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Fw: [MW:20602] Suitable electrode for SAE 4130 Pipe

By Materials & Welding
 
 
AISI 4130 type materials attain their good mechanical properties through a process called quenching and tempering.
In quenching and tempering, the steel manufacturer heats the steel above a critical point of 850°C, then cools the
material very quickly (quenching) to create martensite (a very hard, brittle but strong micro structure), and then re-heats
the material to soften (reduce hardness and strength) and add ductility and toughness (tempering.)

In Q & T steels, Critical cooling rate must be exceeded to produce 100% martensite and hardness is determined by its
carbon content  During welding, HAZ (adjacent to weld )  heated above the critical temperature of 850°C and then gets
cooled very quickly to  RT forming  martensite that readily cracks. For this reason, welding on AISI 4130, 4140, and 4340
without preheat is not recommended, no matter what filler metal is used. Preheat slows down the cooling rate and helps to
prevent  fast quenching in the HAZ, and thus  helps to  prevent martensite in the base metal.

  • The amount of preheat is determined by the amount of carbon and other alloys.  For 4130 Preheat could be 200 to 250 deg.C and  inter pass temp.to be maintained at 250 deg.C max.
  • The heat from welding makes the base material expand during heating and contract when cooling. This creates residual  tensile stresses  around the weld  (HAZ) that can cause cracking or shorten the life of the part. Stress relief at 650°C  and held for 1 hour per inch of thickness after welding will help to eliminate these residual stresses. 
  • Stress relief cycle immediately after welding promotes hydrogen diffusion out of weld metal and HAZ to help to prevent   hydrogen cracking.
  • For 4140 and 4130 type materials,, cooling in a controlled furnace (or using an insulated welding blanket) is required to  slow the cooling  rate (after holding) down to below 60°C per hour.
  • Welding AISI 4130 to EH 36 or any carbon steel, only need to match the lower strength.   E7018-A1 or ER70S-6 filler may suffice if impact properties below -20 deg. C is not required. For, higher impact requirement AWS SFA 5.5 E 8018 C1 is good.
  • Using a lower-strength filler metal may result in a weldment that is less susceptible to cracking.
  • Whether or not the weld metal matches the base metal, for AISI alloy steels preheat, inter pass temperature management as well as post-weld cooling rate is to be mainlined to get best  out of welding.
    sridhar
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
 

From: Rudolf <rudolf_jude@yahoo.com>
To: "materials-welding@googlegroups.com" <materials-welding@googlegroups.com>
Sent: Tuesday, 15 April 2014 6:24 AM
Subject: Re: [MW:20595] Suitable electrode for SAE 4130 Pipe

Dear fellow members
In continuation to this thread, can I have some suggestions to weld 4130 plate to EH36 plate. This is dissimilar thickness 120 mm 4130 welded to 65 mm EH36 plate.
Intend to use 8018-C1 for root and E81T-1. 
Seek your advise on preheat, parameters,  any extra care to be taken to allow slow cooling. Any PWHT can be done. 
The requirements are just 4130 and not specified to be QT or normalised,  but the plate that is available is QT. Can I send the plate for normalising before welding. Will it improve the toughness and help avoid PWHT.  
Your response will be highly appreciated.
Regards


Sent from Samsung Mobile


-------- Original message --------
From: c sridhar
Date:14/04/2014 16:39 (GMT+08:00)
To: materials-welding@googlegroups.com
Subject: Re: [MW:20582] Suitable electrode for SAE 4130 Pipe

 If you are particular about impact retirements,  then AWS SFA 5.5 E 8018 - C1
could be used. Similarly SFA 5.28 ER 80 Ni2 is recommended for root pass in TIG process.

If impact is not a criteria, then, SFA 5.18 ER 70 S-6 can be used for root and
SFA 5.5 8018 / E8018-C1  for filler & cap.

sridhar
 
 
From: "rhmalhotra84@gmail.com" <rhmalhotra84@gmail.com>
To: materials-welding@googlegroups.com
Sent: Sunday, 13 April 2014 8:43 PM
Subject: [MW:20578] Suitable electrode for SAE 4130 Pipe

Dear Experts,
Could you suggest me suitable and weldable electrode and its sfa/aws no. for Pipe SAE 4130 material.
Rgds,
Rohit

----------
Sent from my Nokia phone

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