Weldability New Generation SS

8/12/2019 Weldability New Generation SS

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The welding of stainless steels: experiences and innovations 1

METALLURGICAL AND WELDABILITY ASPECTSOF THE NEW-GENERATION MARTENSITICSTAINLESS STEELS: A CASE STUDY

Marcello Mandina IIS Service GenoaMarco Magnasco GE Oil & Gas Nuovo Pignone Massa

Luca Moracchioli GE Oil & Gas Nuovo Pignone MassaLuca Giorgini GE Oil & Gas Nuovo Pignone Massa

Abstract

In addition to brief accounts on the metallurgy and

weldability of 13%Cr-4%Ni steel, the results of

experimental welding tests aimed at supporting repair,

by means of a coated electrode process and the use of

homologous welding material, of possible forging

defects and/or defects from mechanical machining, on

stator parts and cases of centrifugal compressors, as

allowed by the reference standard ASTM A182, areprovided in this document. In particular, the effects of

the chemical composition of the base material, of the

welding material, as well as the post-welding heat

treatment (PWHT) on the mechanical properties of the

welded samples have been investigated from the

perspective of searching for the best conditions to

minimize the hardness levels in fused zones and heat

affected zones.


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1. INTRODUCTION

For several years, the petrochemical industry has been using 13%Cr-4%Ni -type martensitic

stainless-steel materials for the manufacture of valves, pump casings, cases, and stator parts ofcentrifugal compressors, both as castings (for example, ASTM A487 Grade CA6NM) and as

forgings (for example ASTM A182 Grade F6NM). For steels of this type/grade, the combination, in

terms of chemical composition, of a low carbon content, together with the addition of nickel at a

percentage between 3.5 and 4.5%, inclusive, allows fine and acicular martensite structures to be

produced with fine dispersion of stable austenite that, after tempering heat treatment, can

guarantee mechanical properties superior to those typical of martensitic steels at just 13%Cr,

which they have replaced in all those applications intended to process fluids containing CO 2 and

H2S. It is a well-known fact that 13%Cr-4%Ni steel is potentially susceptible to Sulfide StressCorrosion Cracking (SSCC) in environments containing H2S, specifically in the presence of welds

and, therefore, of structures with greater hardness. In fact, the sensitivity of F6NM steel to SSCC

can be correlated with high levels of hardness that standard NACE MR0175-ISO 15156-3 (2009)

limits to a maximum of 23 HRC for applications intended for the production of oil and gas in

environments containing H2S [1].

In addition to brief accounts on the metallurgy and weldability of 13%Cr-4%Ni steel, the results of

experimental welding tests aimed at supporting repair, by means of a coated electrode process

(SMAW/111) and the use of homologous welding material, of possible forging defects and/or

defects from mechanical machining, on stator parts and cases of centrifugal compressors, as

allowed by the reference standard ASTM A182, are provided in this document. In particular, the

effects of the chemical composition of the base material, of the welding material, as well as the

post-welding heat treatment (PWHT) on the mechanical properties of the samples welded have

been investigated from the perspective of searching for the best conditions to minimize the

hardness levels in fused zones and heat affected zones.

2. BRIEF ACCOUNTS ON THE METALLURGY AND WELDABILITY OF 13%Cr-4%Ni STEEL

13%Cr-4%Ni steel is associated with the family of the 13%Cr martensitic stainless steels and, with

the sub-group of steels defined as Soft Martensitics. In the steels of this sub-group, the austenite-

martensite transformation is achieved by the addition of nickel with a minimum percentage of 3% to

balance the reduction of carbon content to values less than 0.05% with respect to the martensitic

steels at just 13%Cr. The resulting low-carbon acicular martensite (called soft lath-type

martensite), together with a fine dispersion of stable austenite, guarantees a combination of

excellent tenacity, high tensile characteristics, and good ductility. Furthermore, these steels can


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offer a weldability level, as well as mechanical properties in welding, decidedly better than the

martensitic steels at just 13%Cr.

In the Soft Martensitics sub-group, the mechanical properties of the various grades of steel

depend on the chemical composition and on quality heat treatment. With specific reference to the

13%Cr-4%Ni grade, the chemical composition and strength and hardness requirements for F6NM

forgings in accordance with the standard ASTM A182 are shown in Tables 1 and 2, respectively;

although not specified by the standard, the material F6NM typically displays KV impact strength

values greater than 80 J even at test temperatures below -50C.

Table 1 - Chemical composition requirements in accordance with ASTM A182

Grade UNS C, % Mn, % P, % S, % Si, % Ni, % Cr, % Mo, %F6NM S41500 0.05

max0.50

-1.00

0.030max

0.030max

0.60max

3.5-

5.5

11.5-

14.0

0.50-

1.00

Table 2 - Strength and hardness requirements in accordance with ASTM A182

GradeUltimate strength

[MPa]

Yield Point

[MPa]

Ultimateelongation

[%]

Ultimate necking

[%]

Brinellhardness

[HB]

F6NM 790 min. 620 min. 15 min. 45 min. 295 max

The presence of nickel up to a maximum near 6% reduces Ac1 temperature (the start of the

transformation of the austenitic phase! into the ferritic phase ") of the 13%Cr-4%Ni material, as

shown in the phase diagram in Fig. 1.

Fig. 1 The influence of nickel on the position of the Ac1 curve in the Fe-Cr phase diagram [8].


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It follows that its martensitic structure, obtainable from a quenching treatment at a temperature

between 950 and 1050C and subsequent cooling in air or oil, may undergo partial re-austenitizing

subsequent to tempering heat treatments conducted at temperatures even considerably lower (forexample, 620C) than those at which steels with just 13%Cr are tempered (for example. 720C)

and the resulting subsequent hardening to form untempered martensite (called fresh martensite)

during final cooling to ambient temperature [4]. The percentage of austenite transformed during the

tempering process can be correlated not only with the chemical composition of the material (more

specifically with its nickel content), but also with the maximum temperature attained, as the graph

in Fig. 2 [3] shows, for example.

Fig. 2 Percent volume of austenite retransformed as a function of maximum tempering

temperature [3].

The nickel content of the 13%Cr-4%Ni steel is greater and the M s(where the austenite-martensite

transformation starts) and Mf(where the austenite-martensite transformation finishes), which may

lie in the interval 245-325C (Ms) and 30-100C (Mf), respectively, will be lower. For nickel contents

very close to the limit of 6%, the lowering of the Mf temperature is such that some non-transformed

austenite (called unstable austenite), able to be transformed into stable martensite (hard and

fragile) during the subsequent quenching treatment, may remain after quenching. To this, we can

add the portion of austenite deriving from the partial re-austenitizing of the quenched martensite

during tempering that will grow appreciably as the nickel content grows and which is capable of

being transformed into fresh martensite during final cooling at room temperature. Therefore, the

13%Cr-4%Ni material subject to single quality-type treatments (quenching at 950-1050C +

tempering at 590-650C) is susceptible to considerable hardening, with hardness not greater thanthe limit of 295 HB prescribed by standard ASTM A182 for the forgings.

Temperature (C]

Percentvolumeofaustenite


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In the presence of particular restrictions on the maximum hardness as specified by the standard

NACE MR0175-ISO 15156-3 (2009) for applications intended for the production of oil and gas in

environments containing H2S, the limit of 23 HRC can be obtained only with carbon percentagesless than 0.03%, which implies an ultimate strength and yield point below the values specified by

the product standards (for example, ASTM A182 for the forgings and ASTM A487 for the 13%Cr-

4%Ni castings). The improvement of its resistance to SSCC, with resulting full observance of the

hardness limit of 23 HRC, may be achieved by subjecting the 13%Cr-4%Ni material to double

tempering after quenching (at 950-1050C). Initial tempering is conducted at temperatures in the

region of 670C (greater than Ac1) that allows softening of the untempered martensite, but, at the

same time, results in a partial re-austenitizing of it into austenite; during the subsequent cooling

process, the unstable austenite is transformed into fresh martensite, therefore resulting in a

mixed structure of tempered martensite and untempered martensite. The second heat treatment is

conducted instead at lower temperatures (typically in the interval 590-620C), in any case high

enough to induce suitable tempering of the fresh martensite, but such as to produce a definite

percentage (typically equal to 15-20%) of retransformed austenite that remains more or less stable

(i.e. it cannot yet be converted into fresh martensite, with the exception of a minimum part) down

to ambient temperature (see Fig. 3) [1.4].

Fig. 3Examples of metallographic examination on ASTM A182 F6NM base material: structure of

tempered martensite.

Soft Martensitic steels are generally welded with homologous, low carbon content welding

material (in the region of 0.04%, even though the reference standards limit their content to a

maximum of 0.06%), employing the most common welding processes (for example, GTAW/141,

SMAW/111, GMAW/135, and FCAW/136). Although the weldability of these materials is better than

that of the martensitic steels of just 13%Cr, thanks to the formation of low-carbon martensite in the

fused zone (FZ) and in the heat affected zone (HAZ), which reduces the susceptibility to hydrogen

cracking, and with low-ferrite content martensite, that reduces the tendency for coarsening, it is


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however necessary/expedient to adopt the normal precautions to reduce the risk of hydrogen

cracking in the HAZ and/or FZ: Therefore, low hydrogen-content electrodes (< 5ml/100g of

deposited weld) must be employed and the pre-heating and interpass temperatures must be keptat 100-200C (especially in the presence of thicknesses greater than 20 mm and of highly stiffened

structures) so as to remain within the Ms # Mf martensite transformation range (typically 100-

250C); interpass temperatures greater than Ms lead, in general, to the formation of columnar

dendritic microstructures with coarsened grains, having inferior mechanical characteristics after

transformation [2].

In the majority of practical applications, such as the repair of castings and/or forgings with welding,

the manufacture of forged bodies, etc., the post-welding heat treatment (PWHT) is conducted at

temperatures between 580 and 620C, inclusive, and with holding times up to 20 hours, although

satisfactory ductility and/or toughness requirements can also be obtained with much shorter

treatment times. Before PWHT, it is important that the weld be cooled below 100C to allow its

complete transformation in martensite.

In the presence of restrictions on the maximum hardness levels, as specified by the standard

NACE MR0175-ISO 15156-3 (2009), the limit of 23 HRC can be obtained, as with the base

material, with double PWHT in combination with low carbon percentages (


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3. EXPERIMENTAL WELDING TESTS

The welding tests were conducted on two test coupons of steel ASTM A182 F6NM identified as

BM1 and BM2 in Table 3, the chemical analyses of which differ from each other essentially due to

the carbon content and quality heat treatment. Material BM1 has a carbon content of 0.038% and

was supplied with single-type quality heat treatment (air hardening at 1020C + tempering at

580C). BM2 presents a carbon content of 0.024% (less than the value of 0.03%, typically

necessary to respect the limit of 23 HRC of standard NACE MR0175-ISO 15156-3 and supplied

with double-type quality treatment (air hardening at 1020C + 1 tempering at 675C + 2

tempering at 620C).

Table 3 Chemical analysis of welded base materials [%] %Fe remaining

Identifier

code

C Si Mn P S Cr Mo Ni Cu Sn Al Ti V Nb N

BM1 0.038 0.36 0.66 0.024 0.004 13.45 0.52 3.89 0.2 0.007 0.01 0.002 0.04 0.009 0.009

BM2 0.024 0.33 0.59 0.019 0.005 13.60 0.49 3.86 0.11 0.006 0.007 0.002 0.017 0.008 0.013

The results of the mechanical (tensile and hardness) tests conducted on the two base materials

BM1 and BM2, as supplied, are summarized in Table 4. The low carbon content (


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Table 5 Chemical analysis of material used %] %Fe remaining On non-diluted deposited weld

Identifier

code

C Si Mn P S Cr Mo Ni Cu Sn Al Ti V Nb N

FM1 0.023 0.42 0.67 0.09 0.016 11.26 0.52 4.07 0.04 0.005 0.006 0.008 0.022 0.011 0.06

FM2 0.023 0.29 0.46 0.006 0.005 12.49 0.48 4.4 0.01 0.004 0.008 0.009 0.019 0.010 0.03

FM3 0.058 0.51 0.84 0.01 0.005 11.52 0.54 4.38 0.06 0.005 0.006 0.007 0.018 0.007 0.017

The test-coupon thickness (equal to 40mm) and the deposited weld thickness (equal to 15mm)

were chosen in accordance with the criteria of Code ASME IX, QW-451.1, so as to support the

repair welds of typical depth (up to 30mm) on base material up to 200mm thick (also see Fig. 4).

Fig. 4Test coupons: dimensions and preparation of the caulking (a), diagram of the deposited

welds and corresponding sequence of the beads (b).

The deposited welds were carried out in accordance with the procedure summarized below inTable 5, using, as mentioned previously, the base materials BM1 and BM2 and the welding

materials FM1, FM2, and FM3, experimenting with two post welding heat treatment conditions (HT

and HT1), simulated in the laboratory (in an oven).

The heat treatment HT was selected observing the holding temperature interval (580 - 621C)

prescribed by the standard NACE MR0175-ISO 15156-3 (2009) for PWHT with single tempering

heat cycle on low-carbon martensitic stainless steels such as those under consideration. Similarly,

heat treatment HT1 was selected observing the temperature holding interval (671 - 691C for the

first tempering, cooling cycle down to ambient temperature and 580 - 621C for the second cycle

prescribed by the standard NACE MR0175-ISO 15156-3 (2009) for PWHT with double- tempering

(a)

(b)


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heat cycle. The duration of the respective holding times was chosen based on preliminary tests

and data available in the bibliography, with the goal of satisfying the hardness limit of 23 HRC in

welding (in FZ and HAZ).

Table 6 - Welding procedure

Welding process SMAW (111)

Preparation of ends See Fig. 4

ASTM A182 F6NM (for BM1 and BM2)Base material

Thickness 40 mm

AWS A5.4: E410NiMo-16 (for FM1 and FM2)

AWS A5.4: E410NiMo-15 (for FM3)Welding material

electrode diameter = 4.0 mm

Welding position PA / 1G (Plane)

min. 200C

max 350C

Post-heating: none

Pre-heating /

Post-heating

Final cooling (below insulation) until ambient T

Welding technique narrow and tight beads

Specific heat added 10.5 -11.5 kJ/cm

SINGLE heat treatment

after welding

(HT)

615 5C $20 hours (heating rate 100C/h)

Cooling down to ambient T in calm air (from 615C)

1st Treatment:



DOUBLE heat treatment

after welding in accordance

with NACE

MR0175-ISO 15156-3

(HT1)

2nd Treatment:



3.1 Mechanical tests conducted and results obtained

The mechanical tests summarized in Table 7 were conducted on the two test coupons made from

the base materials already identified as BM1 and BM2. For further details on the test samplingpoints, see the diagrams in Fig. 5.


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Table 7 Mechanical test on the test coupons (BM1 and/or BM2)

Test Welding material Sampling

position

Test-piece

dimensions

[mm]

Treatment condition

simulated (*)

Reference standards

Longitudinaltension@+20C

FM1 + FM3 FZ 6.25 HT1 ASTM A370

KV @ -46C FM1 + FM3 FZ 10 $10 $55 HT1 ASTM A370

Macro FM1 + FM2 + FM3 Transversal - HT + HT1 ASTM E340

HRCHardness

FM1 + FM2 + FM3 FZ + HAZ - HT + HT1 ASTM E18

UNI EN ISO 15156-2

NACE MR 0175

HV10Hardness

FM1 + FM2 + FM3 FZ + HAZ - HT + HT1 ASTM E92

UNI EN ISO 15156-2

NACE MR 0175

(*) HT =615 5C $20 hoursHT1 = 675 5C $10 hours + 615 5C $20 hours

Fig. 5Test coupons: positioning of the mechanical test: tensions at ambient T, impact strength

KV@-46C, macro sections with HRC and HV10 Hardness.

Longitudinaltension and

impact strength

Macro Sectionsand hardness

Impact strength KV @ -46C in FZ Longitudinal tension in FZ and BM (inaccordance with ASTM A370 (diameter6.25 mm

Macro Sections with HRC and HV10Hardness in accordance with NACEMR0175-ISO 15156-3

=

=

=

=


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Furthermore, regarding the base materials BM1 and BM2, the mechanical tests summarized in

Table 8 were conducted.

Test Base material Test-piecedimensions

[mm]

Treatment conditionsimulated (*)

Reference standards

Tension @+20C BM1 + BM2 12.5 As-supplied + HT1 ASTM A370

KV @ -46C BM2 10 $10 $55 As-supplied + HT1 ASTM A370

HRC Hardness BM1 + BM2 - As-supplied + HT1 ASTM E18

HV10 Hardness BM1 + BM2 - As-supplied + HT1 ASTM E92

(*) HT =615 5C $20 hoursHT1 = 675 5C $10 hours + 615 5C $20 hours

The results obtained from the mechanical tests conducted were charted as a function of the heat

treatment conditions simulated, in order to demonstrate the effect of the single- and double-heat

treatment in welding, with particular reference to the hardness levels obtained in the FZ and HAZ

for the various base-material and welding-material combinations.

Figures 6 and 7 show the results of the tensile strength characterization for base materials and

welding materials as supplied and after tempering heat treatment HT1, noting an expected

improvement in the zones mentioned whenever the relative percentage of carbon is greater. With

reference, in fact, to the relevant minimum requirements imposed by ASTM standard A182 F6NM,

applicable only to grade BM1 in conformity with the supply heat treatment conditions (minimum

ultimate strength of 790MPa, minimum yield point of 620MPa), it only complies with said standard.

It must, however, be emphasized that the effect of the double-cycle tempering heat treatment HT1

results in a significant decline in the tensile characteristics also rendering material BM1, albeit with

a greater carbon content (0.038%), non-compliant with the ASTM requirements.

Similar considerations apply to the behavior of welding materials although the greater carbon

content of the welded zone FM3 (0.02% greater also than the percentage of the base material

BM1) results in a mechanical response compliant with the ASTM requirements, even after heat

treatment HT1.

The material's toughness, measured by resilience tests on base material, HAZ and FZ, is not a

critical factor always presenting energy absorption values greater than 27J even at low

temperatures (-46C). The fused zone and heat affected zone nevertheless show more fragile

behavior with values in the interval 50-80J, inclusive, versus the values in the 145-155J range for

base material at -46C under the heat treatment conditions HT1 (also see Fig. 8).


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Fig. 6Comparison between the values of the ultimate strength [in MPa] observed in the base

material (BM1, BM2) and FZ (FM1, FM3), under the various heat treatment conditions (As

supplied, HT1).

Fig. 7 Comparison between the values of the yield point [in MPa] recorded in base material

(BM1, BM2) and FZ (FM1, FM3), under the various heat treatment conditions (As supplied, HT1).

Heat treatment conditions

Minimum load in accordance with ASTMA182

Yield

ointMPa


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Fig. 8Comparison between the absorbed energy values [in Joules] during KV resilience tests at -

46C measured in the base material (BM2), HAZ and FZ (FM1, FM3), under tempering heat

treatment HT1 conditions.

Analyzing in Fig. 9 and 10, and Fig. 11 and 12, the trend of the HRC and HV10 hardness values as

a function of tempering heat treatment conditions after welding, HT and HT1, as the carbon contentvaries (expressed by the respective percentage of base materials BM1 and BM2 and of the

welding materials FM1, FM2, and FM3 as shown in Table 3 and 5), it can be observed that the

hardness values in the HAZ have a higher carbon content, subsequent to greater material

hardenability.

Nevertheless, even limited values of the carbon concentration, like for the material BM2, do not

suffice to reliably determine hardness in compliance with the maximum requirement of

23 HRC set down by the standard NACE MR0175-ISO 15156-3 (2009), not even under the

condition of heat treatment with double cycle HT1. The latter tempering heat treatment condition

proves to be more effective in achieving greater softening of the material with respect to the single

heat cycle (HT). The fused zone instead displays contrary behavior with respect to that observed

for the base material and the respective HAZ.

In the case in point, it was found that a greater carbon content in the welded area is favorable for

obtaining lower hardness values. The explanation for this phenomenon has not yet been clarified;

however, it is assumed that the greater carbon content may produce greater formation of the

austenitic phase during the first heat treatment cycle at 675C, consistent with the trend described

in Fig. 1.

AbsorbedEnergy[J]

Minimum value of BM2 as supplied

Sampling position


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Carbon, just like nickel and nitrogen, is in fact an austenitizing element that can promote the

formation of a larger austenitic phase more stable during the first tempering cycle that, therefore,

cannot be transformed in greater quantities into martensite during cooling to ambient temperature.Proving this point, however, would require further microstructural analysis of the zone welded using

transmission electronic microscopy (TEM) which in this phase of the study was not conducted.

Fig. 9Comparison between the HRC hardness values recorded in HAZ (BM1, BM2), under the

tempering heat treatment conditions HT and HT1.


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Fig. 10Comparison between the HRC hardness values recorded in FZ (FM1, FM2, FM3), under


Fig. 11Comparison between the HV10 hardness values recorded in HAZ (BM1, BM2), under


Maximum hardness inaccordance withMR0175-ISO 15156-3(2009)

Heat treatment conditions

HardnessHRC


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Fig. 12Comparison between the HV10 hardness values recorded in FZ (FM1, FM2, FM3), undertempering heat treatment conditions HT and HT1.

The HRC (Rockwell C) hardness values and the corresponding HV10 (Vickers) hardness values

obtained on the test coupon in correspondence with the three characteristic welding zones are

reported in the graph in Fig. 13: fused zone (FZ), heat affected zone (HAZ), and base material

(BM). The graph also shows the correlation between the HRC/HV10 hardness values proposed by

Hays-Patrick for the 13%Cr-4%Ni material, and the conversion of the hardness in accordance with

the standards ASTM E140:97 and EN ISO 18265:2003.

With reference to the population of data available, it can be observed that the conversion of

hardness in accordance with the standards ASTM E140:97 and EN ISO 18265:2003 are

inappropriate for the 13%Cr-4%Ni material, in agreement with that specified by the bibliography on

the matter [1]. Even the correlation proposed by Hays-Patrick seems less appropriate for the

hardness measurements in the fused zone with respect to those in the HAZ.

Most of the hardness data generated by this study exceed 254 HV10 which represents the value

equivalent to the limit of 23HRC in accordance with standards ASTM E 140:97 and

EN ISO 18265:2003, with specific reference to the FZ and to the HAZ of the coupons after PWHT


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(HT and HT1), bearing witness to the difficulties the industry often experiences in satisfying the 23

HRC hardness limitation such as the conversion of Vicker hardness measurements.

Fig. 13 Comparison between HRC Hardness (Rockwell) and HV10 Hardness (Vickers) in FZ,

HAZ, and the base material (BM).

4. CONCLUDING CONSIDERATIONS

The experimental welding tests conducted within the scope of this study focused on supporting the

repair, by means of a coated electrode process (SMAW/111) and the use of homologous welding

material, of any possible forging defects and/or defects from mechanical machining, on cases and

stator parts of centrifugal compressors, investigating the effects of the chemical composition of the

base material and welding material, as well as the post-welding heat treatment (PWHT) on the

mechanical properties of the welded test pieces, from the perspective of searching for the best

conditions to bring the hardness levels, in the fused zone and the heat affected zone, within the

limit of 23HRC prescribed by the standard NACE MR0175-ISO 15156-3 (2009), for applicationsintended for the production of oil and gas in environments containing H2S. The final considerations,

based on the results obtained, are given below.


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For both base materials tested (BM1 and BM2), the ultimate strength and the yield point are

less than the respective minimum requirements prescribed by ASTM A182 for grade F6NM, in

the condition of double PWHT (HT1), demonstrating a drop with respect to the as-suppliedstate and lower values for the low-carbon (27J) even at low

temperature

(-46C) under the condition of double PWHT (HT1), although less than those offered by the

base material.

The tests confirm the practical difficulty in satisfying the hardness limitation of 254HV10,

assumed to be equivalent to the NACE limit of 23HRC in accordance with the standards

ASTM E140:97 and EN ISO 18265:2003, while the limitation of 275HV10, as an equivalent to

23HRC in accordance with the correlation proposed by Hays-Patrick, may be satisfied through

a suitable PWHT sequence, in combination with an appropriate chemical analysis for the base

material and the welding material.

The HRC hardness levels measured in the FZ and the HAZ after single PWHT (615 5C $

20 hours) are essentially greater than the NACE 23HRC limit. Similarly, the hardness HV10

measured in the same zones complies with neither the 254HV10 limit nor the 275HV10 limit.

A significant reduction of the hardness levels can be obtained in the FZ and the HAZ with

double PWHT (675 5C $10 hours + cooling to ambient temperature in calm air +

615 5C $ 20 hours), without being able, in any case, to respect the 254HV10 limit. The

limits of 23HRC (for the HRC hardness measurements) and 275HV10 (for the HV10 hardness

measurements) were respected, though with an insufficient degree of regularity/repeatability.

The minimum HRC and HV10 hardness values in the HAZ were measured on the lower

carbon content base material BM2 (0.03%). In a different way, the minimum HRC and HV10

hardness values in the FZ were obtained for the higher carbon content (>0.03%) welding

material FM3; the possible metallurgical justifications for this were not subject to in-depth

analysis in this study.

For greater confidence regarding the obtainable results, it is preferable to perform the welding

hardness tests (in the FZ and the HAZ), both with the Rockwell (HRC) method and with the

Vickers (HV10) method, to be able to make a double comparison between homologous

acceptability limits and dimensions.


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BIBLIOGRAPHY

1. T. Gooch, Heat Treatment of Welded 13%Cr-4%Ni Martensitic Stainless Steels for SourService, Welding Research, Welding Journal, July 1995.

2. A. Marshall, J. Farrar, T. Gooch, Welding of Ferritic and Martensitic 11-14%CrSteels, Weldingin the World, Vol.45, n5/6, 2001.

3. J. Crawford, CA-6NM An Update, Climax Molybdenum Company, 1995

4. Materials Facts Sheet Section C 13%Cr4% Ni Steel, The Castings Development Centre,

19915. J. Svoboda, Literature Review of Martensitic Stainless Steels, Steel Founders Society of

America, 1982

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