Pure iron is characterized by a limited list of properties and both the base metal is of little interest.But its alloys possess enormous potential, it is necessary only to determine the chemical composition and make the correct heat treatment.
most common structural steel
All the steel on the basis of iron are steel and have numerous classification.It is produced by various parameters: the chemical composition, purpose, content of harmful elements, strength and toughness, flexibility, and many others.Structural - become the most common in use.Some of them have universal characteristics and are interchangeable.
Structural Steel 20 refers to a class of medium-carbon, it has a ferrite-pearlite structure.Steel quality, t. E. It has a reduced content of harmful elements: sulfur and phosphorus.No restrictions on the weldability.The optimum combination of strength and ductility makes it a universal material for the production of tubular rolled parts subjected to subsequent thermomechanical and thermochemical treatment (cementation, galvanizing and chromium plating).Twenty
found its use
Steel 20, the properties of which can vary within wide limits by means of chemical-thermal, thermomechanical treatment, the most in demand in pipe production in the manufacture of parts with a solid surface and a soft middle.It can be shafts, sprockets, transfer, bolts, hooks faucets, valves, sheets for stamping (profiles), the nuts and bolts for mounting irresponsible.Produce pipes of this grade of steel is used for the transmission of gas, steam, non-corrosive liquids, is supplied under pressure.This superheater pipes, pipelines, high-pressure boilers and collectors.
Restructuring thermochemical treatment
The same brand can change their characteristics by heat treatment.Steel grade 20, has good plastic properties, so the products it is prepared in several ways: casting, cold or hot rolled or drawing.Upon receipt of parts by casting them can be used thermochemical treatment.The purpose of this procedure - to get a hard wear layer, is not amenable to corrosion, plastic and soft middle.
For this finished part is placed in an appropriate environment (obkladyvaetsya dry carbonaceous substance is placed in a gaseous or liquid medium), and allowed to stand for several hours to 1.5 days at high temperature.Mechanical treatment of details at this point should be completed as a product after the thermochemical treatment would have been the final structure.Element saturates topsheet products (from 0.3 to 3.0 mm), respectively, by improving its structure and properties.
Depending on the material used treatment is called: cyanidation (zinc coating), cementation (carbon), chromium (chromium).Carbon gives strength, zinc - corrosion resistance, chromium, in addition to everything listed, making the surface of the mirror.
Restructuring machining
Unlike the previous method of treatment, which is carried out exclusively for imparting hardness in the upper layer of the metal and flexibility of domestic thermomechanical treatment - is a method of shaping.Steel 20 can be deformed both hot and cold way.Each form has its own advantages and disadvantages.But they are used according to the most relevant properties.
hot deformation is applied to articles having a wall thickness greater than 5 mm.Since the heated metal and slag formed decarbonized microlayer (undesirable structure) is used for this type of rolling thin-walled parts impractical.But he has one big advantage over the cold deformation.
cold deformation applied to detail, having a thickness of less than 5 mm.For cold drawing only suitable "soft" types of steel.During rolling metal undergoes significant deformation or work hardening.This leads to an increase in its strength and the presence of high stresses in the structure.Such metal because of its thin walls can not be heated (to spend a vacation, t. E. To restore the old structure).It is more susceptible to impact damage and other dynamic loads.Structural steel pipe (steel 20) different methods of manufacture, and receive technical characteristics that affect the application.For the production of each kind of pipes have their own state standards, rules and equipment.
Cold pipe straight seam
The production process begins with the preparation of the steel strip.For this steel sheets are cut into strips and welded into one long belt.Served tape bending rolls, where it takes the form of a pipe.The next step - welding.For any construction is the weakest link.To overcome the disadvantages which arise when welding (occurrence of burnout and carbon oxides) is completely impossible, but using some of the techniques, can be reduced.To connect the steel 20 is used in electric arc welding of protective inert gas (argon) or induction welding (high-frequency currents).The pipe passes a mandatory inspection of the weld, and then cut to the desired length and detail stored.
cold drawn tubes with spiral seam
Preparations began for the production of this type of pipe repeats the same process as for the tubes with a direct view of the seam.It is also identical: welding, control and pruning.It features only the angle of folding the tape, in which the subsequent seam surrounds the pipe on the spiral curve.By virtue of its design features this method is the most durable.And withstand large tensile loads than the data items with straight seam.
Seamless pipe Seamless pipe
particularly strong, have several advantages: they have no welded (weaknesses) in the steel structure, there are no voltage, the thickness of the pipe is at least 5 mm.Their production - more complicated, and therefore expensive.Steel 20 is unique in that the pipe can be made in two ways - hot and cold drawing.Hot-rolled seamless
After heating above 1100 ° C blank stitched sleeve and forms an inner diameter.As further drawing pipe receives a predetermined size internal, outer diameter and wall thickness.During the whole process the temperature of the rolled product remains high.It was only after the adoption of the final form of tube cools.During long-term cooling takes vacation, removed all the negative consequences of rolled, high strength and fragility.At full cooling gets steel 20 characteristics that were originally.This process involves the production of only pipes with walls of at least 5 mm and maximum thickness can reach 75 mm.
Cold Drawn Seamless
Unlike the previous method, this small temperature observed nuance.The preform is heated, but after the initial temperature of the sleeve firmware is not supported, and the workpiece is pulled in the cold state.This method differs from a hot-rolled so that it is possible to produce solid-walled thin tube, whereas the hot-rolled method provides only thick walls.For a finite structure, the two methods are identical, since after cold rolling tubes undergo normalization, in which the structure is partially restored, and pressure leaves.
This is not the whole list of products, which are based on lies steel 20 GOST 1050-74.Increasing needs of the population, there are new ideas and production.But this brand only changes form and destination, reserving the right to exist.
