Select the width of the highfrequency welded steel raw materials
Select the correct strip width dimensional accuracy and weld quality of the finished tube has a very important significance. Effect of highfrequency welding material width affected by various factors, such as material, welding current frequency, the state of the edge strip, welding margin sizing margin and the like. Generally can be calculated according to the following empirical formula:
1) B = π (Dt) + Δ1 + Δ2 + Δ3
Where B  raw material width, mm;
D  Finished pipe diameter, mm;
T  finished pipe thickness, mm;
Δ1  forming margin, mm;
Δ2  welding margins, mm
Δ3  sizing allowance mm.
Δ1, Δ2, Δ3 value following table selection.
Forming margin Δ1, mm
D/t

10～15

15～25

25～40

40～60

Δ1

1/2 t

2/3 t

3/4 t

t

Welding margin Δ2
t

≤1.0

1.0～4.0

4.0～6.0

Δ2

T

2/3t

1/2t

Sizing margin, mm
D

6～
22

22～
35

35～48

48～
70

70～95

95～121

121～146

146～170

172～200

Δ3

0.7

1.0

1.3

1.5

2.0

2.6

2.9

3.2

3.5

Use: pipe diameter of 219 mm or less.
2) B = π (DT + ΔDk t) + kt, mm
DT  sizing mill pass a final diameter, mm. Preferably DT = D  (0.2 ~ 0.3);
ΔDk  sizing margin, mm;
k consider welding margin coefficient.
ΔDk decided in the finished tube diameter and sizing mill structure. For diameter 76 mm or less cantilevered structures sizing machine, ΔDk desirability of 0.25 to 0.50 mm; gantry structure for sizing machine, ΔDk can be increased to 0.80 mm. Quality control as when a diameter greater than 168 mm, ΔDk preferable 1.2 to 1.5 mm; diameter greater than 216 mm, it is desirable 2.9 to 3.5 mm.
Coefficient k depends on the pipe wall thickness, material and diameter of the tube but also to have a certain relationship. The smaller wall thickness, the larger the diameter, the smaller the amount of carbon in the steel, the greater the value of k. According to production experience, k value generally take 0.5 to 2.75, the values refer to the following table.
Coefficient (k)
pipe OD.mm

thickness mm

K

OD.MM

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

5～10

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 formula is the minimum width of the strip trimming, the upper limit may be increased again about 1 mm. When using the direct production of hot strip, consider rounded edges, scale and other factors, plus the minimum size should be 0.5 mm.
The formula using a wide range, to a diameter of 508 mm.
3) B = π (D0.5t), mm
The general formula for the water gas pipe
4) B = π (Dt) × 1.04 ~ 1.05, mm
When D> 40 mm, whichever is 1.040 ~ 1.045; when D≤40 mm, whichever is 1.046 ~ 1.050.
Or B = π (Dt) + 4 ~ 5, mm
The formula used in the thinwalled tube.
5) B = πD2t + 1 + z, mm
Where z is a coefficient, the following table selection.
Z coefficient values
OD mm

≤18

18.1～25

25.1～40

41～50

>51

Z

0.4π

0.48π

0.56π

0.6π

0.72π

1.26

1.51

1.76

1.89

2.26

The formula for the dual use of raw materials width radius pass design calculations.
These are the five kinds of formulas bandwidth, due to different circumstances the unit, according to the calculated results also need to be tested and corrected in the production practice.
If the selected raw materials but also trimming the welded pipe mill, it must also consider trimming the width margin of 10 to 15 mm.