Knitting wire only at first glance may seem like insignificant building material, but still it should not be underestimated. This product is an indispensable component, which is widely used for the construction of durable structures made of reinforced concrete, securing cargo during transportation, for masonry nets and the manufacture of the foundation frame. The use of knitting wire allows you to perform some types of work, reducing the cost of their total cost.
For example, if a building frame made of reinforcement is knitted using wire, it will cost several times cheaper than if it had to be fastened using electric welding . Thick and strong sebaceous ropes are woven from knitting wire, they make a well-known netting net, and are also used in the manufacture of barbed wire. Knitting wire rod made of steel is an indispensable component that is used in various fields of industry and national economy.
What is it and where is it used?
Knitting wire belongs to an extensive group of building materials made of low carbon steel, where in combination with carbon steel contains not more than 0.25%. Steel billets in molten form are subjected to the drawing method, pulling them through a thin hole, applying high pressure for this - this is the end product, called wire rod. To make the wire strong and give it its basic properties, the metal is heated to a certain temperature level and subjected to high pressure treatment, after which the material undergoes a slow cooling process. This technique is called annealing - the metal changes the crystal lattice under pressure, and then it slowly recovers, thereby reducing the stress process inside the material structure.
The use of knitting steel material is most in demand in the construction industry. Using this material, you can knit steel reinforcing bars, creating frames from them, perform floor screeding, flooring. Knitting wire is a strong, but at the same time elastic element for fastening. Differing from the welding fastener, the wire does not impair the properties of the metal at the heating place, and it does not need heating itself. This material resists various repeated strain loads and bends.
In addition, the coated knitting wire is reliably protected from metal corrosion, which only enhances its positive consumer characteristics.
Obeying the requirements of GOST, the knitting wire is made of annealed steel with a low percentage of carbon content, so it has ductility and soft bending. The wire can be white, with a steel sheen that gives it a zinc coating, and black, without additional coating. GOST also regulates the cross section of the wire, which is selected for frame reinforcement in a certain way.
For example, the diameter of the reinforcement is 14 mm, which means that to fasten these rods you need a wire with a diameter of 1.4 mm, and for reinforcement with a diameter of 16 mm, a wire diameter of 1.6 mm is suitable. The batch of wire produced by the manufacturer without fail has a quality certificate, which contains the physicochemical characteristics of the material, the diameter of the product, the batch number and its weight in kg, coating, as well as the date of manufacture. Knowing these parameters, it is possible to calculate the weight of 1 meter of knitting wire.
When choosing a material for knitting reinforcement, you should know that diameters from 0.3 to 0.8 mm are not used for these purposes - such a wire is used to weave a mesh netting or is used for other purposes. Diameter sizes from 1 to 1.2 mm are often used when working in the low-rise housing sector. And for the construction of powerful reinforced frames take a wire with a diameter of 1.8 to 2 mm. When linking the frame, the wire is most often used after heat treatment, unlike the usual one, it is more resistant to corrosion and less susceptible to stretching, which means it makes it possible to build a truly reliable and durable frame.
The diameters of galvanized knitting wire differ from uncoated analogues. Galvanized wire is produced in sizes from 0.2 to 6 mm. A wire without a galvanized layer is from 0.16 to 10 mm. In the manufacture of wire, differences with the specified diameter of 0.2 mm are allowed. As for products with galvanization, their cross-section may become oval after processing, but the deviation from the diameter specified by the standard cannot exceed 0.1 mm.
At the factory, the wire is Packed with coils, their winding is from 20 to 250-300 kg. Sometimes the wire is wound on special coils, and then it goes for wholesale from 500 kg to 1.5 tons. It is characteristic that in the winding the wire according to GOST is a whole thread, while up to 3 pieces are allowed to be wound on a spool.
The most demanded wire for reinforcement is the BP brand, which has corrugations on the walls, which increases its adhesion strength to reinforcing bars and its own coils.
In 1 meter of wire grade VR contains a different weight:
- diameter 6 mm - 230 gr.;
- diameter 4 mm - 100 g .;
- diameter 3 mm - 60 g .;
- diameter 2 mm - 25 g .;
- diameter 1 mm - 12 gr.
BP brand is not available with a diameter of 5 mm.
For various purposes not only related to construction, steel knitting wire is used according to its nomenclature specifics. Annealed wire is considered more ductile and durable. When choosing a material for certain types of work, one should take into account the characteristics of the wire.
White and black
Based on the type of thermal hardening, the knitting wire is divided into untreated and one that has gone through a special cycle of high-temperature annealing. Heat-treated wire in its nomenclature marking has an indication in the form of the letter “O”. Annealed wire is always soft, with a silvery sheen, but despite its ductility, it has a rather high strength to mechanical and explosive loads.
Annealing at the knitting wire is divided into 2 options - light and dark.
- A light version of the steel wire rod annealing is performed in special furnaces with bell-shaped installations, where instead of oxygen a protective gas mixture is used that prevents the formation of an oxide film on the metal. Therefore, such an output wire turns out to be light and shiny, but it also costs more than a dark analogue.
- Dark annealing of a steel wire rod is carried out under the influence of oxygen molecules, as a result of which an oxide film and scale are formed on the metal, which creates a dark color for the material. Dross on the wire does not affect its physico-chemical characteristics, but when working with such material, the hands are very dirty, so the price of the wire is lower. Work with black wire is carried out only in protective gloves.
The annealed wire, in turn, can be coated with a zinc layer or released without such a coating, and some types of wire can be coated with a protective anticorrosive polymer composition. The light annealing wire has the letter “C” in the nomenclature, and the dark annealing wire is marked with the letter “H”.
Plain and rugged
The most important property of a steel rod is its strength. In this category there are 2 groups - ordinary and high strength. These strength categories differ from each other in that a low-carbon steel composition is used for ordinary wire, and special alloying components are added to the alloy for high-strength products. In the nomenclature, the strength of the product is marked with the letter “B”.
For wire of ordinary strength, “B-1” will be indicated, and for high-strength products, you will see the mark “B-2”. If it is required to assemble a building frame from prestressed reinforcing bars, for this purpose a product with the marking “V-2” is used, and when performing installation from reinforcement of a non-tensile type, the material “B-1” is used.
1 and 2 groups
Knitting material must be resistant to tearing, based on this, the products are divided into 1 and 2 groups. The assessment is based on the resistance of the metal to elongation during the drawing process. It is known that annealed wire rod can show stretching from the initial state by 13-18%, and products that have not been annealed can be stretched by 16-20%.
At breaking load, the steel exerts resistance, it changes depending on the diameter of the wire. For example, in a product without annealing with a diameter of 8 mm, the tensile strength index will be 400-800 N / mm2, and with a diameter of 1 mm, the index will already be 600-1300 N / mm2. If the diameter is less than 1 mm, then the tensile strength will be 700-1400 N / mm2.
With a special coating and without
Steel wire rod can be with a protective layer of zinc or is available without coating. Coated wire is divided into 2 types, and the differences between them are in the thickness of the zinc layer. A thin layer of galvanization is marked as “1C”, and a thicker coating is designated “2C”. Both types of coating indicate that the material has stainless protection. Sometimes knitting material is produced and coated with an alloy of copper and nickel, it is marked as "MNZHKT". The cost of such a product is very high, for this reason it is not used for construction, although it has high anti-corrosion properties.
How to calculate the flow?
Calculation of the amount of reinforcing wire helps to understand how much material is needed to complete the work and how much it will cost. In bulk purchases, the cost of the material is usually indicated per ton, although the maximum weight of the coil with wire rod is 1,500 kg.
The norm of the knitting wire, which is required to carry out a certain set of works, is calculated based on the thickness of the frame reinforcement and the number of nodal joints of the structure. Usually, when joining two rods, you will need to use a piece of knitting material, the length of which is not less than 25 cm, and if you need to connect 2 rods, then the consumption rate will be 50 cm per 1 docking unit.
To simplify the task of counting, you can clarify the number of docking nodes and multiply the resulting number by 0.5. It is recommended to increase the finished result by about half (sometimes enough and a half times) in order to have a margin in case of unforeseen situations. The consumption of knitting material can be different, it can be determined empirically, focusing on the method of performing knitting technology. To more accurately calculate the consumption of wire per 1 cube. m of reinforcement, you will need to have a layout of the docking nodes. This method of calculation is quite complicated, but judging by the standards developed by the masters in practice, it is believed that at least 20 kg of wire is needed per 1 ton of rods.
As an illustrative example, consider the following situation: it is required to build a strip type of foundation 6x7 m in size, in which 2 reinforced belts containing 3 bars in each will be made. All connections made in horizontal and vertical direction should be made in increments of 30 cm.
First of all, we will calculate the perimeter of the future framework of the foundation, for this we multiply its sides: 6x7 m, as a result we get 42 m. Next, we calculate how many connecting nodes there will be at the intersections of the reinforcement, remembering that the step is 30 cm. For this, divide 42 by 0, 3 and as a result we get 140 intersection points. On each of the jumpers 3 rods will be docked, which means that there are 6 docking nodes.
Now we multiply 140 by 6, as a result we get 840 places of connection of bars. The next step is to calculate how much knitting material is needed to join these 840 points. To do this, we multiply 840 by 0.5, and as a result we get 420 m. To avoid a lack of material, the finished result needs to be increased by 1.5 times. We multiply 420 by 1.5 and we get 630 meters - this will be an indicator of the consumption of knitting wire necessary for frame work and the manufacture of a foundation measuring 6x7 m.
The next video talks about how to prepare a knitting wire.