Alloy Steel 4340 CNC Machining Services In China

As a leading custom CNC machining services company in China, EJCNC offer a wide range of alloy steel 4340 CNC machining services, which will allow you to produce highly accurate and of good quality 4340 parts to meet even your most stringent requirements.
Listed below are the two main services for machining Alloy Steel 4340.

our Alloy Steel 4340 CNC machining Capability

Here are two popular services we provide for alloy steel 4340.


CNC Milling for Alloy Steel 4340

Our company has the capability to perform CNC milling of Alloy Steel 4340. Alloy Steel 4340 can be machined to near-net shape with tight tolerances, making it suitable for precision machining operations. We are equipped with the latest CNC equipment and use cutting-edge technology to ensure accuracy and repeatability. Our CNC Milling capabilities for Alloy Steel 4340 are unparalleled in the industry, giving us an edge in producing quality parts with quick turnaround times.

CNC turning for Alloy Steel

CNC Turning for Alloy Steel 4340

Our company’s CNC turning capability for Alloy Steel 4340 is one of the most versatile in the industry. Our CNC machines are equipped with advanced cutting tools that allow us to cut complex shapes while still maintaining a high level of accuracy. Additionally, our machinists have extensive experience working with Alloy Steel 4340 so they know how to maximize its properties and create high-quality parts. From prototype production to large-volume production runs, we can turn Alloy Steel 4340 into custom parts and components that meet your exact specifications.

What is Alloy Steel 4340

AISI 4340 steel is a medium carbon, low alloy steel known for its toughness corrosion resistance, and strength in relatively large sections. It is also one kind of nickel chromium molybdenum steel. 

chemical components

Alloy steel 4340 is composed of iron, carbon, chromium, molybdenum, and other alloying elements. The addition of these elements gives the steel specific mechanical and physical properties that are superior to those of other steels.

Alloy Steel 4340 CNC Machining chemical components

mechanical properties

 The following table outlines the mechanical properties of alloy steel 4340.

Steel 4340 CNC Machining

alloy steel 4340 Alternative names / Designation

4340 Alternative names

Heat treatments for alloy steel 4340

AISI 4340 alloy steel is heat treated at 830°C (1525°F) followed by quenching in oil.
Some common heat treatments include normalizing, annealing, hardening, tempering, and stress relief.


Heating to 830 to 860 °C (1525 to 1575 °F) and maintaining it for a period of time, which depends on the thickness of the section or furnace load; furnace cooling.


Heat to 845 to 900 °C (1550 to 1650 °F) and hold for a period of time, which depends on the thickness of the section; air cooling.


Heat to 800 to 845 °C (1475 to 1550 °F) for 15 minutes (minimum 15 minutes) per 25 mm (1 inch) thickness; oil quench to below 65 °C (150 °F), or quench in fused salt at 200 to 210 °C (390 to 410 °F), hold for 10 minutes, and then air-cool to below 65 °C (150 °F).


Hold at 200 to 650 °C (400 to 1200 °F) for at least 1/2 hour; air cooling. The temperature and the time at the temperature mainly depend on the required final hardness.

Stress Relief

After straightening, forming, or processing, the stress of the part can be released at a temperature of 650 to 675 °C (1200 to 1250 °F).

Why choose our services

Why choose our Alloy Steel
4340 CNC Machining?

We have over 10 years of experience in CNC machining, and our state-of-the-art facilities allow us to produce high-quality 4340 parts, which are able to meet the most demanding tolerances and specifications. 
In addition, we offer a variety of surface finishes and coatings to suit your needs. Whether you need a single prototype or a large production run, we can provide the quality 4340 parts you need when you need them.
We also provide other materials’ custom CNC machining services, like alloy steel 4140alloy steel 1215alloy steel 1.7225alloy steel 1.7131  and carbon steel.

Surface Finishing Options for Alloy steel 4340

There are many finishing options available for 4340 steel when using CNC machining.

black coating

Black coating is an option for 4340 steel. This finish is often used in the automotive industry because it provides a sleek, finished look.


Plating is another popular finish for 4340 steel. This process can be used to add a variety of different colors to the metal, which can be used for aesthetic or functional purposes.


Polishing is often used to create a high-quality, mirror-like finish. It can also improve the functionality of the 4340 part by reducing friction or making it easier to clean.

powder coating

Powder coating is ideal for 4340 parts that will be exposed to high temperatures or harsh chemicals. It is a strong, wear-resistant finish.


SAE AISI 4340 steel is usually used in places where severe conditions exist and heavy parts require high strength and can be widely used as a billet, bar, bar, forging, sheet, pipe, and welding wire. 
AISI 4340 steel can also be produced as light plates and castings. Typical applications include bolts, screws, and other fasteners. Gears, pinions, shafts, and similar mechanical components; crankshafts and piston rods of engines; and landing gear and other key structural components of aircraft.
You can see the below chart for reference.
Application Vc (m/min) Vc (SFM)
Turning 215-290 710-950
Milling 130-180 430-590

Machining is best done with the alloy steel 4340 in the annealed or normalized and tempered condition. It can be readily machined by all conventional methods such as sawing, turning, drilling, etc. However, in the high strength conditions of 200 ksi or greater the machinability is only from 25% to 10% that of the alloy in the annealed condition.

Are you looking for a reliable alloy steel 4340 CNC machining China services?

 Look no further than EJCNC. Our experienced team of professionals is committed to providing superior quality and high-precision parts for a wide range of applications.

Contact us today to learn more about our services and to get started on your project.