Coils, sheets and slabs
A defined finish
- Service life is particularly important for finish grinding on coils: and the VSM COMPACTGRAIN long-term abrasive turns in an impressive performance
- Apart from guaranteeing a long service life, the abrasive also achieves a more uniform scratch pattern and a more consistent surface roughness
- From laser-cut to die-cut or even fired workpieces: VSM offers a broad portfolio of abrasive products ranging from fine to coarse
- Descaling is heavy work that requires appropriately high-performance abrasives
- Coarse grain sizes, high stock removal and robust backings are key advantages here
- VSM ceramic grain abrasives – 100% Made in Germany – offer impressive performance across the board for descaling
Coils, sheets and slabs: important preliminary products
Coil, sheet and plate production is one of the biggest and most diverse industries in the world. According to the experts, around half of the world’s steel production (2021: a total of around 1.95 billion tonnes) goes into the production of sheets and plates. Over the past decade, production has grown by around three to four percent on average – per year! From 2020 to 2021, it has recently even increased by 6.8 percent.
The large steel companies are now predominantly based in Asia. China is the largest player with a share of 45 percent of total steel production (2021). The most well-known steel manufacturers in Europe and Germany are ArcelorMittal and Thyssenkrupp. The most important purchasers of steel in Germany are the construction (35 percent of total demand), automotive (26 percent), metal goods (twelve percent), mechanical engineering (eleven percent) and tubes sectors at nine percent.
Definition of coils, sheets and slabs
Coils, sheets and slabs are the main preliminary products or the starting material for the metal processing industry. Slabs are rectangular blocks of metal made of raw steel, aluminium or copper, the width and length of which are many times their thickness. (Steel) slabs are the semi-finished product for coils or sheets: Coils are mainly steel strip rolls that can reach weights of up to 45 tonnes. Sheets, on the other hand, are metal strip roller products in sheet form. Almost any metal can be processed into turned sheet form. They are categorised as sheet metal (up to 3 mm thick) and heavy plate.
Coils, sheets, plates and slabs are made of either non-ferrous metals such as aluminium and aluminium alloys, titanium and titanium alloys or brass and bronze. They are mostly made of ferrous materials such as steel and especially corrosion-resistant steel. Corrosion-resistant steel in particular is becoming increasingly important: Its share of global steel production has roughly doubled in the last decade alone.
Increasing grinding requirements
Recently, the demand for consistent, high-quality workpiece surfaces has continued to rise. There is also a trend towards ever finer surfaces. Every error on the workpieces becomes visible. This goes hand in hand with the development towards greater demand for stainless steel. Especially corrosion-resistant steel, which is used for structural parts, for example, places high demands on the abrasive due to its material properties. It is considered particularly tough, has low machinability and poor thermal conductivity. All of this raises heat generation on the workpiece and grain wear – so abrasives are required here to counteract this. With “cool” grinding, VSM ceramic grain abrasives reduce the temperatures in the grinding zone and thus ensure significantly longer service lives and high stock removal when processing stainless steels.
Grinding tasks from coarse to fine
In the surface processing of coils, sheets and slabs, the entire range of grinding applications, from coarse to fine, is used throughout the entire production process. First of all, deburring sharp edges, fraying and burrs on the cut edges must be completely removed. Surface unevenness or even damage is also ground during reclamation grinding. There is also the descaling of thermally processed, hot-rolled surfaces. The undesired oxide layer can be easily abraded, but, like all the applications mentioned here so far, requires powerful, durable and low-wear abrasives with high stock removal, such as such as VSM Ceramics, Ceramics Plus or Actirox. The next step is refinement to fine surfaces with specific scratch patterns, for example the well-known industrial finish on fronts of electrical appliances, for cladding of lifts or entire building facades. Depending on the specific requirements or specifications of the customer, where a clearly defined, specific surface roughness or gloss level is desired, technically or visually assessed surfaces can be produced. When it comes to a long service life and a uniform scratch pattern, the long-term abrasive VSM CompactGrain is the right choice. If the goal is perfect high-gloss or mirror-gloss surfaces with a high Gloss Unit, polishing may be required. A case for VSM Ilumeron, the specialist for perfect surfaces and the highest gloss levels in the VSM portfolio.
Overview of flat grinding processes
Since coils, sheets and slabs are usually very large workpieces, machining with wide belt machines is the standard. There are specific grinding machines in a wide range of dimensions and designs for every application, such as specially designed coil grinding machines. Four grinding processes in particular are used, also in combination with successive grinding stations, to achieve an ideal, uniform surface:
- Flat grinding with support roller: Here the workpiece is held with rollers, supported by a roller in the grinding zone and transported with feed rollers. This process is particularly suitable for flat workpieces of all lengths and medium to low thicknesses, where a constant surface quality is desired. The main products are coils, sheets, square bars and tubes. Users include, in particular, sheet steel manufacturers, dealers and service centres that, for example, subject coils from the steelworks to surface processing.
- Flat grinding with transport table: This grinding process operates without feed rollers that guide and transport the workpiece. Rather, the workpiece is fixed on a table that moves in a reverse direction under the grinding head. It is very low-vibration and also well suited for particularly thin sheets, or for the reclamation grinding of hard workpieces. Sheets made of nickel and titanium alloys can also be machined with it. Sheet steel manufacturers and mechanical and plant engineering in particular rely on flat surface grinding with a transport table.
- Surface grinding with portal grinding machines: This grinding process is ideal for processing very large workpieces. Plates or sheets are ground lying on the machine substructure or on the ground. The grinding unit travels above the workpieces and partially processes the surface over the entire surface in several passes. This mainly involves rough machining such as descaling and reclamation grinding.
- Flat grinding with upper belt machines: With these long belt sanders, the workpieces are clamped onto a table or into a handling device and the abrasive belt is pressed onto the workpiece. This method is suitable for flat workpieces of small and medium lengths and all thicknesses (up to large housings) as well as for applications requiring high contact pressure. Users from machine and plant engineering as well as sheet steel manufacturers and dealers primarily process sheets, welded parts, containers, housings, profile tubes, control cabinets, stainless steel cladding and cast steel parts.
Environmental aspects in coil, plate and slab production and grinding
Steel production is one of the most energy- and resource-intensive productions in the world, accounting for eight percent of the world’s CO2 emissions. The production of one tonne of crude steel consumes around 5,700 kWh of electricity – the energy required by a two-person household each year. For this reason, steel manufacturers are trying to integrate new, more climate-friendly processes, such as the use of hydrogen produced from renewable sources instead of coal in ore processing. The German steel industry, for example, has set its sights on the path to “low-CO2 steel production”.
Environmental aspects are also becoming increasingly important when processing steel or non-ferrous metals. Abrasives that have the longest possible service life are particularly advantageous here. Compared to conventional products, VSM long-term abrasives achieve up to six times the service life. This means: Only one sixth of the time and effort is spent on production, transport and storage. And, of course, only a sixth of the waste. An effective contribution to the most resource-efficient production possible.