Cold Sheet Rolling, Processing, Coating & Finishing
In the cold rolling process, good lubrication can reduce roll forces, but for hard steel types there are limits to what can be achieved with a particular mill. In this paper, various options to improve lubrication are explored, related to lubricant design and application. A numerical roll bite model is used to investigate the effect of various lubricant properties on roll forces when rolling hard steel types. Experimental work is presented.
This paper introduces an innovative drawer transverse flux technology that serves as an alternative to high-temperature radiant tubes for the production of new advanced high-strength steel strips. A 3.4-MW strip heater using that drawer technology was commissioned in September 2016. It heats steel strip up to 900°C with a width range of 900–1,650 mm and a thickness range of 0.7–2 mm. Typical measured temperature profiles confirm the drawer technology is not only able to uniformly heat a variable width non-magnetic strip but is also able to correct a non-uniform incoming strip temperature profile.
Leading manufacturers are constantly seeking out ways to increase yield, improve quality and reduce operating costs. Automatic gauge control using mass flow and elongation control has become a standard controls technique used in cold rolling to achieve these goals. Within these techniques, laser velocimeters are well known for improving control by offering a more accurate strip speed measurement as compared to contact methods, especially during acceleration/deceleration transition events in mill speed. This paper discusses differences between the two measurement techniques, as well as best practices for configuring, installing, integrating and optimizing a laser velocimeter measurement signal.
On any continuous galvanizing line, the snout and its associated quality issues cause many problems for galvanizers. As customers become more demanding in terms of surface quality and, in particular, for automotive exposed panels, the snout and its control becomes more important. This paper looks at the issues in the snout and the quality problems that are generated, and discusses practical methods that have been used to minimize and, in some cases, eliminate the concerns, allowing a much-improved surface to be manufactured. The solutions are a mix of equipment know-how and operating procedures that together allow the CGL to operate effectively in this demanding market sector.
This paper introduces a new innovation, an automatic roll mark detector, designed to save cold rolling mills from costly roll mark defects. The solution is an on-line installation into the exits of cold mills to automatically inspect every coil for roll marks — even for non-visible roll marks, which require manual chalking. The system alarms the operators from the first affected coil. Operators can take corrective actions without delay with the help of the images the detector displays in the operator pulpit human-machine interface. Records from a full-sized industrial pilot show major savings in downgrading costs and more full-speed rolling time since detector hand-over in late 2015. Furthermore, better reassignment for the fewer affected coils, higher-scoring customer key performance indicators, and many more cost benefits are experienced thanks to keeping the rolling operation more process-focused.
The transverse, spatial waveform patterns of the highly coupled shape actuators’ influence functions can be difficult to accurately determine. Traditional methods disable the on-line, closed-loop shape control and use large-amplitude, bipolar step functions to expose these influence patterns, which can lead to regions of the rolled strip being out of specification. This article introduces a method that employs very small-scale, multi-input excitation coupled with the heterodyne-like mixing of phase-sensitive detection, to provide on-line, multi-variable parameter identification while not disturbing the activities of the closed-loop shape control system. The key is a frequency and phase-locked mixing action that provides a means of extracting very feeble signals from high ambient noise and/or process dynamics, thereby requiring less excitation energy. This is a time-tested technique that forms the basis of specialized scientific instrumentation.