# How to measure radius of steel sheet?

December 14, 2021

### PIPE BENDING: THE IMPORTANCE OF THE BENDING RADIUS

The bending radius is a fundamental value for the feasibility analysis of the bending of the steel sheet: it is an indispensable value as it serves to define the coefficient that indicates the degree of difficulty of cold deformation.

The bending of a sheet is a process that takes place on particular sheet bending machines through the use of specific equipment.

Content index

• The radius of curvature and its matrix
• Special features of the bending radius in round sheets
• The radius in square and rectangular sheets
• Metal alloys and radius of curvature
• Differences between matrices

### The radius of curvature and its matrix

To impart a certain radius of curvature to a tubular you need a matrix with a diameter. Moreover, it is corresponding to that of the sheet that curved and the desired radius of curvature. These matrices, designed by our technical department with 3D software, obtained from an initial block of tempered steel.

Then they undergo a hardening treatment to increase their resistance. Thus prevent them from damage during the bending of the sheet. The radius of curvature is the measure that the matrix applies to the tubular. In the case of round sheets, reference is always there to the average radius of steel sheet.

Therefore, it is referring to the median axis passing through the sheet, while for square and rectangular tubular.  Reference is there to the internal radius, thus passing through the curved internal part of the tubular. In the latter case, however, for the feasibility formulas we always refer to the average radius.

### FIND OUT HOW DOES STEEL SHEET BENDING WORKS

The radius of curvature refers to the average axis of the steel sheet: this is its neutral axis as it passes through its median line. The mean axis provides important information on the feasibility of the curvature. It is also the value on the basis of which, thanks to a formula, the length of the bent sheet.

The possible radii of curvature, referred to a given pipe diameter, usually vary from a minimum of 1.5 to a maximum of 5 times with respect to the diameter of the pipe. These two values ​​are defined as the minimum mean radius and maximum mean radius of curvature of the sheet.

EXAMPLE: For a pipe Ø70mm, the average minimum bending radius is 105 mm while the maximum average bending radius is 350 mm. It is sometimes possible that these values ​​may vary thanks to the use of special tooling for the various sheet benders.

### PARTICULARITY OF THE RADIUS OF BENDING IN ROUND STEEL SHEETS

Round sheets are bending for the reference radius, for the calculation formulas. Also for the indication of how to bend it, is the average bending radius.

This is because we theoretically refer to the neutral axis of the sheet, therefore through that imaginary line that crosses it centrally.

### THE RADIUS IN SQUARE AND RECTANGULAR SHEETS

Also for square / rectangular sheets the analysis of the feasibility of the sheet bending found out considering the average axis and therefore the average radius of curvature.

When ordering, it is important to refer to the internal radius of steel sheet. This is because the bending matrix for a square / rectangular sheet is different than a matrix for round sheets. While in the latter the radius of the matrix corresponds to the average radius of the bent sheet.

In the square sheets the radius of the matrix corresponds to the internal radius of the deformed (cold) product. Below is an example of a matrix for square / rectangular tubulars.

### METALLIC ALLOYS AND RADIUS OF CURVATURE

Each bending radius has link to the matrix used. So there are no differences if you want to use a steel, stainless steel sheet or aluminum sheet.

If we have a Ø70 steel pipe to bend with an average radius of 105 mm, the same matrix will also be useful for a Ø70 aluminum pipe.

### DIFFERENCES BETWEEN DIES

Each radius of curvature has its own matrix. It is produced based on the diameter of the sheet to be machined. For example, for an average radius of 50 mm there will be more matrices: one for the pipe Ø20, Ø26.9, Ø30 and so on as long as the bending feasibility formulas allow it.

In square and rectangular tubular you have a little more flexibility. In fact, it is possible to bend several sheets of different dimensions on the same matrix according to the height of the same and the thicknesses used to adapt it to the different measures.

We have more than 250 matrices for round steel sheet and about 30 matrices for tubularThe former are precisely for 250 pipe sections with different bending radii while the latter, due to the particularity that they can be used for several sections, can satisfy the needs of 500 types of tubular.

Also for sheet calendaring, there are formulas to evaluate the value of the calendaring radius. They are the same as the curvature but the coefficients we are going to consider are different. This is decisive for the purposes of the feasibility of the processing.

Unlike bending, the calendaring radius is much larger and ranges from 5 times the diameter of the sheet to infinity. To remain within the scope of the previous example, for a Ø70 sheet the minimum calendaring radius will be 350 mm and the maximum will be a theoretically infinite value.

### Summary steel sheet

The radius of a calendared steel sheet, however, is no longer by a matrix with fixed measurements. But by a set of three rollers which, approaching or distancing them from each other, deform when cold and impart the desired radius.

Steel is widely present in the mechanical construction of metallic structures, equipment, appliances, automobiles, machinery and parts in general, having a wide variety of applications.

Industry is a sector that benefits greatly from the use of steel, starting with the manufacture of the machines themselves. Among their characteristics, one of the most striking is the fact that they are fully recyclable

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