Aobo Steel

Choose Aobo Steel for consistent, reliable quality

Aobo Steel: Your 4340 Steel Supplier for Quality & Service

Premium 4340 Steel Supplier for Unmatched Durability

At Aobo Steel, we’re proud to be your reliable 4340 steel supplier and 4340 steel distributor. We deliver high-quality steel that meets tough industry standards, ensuring your projects perform at their best. Count on us as your 4340 steel supplier for top service and expertise. Curious about 4340 steel? It’s a strong, durable low-alloy steel, perfect for aerospace, automotive, and heavy machinery thanks to its toughness and fatigue resistance.

Durability You Can Trust from Aobo Steel

When durability matters, Aobo Steel is your premier 4340 steel supplier. This low-alloy steel, celebrated for its wear resistance, excels in heavy machinery like gears and bolts. As a dependable 4340 steel distributor, we provide materials that withstand the toughest conditions, from mining equipment to oil rigs. Our rigorous quality checks ensure you receive 4340 steel that lasts, reducing downtime and boosting efficiency. At Aobo Steel, we’re more than a supplier—we’re a partner committed to your operational success. Choose us for 4340 steel that delivers long-term value and performance you can count on every time.

Precision Engineering Starts with Aobo Steel

At Aobo Steel, we take pride as a leading 4340 steel distributor, supplying this versatile alloy to precision-driven industries. Known for its excellent fatigue resistance, 4340 steel powers automotive parts like crankshafts and transmission gears. We source only the finest materials, ensuring you get consistent quality as your trusted 4340 steel supplier. Our team understands the needs of engineers crafting high-stakes components and delivering steel that performs under pressure. With Aobo Steel, you gain a partner dedicated to precision and reliability. Let us support your next project with 4340 steel that meets your exact specifications—because at Aobo Steel, your success drives us.

Suply Range

Shape	Size	Length	Surface finish	tolerance
round bar	diameter 20mm-400mm	length 2500mm-5800mm	black	0/+5mm
			peeled	0/+5mm
			turned(machined)	0/+2mm
plate	widththickness 100mm-800mm10mm-400mm	length 2500mm-5800mm	black	0/+5mm
			peeled	0/+5mm
			turned(machined)	0/+2mm

4340 Steel Chemical Composition

Carbon (C)	Chromium (Cr)	Nickel (Ni)	Molybdenum (Mo)	Manganese (Mn)	Silicon (Si)	Phosphorus (P)	Sulfur (S)
0.38 – 0.43%	0.70 – 0.90%	1.65 – 2.00%	0.20 – 0.30%	0.60 – 0.80%	0.15 – 0.35%	≤ 0.035% (max)	≤ 0.040% (max)

4340 Steel Equivalent Grades

Country/Region	Equivalent Grade
America	AISI/SAE 4340
Japan	JIS SNCM439
China	GB 40CrNiMoA
EU	EN 34CrNiMo6 (1.6582)

4340 Steel Heat Treatment

(1) Normalizing

First, heat the steel to 845-900°C (1550-1650°F). Then, cool it in the air. This process refines the grain structure, enhances material uniformity, and boosts mechanical properties.

(2) Annealing

Next, raise the temperature to 830-860°C (1525-1575°F). Then, cool it slowly in the furnace. This reduces hardness, improves machinability, and effectively relieves internal stresses.

(3) Quenching

To begin, heat the steel to 800-845°C (1475-1550°F) and hold it for 15 minutes per 25 mm thickness. Then, quench it in oil to below 65°C (150°F) or use molten salt at 200-210°C (390-410°F). This increases hardness and strengthens the material significantly.

(4) Tempering

After quenching, heat the steel to 200-650°C (400-1200°F) and maintain it for at least 30 minutes. Next, cool it in the air. This adjusts hardness and toughness while eliminating quenching stresses.

(5) Spheroidizing

Start by preheating to 690°C (1275°F) for 2 hours. Then, increase the temperature to 745°C (1375°F) for 2 hours. Afterward, cool it to 650°C (1200°F) for 6 hours, furnace cool to 600°C (1100°F), and air cool. This enhances machinability for cutting operations.

(6) Stress Relieving

Finally, heat the steel to 650-675°C (1200-1250°F). This removes residual stresses from machining or welding efficiently.

4340 Steel Applications

Aerospace Industry: Thanks to its high strength and reliability, manufacturers often use 4340 steel to produce critical components like aircraft landing gear, engine parts, and fasteners.

Automotive Industry: Engineers apply 4340 steel to craft key parts such as transmission gears, bearings, crankshafts, and connecting rods, boosting vehicle performance and dependability.

Heavy Machinery Industry: When building heavy machinery, companies utilize 4340 steel for high-strength bolts, shafts, and gears, ensuring stable and reliable equipment operation.

Mold Industry: After heat treatment, fabricators employ 4340 steel to create various molds, including injection and die-casting molds, leveraging its enhanced properties.