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AISI 4340 steel, 4340 Steel Hardness, 4340 alloy steel, AISI 4340 Steel Properties, AISI 4340 Material Properties, AISI 4340 Ficha Técnica, AISI 4340 Price,

Preheat the steel 4340 first, to a maximum temperature of 1150°C – 1200°C for forging, and hold until the temperature is homogeneous throughout the section.

Forge at a temperature of 850°C or higher. 4340 has strong forging properties, although cooling must be done with caution because the steel is prone to cracking. The work item should be cooled as gently as feasible after the forging operation. Also, chilling in sand or dry lime is recommended, among other things.

Heat Treatment for AISI 4340 Steel Grade

Stress Relieving

Steel 4340 is stress relieved by heating it to between 500 and 550°C for pre-hardened steel. Heat to 600–650°C, hold until temperature is consistent throughout the section, soak for 1 hour for each 25 mm segment, and cool in still air.

Annealing

A full anneal at 844°C (1550°F) can be followed by controlled (furnace) cooling down to 315°C at a pace of no more than 10°C (50°F) per hour (600 F). It may be air-cooled from 315°C to 600°F.

Tempering

Before tempering, AISI 4340 alloy steel should be heat treated or normalized and heat treated. The tempering temperature is determined by the desired strength level. Temper at 232°C for strength values between 260 and 280 ksi (450 F). Temper at 510°C for strength in the 125–200 ksi range (950 F). Also, do not temper 4340 steels with a strength range of 220 – 260 ksi, since tempering can result in a loss of impact resistance at this strength level.

 Due to temper brittleness, tempering should be avoided if possible within the range of 250 °C – 450 °C.

Flame or Induction Hardening

Pre-hardened and tempered 4340 steel bars or plates can be further surface hardened using the flame or induction hardening techniques, resulting in a case hardness of greater than Rc 50. AISI 4340 steel components should be heated to the austenitic temperature range (830 °C – 860 °C) and desired case depth as rapidly as possible, then immediately quenched in oil or water, depending on the hardness required, workpiece size/shape, and quenching arrangements.

Tempering at 150°C – 200°C after quenching to hand warm will minimize tensions in the case while having a negligible effect on its hardness.

To achieve the optimum results, all de-carburized surface material must be removed first.

Nitriding

Nitriding hardened and tempered 4340 alloy steel results in a surface hardness of up to Rc 60. Heat to 500°C – 530°C and leave to cool for 10 to 60 hours to develop the depth of the case. To reduce the problem of distortion, nitriding should be followed by slow cooling (no quench). As a result, the nitrided grade 4340 materials can be machined to near the final size with only a minimal grinding allowance. Because the nitriding temperature range is typically lower than the initial tempering temperature, the tensile strength of the 4340 steel material core is usually unaffected.

The surface hardness that can be achieved is 600 to 650HV.

Machinability

The alloy steel 4340 in the annealed or normalised and tempered form is best for machining. All common machining procedures, including as sawing, turning, and drilling, can be used to machine it. The machinability of the alloy in high strength circumstances of 200 ksi or above, on the other hand, is only 25% to 10% of that of the alloy in the annealed condition.

 Welding

Welding steel 4340 in the hardened and tempered condition (as supplied) is not advised and should be avoided if at all feasible due to the risk of quench cracking and the alteration of mechanical properties within the weld heat-affected zone.

If welding is required, set the temperature to 200 to 300°C and keep it there while welding. Prior to hardening and tempering, stress released immediately after welding at 550 to 650°C.

If welding in the hardened and tempered condition is absolutely necessary, the workpiece should be stress relieved at 15 °C below the initial tempering temperature as soon as practicable after cooling to hand warm.

In most industries, AISI 4340 steel is utilized for applications that require more tensile/yield strength than 4140 steel can supply.

Here are a few examples of typical applications:

Landing Gear for Aircraft

Drilling for oil and gas, forging, warm and cold forming, machine building, and transfer systems, such as power transmission gears and shafts.

Heavy-duty shafts, gears, axles, spindles, couplings, pins, chucks, molds, and other general engineering and structural applications

Lakshya International is a prominent provider of AISI 4340 steel for a variety of applications such as those listed above. We also have 4140 and 4130 steels in stock. Please contact me at any time with your requests.