Cold formed steel sections are a steel type item thats very high in demand nowadays. Cold forming or cold forging, is a method of shaping done mostly with metals.
What is Cold Forming? (Cold Forged)
Cold forming is a chipless forming method that is applied by reducing the cross-section and extending the material length by passing the sections of hot rolled steels through a smaller mold in order to obtain a more precise surface quality.
The desired hardness can be achieved on the surface without heat treatment. However, problems may occur in the structure of the material as it interferes with the cold formed steel sections material structure. For this reason, it is necessary to apply surface crack control after cold forming.
Hot Finishing Processes
Classically; Hot rolled products are brought to their final dimensions with machining methods and a serious level of surface smoothness is ensured. However, labor and material costs are more than the cold formed steel sections. The main facilities for finishing processes, which are the main indicator of quality after hot rolling:
· Scale Cleaning
· straightening machine
· Steel Shot Spraying Machine
· Ultrasonic Tester
· Surface Crack Tester
· Grinding Stations
· Quality Control and Packaging System
Precision Steel Production Lines,
· Sandblasting Plant
· Cold Forming Plant
· Straightening Bench
· Peeling Plant
· Straightening Bench
· Grinder
Cold Forming Process
Cold forming of steel is generally done in EN10278 standard and h9 - h11 dimensional tolerances are provided. Cold finished bars are produced by forming hot rolled bars from a die and grinding or peeling. Depending on the application production methods, cold finished steel bars are collected in 4 basic sections.
· Cold Drawn Rods
· Accepted peeled + Polished sticks
· Cold drawn + Ground + Polished Bars
· Peeled + Ground + Polished Sticks
Among them, cold formed steel framing and Cold Drawn rods are the most widely used.
The tensile and yield strengths and machinability of cold formed steel sections, ground and polished bars are higher than those of cold drawn bars. In addition, the dimensional tolerances are in lesser ranges.
Strenghts of the Cold Forming
Among the cold formed steel sections, the ones chosen for their mechanical properties are cold drawn bars. The tensile and yield strengths of cold drawn bars are higher than those of hot rolled bars. This is due to the phenomenon known as "work hardening" or "hardening" created by cold working.
Surface defects of cold rolled bars cannot be easily determined by visual methods. Therefore, when the surface of standard quality and ordinary cold rolled bars is required to be free from surface defects, a certain amount of surface chipping is required with cold formed steel structures.
Cold Forming Benefits
Cold forming is a metal forming process in which a piece of metal is forced through a single series of molds, thereby reducing the cross-sectional size of the original part. The cold forming process increases both yield and tensile strength while yielding a dimensionally consistent final cold formed steel sections. The resulting surface is clean and free of scale or other defects. Cold forming is typically used to produce precision steel, copper and aluminum bars, rods and wire that must conform to stringent physical and mechanical properties.
During the cold formed steel process, a stationary platform, called a forming bench, is used to hold the die in place. The machine has an infeed and outfeed side. The outfeed side consists of a long roller platform used to catch the finished stock after it has passed through the die. Metal material, usually in the form of rods or wires, is loaded on the feed side. One end of the metal stock is reduced in size so it can pass through the die. A hydraulic cylinder or winch is then used to pull the metal through the die and onto the outfeed rollers.
Types of Cold Forming
There are three main types of cold forming including cold formed steel sections: tube forming, bar forming and wire forming. Pipe forming decreases both the inside diameter (ID) and the outside diameter (OD) while increasing the pipe length. The thickness of the pipe wall remains constant. Bar pull increases the length while decreasing the cross section of the original bar stock.
The width or height of the original stock can remain constant, although often both dimensions are reduced. Wire forming decreases the OD of the wire stock while increasing the length. Depending on the cold formed steel design, the volume of the wire remains constant. Wire forming usually requires several steps to reduce the wire to the desired size. The dies used in wire forming are usually produced from tungsten carbide or diamond.
Changing the Mechanical Properties with Cold Forming
In addition to changing the physical dimensions, cold formed steel sections also changes some of the mechanical properties of the original stock. Increases in tensile strength of 30% are possible, and increases in yield strength of 80% are common with most materials.
Cold former steel is used in the manufacture of copper electrical wiring and household wiring, as well as structural steel and industrial piping. The cold forming process produces many common everyday items such as paper clips, guitar strings, and bows. Other applications include hydraulic tubing and tubing as well as various musical instruments and electrical components.
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