The higher levels of carbon, chromium, and molybdenum in these steels make them highly durable and strong, but they are also more susceptible to cracking. Learn how the right filler metal can help make welding these steels easier when fabricating or repairing new products.

In addition to the fabrication and repair of shafts, gears, forgings, and other components for heavy machinery, shafts, gears, forgings, and other components are subject to tough, demanding environmentsuire low-alloy steels such as AISI/SAE la 4130 steel weldability and 4130 weldability, which have a chemical composition that allows them to be heat treatable into high-tensile steels. 

Mechanical properties are not included in AISI  4130 properties and 4140 specifications, only chemical composition. As with 4130, 4140 is primarily made up of carbon, chromium, and molybdenum. Carbon content is only slightly different between 4130 and 4140, with 4130 having 0.3 percent carbon and 4140 having 0.4 percent. 

All of these processes can greatly affect the strength of these materials when they are annealed, normalized, quenched, and tempered. Adding flame hardening to these materials can increase their hardness on the outside while preserving their soft interiors.

All of these processes can greatly affect the strength of these materials when they are annealed, normalized, quenched, and temperediring high strength and durability. 

Due to their high levels of carbon, chromium, and molybdenum, these materials are strong and highly hardenable, but also prone to cracking. Our goal in this article is to provide you with the best welding practices and challenges for 4130 and 4140 steels, whether you are fabricating new parts or repairing existing ones. In addition, we will cover the most efficient filler metals to ensure success.


There are many challenges and best practices that remain the same whether welding new steel or repairing 4130 and 4140 steel sheets. The following six steps should be followed when welding or repairing 4130 or 4140:

1. It is important to identify thermotherapy. 

Typically, new fabrications are performed on material that is in the normalized or annealed state. In order to weld 4130 or 4140 steel in the case-hardened or quenched and tempered condition without first conducting annealing or normalizing on the area to be welded, it is not recommended to weld it under those conditions.

2. Filler metals should be selected.

It is important to choose the proper filler metal for 4130 and 4140 steels based on their quality before welding, their design requirements, and their desired finish after welding. Filler metal selection is often determined by matching the tensile strength of the base metal as supplied when the material is left in the as-welded or stress-relieved state. When using a low-alloy filler metal, it is typically used as a substitute for the 4130/4140 base material to achieve sufficient mechanical properties for both the as-weld and post-weld heat treatment (PWHT) conditions. However, it is often necessary to use a filler metal that does not share the 4130 chemical composition of the base material. Make sure that the filler metal continues to provide desired mechanical properties after the total stress-relief time if a component is to be repaired multiple times over its lifetime – with each repair demanding a post-weld stress-relief cycle.

3. Preheat by applying. 

An intensity impacted zone or weakened weld metal framed from 4130 or 4140 steel plates has a harder, fragile microstructure because of its higher hardenability. For superior grade, steady welds, preheating is vital. The motivation behind laying out and keeping a base preheat and interpass temperature is to decrease the cooling pace of the weld and base metal to forestall or limit the development of weak microstructures in the welding at adequate temperatures, normally from 550 deg F to 800 deg F while welding thick parts, and warming through the whole thickness of the base material, as opposed to just accomplishing temperature on a superficial level. Warming a section with enlistment can be a successful method for guaranteeing that the whole part is equally warmed. It is likewise critical to set the preheat temperature away from the weld joint at an adequate distance, generally three creeps toward each path. Weldments with bigger joints might profit from considerably really preheating.

4. Welding is performed.

In the 4130 welding procedure Heat input is like preheating and intervening: when it is too low, the weld cooling rate advances to the moment that weak microstructures structure, harming malleability and durability. A decrease in movement speed and an expansion in voltage and amperage will increment heat input. It is vital to consider these factors while planning a welding technique for joining aisi 4130 density sheets and 4140 sheets.

5. Cooling takes time.

It is valuable to hold the weldment at the preheated temperature for quite a while subsequent to welding, trailed by covering the weldment with clay protection since this permits hydrogen to diffuse from the intensity impacted zone (HAZ). Contingent upon the thickness of the base material, a holding season of 30 minutes to an hour is suggested. Post-weld pressure alleviation is not quite the same as hydrogen prepare out, which is officially known as hydrogen heat out.

6. Thermal treatment should be applied after welding.

It is feasible to lessen breaking in the completed weld by giving intensity therapy in the wake of welding. To keep up with tight resiliences, delivering these lingering stresses may likewise be helpful preceding machining. Stress alleviation is normally not needed for slim materials (under 1/8 in thick) since breaking is more uncertain. It is normal to stretch assuage thicker materials at 1,050°F to 1,250°F for roughly one hour for each inch of base material thickness. For filler metals to give or keep up with sufficient mechanical properties, consistently consider the times and temperatures of post-weld warm medicines – like PWHT, strengthening, normalizing, or extinguish and treating.

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