Hardness Issue on weld metal

[williams p wilson]

Dear Experts,

During the PQR qualification of ASTM A 519, Grade 4130 , Pipe 3" x Sch XXS material hardness value in SMAW weld metal area observed in b/w 247 to 283 HV.

The required value is in blw 201 to 241 HV, Base metal hardness also is in the same range.

Preheat temperature : 200 ° C

Interpass temperature : 300 ° C (Max)

Stress relieving details as follows,

600 ° C ± 10  ° C, Holding Time : 01 Hour

Cooling Rate : 150 ° C / Hour
Heating rate : 150 ° C / Hour
Unrestricted heating up to 300 ° C
Controlled cooling upto to 300 ° C

Please reply with your valuable comments to reduce the high hardness observed in the weld metal.

Thank You & Regards

Williams P Wilson

QA/QC Engineer

Welding Inspector (CSWIP 3.1)

Cell: (+968) 94600828

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[pradip kumar Sil]

Re PWHT you can do to minimize hardness

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[williams p wilson]

Dear,

What will be the range, please explain

Thank You & Regards

Williams P Wilson

QA/QC Engineer

Welding Inspector (CSWIP 3.1)

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[james gerald]

Supported by Simulation coupon as Tensile strength also reduces.

Thanks & Regards

J.Gerald Jayakumar

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[pradip kumar Sil]

One recommended practice is to reduce hardness is cooling rate is longer than heating rate.

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[williams p wilson]

Dear,

I am not clear, could you explain in detail

Thank You & Regards

Williams P Wilson

QA/QC Engineer

Welding Inspector (CSWIP 3.1)

Cell: (+968) 94600828

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[srinivas rao]

Hi Williams P Wilson,

following points to be verified before going to further details for investigation 

1. Have you checked for consumable mechanical properties with heat treatment conditions before using it PQR qualification ..? 

2. Have you verified Harness on base metal ? 

3. What is the tempering temperature of base material? 

4. Have you Checked Consumable certificates  before welding?  Are your consumables are guaranteed for PWHT applications? 

5. Have you tried other hardness methods for cross verification??

In general PHWT will not increase/affect the hardness, it is just for relieving the stresses only ,On the other hand, PWHT is usually in the same temperature range as the tempering heat treatment operates. Therefore, you should expect the same effects & results which include an increase in hardness. In such cases some of the codes and standards are recommending to control the PWHT temperatures just below 25-30 deg C below the tempering temperatures to control the mechanical properties.

you should check the filler metal certificates and data sheets for better understanding of weld metal mechanical properties before & after PWHT ,  check PMI of weld metal which will give some clarity to easily spot elements  which cause high hardness. 

Regards,

Srinivas Rao 

Welding Engineer

--

[srinivas rao]

Hi Williams P Wilson,.

Increase in hardness & strength after a heat treatment is due to Secondary Hardening effect. This phenomenon happens in steels that contains strong carbide forming elements mainly Cr, Mo, Ti, W and V Mostly, normal carbon steels are very less susceptible to such phenomenon and this is very common in Cr-Mo steels, unless there is an excess carbide forming elements present in the steel or supplied thru filler metal. In your case the increase in hardness is seen only on the weld metal. /hardness of base metal hardness to be verified to confirm.

Nowadays most of the clients asked for three cycle PWHT requirements, hence consumable manufacturers left with no other options rather than increasing these micro- alloying elements to the possible extent within the acceptable as per codes. In order to achieve the required mechanical properties after extended hours of PWHT, check with your manufacturer about received a lot/batch containing for the same, kindly check the batch test certificate

you have to report this problem to the consumable manufacturer and seek further advice on consumable selection, it is highly recommended to go with reputed manufacturer for welding consumables procurement for better control on welding

specify the technical requirements to consumable supplies through TDC prior to the obtaining of consumables.

 

 Best Regards,

Srinivas Rao 

Welding Engineer

[williams p wilson]

Dear Srinivas Rao,

First of all, thanks for your comments.

Consider my below reply marked in "Blue"

1. Have you checked for consumable mechanical properties with heat treatment conditions before using it PQR qualification ..? 

    Yes., MTC is attached below for your cross verification.

2. Have you verified Harness on base metal ? - No.Just followed values available in the MTC of the Pipe.

    Cross verified during the lab test, No PMI inspection done.

3. What is the tempering temperature of base material? - 630 degree C

4. Have you Checked Consumable certificates  before welding?  Are your consumables guaranteed for PWHT applications? - MTC is attached below for your cross verification.

5. Have you tried other hardness methods for cross verification?? - No.

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[james gerald]

Please Experts can anyone explain the effect of strain Hardening due to residual stresses and how PWHT reduces Hardness by reducing the dislocation density.

Thanks & Regards

J.Gerald Jayakumar

https://groups.google.com/d/msgid/materials-welding/CAHdRSOM_Gq%2BbhieF9QbK0jsVsXvBhmLYLVd-chYTYMWVHp%3DRvA%40mail.gmail.com

.

[williams p wilson]

Based on the below comments,  Manganese content on the filler metal is the reason for high hardness on the weld metal.

But in my case the hardness is in acceptable range at the hot pass areas welded with ER80S-D2 having 1.9% Mn.

Lab test report is attached below FYR

On Thu, Jul 14, 2022 at 9:44 AM williams p wilson <william...@gmail.com> wrote:

Dear All,

Below email is received from Mr.George Dilintas regarding the same matter on Tue, May 24, 2016

George Dilintas <dili...@gmail.com>	Tue, May 24, 2016, 3:02 PM
to Meghanadh

The manganese values you have in the filler metal composition justify such high hardness on the weld metal.

Manganese is increasing hardenability and lowers critical cooling rate.

It is very probable that the high hardness is due to martensite formation and not only to residual stresses.

So you should use a filler metal with lower Mn content or revise the PWHT

 

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Dr. Georgios Dilintas,

Dipl. Ing. In Aeronautic and Space Engineering

Ph.D in Mechanics of Solids - Computational Mechanics

A.I.S, A.N.I, IRCA Lead Auditor

Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis

Thank You & Regards

Williams P Wilson

QA/QC Engineer

Welding Inspector (CSWIP 3.1)

Cell: (+968) 94600828

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[williams p wilson]

Dear All,

Below email is received from Mr.George Dilintas regarding the same matter on Tue, May 24, 2016

George Dilintas <dili...@gmail.com>	Tue, May 24, 2016, 3:02 PM
to Meghanadh

The manganese values you have in the filler metal composition justify such high hardness on the weld metal.

Manganese is increasing hardenability and lowers critical cooling rate.

It is very probable that the high hardness is due to martensite formation and not only to residual stresses.

So you should use a filler metal with lower Mn content or revise the PWHT

 

--

Dr. Georgios Dilintas,

Dipl. Ing. In Aeronautic and Space Engineering

Ph.D in Mechanics of Solids - Computational Mechanics

A.I.S, A.N.I, IRCA Lead Auditor

Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis

Thank You & Regards

Williams P Wilson

QA/QC Engineer

Welding Inspector (CSWIP 3.1)

Cell: (+968) 94600828

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On Thu, Jul 14, 2022 at 9:16 AM 'james gerald' via Materials & Welding <material...@googlegroups.com> wrote:

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[james gerald]

Gentlemen,

This is a learning forum and from the start, we were just learners before posting comments. So contributions from Experts will not only solve the individual problems in work technically but will also pave way for learning.

Just to share.

Except cobalt all metals including Manganese increases Hardenability by shifting the Nose of the CCT curve to the Right (t8/5). Since it is pertaining to C-Mn steel, Mn limits were explained. One PWHT cycle in C-MN steel also converts any martensite formed during welding to Tempered martensite

Thanks & Regards

J.Gerald Jayakumar

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[williams p wilson]

Dear Experts, 

Regarding my query about the high hardness, the higher value is coming near the portion of final fill (1.5 mm down from the top weld line).

What will be the reason behind this?

Thank You & Regards

Williams P Wilson

QA/QC Engineer

Welding Inspector (CSWIP 3.1)

Cell: (+968) 94600828

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[srinivas rao]

below points to be verfied to analysie the hardeness issue 

1. Travel speed followed 

2. How weld pass is deposited at different positions (what is the location of  specimen 6 O clock or 12 clock or 3clock )

3. Check tempering effect of last pass over the previous pass (bead overlaping may not made properly ) - to get proper tempering effect minimum bead overlap to followed.

the reason for increse of Hardness & strength after a heat treatment could be due to Secondary Hardening effect.

Thanks & regards,

Srinivas Rao

welding Engineer 

[Sudhakar Kuppuswamy]

Hi, 

With 600 Deg C as holding temp and one hour holding time is not adequate to bring down the hardness . Increasing  the holding time to 2 hours minimum will definitely help. 

Otherwise , holding temp of about 650 Deg C will greatly help in reducing the hardness.

To have a good control on the cap side hardness (I.e the  last layer hardness) please try to slightly increase the pre-heat temp to the maximum possible extent. let say, in your case above 220 degrees C but less than 260 degree C. Also deposit the cap pass with temper bead technique. By doing so, the layer underneath the cap pass gets well annealed, so the hardness limit will fall within the acceptable limits.  

Hope this helps!

Regards,

Sudhakar K 

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Regards,

Sudhakar K CEng MWeldI,IWE.

Welding & Metallurgical Engineer,

Email: sudhak...@gmail.com.

[Kannayeram Gnanapandithan]

Why donot use temper bead technique on Caping

THANKS & BEST REGARDS,

KG.PANDITHAN, BE, IWE,  CSWIP 3.1,

ISO 9712 Level 2 in VT,

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[williams p wilson]

Dear Sir,

Thanks for your email.

Consider my reply marked in "Blue"

On Tue, Jul 19, 2022 at 7:22 AM srinivas rao <engr....@gmail.com> wrote:

below points to be verfied to analysie the hardeness issue 

1. Travel speed followed 

     

Root	GTAW	ER80S-D2	2.4	200° C	200 - 285 ° C	102	10	101.45	0.603
Hot Pass	GTAW	ER80S-D2	2.4	-	200 - 285 ° C	175	11.4	130.20	0.919
Fill	SMAW	E10018-D2	2.5 & 3.2	-	200 - 285 ° C	111.1	22.8	84.10	1.807
Cap	SMAW	E10018-D2	2.5 & 3.2	-	200 - 285 ° C	84	22.70	106.20	1.077

 

Root & Hot Pass - GTAW

Fill Pass No.1 - 2.5 mm Dia - SMAW

Fill Pass No.2,3,4 - 3.2 mm Dia - SMAW

Cap 1,2,3 - 2.5 mm Dia. - SMAW

 

2. How weld pass is deposited at different positions (what is the location of  specimen 6 O clock or 12 clock or 3clock )

      1G Position  

[williams p wilson]

Dear Sir,

We will start doing this method.

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[williams p wilson]

Dear Sir,

Thanks for your email.

Consider my reply marked in "Blue"

On Thu, Jul 28, 2022 at 7:25 AM Sudhakar Kuppuswamy <sudhak...@gmail.com> wrote:

Hi, 

With 600 Deg C as holding temp and one hour holding time is not adequate to bring down the hardness . Increasing  the holding time to 2 hours minimum will definitely help. 

Otherwise , holding temp of about 650 Deg C will greatly help in reducing the hardness. - This material tempering done at 630°C

    That's why we decided to conduct the PWHT at 600 °C (lower than the tempering temp.)

To have a good control on the cap side hardness (I.e the  last layer hardness) please try to slightly increase the pre-heat temp to the maximum possible extent. let say, in your case above 220 degrees C but less than 260 degree C. Also deposit the cap pass with temper bead technique. By doing so, the layer underneath the cap pass gets well annealed, so the hardness limit will fall within the acceptable limits. - We will start doing this method  

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[srinivas rao]

Hi williamswilsonp 

After referring the welding parameter details in your mail please note my findings

1. Heat input followed during welding seems to be considerably low

2. Travel speed is little higher. 

3. bead width /bead overlap/ welding sequence followed to for PQR is to be checked for mail we cannot conclude for root causes          

based on parent material and consumable strength /metallurgy more heat input may require Say the range is 1.5 - 2.5kJ/mm for these sizes of electrodes to slow down the cooling during welding/ control of Cooling rate i.e. considerably Lower travel speeds are recommended for this material 

if base material heat treatment condition quenched and tempered, we cannot go PWHT temperature more than tempering temperature of material as strength may reduce considerably and may not meet the requirement of minimum strength. (for other material heat treatment conditions, we can go with PWHT soaking temperature 650-680°C for controlling the hardness as per some of the material/consumable suppliers. 

The stress relieving temperature is normally kept below (normally by about 30°C) the tempering temperature If the temperature exceeds this more metallurgical changes occur where by strength or hardness reduction is rapid. so the heat treatment is done below the known as tempering temperature.

In general higher the stress relieving temperature lower are the residual stresses and higher is the reduction in hardness. if the holding time kept higher there is a considerable reduction in hardness and residual stresses will be lower. the weld shall be allowed to cool slowly.
hardness reduction is depending on other factors like welding technique, parent metal and welding rod composition, preheat/inter-pass temperature, welding electrode or rod size, travel speed followed during welding. The hardness reduction after PWHT is dependent on its initial value as measured before PWHT. after PWHT the reduction in hardness is may not be same in all the three regions.

recommended to consider the below if you are going ahead with new PQR qualification:

1.       Minimum recommended Preheat temperature for welding is 200°C, increase this to 220- 230°C ensure inter- pass temperature is shall not cross more than -300-315°C

2.       Since PWHT temperature is lower cannot be increased further due material heat treatment for this material it is recommended to increase the Soaking time to achieve required hardness

3.       Heat input range: 1.5 to 2.5Kj/mm or considerably with lower travel speed to keep heat input in control

4.       Temper bead technique or ensure minimum 40-% bead overlapping during welding to get proper tempering effect

5.       Weld interruption shall be avoided, during unavoidable situation, the weld shall be wrapped by thermal insulating blanket for slow cooling.

6.       To avoid hardening peaks, last filler pass should be flush with the pipe surface so that the edges of the joint preparation are melted.

7.       Before last capping pass apply minim 270-280°C Preheat

Experts , correct me if any changes required in above undestding .

Thanks & Regards 

Srinivas Rao

welding Engineer