Wherever you look, you will find steel sheet – be it the hood of the car or buckle on your boots, the case of a washing machine or a space satellite. Of course, if you understand the details, varieties of sheet metal, a great many, but mostly this products are divided into cold-rolled products and hot-rolled sheet.
Steel sheet itself used for the manufacture of other parts and the quality of the final product, for example, in the construction industry. You never wondered how is it to produce such a thin sheet of metal? The process resembles the rolling test, but instead of test – high quality carbon and alloy steel. The presence of carbon (up to 2.14 %, if more – formed cast iron) is responsible for the strength and alloying additives for plasticity, brittleness, ductility, internal stress of the metal. Carbon and alloying steels combine all of these benefits.
Initially, the workpiece is cleaned from dirt and level the surface to get the most smooth material. Then, billets of steel are under a huge amount of beads and the interaction with each becoming thinner, wider and longer. That is, the metal is rolled into thin "crust" like dough.
Depending on what condition under the rollers is preset, and share rolled to cold rolled and hot rolled. Accordingly, we have sheet cold - or hot-rolled metal. From a school bench we know that in heated the metal becomes more ductile, malleable, therefore, it is much easier to roll out. But on the other hand, the manufacturer should take care of the maintenance of the temperature at the desired level around the perimeter of the sheet and throughout the whole time rolling, increased fire safety, on additional energy costs. When heated, the sheet is formed scale, from which in subsequent use, you need to get rid of, and cools the workpiece unevenly, resulting in noticeable irregularities.
However, the "cold" technology compared to hot has a higher cost, which automatically increases the cost of the finished product. To roll the billet at normal temperatures, require much more powerful machines. However, in such procedure, the metal is not deformed, its thickness is close to the ideal value around the perimeter of the sheet, and the appearance is much better. That does not eliminate the need to heat annealing and compressing the leaves to eliminate the internal stress of the metal. In sum, it turns out that hot-rolled steel sheet is much cheaper than the cold counterpart.
"Cold" technology has another drawback, or rather a limitation – roll steel sheet obtained only to a thickness of not less than 0.5 mm. For many industries, this limitation is a stumbling block that cannot jump, and for this reason they are forced to use hot-rolled sheets.
Cold-rolled sheets of higher-quality, hot rolled – a cheap and more subtle.
So what to choose? It all depends on the scope of application of the material. If the surface there are no special requirements, the hot rolled material would be a great decision, because in terms of the operation and the strength of the particular difference is not seen. Sometimes manufacturers combine both technologies machining hot-rolled products cold rolling. In such cases, the thickness of the sheets becomes more uniform, the neat sheet becomes smooth and shiny look.
Of course, in the production of this important material could not do without a lot of Standards and classifications. With their help, the specialist will make the choice in which he or his company needs. Newcomers also can not do without a crib!
Let's start with the thickness of sheets up to 4 mm are considered to be the result of sheet rolling, from 4 mm to 160 mm – thick plate. Accuracy rolling there are two categories: A and B. the First letter of the alphabet indicates a higher accuracy, and "B" is just normal. With cut edges, the leaves will be marked "O", and no such – "BUT".
Flatness – with this option more difficult. The leaves are particularly high flatness is indicated as "ON" and high – "PV", but there is "PU" and "PN" is the normal and improved flatness. And don't try to fix experienced Metallurgist, hearing the word "assortment". It represents, essentially, the same as range, but metallurgists only way to put it – "assortment". Now, the assortment of rolled steel share also on sheet and roll. According to the type of base rental divided into cold-rolled sheet cold-rolled sheet or hot-dip galvanized. The second indicates that the sheets of steel dipped into molten zinc so that the metal gets protection from corrosion.
The leaves were also divided into categories based on the ability to draw. Steel normal drawing, deep drawing, deep-drawing very difficult and hoods – it's all about the sheet metal. Hot-rolled flat products are regulated and classified by the GOST 19903-74. We should not forget about the appearance of the coating surface. 1st class sheet metal sheet with a solid surface, with individual scratches that do not penetrate to the Foundation. Such sheets are used in printing inks. Class 2 permits, with areas of different shades, uneven coating, scratches and defects of the edges.
In addition to the quality of the steel, should pay attention to the quality of the coating. The leaves were separated by species cover to:
Steel sheet rolling, covered with organics used for the construction of building structures and various devices, as well as in heat insulation of equipment and machinery in the premises and in open space. Cover sheet (paint, organizalion or plastisole) can be both sided, denoted as I or II.
This standard applies to hot-rolled steel sheet width of 500 mm or more, manufactured in sheets with a thickness of 0.40 mm to 160 mm and coils with thickness from 1,2 to 12 mm.
The standard fully complies ST SEV 1969-79 in part rolled non-alloy structural, ordinary quality and low-alloy thickness from 1.00 to 2.80 mm in sheets and rolls and ST SEV 3901-82 in terms of products with thickness from 3.00 mm to 160 mm in the leaves.
Sheet steel is subdivided:
a) accuracy rolling with thickness up to 12 mm:
very high flatness - SOFTWARE;
high flatness - PV;
improved flatness - PU;
normal flat surface accuracy;
c) type of edge:
mill edge BUT
with cut edge;
with dimensions of thickness, width and length in accordance with the dimensions listed in the application - form I;
with dimensions according to thickness within the limits specified in table. 1, without specifying the size, width and length - form II;
with dimensions that are multiples of the width and length dimensions specified in the order, within the limits established in table. 1, to form III;
indicating volumetric size, within the limits specified in table. 1, with intervals of 10 mm in width and 50 mm in length - form IV. By agreement between the consumer and the manufacturer intervals along the width or length may be less than indicated.
Manufacturer of sheet metal, dimensional size that is different from the size specified in the application, made at the request of the consumer.
Maximum deviations in thickness of rolled manufactured in sheets and rolls, at any measurement point shall not exceed the limits specified in table. 3 and 4.
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