The data calculated by this program are for information only and do not cover all details of a welding procedure. Therefore, this program does not give an assurance in respect to the properties of the welded joints. In any case the underlying welding and construction standards have to be obeyed. Furthermore the description of fabrication properties of our material data sheets should be taken into account and all necessary levels of a careful quality control be respected.
The carbon equivalents are simplified parameters which try to estimate the influence of the alloying content of a steel by summarising the content of the various alloying elements by a particular averaging procedure. Plenty of carbon equivalents have been developed until now with different suitability for a special welding situation and steel grade. The four carbon equivalents the most common are calculated here (in weight-%):
|CET||:=||C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40|
|CE||:=||C + Mn/6 + (Cr + Mo + V)/5 + (Ni+ Cu)/15|
|CEN||:=||C + [ 0.75 + 0.25*tanh(20*(C - 0.12))] *
[Si/24 + Mn/6 + Cu/15 + Ni/20 + (Cr + Mo + V + Nb)/5 + 5*B]
|Pcm||:=||C + Si/30 + (Mn + Cu + Cr)/20 + Mo/15 + Ni/60 + V/10 + 5*B|
Fill in the alloying contents given in your inspection certificate. The program will calculate the various carbon equivalents.
For the CET-equivalent, which is a prerequisite for the following welding parameter calculation, the range of validity is as follows (in weight %):
|C:||0.05 - 0.32|
|Mn:||0.50 - 1.90|
If an alloying content hurts this range of validity, this element as well as the CET-parameter is marked in red.
The calculation of welding parameters is based on the method B in EN 1011-2 (Welding - Recommendation for welding metallic materials - Part 2 Arc welding of ferritic steels) described in annex C and D of this code.
This method describes how welding parameters should be selected in order to avoid especially cold-cracking in the heat-affected zone (HAZ). In any case the fabrication properties recommendations in our material data sheets should be taken into account for a particular steel. Furthermore, the user has to ensure that the relevant standards, such as EN 10 11, are fulfilled.
Preheating is very useful in order to avoid the phenomena of cold cracking as it decelerates the cooling of the HAZ and enables the hydrogen induced during welding to escape. Furthermore preheating improves the welding-induced constraints. Multi-layer welds can be begun without preheating if a suitable welding sequence is chosen and the interpass temperature is sufficient.
The preheating temperature is the lowest temperature before the first welding pass which has not to be fallen below in order to avoid cold-cracking. For multi-layer welds this term refers to the temperature of the second and the subsequent weld passes and is also called interpass temperature. In general the two temperatures are identical.
The preheating temperature depends on the following input data:
Typical hydrogen content for welding consumables
|Method||Common hydrogen content [ml/100 g]|
|Manual Metal Arc MMA||5|
|Gas Shielded Metal Arc MIG/MAG||3|
|Flux Cored Arc Basic FCAW||5|
|Submerged Arc Basic SAW||5|
From the data above the minimum preheating temperature is calculated as follows:
|Tp =||697*CET+ 160*tanh(d/35)+62*HD0,35 + (53*CET-32)*Q-328|
The range of validity for this formula is:
0.2 % - 0.5 %
10 mm - 90 mm
|HD:||1 ml/100g - 20 ml/100 g|
0.5 kJ/mm - 4.0 KJ/mm
The temperature-time cycle is of major importance for the mechanical properties of the welded joint after welding. It is influenced in particular by the welding geometry, the heat input applied, the preheating temperature as well as the weld layer details. Normally the temperature-time cycle during welding is expressed by the time t8/5 which is the time in which a cooling of the welding layer from 800°C to 500°C occurs.
The maximum hardness in the HAZ normally decreases with growing cooling time t8/5. If a given maximum hardness value is not to be exceeded for a particular steel, the welding parameters have to the chosen in such a way that the cooling time t8/5 does not fall under a particular value.
On the other hand, increasing cooling times cause a decrease of the toughness of the HAZ, that means a decrease of the impact values measured in the Charpy-V-test or an increase of the transition temperature of the Charpy-V-impact energy. Therefore the welding parameters have to be selected in such a way, that the cooling time does not exceed a particular value.
In general, for weldable fine -grain structural steel grades the cooling time for filling and covering weld layers should be in the time 10 s and 25 s dependant on the steel grade given here. After corresponding verification, there is no problem to apply also other values of the cooling time t8/5 under the condition that the quality demands on the structure to be welded are completely fulfilled and suitable welding procedure qualification have been performed.
Furthermore you can calculate a welding parameter diagram which shows you the possible heat-input - preheating temperatures for given maximum and minimum cooling times. If you want to calculate explicit cooling times please use the next section (_Cooling time_).
The following parameters have got an influence on the cooling time, either on its calculation or on its selection and can be inserted here in order to obtain optimised welding parameters:
|Filling passes of butt welds||0.9||0.9|
|Covering passes of butt welds||1.0||0.9 - 1.0|
|One-pass fillet weld (Corner joint)||0.9 - 0.67*||0.69|
|One-pass fillet weld (T-joint)||
0.45 - 0.67*
The welding geometry factor F2 depends on the relation effective heat input to plate thickness. Approaching the three-dimensional heat flux F2 decreases for the case of a one-pass fillet weld on a corner joint and increases for the one-pass fillet weld on a T-joint. Therefore an adaptive calculation may be necessary here.
The factors given above can be selected here. Moreover a free input of the data in the range between 0 and 1 is also possible.
Form the above parameters a welding parameter box is created giving the possible combinations of effective heat input Q and preheating/interpass temperature Tp fulfilling the following conditions:
Moreover a direct calculation of the preheating temperature by specifying either the effective heat input Q or the heat input E and the efficiency factor h is enabled.
One determining parameter during the calculation of welding parameters is the effective heat input. By the input data
first the heat input E [kJ/mm] is calculated by the formula
E = U*I/v * (60/1000) in KJ/mm.
The effective heat input Q results form the heat input by the multiplication with an energy efficiency factor h which depends on the welding process applied.
Q = h * E
with the efficiency factor
Energy efficiency factor for various welding processes
|Welding process||Efficiency factor h|
|Manual Metal Arc||0.8|
|Metal Active Gas (MAG)||0.8|
|Metal Inert Gas (MIG)||0.7|
|Flux Cored Ard (FCAW)||0.9|
|Tungsten Inert Gas (TIG)||0.7|
The cooling time between 800°C and 500°C t8/5 is the most important parameter in order to determine the welding parameters applied during welding of fine-grain structural steels. The underlying reasons are explicitly described above.
In this menu you can easily calculate this cooling time by specifying the following values:
From the data given above the cooling time t8/5 can be calculated if a three-dimensional heat flux is assumed:
t8/5 = (6700-5*TP)*Q* (1/(500-TP)-1/(800-TP))*F3
If the heat flux is two-dimensional the cooling time depends on the plate thickness an the following formula is used:
t8/5 = (4300-4.3*TP)*105*Q2/d2* (1/(500-TP)2-1/(800-TP)2)*F2
Only the greater values obtained from the two formulas above is physically valid. Often, a transition plate thickness dt is calculated, at which the transition between the two-dimensional and the three-dimensional heat flux occurs. This transition plate thickness is determined as follows:
dt = SQR(((4300-4.3*Tp)*105/(6700-5*Tp)*Q*(1/(500-TP)2-1/(800-TP)2)/ (1/(500-TP) -1/(800-TP))*F2/F3)
Moreover it is signed whether a two- or three-dimensional heat flux occurs.
It should be considered that the assumptions underlying the formulas for the cooling time are often not perfectly fulfilled. Therefore the values calculated can deviate form the real values by up to 10 %.
The peak hardness in the heat affected zone (HAZ) is often to be considered to be a sign of the fabrication quality of the weld joint and is therefore often measured during welding procedure approvals and welding test. Upper limits for the HAZ hardness are determined in the welding standards such as DIN EN ISO 15614-1.
Physically the maximum hardness depends on the cooling speed in the coarse-grain zone of the HAZ. The faster the cooling speed the higher is the resulting hardness in the HAZ. A slower cooling speed results in a smoother grain structure such as bainite and ferrite. Therefore also the cooling time t8/5 is often used to evaluate the maximum hardness in the HAZ zone.
The second important influencing factor is the chemical composition of the steel because it determines the quantity of the various grain structures which are formed during cooling. Normally alloying elements such as carbon, molybdenum, manganese and chromium increase the hardability and shift the hardness drop to longer cooling times. But also the hardness of the various grain structures is influenced by the alloying composition.
The program offers two routines to evaluate the peak hardness in the HAZ, the formula of Düren and the formula of Yurioka. Both formulas have been developed by systematically performed investigations together with a regression analysis of the HAZ-hardness in dependence of the chemical composition and the t8/5-cooling time.
Here the chemical composition can be entered and then the theoretical hardness according to the Düren- respectively Yurioka-formula is calculated in dependence of the cooling time.
Moreover the value of the peak hardness for a special cooling time can be calculated by inserting a cooling time.
The Düren-hardness is calculated according to the following formulas:
Martensite hardness HVM
HVM = 802 x C + 305
Bainite hardness HVB
HVB = 350 x CE* + 101
CE* = C +Si/11 +Mn/8 +Cu/9 +Cr/5 +Ni/17 +Mo/6 +V/3
HV = 2019x[ C(1- 0,5 * log t8/5) + 0,3(CE*-C)] + 66x[1 - 0,8 x log t8/5 ]
If HV < HVM and HV > HVB, the Yurioka-hardness is calculated according to the formulas
HV = 0,5 (HVM + HVB) - 0,455 (HVM - HVB) arctan t*
884 x C (1 - 0,3 C²) + 294
|HVb||:=||145 + 130 x tanh (2,65 CE2 - 0,69)|
|CE1||:=||C + Si/24 + Mn/6 + Cu/15 + Ni/12 + Cr/8 + Mo/4 + ΔH|
C + Mn/3,6 + Cu/20 + Cr/5 + Ni/9 + Mo/4
4 (ln t8/5 - ln tnb)/(ln tnm - ln tnb) -2
exp (10,6 x CE1 - 4,8)
|:=||exp (6,2 x CE3+ 0,74)|
Note that ΔH is a term introduced to account for the strong hardening effect of boron, such that;
|ΔH||=||0||when B ≤ 1ppm,|
|ΔH||=||1.5 (0.02-N)||when B ≤ 2ppm,|
|ΔH||=||3.0 (0.02-N)||when B ≤ 3ppm, and|
|when B ≤ 4ppm,|
Moreover the maximum hardness values admissible by DIN EN ISO 15614-1 can be called by the button "Max. Hardness" and a maximum hardness value can be selected and inserted in the hardness diagrams
Maximum admissible hardness values, HV 10 according to DIN EN ISO 15614-1.
|Steel group CR ISO 15608||
without heat treatment
|with heat treatment|
a If hardness tests are demanded
b For steels with ReH, min > 890 MPa special agreements are required.
1) Steels with mind. ReH ≤ 460 MPa
2) Thermomechanically rolled steels with min. ReH > 360 MPa
3) Quenched and tempered steels with min. ReH > 360 MPa
For welded joint which are treated by a post-weld heat treatment also the hardness decrease due to this heat treatment can be calculated using the formula of Okumura :
|+[ 18 ( HP-18)2 - 138 ] V1/2|
|+[ 20 ( HP-18)2 - 268 ] Nb1/2|
|+[ 25 ( HP-17,3)2 - 55 ] Mo1/2|
|with MM =||martensite share = 0,5 - 0,455 arctan t*|
|CE2 and t*||from the Yurioka formula|
Herein HP is the so-called Hollomon-parameter HP = (T+273)/1000 x (20 + log t) with the heat treatment temperature in °C and the annealing time t in hour. For the calculation this parameter has to be entered or the annealing time and temperature can be input.
After entering the input data a diagram shows the dependence of the PWHT-induced hardness drop from the cooling time as well as the difference function between Yurioka hardness and Okumura hardness decrease. A special value can be evaluated by entering a cooling time.
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