a These materials require transformation to martensite prior to post-weld heat treatment (PWHT).
b Only for filler of the type 2%Cr1 Mo.
c No PWHT required if the joint is welded with similar filler using TIG process and minimum specified weld thickness e 10 mm.
d No PWHT required on tube butt welds (W1) and attachment welds (W2) if all the following conditions are fulfilled: d0< 120 mm and e £ 13 mm.
e No PWHT required on tube butt welds (W1) and attachment welds (W2) if all the following conditions are fulfilled: calculation temperature > 480 °С; nominal diameter d0 < 120
mm and minimum specified weld thickness e < 13 mm.
NOTE 1 Other material combinations not covered by the table above, and variations from the temperatures given in the table above, may be acceptable, provided the manufacturer can ensure that, by their use, the safety of the boiler is not impaired.
NOTE 2 The temperature for PWHT of dissimilar joints between austenitic and ferritic materials should be required for the ferritic side of the joint.
Table 10.4-3 — Holding time for post-weld heat treatment conditions for welded joints
|
Typical steel type |
Steel group |
Zone 1 |
Zone II |
Zone III |
|||
|
Min. specified weld thickness e mm |
Min. holding time h min |
Min. specified weld thickness e mm |
Min. holding time <2 min |
Min. specified weld thickness e mm |
Min. holding time '3 min |
||
|
C-Mn |
1.1 -1.4 |
e < 35 |
PWHT n.r |
35 < e < 90 |
t2= 1 x e |
e > 90 |
/3 = 90 + 0,5 x (e - 90) |
|
0,3Mo |
1.1 |
e < 35 |
PWHT n.r. |
35 < e < 90 |
t2 = 1 x e |
e > 90 |
/3 = 90 + 1 x (e - 90) |
|
20MnMoNi 15MnCrMoNiV 15NiMoCuNb |
2.2 4.1 4.2 |
e< 13 |
/, = 15 |
13<e<60 |
<2 = 1 xe, min. 15 |
e > 60 |
/3 = 60 + 0,5 x {e - 60) |
|
1CH/2MO |
5.1 |
e< 13 |
r, = 30 |
13<e<60 |
i2 = 2 x e, min. 30 |
e > 60 |
/3 = 120 + 1 x (^ • 60) |
|
14MoV |
6.1 |
e< 15 |
r, = 15 |
15 < e < 60 |
/2 = 1 x e, min. 15 |
e > 60 |
Z3 = 60 + 0,5 x (e - 60) |
|
2%Cr1 Mo |
5.2 |
e < 13 |
h = 30 |
13<e<60 |
/2 = 2 x e, min. 30 |
e > 60 |
<3 = 120 + 1 x(e-60) |
|
Cr-Mo-V |
6.2 |
e< 13 |
/; = 30 |
13<<?<60 |
i2 = 2 xe, min. 30 |
e > 60 |
/3 = 120 + 1 x (e -60) |
Table 10.4-3 (continued)
|
Typical steel type |
Steel group |
Zone 1 |
Zone II |
Zone III |
||||||
|
Min. specified weld thickness e mm |
Min. holding time h min |
Min. specified weld thickness e mm |
Min. holding time <2 min |
Min. specified weld thickness e mm |
Min. holding time >3 min |
|||||
|
9Cr1Mo 9Cr2Mo |
6.4 |
e < 13 |
h = 30 |
13 < e < 90 |
І2 = 2,5 x e |
e > 90 |
/з = 225 + 1 x (e - 90) |
|||
|
12Cr1MoV |
6.4 |
e < 13 |
h = 30 |
13<e<90 |
t2= 2,5 x e |
e > 90 |
/3 = 225 + 0,5 x (e - 90) |
|||
|
NOTE 1 The holding times to be used for joints of dissimilar materials should be in accordance with the manufacturer's own proven procedure which shall ensure that, by their use, the safety of the boiler is not impaired. NOTE 2 See Figure 10.4.-1 for example of applying this table. |
Key a minimum holding time r b minimum controlling weld thickness e c see column 4 d i2 = (1 ...2,5) x e (see column 6) e r3 = r2 + (0,5...1) (e-e2) see column 8 f Zone I g Zone II h Zone III n.r. = not required |
f A |
d / / |
/ I / I I I I I I I I I I і |
||||||
|
/' / I |
||||||||||
|
|
fl *2 t g h |
|||||||||
|
NOTE 3 Read in conjunction with Table 10.4-3. NOTE 4 The controlling weld thickness is given in 10.4.1.6 and 10.4.1.7. Figure 10.4-1 — Examples of applying minimum holding times for different controlling weld thicknesses |
||||||||||
Where the component contains welded joints connecting parts which differ in thickness, the controlling thickness to be used in determining the requirements for post-weld heat treatment times shall be as given in Table 10.4-4.
Table 10.4-4 — Controlling thickness for different joint types
|
Joint type |
Controlling thickness |
|
Butt welds (W1) |
The thickness of the thinner part at the welded joint. |
|
Fillet welds (W2) |
The specified throat thickness of the weld. |
|
Set-on branch (W3) |
The thickness of the branch at the joint. |
|
Set-in or set-through branch (W4) |
The thickness of the shell at the joint. |
|
NOTE See Figure 10.4-2 for examples of W1, W2, W3 and W4. |
|
When the component to be post-weld heat treated contains welds with different individual controlling thicknesses, the governing thickness to be used to determine the overall post-weld heat treatment shall be the greater of the individual controlling thicknesses.
When weld repairs or modifications have been made to a component after the final post-weld heat treatment stage, except as in the case covered by 8.8, further heat treatment shall be carried out in accordance with the requirements of 10.4. The controlling thickness to be used in defining the time required at temperature shall be one of the following:
the depth of the weld repair (W5);
the throat thickness of the weld where additional welds are added for modification purposes, see 10.4.1.6;
the thickness of the additional weld runs where reinforcement is added (W6).
See Figure 10.4-2 for examples of W5 and W6.
NOTE Dimensional and operation temperature limitations are given in Table 10.4-2 and Table 10.4-3.
Figure 10.4-2 — Typical examples of controlling thicknesses
Intermediate heat treatment shall be implemented at the manufacturer's discretion to facilitate fabrication. The duration of such intermediate heat treatment shall be decided by the manufacturer but the temperatures employed shall not exceed those given in Table 10.4-2. Temperatures and times of intermediate heat treatment shall be recorded.
Methods of post weld heat treatment
Wherever possible, the component should be heat treated as a whole in an enclosed furnace heated by gas or by electricity. Where this is impracticable, it is permissible to adopt the methods described in 10.4.2.2 to 10.4.2.5 (see also Figure 10.4-3).
It is permissible to heat treat sections of the completed component in an enclosed furnace, provided the overlap of the previously heat treated sections is at least 1 500 mm or 5 x ^ses , whichever is the greater, where ris is the internal radius of the component and es is the nominal thickness at the weld.
Where this method is used, the portion outside the furnace shall be shielded so that the longitudinal temperature gradient is such that the distance between the peak and half-peak temperatures is not less than 2,5 x -Jrlses.
It is permissible to locally heat treat circumferential seams by heating an insulated band around the entire circumference of the component. The width of the heated band shall not be less than 5 x^rlses , the weld being in the centre.
Where the circumferential weld to be heat treated is between component strakes and a dished or hemispherical end, the whole of the end shall be included in the heated band. The heated band width on the component course side shall be at least 2,5 x ^ses .
Sufficient insulation shall be fitted to ensure that the temperature of the weld and its heat affected zones is not less than that specified and that the temperature at a distance of 2,5 x^rises from the centre line of the weld is not less than the half-peak temperature. In addition, the adjacent portion of the component outside the heated zone shall be thermally insulated such that the temperature gradient is not harmful.
NOTE A minimum total insulated band width of 10 x ^rises is recommended for the purpose of complying with this requirement.
Where tubes or fittings are subsequently butt welded to branches or stubs on a shell, and postweld heat treatment is required according to 10.4.1, it is permissible to locally post-weld heat treat the butt welds by heating insulated bands around the component as shown in Figure 10.4-3. The disposition of the heating elements and insulation around the butt weld shall be such as to produce a temperature profile which is approximately symmetrical about the weld and circumferentially uniform.
<?b
Key
1 site weld 2 heated zone 3 thermocouples NOTE Minimum requirements are one near side (N/S) and one far side (F/S) per position as indicated.
Figure 10.4-3 — Minimum heated band widths for local heat treatment
Where the attaching butt weld is at a distance not less than 5 x ^rlbeb from the branch/stub to shell weld it may be post-weld heat treated in isolation (see Figure 10.4-3 right side). Where the attaching butt weld is at a distance less than 5 x ^qbeb from the branch/stub to shell weld the post-weld heat treatment shall be applied simultaneously to the butt weld and the branch/stub to shell weld as shown in Figure 10.4-3 at left side.
The temperatures measured at a distance of not less than 2,5 x ^г|Ьеь from the centreline of the butt weld, or 2,5 x yjrises from the outside surface of the branch/stub axis where appropriate, shall not be less than one- half the specified temperature measured at the butt weld.
Care shall be taken during welding and post-weld heat treatment of the butt weld to ensure harmful temperature gradients do not occur local to the weld between the shell and the branch/stub.
10.4.2.5 When a component is heat treated by internal means it shall be fully encased with thermal insulating material.
10.4.3 Post-weld heat treatment procedures
During the heating and holding periods, the furnace atmosphere shall be such as to avoid excessive oxidation of the surface of the component. There shall be no direct impingement of flame on the surface of the component.
During the heating and cooling stages on drums and headers in the range up to and including 500 °С, variations in temperature throughout the component shall not exceed 150 °С within a distance of 4 500 mm, and any temperature gradient shall be gradual. Above 500 °С temperature variations shall not exceed 100 °С.
In the case of furnace post-weld heat treatment of ferritic steels, the temperature of the furnace at the time when the component is placed into or taken out of the furnace shall not exceed:
400 °С - for components of less than 60 mm thickness and not complex in shape;
300 °С - for components of 60 mm thickness and over, or of complex shape.
The furnace heating and cooling rate up to or down from the component temperatures specified in Table 10.4.2 shall not exceed:
220 °C/h - for component thicknesses e < 25 mm;
5 500/e °C/h - for component thicknesses within the range 25 mm < e < 100 mm;
55 °C/h - for component thicknesses e > 100 mm.
where e is the nominal thickness of the component in mm.
10.4.3.4 The temperature specified shall be the actual temperature of any part or zone of the component being heat treated and shall be measured normally at the outside surface by thermocouples in effective contact with the component and protected from heat transfer to/from surroundings in order to ensure a true temperature measurement.
Welds attaching thermocouples to components shall be ground flush after heat treatment has been completed.
NOTE Where a furnace charge comprises a number of similar components, the thermo coupling may be to one component provided it can be demonstrated that the temperature distribution within the furnace is uniform.
A sufficient number of temperatures shall be recorded continuously and automatically. Several thermocouples shall be applied to ensure that the whole component or zone being heat treated is within the range specified.
The manufacturer shall demonstrate that the thermocouples and temperature recording instrumentation are accurate over the temperature range covered by the heat treatment, or such equipment shall be included in an approved calibration programme.
An automatic temperature/time record of the heat treatment of each component shall be available for inspection and shall be retained as a record.
10.5 Heat treatment of production test plates
Test plates provided in accordance with EN 12952-6:2011, Clauses shall be subjected to the same heat treatment conditions after welding as that applied to the shell or drum they represent.
NOTE Test plates may be heat treated independent of the drum they represent.
Annex A
(normative)
Tube bending procedure tests
A.1 General
A.1.1 The requirements to be met by procedure tests covering the bending and forming of tubular components, as defined in 7.3.2 are given in the following clauses. Procedure tests for tubular products are divided into three groups, depending on outside diameter and the forming processes employed, as follows:
A.2 Hot or cold formed bends in tubes with outside diameter < 142 mm
A.3 Cold formed bends in tubes with outside diameter > 142 mm
A.4 Hot formed bends in tubes with outside diameter > 142 mm
A.1.2 Procedure tests carried out within the material groups defined in EN 12952-2:2011, Table A.1 qualify other lower alloyed or softer materials (lower ultimate tensile strength) in the same group, in particular materials in steel group 1.2 cover 1.1 and 5.2 cover 5.1.
A.1.3 The validity ranges of the tube bending procedure tests are defined in A.2.3, A.3.3 and A.3.4.
A.1.4 Procedure test bends shall be bent to an angle of at least 90°. This shall be deemed to represent the minimum requirements for all bend angles. The thickness and DFC measurements shall be taken at 30° intervals from within this bend angle. Thickness determination shall normally be by sectioning but, for tubes above 80 mm nominal outside diameter, thickness may be determined by ultrasonic means. Any mechanical test specimens required shall, where possible, be taken from within this bend angle. However, where this is not possible, required specimens shall be taken from the straight tube adjacent to the commencement of the bend, which has been subject to the same heat treatment, if any, as the bend.
A.1.5 The manufacturer shall prepare documented records of all tube bend procedure tests.
A.1.6 This annex does not apply to fittings in accordance with EN 10253-2:2007 and EN 10253-4:2008.
A.2 Hot or cold formed bends in tubes with outside diameter <142 mm
A.2.1 Types of bending processes
The bending process is normally characterised by specific machines using different forms of tooling. A change to a similar machine, of different load capacity, using the same tooling shall not require re-qualification.
The following shall be permitted types of tube bending processes, but these are not to be considered as limiting:
rotary draw bend (without mandrel);
rotary draw bend (with mandrel);
boost bending (without mandrel);
boost bending (with mandrel);
press or squeeze bending;
roll bending;
any of the above in conjunction with local automatic strip heating on the intrados of the bend;
gang bending for water wall panels.
Other than for local automatic strip heating on the intrados of the bend, where hot bending is employed, heating shall be by an induction process or by heating in a gas fired or other form of furnace/muffle.
A.2.2 Post bending heat treatment (PBHT)
Bends shall be subject to PBHT in accordance with 7.3.8 and 7.3.9 prior to testing.
Separate qualification shall be required for:
cold bend (without PBHT);
cold bend (with PBHT);
hot bend (without PBHT);
hot bend (with PBHT).
Any test bends made using controlled local automatic strip heating on the intrados of the bend, except those in steel group 1.1 and 1.2, shall be normalised, or normalised and tempered, as appropriate, in accordance with the requirements of the base material specification or data sheet.
A.2.3 Validity range of tests
A.2.3.1 Any combinations of tube outside diameter, wall thickness and bend radius for a given material grouping (see A.1.2) and given types of bending process shall be acceptable, provided the requirements for the tube forming ratio (TFR) given in A.2.3.2 are met.
A.2.3.2 The TFR shall be determined by a particular set of bending test parameters d0, e and rb in accordance with A.2.3.3. Any other combination of parameters, within a given steel group and bending process up to a TFR of 110 % of the one determined in the test, shall be covered.
A.2.3.3 TFR shall be:
TFR=-^— (A.1)
exrb
where
d0 is the tube outside diameter, in mm;
e is the nominal tube wall thickness, in mm;
rb is the radius of bend measured to the centre-line of the tube, in mm.
The following example illustrates how TFR shall be applied:
Dimensions of test bend:
Outside diameter of tube do 51
Nominal tube thickness e 5
Radius of bend rb 150
Steel group: 1
Bending process: Cold rotary draw.
_ 512
TFR = = = 3,468 validity range: 3,468 x 110 % = 3,815
exrb 5x150
Other tube bends made with the same bending process in the same steel group would be compared for qualification within the validity range of the test bend in accordance with Table A.1:
Table A.1 — Validity range for different bends
|
d0 |
e |
|
TFR |
Within validity range |
|
44,5 |
4 |
133 |
3,772 |
Yes |
|
44,5 |
5 |
133 |
2,978 |
Yes |
|
51 |
4 |
150 |
4,335 |
No - New qualification required |
|
51 |
6 |
200 |
2,168 |
Yes |
|
63,5 |
5 |
190 |
4,244 |
No - New qualification required |
|
63,5 |
8 |
150 |
3,360 |
Yes |
|
70 |
6 |
210 |
3,889 |
No - New qualification required |
|
70 |
8 |
250 |
2,450 |
Yes |
|
76,1 |
7 |
228 |
3,628 |
Yes |
|
76,1 |
8 |
190 |
3,810 |
Yes |
