40NiCrMo7 (1.6562 / SAE 4340 / ASTM L43)

ASTM A320 / ASTM A29 / UNI 7845

Quenced Tempered (+QT)

PROPERTIES AND EMPLOYEMENTS

It is an alloy steel with elevated resistance and good toughness. it is employed when it is necessary to have elevated characteristics that are more elevated than those offered by 39nicrmo3, especially for parts of remarkable thickness. it has a very elevated hardenability, in fact those parts of small dimensions (ø < 15 mm) can be hardened in air. it is suitable for superficial hardening where it reached a hardness of 54÷59 HRC according to carbon content. It has an elevated fatigue strength up to a temperature of 450°c more or less and it behave very good even at a low temperature. it can be submitted to heat treatment of nitriding, reaching a remarkable increase in the fatigue limit and elevated superficial hardnesses. due to its elevated hardenability, it is generally destined to the construction of parts of relevant dimensions that work in heavy conditions, for example trees for hydroelectric turbines. it is successfully employed for bolts at high resistance.

Steel grade 40NiCrMo7, designated as 1.6562 in the European EN standard, is a nickel-chromium-molybdenum alloy steel renowned for its exceptional strength, toughness, and hardenability. This steel is particularly significant when aligned with the ASTM A320 standard, specifically under the L43 grade, which governs alloy steel bolting materials for low-temperature service.

The ASTM A320 standard, developed by the American Society for Testing and Materials, covers alloy and stainless steel bolting materials designed for low-temperature service, such as in pressure vessels, valves, flanges, and fittings. Grade L43 within this standard specifies 40NiCrMo7 (or its equivalent, such as AISI 4340) for fasteners, ensuring they maintain structural integrity and toughness under subzero conditions. The standard mandates strict requirements for chemical composition, heat treatment, and mechanical properties, including notch toughness, to guarantee performance in critical applications.

The primary application of 40NiCrMo7 under ASTM A320 L43 is in the manufacturing of fasteners such as bolts, studs, and nuts for low-temperature environments. These are critical in industries like oil and gas, petrochemical, and power generation, where they secure pressure vessels, valves, and fittings operating in subzero conditions

Beyond fasteners, 40NiCrMo7's high hardenability and toughness make it suitable for a range of engineering applications:

• Large Axles and Shafts: Used in hydroelectric turbines and heavy machinery, leveraging its ability to handle significant stress and impact;
• Machine Components: Employed in gears, crankshafts, and connecting rods, where high stress, torsion, and vibration are common;
• Engineering Components: Utilized in mining, construction, and aerospace for components requiring reliability under extreme conditions;
• Surface-Hardened Parts: Applied in camshafts and tool holders, where wear resistance is enhanced through processes like nitriding.

CORRESPONDENCE TO INTERNATIONAL DESIGNATIONS

CHEMICAL ANALYSIS (ASTM A 320)

MECHANICAL CHARACTERISTICS

USUALLY AVAILABLE EX STOCK

M.T. COLORATION	QUALITY	HEAT TREATMENT	SURFACE	DIAMETER (mm)
	40NiCrMo7 / L43	Quenched and tempered (+QT)	hot rolled peeled	40-300

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