Carbon Equivalents
Generally the minium interpass temp is your preheat temp. Preheat temp can be calculate as per BS EN 1011-2. On 2 Aug 2017 6:52 a.m., 'samaran sadasivam' wrote. 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.
Welding Parameters / PreheatingAWS D1.1, Table 3.2 Prequalified Minimum Preheat and Interpass Temperature °F (°C): Preheat and Interpass temperature is provided for each material and thickness and process type on this material group. Guideline on Alternative Methods for Determining Preheat/Interpass: See Annex XI of AWS D1.1 Preheat requirements shall be based on Welding. Pre-Heat Calculator to EN1011 Part 2 - Non Alloyed And Low Alloy Steels.
Effective Heat Input / Cooling Time Hardness in the HAZ IndexThe 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.
______________________________________________________________________________________________________CARBON EQUIVALENTS
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 |
| Si: | ≤ 0.80 |
| Mn: | 0.50 - 1.90 |
| Cr: | ≤ 1.50 |
| Ni: | ≤ 2.50 |
| Mo: | ≤ 0.75 |
| Cu: | ≤ 0.70 |
| V: | ≤ 0.18 |
| Nb: | ≤ 0.06 |
| Ti: | ≤ 0.12 |
| B: | ≤ 0.005 |
If an alloying content hurts this range of validity, this element as well as the CET-parameter is marked in red.
______________________________________________________________________________________________________________WELDING PARAMETERS / PREHEATING
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:
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:
- Carbon equivalent CET (see above): The CET can be explicitly filled in here or be calculated by the contents of the alloying elements in the menu carbon equivalent. The CET is inserted in weight-%
- Plate thickness d: The plate thickness is inserted in mm. It should be considered that the influence of the plate thickness is of minor importance for plate thicknesses above 60 mm due to the three-dimensional heat flux.
- Hydrogen content HD: The hydrogen content H2 is inserted in ml/100g. Here either a value between 1 and 20 ml/100g can be inserted directly or a typical value depending on the weld process used can be selected:
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 |
- Effective Heat Input: The effective heat input Q, which is given by the product of the heat input E multiplied with an efficiency factor h , Q = h *E, is given here in kJ/mm. There are two ways to take the influence of the effective heat input.
- The dependence between the preheating temperature and the weld energy is shown in the weld parameter box which is shown after filling in all necessary data.
- Moreover, the preheating temperature can be explicitly calculated by inserting either the effective heat input Q in kJ/mm or the heat input E in kJ/mm and the efficiency factor h , which depends on the welding process used. The efficiency factor the explicitly explained in the _next section_.
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:
| CET: | 0.2 % - 0.5 % |
| d: | 10 mm - 90 mm |
| HD: | 1 ml/100g - 20 ml/100 g |
| Q: | 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:
- Plate thickness d: The plate thickness is inserted in mm. It should be considered that the influence of the plate thickness is of minor importance for plate thicknesses above 60 mm due to the three-dimensional heat flux. Welding geometry: The influence of the welding geometry is taken into consideration by weld geometry factors F2 and F3 for two- and three-dimensional heat flux. The values of the weld geometry factor for typical weld geometries are:
| Weld geometry | F2 (two-dimensional) | F3 (three-dimensional) |
| Building-up weld | 1.0 | 1.0 |
| 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* | 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.
- Effective Heat Input: The effective heat input Q, which is given by the product of the heat input E multiplied with an efficiency factor h , Q = h *E, is given here in kJ/mm. The influence of the effective heat input in dependence of the preheating/interpass temperature and the minimum and maximum cooling time t8/5 is shown in the welding parameter diagram which is built up after completion of the values needed.
- Preheating/Interpass-temperature: The influence of the preheating time is also expressed in the welding parameter diagram.
- Maximum and minimum cooling time:
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 and 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 value 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:
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)))
The maximum and minimum cooling times depend on the steel grade which is to be welded. The cooling times recommended by Dillinger brand products can be selected here. As described above, other cooling times can be chosen under the condition that the quality demands on the structure to be welded are completely fulfilled and suitable welding procedure qualification have been performed. Therefore also a free input of the cooling time is possible. In any case the recommendations given in our material data sheets have to be taken into account too.
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:
- sufficient preheating,
- Cooling time smaller than a maximum value defined above,
- Cooling time bigger than a minimum value defined above.
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.
______________________________________________________________________________________________________________EFFECTIVE HEAT INPUT/ COOLING TIME
One determining parameter during the calculation of welding parameters is the effective heat input. By the input data
- Electric Tension U [V]
- Electric Current I [A]
- Welding Speed v [mm/min]
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 |
| Submerged Arc | 1.0 |
| 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:
- Effective Heat Input Q [in kJ/mm]
- Preheating temperature Tp [°C]
- Plate thickness d [mm]
- Welding geometry factors F2/F3: For the welding geometry factors the suitable welding geometry has to be selected from a table, Moreover also a free input in the range 0 to 1.0 is possible.
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 %.
______________________________________________________________________________________________________________PEAK HARDNESS IN THE HEAT-AFFECTED ZONE
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
Resulting hardness:
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*
| with | HVm | := | 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 | |
CE2 | := | C+Si/24+Mn/5+Cu/10+Ni/18+Cr/5+Mo/2,5+Nb/3+V/5 | |
| CE3 | := | C + Mn/3,6 + Cu/20 + Cr/5 + Ni/9 + Mo/4 | |
| t* | := | 4 (ln t8/5 - ln tnb)/(ln tnm - ln tnb) -2 | |
tnb | := | exp (10,6 x CE1 - 4,8) | |
tnm | := | 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 |
| ΔH | = | 4.5 (0.02-N) | 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 |
| 1a, 2 | 380 | 320 |
| 3b | 450 | 380 |
| 4, 5 | 380 | 320 |
| 6 | — | 350 |
| 9.1 9.2 9.3 | 350 450 450 | 300 |
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 :
VRC-PRO is the world's best RC Racing simulator. Join the other thousands of drivers for unlimited practice, online racing and online community. VRC-PRO features all the top classes of RC racing with more being added all the time. Choose from over 50 on-road and off-road tracks to race on. Not only is VRC-PRO the quickest, cheapest and easiest way to improve your driving and get more track.
| DHV = | [884C+177-197CE2+16,5(HP-21,5)]xMM-7CE2+26 Copyright © 2017-2020 Let's Play Index. All Rights Reserved. Page generated in 1. Sims 4 fnaf mod. |
| +[ 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.
INDEX
Carbon EquivalentsCET-equivalents
Cooling time
Düren-hardness
Efficiency factor
Hardness in the HAZ
Heat Affected Zone
Effective Heat Input
Hollomon-parameter
Hydrogen
Heat Input
Okumura-hardness
Preheating
Preheating temperature
Transition thickness
Weld geometry
Yurioka-Hardness
I. Preheat for welding process
Preheating is the process applied to raise the temperature of the work piece in the weld zone immediately before any welding operation (including tack welding!).
Note: A preheating temperature 𝑇𝑝 measured only once immediately before any welding operation according to EN ISO 13916. If required a maintenance temperature 𝑇𝑚 shall be mantained on a minimum temperature in the weld zone when welding is interruped
The purpose of preheat:
- Reduce the risk of hydrogen cracking
- Reduce the hardness of the weld-heat affected zone (HAZ)
- Reduce shrinkage stresses during cooling and improve the distribution of residual stresses.
- Drive off any surface moisture
Preheating should be considered when there is a significant risk of hydrogen cracking in the welded joint. For the above reasons preheating finds more use and is fully recommended for the production of welded joints on steel structures and fittings that will be in the influence of pressure and continuous cyclic stresses (i.e pressure vessel, piping systems, pipeline transportation, bridge structures, ship vessels etc.) The most commonly carbon steel materials used are normalized fine-grain steels, steels with improved atmospheric corrosion resistance, thermomechanically treated fine-grain steels, quenched and tempered fine-grain steels,
Preheat is commonly applied:
- Electrical resistance heaters
In photograph no.1 electrical induction coil for 48' pipeline
- With fuel gas torches
In photograph no.2 internal pipe end PLG heating torch for 48' pipeline
In photograph no.3 partially applied preheating for repair welding with PLG pre heating torch
Test equipment according to EN ISO 13916:
Welding Preheat And Interpass Temperature Calculator Conversion
- (TS) Temperature sensitive materials
- (CT) Contact thermopeter
Preheat Temperature For Welding
- (TE) Thermocouples
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 %.
______________________________________________________________________________________________________________PEAK HARDNESS IN THE HEAT-AFFECTED ZONE
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
Resulting hardness:
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*
| with | HVm | := | 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 | |
CE2 | := | C+Si/24+Mn/5+Cu/10+Ni/18+Cr/5+Mo/2,5+Nb/3+V/5 | |
| CE3 | := | C + Mn/3,6 + Cu/20 + Cr/5 + Ni/9 + Mo/4 | |
| t* | := | 4 (ln t8/5 - ln tnb)/(ln tnm - ln tnb) -2 | |
tnb | := | exp (10,6 x CE1 - 4,8) | |
tnm | := | 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 |
| ΔH | = | 4.5 (0.02-N) | 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 |
| 1a, 2 | 380 | 320 |
| 3b | 450 | 380 |
| 4, 5 | 380 | 320 |
| 6 | — | 350 |
| 9.1 9.2 9.3 | 350 450 450 | 300 |
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 :
VRC-PRO is the world's best RC Racing simulator. Join the other thousands of drivers for unlimited practice, online racing and online community. VRC-PRO features all the top classes of RC racing with more being added all the time. Choose from over 50 on-road and off-road tracks to race on. Not only is VRC-PRO the quickest, cheapest and easiest way to improve your driving and get more track.
| DHV = | [884C+177-197CE2+16,5(HP-21,5)]xMM-7CE2+26 Copyright © 2017-2020 Let's Play Index. All Rights Reserved. Page generated in 1. Sims 4 fnaf mod. |
| +[ 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.
INDEX
Carbon EquivalentsCET-equivalents
Cooling time
Düren-hardness
Efficiency factor
Hardness in the HAZ
Heat Affected Zone
Effective Heat Input
Hollomon-parameter
Hydrogen
Heat Input
Okumura-hardness
Preheating
Preheating temperature
Transition thickness
Weld geometry
Yurioka-Hardness
I. Preheat for welding process
Preheating is the process applied to raise the temperature of the work piece in the weld zone immediately before any welding operation (including tack welding!).
Note: A preheating temperature 𝑇𝑝 measured only once immediately before any welding operation according to EN ISO 13916. If required a maintenance temperature 𝑇𝑚 shall be mantained on a minimum temperature in the weld zone when welding is interruped
The purpose of preheat:
- Reduce the risk of hydrogen cracking
- Reduce the hardness of the weld-heat affected zone (HAZ)
- Reduce shrinkage stresses during cooling and improve the distribution of residual stresses.
- Drive off any surface moisture
Preheating should be considered when there is a significant risk of hydrogen cracking in the welded joint. For the above reasons preheating finds more use and is fully recommended for the production of welded joints on steel structures and fittings that will be in the influence of pressure and continuous cyclic stresses (i.e pressure vessel, piping systems, pipeline transportation, bridge structures, ship vessels etc.) The most commonly carbon steel materials used are normalized fine-grain steels, steels with improved atmospheric corrosion resistance, thermomechanically treated fine-grain steels, quenched and tempered fine-grain steels,
Preheat is commonly applied:
- Electrical resistance heaters
In photograph no.1 electrical induction coil for 48' pipeline
- With fuel gas torches
In photograph no.2 internal pipe end PLG heating torch for 48' pipeline
In photograph no.3 partially applied preheating for repair welding with PLG pre heating torch
Test equipment according to EN ISO 13916:
Welding Preheat And Interpass Temperature Calculator Conversion
- (TS) Temperature sensitive materials
- (CT) Contact thermopeter
Preheat Temperature For Welding
- (TE) Thermocouples
- (TB) Optical or electrical device for contactless measurment
Designation preheating temperature on welding procedure (WPS) according to EN ISO13916
Example - Temperature: EN ISO13916-Tp 90/120-CT
Preheating temperature Tp,with the range of values from 90°C to 120°C using a contact thermopeter (CT)
II. Calculation of the preheat temperature according to EN 1011-2:
Factors influencing the preheat temperature calculation:
- Base material (chemical composition)
- Plate thickness
- Hydrogen content
- Heat input
Calculation preheat temperature for each factors:
1. The relationship between the carbon equivalent, 'CET' of base material, and the preheat temperature, Tp𝐶𝐸𝑇 = 750𝑥𝐶𝐸𝑇 − 150(°𝐶), When this formula provides information on the effect on the individual alloying elements on these properties in relation to that of the carbon 𝐶𝐸𝑇=𝐶+(𝑀𝑛+𝑀𝑂)/10+(𝐶𝑟+𝐶𝑢)/20+𝑁𝑖/40 (%)
2. The relationship between plate thickness 'd', and preheat temperature. 𝑇𝑝𝑑=160𝑥𝑡𝑎𝑛ℎ(𝑑/35)−100 (°𝐶)
3. The effect of hydrogen content, HD, of the weld metal in accordance with ISO 3690 on preheat temperature 𝑇𝑝𝐻𝐷=62 𝑥 𝐻𝐷^0.35−110(°𝐶)
4. The influence of the heat input, Q, on the preheat temperature 𝑇𝑝𝑄=(53𝑥𝐶𝐸𝑇−32)𝑥𝑄−53𝑥𝐶𝐸𝑇+32(°𝐶)
The effects of chemical composition, characterized by the carbon equivalent 'CET', the plate thickness 'd', the hydrogen content of the weld metal 'HD' , and the heat input 'Q', can be combined by the formula given below to calculate the preheat temperature. 𝑇𝑝=𝑇𝑝𝐶𝐸𝑇+ 𝑇𝑝𝐻𝐷+ 𝑇𝑝𝑄+ 𝑇𝑝𝑑 (°𝐶)
Note: This method covers the arc welding of carbon steels of the groups 1 to 4 as specified in CR/ISO 15608
Welding Preheat And Interpass Temperature Calculator Conversion
Conclusions referring the above formulas:
- With the rise of carbon equivalent also brings growth preheat temperature that will be used
- For thinner material, a change in the plate thickness results in a greater change in preheat temperature
- An increase of the hydrogen content requires an increase of the preheat temperature
- An increased heat input from the welding process permits a reduction of preheat temperature.
III. Case study, calculation of preheat temperature on base material L485ME (ISO 3183) for different welding process used on pipeline construction
Taking into account the following data:
The following Chart of preheat temperature on L485ME for different welding process and different wall thickness
Minimum Interpass Temperature Welding
References
- EN ISO 13916:1997: 'Welding: Guidance on the measurement of preheating temperature, interpass temperature and preheat maintenance temperature.
- EN 1011-2: 2001: 'Welding. Recommendations for welding of metallic materials. Arc welding of ferritic steels'
- AWS-Welding-Handbook_Vol1_9th-Edition
