How to Weld AISI 4130 Steel

AISI 4130 Steel Introduction

AISI 4130 alloy steel contains chromium and molybdenum to work as strengthening elements.  It is available in the 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 is made with high carbon and added chromium and molybdenum. The alloy responds very good to heat treatment and it is possible to achieve a high strength with toughness using the right heat treatment process.

Welding AISI 4130 is not difficult, provided welding procedures and subsequent post-weld heat treatment (PWHT) are carried out in accordance with approved procedures.

AISI 4130 Material Specification

Material specification for ASISI 4130 are AMS 6350, 6360, ASTM A331, ASTM T506, 507, A518 etc. The UNS Number for AISI 4130 is UNS G41300.

AISI 4130 Chemical Properties

AISI 4130 contains 0.28 to 0.33% carbon, 0.8o to 1.1% Chromium and 0.15 to 0.2% molybdenum as main alloying elements. These are also the main elements that affect the weldability of AISI 4130 material.

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.

Tensile strength,560 MPa81.2
Yield strength,460 MPa66.7

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 the maximum hardness allowed is 250HV. Careful selection of the preheat & post heat (Stress relieving) temperature is a critical step.
  2. Avoid hydrogen 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.

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Preheat of AISI 4130 steel

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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.

4130 microstructure