HOW TO CALCULATE THE FEASIBILITY OF BENDING A MILD STEEL PLATE?
The average radius of curvature of the mild steel plate is corresponding to its average axis. It is the imaginary line that crosses the center of the pipe. Moreover, it is a fundamental element of the feasibility study of the bending of pipes, plates and metal profiles.
THEORETICAL FEASIBILITY OF PIPE BENDING
If we have to bend a pipe with the “cold” deformation technique, we must first of all understand if the bending of the pipe is feasible.
To determine the feasibility of the curvature there are theoretical formulas whose result is the K factor. Moreover, the K factor is also useful to determine the feasibility of mild steel plate calendaring.
THE IMPORTANCE OF THE K FACTOR
The coefficient K is on the basis of ranges of values and is useful to determine whether:
- Firstly, it is possible to bend a round, square or rectangular plate (bending feasibility)
- Secondly, the degree of difficulty of the folding
FEASIBILITY STUDY OF THE BENDING OF THE ROUND STEEL PLATE
To verify the feasibility of bending round steel pipes, the ratio between the average radius of curvature, diameter and thickness of the pipe need to consider.
The formula is as follows:
- Rm = mean radius of curvature
- Sp = nominal thickness of the pipe
- Ø = pipe diameter
The result of this formula is the value of the factor K.
How to find degree of difficulty?
The degree of difficulty of the bending of the mild steel plate is inversely proportional to its value. It increases when the K factor is low, while it decreases when it is high.
- K> 0.30 - plate bending is "easier" and there is no need to use specific support equipment, produced "ad hoc".
- 3> K> 0.1 - Bending process of normal difficulty for which it is necessary to use only one internal and fixed spindle.
- 1> K> 0.08 - A counter slide and a fixed internal mandrel are required to bend the plate.
- If 0.08> K> 0.05 - Bending is feasible only with the use of a counter slide and an internal articulated spindle.
- If K <0.05 - Pipe bending is not feasible. In this case, tests must be carried out to assess whether the K value can be lowered and whether it is necessary to build special equipment.
To verify the feasibility of bending mild steel plate, the ratio between the average radius of curvature, diameter and thickness of the pipe is in requirement.
FEASIBILITY OF BENDING SQUARE OR RECTANGULAR MILD STEEL PLATE
The formula for calculating the feasibility of bending square or rectangular steel plate is slightly different from that of round pipes.
The formula is as follows:
- Rm = mean radius of curvature
- Sp = nominal thickness of the pipe
- b = 1st side of the plate (square / rectangular)
- h = 2nd side of the plate (square / rectangular)
As with round mild steel plate, we determine the feasibility and difficulty of bending on the basis of ranges of values of the K factor:
- K> 0.2 - A fixed mandrel is sufficient to bend the plate.
- 2> K> 0.15 - An articulated mandrel is required to bend the plate.
- 15> K> 0.1 - Bending is feasible only using an articulated spindle and a counter slide.
- K <0.1 - The curvature is not theoretically achievable and it is necessary to carry out tests to lower the degree of difficulty.
CALCULATION OF THE K VALUE IN THE BENDING OF THE STAINLESS STEEL AND ALUMINUM PIPE
The formulas we saw earlier serve to determine the feasibility of bending carbon steel pipes. To bend stainless steel and aluminum pipes, which have different characteristics, the K value is lower:
- AISI 304 steel -> Reduce K by about 20%
- AISI 316 steel -> Reduce K by about 25%
- Aluminum 6060 -> Reduce K by about 35%
From the above example, the bending of the mild steel plate is more difficult than that of the AISI 304 steel alloy plate. Moreover, it is less compressible than the latter. This means that the bent stainless steel plate often has "wrinkles" on the inside of the bend.
The K factor of stainless steel (AISI 316) is in fact smaller than that of AISI 304 steel. The bending of the aluminum plate is even more complex, as it has a poor elongation capacity. As a result, the K-factor is reduced by approximately 35%.
DFICULTY IN FINDING OUT IDEAL MEAN RATIO
Metal profiles do not have a standard shape. For this reason, there is no precise formula that allows you to calculate the ideal mean radius of curvature on the basis of the K factor.
To determine in advance the ideal mean radius of curvature of a metal profile with a particular geometric shape, a great deal of experience in bending and calendaring of pipes.
EXTENDING THE PLATE LENGTH: WHAT IT IS AND WHY IT IS IMPORTANT?
Another important factor to take into consideration in mild steel plate bending and calendaring is the elongation of the plate, which is closely related to the length of the plate bend. To know the overall length of the bent plate, including the straight parts, it is in fact necessary to calculate exactly the length of the bend.
To calculate the exact length of the curve, we therefore need to divide the result of the above formula by another coefficient. Furthermore, its value varies according to the diameter of the plate, its thickness, the average radius of curvature and the metal alloy.
For example, a steel pipe Ø30 × 2 mm will have a coefficient, with the same radius, different from an aluminum pipe Ø30 × 2 mm.
Further, the value of the length of the pipe bend is also important. Moreover, it helps to determine the precise point to laser cut and the length of the cut. An incorrect assessment of the position of the laser cutting means that the bent mild steel plate will be longer (or shorter) than it should.
CONCLUSIONS
As we have seen, the K factor is essential in determining the feasibility of bending a pipe. To calculate its value, it is necessary to know the radius of curvature of the plate. However, let us not forget that it is still a theoretical value. In fact, many other variables intervene in the cold deformation of the plate which can determine the success of the bending.
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