**A COMPUTER PROGRAM FOR CHOOSING WELDING PARAMETERS**

**IN SPIRALLY WELDED PIPE PRODUCTION**

**Kahraman ŞİRİN,** Mannesmann Pipe Company

**Şule Y. ŞİRİN,** University of Kocaeli

**Erdinç KALUÇ,** University of Kocaeli

**Abstract:** The main problem faced in the manufacturing of the pipe by
SAW is the choosing of the process variables. Therefore, identification
the effect of the process parameters and finding their limits are
essential in order to get the required bead size and quality. Regarding
with the pipe production, a computer program in Excel is developed to
choose the welding parameters. This program is mainly based on the
relation between welding parameters and weld bead size and quality.

**Introduction:** The principle of the spiral pipe production is simply
the bending of the steel strip into cylindrical shape and ultimately
welding edges together in two steps as inside and outside weld. The
submerged arc welding (SAW) process is widely used for spirally welded
pipe production. In this process, welding parameters namely welding
current, arc voltage, weld speed, diameter of the wire, number of the
electrodes, melt-off rates, edge joint design including bevel angle and
root face, wire configuration and etc. are very effective on welding
quality. All those parameters should be optimized to get satisfactorily
weld quality. This computer program is developed to optimize welding
parameters. The working steps of the program are given below in detail.

**The working steps of the program:**

After entering the diameter and wall thickness of the pipe to the
program, it will be seen automatically permissible number of the
electrodes, which can be used for inside weld. In spirally welded pipe
production, there is only a very limited area to positioning the inner
welding heads, when the diameter of the pipe is getting smaller.
Therefore, the number of electrodes for inside weld should be limited in
accordance with the diameter of the pipe.

Secondly, the program asks the required pipe production to define the
main geometrical dimension of the weld. Penetration, width of the bead
and height of the reinforcement are taken into consideration as main
characteristics of weld by the program. Penetration, for both inside and
outside weld, should be at least 60 per cent of wall thickness to
provide good joint. Width of the bead should be as wide as to give
enough surface area to the gases to leave easily to the weld pool.

As a third step of the program, the grade of the material is asked to
give the lower and upper limits of the heat input. An increase in heat
input could result in a wide heat affected zone (HAZ) with low impact
strength. In spirally welded pipe production, high rates of welding
speeds can be achieved by using multiple electrodes. In two-pass SAW
process, each pass (inside and outside weld) can be considered as one
puddle even using multiple electrodes. Heat input for each pass could be
calculated equation given below;

~n~

*H~n~ = (f Σ I .E) / v*

^1^

where, *H~n~* is net heat input, *I* is welding current, *E* is arc
voltage, *v* is welding speed, *f* is heat transfer efficiency and *n*
is number of electrodes. Also, two-pass multi-electrode SAW process
could be characterized by cooling time, which is around 50 seconds.
Cooling time, between 800 to 500 ^o^C, can be calculated by using
Rosenthal's equations given below.

![](media/image1.jpeg){width="3.251388888888889in"
height="0.5090277777777777in"}

![](media/image2.jpeg){width="3.1256944444444446in"
height="0.46041666666666664in"}

On the next step, user should define the joint preparation in
conjunction with the wall thickness. Generally, Y or X type of joints
could be used for thickness from 8 mm (see figure 1). The main purpose
of joint preparation is to ensure required penetration. Here the main
criteria are the angle of the bevel and the height of the root face. The
bead width and depth ratio (W/D) should be between 1 and 4 to prevent
hot cracking. Therefore, bevel angle should be bigger than 60^o^. This
will also help not to having flux inclusions in the weld. The root face
could be 60 per cent of wall thickness.

> I type Y type X type

Figure 1. Type of joints

After definition of joint type, automatically the cross-sectional area
of reinforcement and bevel are calculated in accordance with weld
geometry design and type of joint. By this way, the cross-sectional area
of the added filler metal in mm^2^ is cleared. This is done for both
inside and outside weld separately. After that, the program easily
computes possible highest weld speed. As a last step of in this stage,
the weld speed is chosen by the user according to permissible limits
given by the computer.

Finally, the user should choose welding currents starting from the first
head of the inside weld then second and third ones if necessary.
Multiple arc welding usually consist of a DC(+) welding head on the lead
arc followed by AC welding heads on trailing arcs. To define the current
levels it is necessary to know the relation between current and wire
melt-off rate. The below equations developed by *Chandel and Baya* could
be used for predicting of the deposition rate of submerged arc welding
process; where MR is melting rate in kg/h, I is welding current, L is
the electrode extension and d is diameter of the wire.

MR ~DC(+)~ = 0.010371.I + (2,2426x10^-6^ .I^2^.L)/d^2^ -- 0,462

MR ~DC(-)~ = 0.016178 .I + (2,087x10^-6^.I^2^.L)/d^2^ -- 0,643

Measured wire feeding values, under various conditions, are plotted in
Figure 2. It can be seen that actual values are closed to the
theoretical values, originated from Chandel's equation (Table 1). There
is around 5,5 % difference which is acceptable to make prediction about
deposition rate.

Table 1. Comparison between actual and theoretical values about
deposition rate.

  -------- --------- --------- ---------- ----------- ------------- --------------- --------------- ---------
  **\#**   Type of   Current   Wire       Wire        Average       Calculated      Deposition rate **(%)**
           current   **(A)**   diameter   extension   feeding speed deposition rate acc. to Chandel 
                               **(mm)**   **(mm)**    **(m/min)**   **(kg/hour)**   **(kg/hour)**   

  1        AC        675       3,2        26          2,77          10,30           10,91           5,6

  2        DC(+)     600       3,2        26          2,02          7,51            7,81            3,8

  3        AC        460       3,2        28          1,87          6,94            6,81            1,9

  4        DC(+)     750       4,0        26          1,59          9,26            9,37            1,2

  5        DC(+)     550       4,0        26          1,05          6,09            6,34            3,9
  -------- --------- --------- ---------- ----------- ------------- --------------- --------------- ---------

![](media/image3.jpeg){width="4.261805555555555in"
height="2.4138888888888888in"}

Figure 2. Wire feeding speed diagrams.

On the real work condition, another experiment is done to check the
deposition rate. 1016 x 17,7 mm dimension pipe is produced under various
conditions. The weld speed is changed while all the other electrical
parameters, given in Table 2, kept constant. Geometrical dimensions are
measured by taking samples from each step of the weld process. Then the
real deposition rate is calculated (Table 3). Maximum 5,4 % difference
is found in compare with the formula basis calculation. The sequence of
the weld seam is given in Figure 3.

Table 2. Electrical parameters of 1016x17,7 mm dimension pipe.

  -------- ------------- ------------- ------------ ------------- ------------- ------------
           Inside weld                              Outside weld                

           **Current**   **Voltage**   **Wire       **Current**   **Voltage**   **Wire
           (A)           (V)           diameter**   (A)           (V)           diameter**
                                       (mm)                                     (mm)

  **DC     1100          30            4,0          1100          30            4,0
  (+)**                                                                         

  **1.     850           30            3,2          750           30            3,2
  AC**                                                                          

  **2.     550           30            3,2                                      
  AC**                                                                          
  -------- ------------- ------------- ------------ ------------- ------------- ------------

Table 3. Electrical parameters of 17,7 mm wall thickness pipe

+-------+------+-------+-----------+-------+--------+---------+----+
| Weld  | Weld | Cross | Cross     | Cross | Depo   | Theo    | \% |
| speed | posi | sect  | sectional | sect  | sition | retical |    |
| *     | tion | ional |           | ional | rate   | dep     |    |
| *(m/m |      | area  | area of   | area  | *      | osition |    |
| in)** |      | of    | the       | of    | *(kg/h | rate    |    |
|       |      | the   | rein      | the   | our)** | for 26  |    |
|       |      | added | forcement | weld  |        | mm wire |    |
|       |      | f     | **        | bead  |        | ex      |    |
|       |      | iller | (mm^2^)** | *     |        | tension |    |
|       |      | metal |           | *(mm^ |        | **(kg/  |    |
|       |      | *     |           | 2^)** |        | hour)** |    |
|       |      | *(mm^ |           |       |        |         |    |
|       |      | 2^)** |           |       |        |         |    |
+-------+------+-------+-----------+-------+--------+---------+----+
| 1,80  | In   | 48,22 | 23,51     | 1     | 40,10  | 28,47   | 4  |
|       | side |       |           | 45,52 |        |         | ,2 |
+-------+------+-------+-----------+-------+--------+---------+----+
|       | Out  | 31,85 | 21,37     | 1     | 26,49  | 27,90   | 5  |
|       | side |       |           | 20,81 |        |         | ,0 |
+-------+------+-------+-----------+-------+--------+---------+----+
| 1,50  | In   | 58,53 | 33,82     | 1     | 40,56  | 38,47   | 5  |
|       | side |       |           | 69,76 |        |         | ,4 |
+-------+------+-------+-----------+-------+--------+---------+----+
|       | Out  | 39,89 | 29,41     | 1     | 27,64  | 27,90   | 1  |
|       | side |       |           | 53,11 |        |         | ,0 |
+-------+------+-------+-----------+-------+--------+---------+----+
| 1,20  | In   | 72,46 | 47,75     | 1     | 40,17  | 38,47   | 4  |
|       | side |       |           | 95,63 |        |         | ,4 |
+-------+------+-------+-----------+-------+--------+---------+----+
|       | Out  | 48,19 | 37,71     | 1     | 26,72  | 27,90   | 4  |
|       | side |       |           | 87,24 |        |         | ,2 |
+-------+------+-------+-----------+-------+--------+---------+----+

![](media/image4.wmf)

![](media/image5.wmf)

![](media/image14.wmf)

> ![](media/image19.wmf) 1,80 m/min 1,50 m/min 1,20 m/min

Figure 3. The sequence of the weld seam with the different weld speeds.

(Pipe dimension : 1016x17,7 mm Grade of the material : St 52)

After the choosing the welding current, the program automatically gives
the diameter of the wire, arc voltage, deposition rate, heat input
applied to the material and cooling rate. Also computer always checks
the results and compare to the permissible values. If the results are
beyond the limits, immediately warning are sent o the user and also
blocked to the next stages of the program. A view of the program is
given in Figure 4.

Figure 4. A view of the computer program.

![](media/image20.jpeg){width="5.753472222222222in"
height="3.678472222222222in"}

**References**

\- ASM Handbook, "Welding, Brazing and Soldering", Metals Handbook,
vol.6, page 115-152, 1983

\- Lincoln Electric Company, "The Procedure Handbook of Arc Welding",
13^th^ Edition, Sec. 6, 1994.

\- G.E.Linnert, "Welding Metallurgy" Fourth edition, vol.1, chapter 7,
1994.

\- J.Tusek, "Mathematical Modeling of Melting Rate in Twin-Wire
Welding", Journal of Materials Processing Technology 100, page: 250-256,
1999.

\- R.S.Chandel, H.P.Seow, F.L.Cheong, "Effect of Increasing Deposition
Rate on the Bead Geometry of Submerged Arc Welding", Journal of
Materials Processing Technology 72, page: 124-128, 1996.

\- M.Graf, K.Niederhoff, "Toughness Behavior of the Heat-Affected Zone
(HAZ) ın Double Submerged-Arc Welded Large-Diameter Pipe", Mannesmann
Röhrenwerke.

\- P.A.Peters, H.G.Frackmann, "The Manufacture of Spiral Welded Pipe
with Integrating Quality Assurance" Mannesmann Röhrenwerke