The thickness, strength and hardness of metals all depends on what the metal will be formed into and eventually used for by consumers. There are hundreds of different grades, thicknesses, and strengths of stainless steel – which are created by alloying different elements (such as chromium with nickel to iron and carbon products that are corrosion-resistant).
The strength of stainless steel is an advantage in many applications, but the downside of adding strengthening alloys is poor machinability, meaning the material is difficult to cut and wears down the tooling. Again, the final product specifications must be kept in mind when manufacturing steel to ensure the appropriate equipment and technologies are being used throughout the process.
What is the difference between hot rolled vs. cold rolled steel? Processing the material through a cold rolling mill helps reduce thickness, increase strength and improve the surface finish. Modern cold rolling mills are able to achieve high speed production of sheet steel that meets a variety of requirements for thickness and uniformity with the help of an x-ray thickness gauge. Thickness gauges detect and correct deviations in thickness in real-time to achieve high quality steel strip.
Hot rolling of steel occurs at very high temperatures, above the recrystallization temperature of the material, producing malleable sheets that can be formed in a variety of shapes. The process produces sheets that can be extremely long, which are then rolled into coils. However, the hot strip steel mill is universally considered one of the harshest environments for process instrumentation and sensors but as the material speed and temperature increases, so does the importance of the measurement values.
X-ray based metal coating weight and thickness sensors are used for accurate, real-time measurements to ensure the stainless steel is on spec, whether the steel is being hot or cold rolled. Stereoscopic x-ray profile gauges have the ability to determine both the cross-thickness profile and the physical position of the strip in space. By using a narrow x-ray fan beam to measure the strip, the system can record the height of each point of the strip in the time domain, and the flatness, or shape, of the strip can be calculated.
Want to know more about hot and cold rolling of steel? Here are our top five articles addressing hot strip mills and cold rolling processes:
How To Gain Better Control of Your Hot Strip Mill Operations
This article addresses some of the sheet metal production challenges that can occur during hot strip mill operation. Obtaining identical properties from coil to coil is challenging because of the heat and speed involved in processing. To ensure product uniformity, hot rolling mills need reliable, repeatable process control data to identify operating issues; off-gauge and off-tolerance product results in the downgrading or even scrapping of coils. Stereoscopic x-ray profile gauges have the ability to determine both the cross-thickness profile and the physical position of the strip in space.
Cold-Formed Steel Shakes Up Building Construction
Cold rolling is a metal forming process in which a sheet of metal is pressed through a pair of rolls to reduce thickness, increase strength and improve surface finish. The cold rolling process happens at ambient temperature, below the steel’s recrystallization temperature. This process changes the mechanical properties of the steel to produce uniform, lightweight steel with a high strength-to-weight ratio. Cold-formed steel is also easy to fabricate, transport, and install; it is moisture-, fire-, wear- and corrosion-resistant; and it is energy efficient.
Are You Wasting Expensive Steel Coating Material?
Coating material is expensive and if applied incorrectly it, along with the steel it is coating, will be wasted. Coating measurement systems are used to verify that the coating meets specifications but when these instruments are located away from the production line, process inefficiencies can go undetected for hours after production is complete, at which point entire coils have to be scrapped. To prevent material waste and re-work, the ideal location for a coating weight measurement instrument is on-line, where it can scan the entire strip and provide feedback in real time. This measurement information can be used to fine tune process variables to improve coating uniformity, optimize raw material use, control energy consumption, and improve product yield. Non-contact sensor technologies used in on-line coating measurement instruments include X-ray fluorescence (XRF) and full spectrum infrared (FSIR).
Maintaining Dimensional Quality in the Hot Strip Mill
There are many derivatives of the modern hot strip mill, from multi-stand to reversing Steckel mills to direct casting, but the end goal is always to produce a coil with uniform mechanical and dimensional properties from head to tail and edge to edge. Advanced process control algorithms use hundreds of variables from various sensors and drives to maximize the prime quality yield from each ton rolled. Starting with the mechanical properties of the steel grade, strip tensions and temperatures are measured between every stand, pressure transducers measure reduction force, and laser-based velocimeters provide line speeds that monitor mass flow for use in feed-back and feed-forward control loops. At the end of the mill prior to strip coiler, a simultaneous profile gauge is used to validate that the strip produced meets the tight dimensional tolerances demanded in the marketplace.
In addition to the cold-formed steel that makes the construction of these amazing structures possible, tons of other steel products are used inside these buildings. Cold-rolled, galvanized and other flat sheet steel is used in the ventilation duct work, fire doors and office furniture. Modern cold rolling mills are able to achieve high speed production of sheet steel that meets a variety of requirements for thickness and uniformity with the help of an x-ray thickness gauge.
Adhere to specifications so you know if hot or cold rolling is the best process, and use gauges to confirm thickness and other measurements. That’s the easiest way to help ensure that the final product comes out just right.
Leave a Reply