AISI 4340 EN24 817M40 Hot Rolled Alloy Steel Round Bar

AISI 4340 EN24 817M40 Hot Rolled Alloy Steel Round Bar

1: AISI 4340 Steel Introduction

AISI 4340 steel is a medium carbon, low alloy steel known for its toughness and strength in relatively large sections. AISI 4340 is also one kind of nickel chromium molybdenum steels. 4340 alloy steel is generally supplied hardened and tempered in the tensile range of 930 - 1080 Mpa. Pre hardened and tempered 4340 steels can be further surface hardened by flame or induction hardening and by nitriding. The 4340 steel has good shock and impact resistance as well as wear and abrasion resistance in the hardened condition. AISI 4340 steel properties offer good ductility in the annealed condition, allowing it to be bent or formed. Fusion and resistance welding is also possible with our 4340 alloy steel. ASTM 4340 material is often utilized where other alloy steels do not have the hardenability to give the strength required. For highly stressed parts it is excellent choice. AISI 4340 alloy steel can also be machined by all customary methods.

4340 Steel Stock in Warehouse

2: AISI 4340 Quality Standard

AISI 4340 steel according to ASTM A29-05.

3: AISI 4340 Steel Equivalent

4: AISI 4340 Steel Chemical Composition

5: AISI 4340 Steel Mechanical Properties 

The mechanical properties mainly include tensile strength, yield strength, elongation, area or reduction, hardness, impact value, non-metalic inclusion etc. Different heat treatment, the mechanical properties will be different, such as normalized, tempered, QT. If you want to know the properties, kindly contact the salesman.

6: AISI 4340 Steel Overviews

7: AISI 4340 Steel Application

4340 alloy steels are used for aircraft landing gear, automotive, oil and gas drilling, warm and cold forming, machine building, transfer systems like power transmission gears and shafts, general engineering industries and structural use applicatios such as heavy duty shafts, gears, axles, spindles, couplings, pins, chucks, molds and so on.

8: AISI 4340 Steel Heat Treatment

Annealing

A full anneal may be done at 844°C (1550 F) followed by controlled (furnace) cooling at a rate not faster than 10°C (50 F) per hour down to 315°C (600 F). From 315°C 600 F it may be air cooled.

Tempering

AISI 4340 alloy steel should be in the heat treated or normalized and heat treated condition before tempering. The tempering temperature for depends upon the strength level desired. For strength levels in the 260 – 280 ksi range temper at 232°C (450 F). For strength in the 125 – 200 ksi range temper at 510°C (950 F). And don’t temper the 4340 steels if it is in the 220 – 260 ksi strength range as tempering can result in degradation of impact resistance for this level of strength.

Tempering should be avoided if possible within the range 250 °C – 450 °C due to temper brittleness.

Hardening

As mentioned above, pre-hardened and tempered 4340 steel bars or plates can be further surface hardened by either the flame or induction hardening methods resulting in a case hardness in excess of Rc 50. AISI 4340 steel parts should be heated as quickly as possible to the austenitic temperature range (830 °C – 860 °C) and required case depth followed by an immediate oil or water quenching, depending upon hardness required, workpiece size/shape and quenching arrangements.

Following quenching to hand warm, tempering at 150°C – 200°C will reduce stresses in the case with minimal effect on its hardness.

All de-carburised surface material must first be removed to ensure best results.

9: AISI 4340 Steel Tolerance

10: Delivery Condition

For hot forged or hot rolled bar, usually the delivery condition is hot forged or rolled, annealed or QT, black surface or rough turned.
For hot forged plate, usually the delivery condition is hot forged, annealed or QT, milled surface.
For hot rolled plate, usually the delivery condition is hot rolled, annealed or QT, black surface.