable of producing useful results but the theories described could be developed further

Analysis of camber formation, suppression and control in hot rolling of wedge-shaped slabs by utilizing fem and analytical concepts

Reducing wedge without generating camber is still a big challenge for today’s process automation systems for hot strip mills. Therefore, detailed transient 3D-models of the underlying severely asymmetric flat hot rolling processes have been developed by the authors with the help of the commercial FEM-package ©Abaqus Explicit. By utilizing suitably positioned edging rolls, the corresponding lateral force acting on the strip induces a lateral material flow inside the roll gap, leading to stress-redistributions such that the outgoing camber-curvature is drastically reduced. Systematic parameter studies performed so far revealed how the lateral edging force and the resulting strip camber-curvature depend on characteristic rolling parameters, such as slab width, thickness, initial wedge and thickness reduction. To understand the underlying highly non-linear elasto-viscoplastic forming processes inside the strip or slab in more detail, and to develop fast simulation-tools, semi-analytical model reduction approaches have been developed. This enables a quantitative analysis of the induced lateral material flow and the occurring stress-redistributions inside the roll bite. By introducing a lateral material transfer parameter directly correlated to the camber-curvature, an analytical relation could be derived for the bending moment (and external work) that has to be applied to eliminate the camber of the strip or slab. These analytical predictions, although based on rough simplifications, correspond quite satisfactorily with those attained by 3D-FEM simulations

Energy efficient engine. Volume 2. Appendix A: Component development and integration program

The large size and the requirement for precise lightening cavities in a considerable portion of the titanium fan blades necessitated the development of a new manufacturing method. The approach which was selected for development incorporated several technologies including HIP diffusion bonding of titanium sheet laminates containing removable cores and isothermal forging of the blade form. The technology bases established in HIP/DB for composite blades and in isothermal forging for fan blades were applicable for development of the manufacturing process. The process techniques and parameters for producing and inspecting the cored diffusion bonded titanium laminate blade preform were established. The method was demonstrated with the production of twelve hollow simulated blade shapes for evaluation. Evaluations of the critical experiments conducted to establish procedures to produce hollow structures by a laminate/core/diffusion bonding approach are included. In addition the transfer of this technology to produce a hollow fan blade is discussed

Automotive leaf spring design and manufacturing process improvement using failure mode and effects analysis (FMEA)

Nowadays human safety and comfort are the most considerable parameters in designing and manufacturing of a vehicle, that is why every organization ensures the quality and reliability of components used in the vehicle. Leaf spring is also a component of vehicle which plays an important role in human safety and comfort. It acts as a structural member and an integral part of suspension system. It is important to eliminate the failures in designing and manufacturing process of leaf springs because of its importance in functionality and safety of vehicle. In this research, failure mode and effects analysis has been used to analyze and reduce the risks of 42 possible failures that can occur in automotive leaf spring. It starts from determining, classifying, and analyzing all potential failures and then rating them with the help numeric scores. The four numeric scores namely severity, occurrence, detection, and Risk Priority Number (RPN) are used to find the high potential failures of semi-elliptical leaf springs. In the end, actions are recommended for RPN greater than 250, to increase quality and reliably of product. </jats:p