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Selection of raw material width of high frequency welded pipe strip
Release time:
2018-12-06 13:53
The correct selection of strip width is of great significance to the dimensional accuracy and weld quality of the finished pipe. The raw material width of high frequency welding is affected by various factors, such as material, welding current frequency, edge state of strip steel, welding allowance, sizing allowance, etc. Generally, it can be calculated according to the following empirical formula:
The correct selection of strip width is of great significance to the dimensional accuracy and weld quality of the finished pipe. The raw material width of high frequency welding is affected by various factors, such as material, welding current frequency, edge state of strip steel, welding allowance, sizing allowance, etc. Generally, it can be calculated according to the following empirical formula:
1)B=p(D-t) D1 D2 D3
where B --- width of raw material, mm;
D --- outer diameter of finished tube, mm;
T --- Thickness of finished tube, mm;
Δ1 -- Forming allowance, mm;
Δ2 -- welding allowance, mm
Δ3 -- sizing allowance, mm.
The values of Δ1, Δ2, and Δ3 are selected from the following table.
Forming allowance Δ1, mm
| D/t | 10～15 | 15～25 | 25～40 | 40～60 |
| D1 | 1/2 t | 2/3 t | 3/4 t | t |
Welding allowance Δ2
| t | ≤1.0 | 1.0～4.0 | 4.0～6.0 |
| D2 | T | 2/3t | 1/2t |
Stake allowance, mm
| D |
6 ~
22
|
22～
35
|
35～48 |
48～
70
|
70～95 | 95～121 | 121～146 | 146～170 | 172～200 |
| D3 | 0.7 | 1.0 | 1.3 | 1.5 | 2.0 | 2.6 | 2.9 | 3.2 | 3.5 |
Scope of use: steel pipe with diameter below 219mm.
2) B = π (DTΔDk-t) kt, mm
DT -- Diameter of the last hole of sizing mill, mm. DT = D -(0.2~0.3) is preferable;
ΔDk-sizing allowance, mm;
k-coefficient considering welding allowance.
ΔDk is determined by the diameter of the tube and the structure of the sizing mill. For the diameter of 76mm below the cantilever structure of the sizing machine, ΔDk can be 0.25~0.50mm; for the gantry structure of the sizing machine, ΔDk can be increased to 0.80mm. When the diameter of the quality control tube is greater than 168mm, ΔDk can be 1.2~1.5mm; When the diameter is greater than 216mm, it can be 2.9~3.5mm.
The coefficient k is determined by the wall thickness of the pipe, but it also has a certain relationship with the material and the diameter of the pipe. The smaller the wall thickness, the larger the diameter, and the smaller the carbon content in the steel, the larger the k value. According to production experience, the value of k is generally 0.5~2.75. Refer to the table below for specific values.
value of coefficient k
| Diameter of steel pipe, mm | Wall thickness, mm | K | Diameter of steel pipe, mm | Wall thickness, mm | k |
| 6.35～25 | 0.6～1.6 | 1～1.5 | 89 | 4 | 0.75 |
| 38 | 1.0～1.5 | 0.9～1.0 | 168 | 5 | 0.7 |
| 16～50 | 0.5～2.0 | 2.0～2.75 | 219 | 5 to 10 | 0.35～0.7 |
| 60 | 3.5 | 0.8 | 508 | 8～12 | 0.2～0.4 |
| 12～76 | 0.8～3.2 | 0.67～2.5 |
The calculation result of the above formula is the minimum value of the strip cutting edge width, and the upper limit can be increased by about 1mm. When the use of hot strip steel direct production, considering the round edge, oxide skin and other factors, the minimum size should be 0.5mm.
This type can be used in a wide range of up to 508mm in diameter.
3) B = π(D-0.5t), mm
This type is used for general water gas pipes.
4) B = π(D-t)× 1.04~1.05, mm
When D>40mm, take 1.040~1.045; when D≤ 40mm, take 1.046~1.050.
or B = π(D-t) 4~5, mm
This type is used for thin-walled tubes.
5)B = πD-2t 1 z, mm
where z is the coefficient, selected from the following table.
Coefficient z value
| Diameter of steel pipe | ≤ 18 | 18.1～25 | 25.1～40 | 41～50 | >51 |
| Z | 0.4p | 0.48p | 0.56f | 0.6p | 0.72p |
| 1.26 | 1.51 | 1.76 | 1.89 | 2.26 |
This formula is used to calculate the width of the raw material for the double radius pass design.
The above are the five calculation formulas of bandwidth. Due to the different conditions of the unit, the calculation results according to the above formula need to be tested and corrected in production practice.
If the selected raw materials have to be cut on the welded pipe unit, the width must also consider the trimming margin of 10~15mm.
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