4340 Steel Casting High Strength Alloy Steel Castings

4340 Steel Casting Product Overview

High-Strength Alloy Steel Castings for Critical Service

I supply 4340 steel castings when you need compact parts to carry very high loads, survive impact, and handle demanding duty cycles. As a nickel-chromium-molybdenum (Ni-Cr-Mo) alloy steel, AISI 4340 alloy steel castings offer a strong combination of:

• High tensile and yield strength
• Excellent toughness and impact resistance
• Good fatigue performance for cyclic and rotating loads
• Heat treatability for a wide range of strength levels

Compared with standard carbon steel castings, 4340 cast steel delivers much higher strength-to-weight ratios and far better toughness, especially in thicker sections and high-stress zones.

Where 4340 Steel Castings Are Used

My 4340 investment casting et 4340 sand casting solutions are typically specified for:

• Aerospace 4340 cast parts – structural fittings, linkages, gear components
• Defense grade alloy castings – heavy duty gear castings, shafts, weapon system parts
• Oil and gas alloy steel castings – high-pressure valves, drilling tools, pump and tool bodies
• Heavy equipment and industrial machinery – axles, hubs, transmission and drivetrain parts

In these sectors, designers use quenched and tempered 4340 castings where failure is not acceptable and parts must withstand shock, bending, and long-term fatigue loading.

4340 vs Standard Carbon Steel Castings

cURL Too many subrequests. 4340 steel casting to common carbon steel castings (like 1020 or 1045):

• Résistance – 4340 can be heat treated to much higher strength levels while maintaining ductility.
• Toughness – Ni-Cr-Mo chemistry provides superior impact and notch toughness, especially at lower temperatures.
• cURL Too many subrequests. – fatigue resistant steel castings such as 4340 significantly outperform standard carbon grades in rotating and cyclic applications.
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  • Complex geometry
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  • Bigger, heavier sections
  • More flexibility on design changes
  • Cost-effective for medium to large parts

This lets us design custom 4340 steel castings around your part’s performance needs instead of forcing you to machine everything from bar or forgings.

4340 Steel Casting Material Specifications

Lorsque nous produisons 4340 steel castings, we stick to tight, traceable specs so your parts match the performance of premium forged and bar stock alloys.

AISI 4340 and Equivalent Grades

We routinely pour and certify to:

• AISI / SAE 4340
• UNS G43400
• EN 34CrNiMo6
• EN 1.6582

These Ni-Cr-Mo alloy steel casting grades give you high strength, toughness, and fatigue resistance in a wide range of heat-treated conditions.

Typical 4340 Cast Steel Chemistry

Typical chemical composition range for our AISI 4340 alloy steel castings (wt%):

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• cURL Too many subrequests. 0.60 – 0.90
• Silicium (Si) : 0.15 – 0.40
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• cURL Too many subrequests. 1.65 – 2.00
• Molybdenum (Mo): 0.20 – 0.30
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• Sulfur (S): ≤ 0.025

We fine-tune chemistry for high-strength alloy steel castings to balance hardenability, toughness, and machinability, especially on thicker sections.

Key Standards for 4340 Steel Castings

We can pour and certify 4340 sand castings et 4340 investment castings à :

• ASTM A915 Grade SC4340 – cast Ni-Cr-Mo alloy steel
• AMS 6414 / AMS 6415 – aerospace-grade 4340 chemistry and quality requirements
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For high-stress, fatigue-loaded parts, I usually recommend quenched and tempered 4340:

• Medium strength (HRC 28–35):
  • Tensile: ~140–170 ksi (965–1170 MPa)
  • Yield: ~120–150 ksi (830–1030 MPa)
• High strength (HRC 38–45):
  • Tensile: ~180–220 ksi (1240–1520 MPa)
  • Yield: ~160–190 ksi (1100–1310 MPa)

Heat treated 4340 steel castings in these ranges are ideal for heavy duty gear castings, shafts, and other fatigue resistant steel castings where failure is not an option. If you want a broader look at how alloy design ties into performance, my full cURL Too many subrequests. goes into more detail.

Impact toughness and Charpy performance

One of the main reasons engineers pick Ni-Cr-Mo steel castings like 4340 is impact toughness:

• Properly quenched and tempered 4340 can deliver high Charpy V-notch values, even at lower temperatures.
• At moderate strength levels (around HRC 30–35), you can get very good toughness for aerospace 4340 cast parts, defense-grade alloy castings, and oil and gas alloy steel castings.

The higher you push the hardness, the more you trade off Charpy impact energy, so we dial that in based on your spec (ASTM, AMS, MIL, or OEM standard).

Section size and cooling rate effects

4340 is hardenability-sensitive, so geometry matters:

• Sections épaisses : slower cooling, lower hardness and strength in the core, more property gradients through the cross-section.
• Thin sections: faster cooling, higher hardness and more uniform properties.
• Complex shapes: varying wall thickness can cause mixed microstructures if heat treatment isn’t tightly controlled.

When we design UNS G43400 cast components, we factor in section size, gating, and heat treatment setup to hit your required 4340 cast steel mechanical properties consistently, not just on test coupons.

4340 Investment Casting vs Sand Casting

What is 4340 Investment Casting?

For 4340 steel casting, investment casting is my go-to when you need precision and clean geometry.

4340 investment casting (lost wax) is ideal when:

• You need tight tolerances and repeatability
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cURL Too many subrequests.	~5 lb – 5,000+ lb (2–2,300 kg)	±0.03–0.06 in/in, depending on size	~0.20–0.30 in (5–8 mm)

*Actual numbers depend on geometry, mold type, and project requirements.

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How I Help You Choose: 4340 Investment vs Sand Casting

Use this as a quick guide for UNS G43400 cast components:

• Go investment casting when:
  • You need tight tolerances and nice surface finish
  • Part is under ~150 lb and fairly complex
  • You want to minimize machining stock and cycle time
• Go sand casting when:
  • Part is large or very massive
  • Cost per pound is critical
  • Tolerances are moderate and you already plan to machine most surfaces

If you share your 3D model, annual volume, and target tolerances, I can tell you fast whether 4340 investment casting or 4340 sand casting will hit your performance and cost targets better.

Heat Treatment Options for 4340 Steel Castings

For 4340 steel castings, heat treat is where we lock in the strength, toughness, and machinability you actually need in service. We set up each heat treatment route based on part size, load conditions, and your spec (ASTM, AMS, MIL, or internal standard).

Normalizing and Stress Relieving 4340 Cast Parts

For many high-strength alloy steel castings, we start with a normalize or stress-relief cycle:

• Normalizing (typically 1600–1700°F, air cool) refines the grain, evens out properties across the casting, and prepares the structure for further heat treating.
• Stress relieving (usually 1050–1250°F) removes residual casting and machining stresses to reduce distortion and cracking risk in service.

This is a common base treatment for large 4340 sand castings and structural Ni-Cr-Mo steel castings before final machining.

Annealing for Machinability and Stability

When machinability and dimensional stability matter more than maximum strength, we recommend full anneal or subcritical anneal:

• Produces a softer, more uniform structure for easy cutting.
• Reduces internal stresses so parts stay stable during and after machining.

Annealed 4340 cast steel usually falls in the Brinell 170–220 HB range, which is ideal for rough and finish machining on complex UNS G43400 cast components.

Quenching and Tempering 4340 Castings

To get the classic high-strength performance from 4340 investment casting or 4340 sand casting, we use quench and temper (Q&T):

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• Shafts, couplings, and drive components
• Weapon system parts, mounts, and support hardware

For defense work, we often pair 4340 castings with strict inspection and certifications similar to AMS 6414 4340 cast steel and related specs.

Automotive and Heavy Equipment 4340 Cast Components

For high-load drivetrain and powertrain parts, 4340 sand casting and investment casting make a lot of sense:

• Axles and differential components
• Crankshafts and power transmission parts
• Hubs, yokes, and high-stress brackets

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Oil and Gas 4340 Cast Steel Applications

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• High-pressure valves and bodies
• Pump housings and impellers
• Drilling tools, subs, and tool joints

Here, quenched and tempered 4340 gives a strong blend of tensile strength, toughness, and wear resistance for harsh field conditions.

General Industrial Machinery 4340 Cast Parts

Across industrial equipment, cURL Too many subrequests. in 4340 work well for:

• Press and mill components
• Heavy-duty couplings and flanges
• High-stress levers, arms, and housings

If you also need mating parts or pipe connections, we can pair these with our de brides en acier allié sur mesure to keep your system consistent in strength and performance: de brides en acier allié sur mesure.

When to Pick 4340 Casting vs 4140 or Other Alloy Steels

I usually recommend 4340 steel casting over 4140 or lower-alloy grades when:

• Vous avez besoin higher strength and toughness in the same section size
• cURL Too many subrequests. severe fatigue or impact (gears, shafts, landing gear, downhole tools)
• Vous souhaitez extra safety margin in critical service (defense, aerospace, oil & gas)

4140 or 4130 castings can be a better fit when:

• Loads are moderate and cost is the priority
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Traçabilité des matériaux et contrôle du numéro de lot

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I run custom 4340 steel casting as a true end‑to‑end service, from design support to finished, ready‑to-install parts.

Design and 4340 Material Selection Support

I help your team lock in the right 4340 casting design and alloy spec up front so you don’t fight problems later.

• DFM for 4340 investment casting and 4340 sand casting
• Wall thickness, gating, riser, and draft advice for high-strength alloy steel castings
• 4340 vs 4140 and other Ni-Cr-Mo steel casting recommendations based on load, fatigue, and cost

If you also need machined hardware with your castings, I can align specs with our low‑carbon and alloy steel machining services for consistent performance.

Rapid Prototyping and Samples

I move fast on prototypes so you can validate 4340 cast parts early:

• 3D-printed patterns and soft tooling for quick 4340 investment casting runs
• Short‑run 4340 sand castings for functional testing
• Full dimensional and mechanical reports with each sample lot

In‑House Machining and Tight Tolerances

You don’t have to coordinate multiple vendors. I cast and machine in one workflow:

• CNC turning and milling for tight‑tolerance 4340 cast components
• Critical surfaces, bores, and threads held to tight GD&T requirements
• Heat treated 4340 steel castings machined to final spec, ready for assembly

Surface Treatments and Coatings for 4340

To protect 4340 and clean up appearance, I offer:

• Shot blasting, grit blasting, and descaling
• Zinc/nickel plating, phosphate, and painting systems
• Surface prep matched to your coating spec and operating environment

Scalable Production Capacity

Whether you’re validating a new design or feeding a mature program, I scale with you:

• Low‑volume, engineering builds and spares
• Mid‑volume production for industrial and defense programs
• High‑volume 4340 investment castings with repeatable quality and stable pricing

Every 4340 steel casting project gets a single point of contact so engineers, buyers, and program managers in the U.S. can move from RFQ to production with clear communication and predictable lead times.

Why Choose Our 4340 Steel Casting Foundry

When you need reliable 4340 steel casting for high‑stress, high‑value parts, we run the process like a true manufacturing partner, not just a job shop.

Deep Experience With High-Strength Ni-Cr-Mo Cast Steels

Nous nous concentrons sur AISI 4340 alloy steel castings and other Ni-Cr-Mo steel castings every day, so we know how to hit tight mechanical property windows and tough specs (ASTM, AMS, MIL).

• Proven history with aerospace, defense, oil & gas, and heavy equipment projects
• Familiar with qualification runs, PPAP, and full documentation for demanding U.S. customers

Advanced Melting, Molding & Process Control

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• Ajouter 1–2 semaines if you need full machining, NDT, and certifications

Rush programs are possible if we lock specs and approval quickly.

How corrosion resistant is 4340 cast steel, and when do I need coatings?

4340 cast steel is a high-strength Ni-Cr-Mo alloy, not a stainless steel. It offers:

• Decent corrosion resistance in dry, indoor, lubricated service
• Poor resistance in marine, salt-spray, or chemical environments

In most U.S. industrial and oil & gas projects, I recommend:

• Zinc or nickel plating, phosphate, ou paint for outdoor use
• Hard chrome or similar for wear + corrosion on shafts, pins, and gears
  If you want built‑in corrosion resistance instead of coatings, we usually move to stainless or other alloy options like 8620 steel depending on the application.

4340 casting vs forged 4340 – what’s the difference?

Performance :

• Forged 4340:
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  • Preferred for ultra-critical aerospace or defense loads
• 4340 steel casting:
  • Excellent mechanical properties when quenched and tempered
  • Idéal pour des formes complexes that would be expensive or impossible to forge

Cost:

• Fonderies win when you need complex geometry, internal passages, or near-net shapes, cutting machining time and material waste.
• Forgeages are cost effective for simple, highly loaded shapes like straight shafts or basic rings.

What tolerances can you hold with 4340 steel casting processes?

Typical achievable tolerances are:

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How to select the right alloy steel casting for your application

When I help customers pick between 4340 steel casting and other alloys, I look at:

• Required strength level
  • Ultra-high strength / fatigue critical → 4340
  • Medium/high strength → 4140 or similar
• Toughness & impact loading
  • Shock, impact, or safety-critical → lean toward 4340 or higher Ni-Cr-Mo grades
• Section size & wall thickness
  • Thick sections that need through-hardening → 4340 or high hardenability Ni-Cr-Mo
• Weldability & fabrication
  • More welding → 4130 or lower alloy steels
• Machinability & stability
  • Complex machining → normalized or annealed machinable alloy steel castings
• Cost targets
  • Tight budgets with moderate loads → 4130/4140 instead of 4340

If you share your load case, part size, and target hardness/strength, I’ll recommend the most cost‑effective alloy steel casting grade that still meets your performance and safety targets.