How to Weld AISI 4130 Steel


AISI 4140 Steel Introduction

AISI 4130 alloy steel contains chromium and molybdenum to work as strengthening element.  It is available in market as a round bar usually in the Quenched and tempered condition having a hardness of 18-22 HRC. AISI 4130 Q &T low alloy steel is used in oil & gas drilling and production components such as wellhead and Christmas tree parts. AISI 4130 has high carbon contents plus additions of chromium and molybdenum and, depending on the heat treatment applied, have strength levels in excess of 774 N/mm. These steels are capable of withstanding the high pressure experienced during drilling operations, i.e., 10–15 ksi plus, depending on wall thickness. Welding AISI 4130 is not difficult, provided welding procedures and subsequent post-weld heat treatment (PWHT) are carried out in accordance with approved procedures.

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AISI 4130 Material Specification

AMS 6348AMS 6371ASTM A331ASTM A829DIN 1.7218
AMS 6350AMS 6373ASTM A506MIL S-18729UNI 25 CrMo 4
AMS 6351AMS 6374ASTM A507MIL S-6758JIS SCCrM 1
AMS 6360AMS 6528ASTM A513SAE J1397JIS SCM 2
AMS 6361AMS 7496ASTM A519SAE J404SS 2225
AMS 6362ASTM A29ASTM A646SAE J412B.S. CDS 110
AMS 6370ASTM A322ASTM A752AFNOR 25 CD 4 (S)SAE J770

AISI 4130 Chemical Properties

PercentageCarbonSiliconMnChromiumMolySulfurPhosphorus
Minimum 0.28 0.15 0.40 0.80 0.15
Maximum 0.33 0.35 0.60 1.10 0.25 0.035 0.025

Mechanical Properties of AISI 4130

NACE MR0175: maximum hardness of 22 HRC as per API 6A.

PropertiesMetricImperial
Tensile strength, ultimate560 MPa81200 psi
Tensile strength, yield460 MPa66700 ps

Welding of AISI 4130

AISI 4130 is having very high tensile & yield strength due to its quenched and tempered (Q & T) conditions. When welding with the SMAW electrode, the matching or higher properties are achieved with the E10018-D2 electrode. GTAW (TIG) or GMAW (MAG) welding shall be done using ER100S-G type filler wire. These electrode or wires gives higher mechanical properties than the base metal for AISI 4130 welding.

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AISI 4130 welding concerns

  1. Meeting NACE MR0175 hardness limits for low alloy steel as maximum hardness allowed is 250HV. Careful selection of the preheat & post heat (Stress relieving) temperature is a critical step.
  2. Avoid hydyogen cracking by ensuring fully baked welding consumables.
  3. Produce a ductile & high strength weld metal.

Welding of AISI 4130 with EH36 or other carbon Steel

Welding of AISI 4130 to carbon steel materials such as EH36, SA516, or SA105 can be carried out using TIG/ MAG filler wire ER70S-6 or SMAW electrode E7018. If a high-strength filler is needed, welding can be done with E10018-D2 or ER100S-G filler wire.

Preheat of AISI 4130 steel

preheat temperature shall be kept around 200 Deg C to 250 Deg C for AISI 4130 material. Click here to use our Free online Preheat temperature Calculation tool.

PWHT/ Stress Relieving of AISI 4130 steel

PWHT of AISI 4130 steel should be carried out at around 600 deg C for a holding time of 1inch/ hour of material thickness. A higher holding time can be kept but it must not decrease the tensile strength below its minimum specified limit.

Also, another important criterion for the selection of PWHT temperature is that the PWHT temperature must be kept below the tempering temperature of the material. as a high PWHT temperature will destroy the tempering effect in the base material.

The below picture shows the microstructure obtained during TIG welding of AISI 4130 at various locations.

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