Quenched and Tempered Steel Round Bar
Hardened and Tempered Steel Round Bar
Hardening and tempering is a heat-treatment process for high-quality steel round bars to give them necessary properties as required. It is a two-stage heat treatment process consisting of Quenching and Tempering.
Stage 1 : Quenching / Hardening
The first stage consists of hardening, in which the round bar is austenitized to approximately 900°C depending on the grade and then quickly cooled. The material is water-quenched or oil quenched or solvent quenched in a quench unit.
Stage 2 : Tempering
It consists of tempering the material to obtain the desired material properties.
The material is then straightened. Material is tested to check if it meets requirement.
Quenching and tempering achieves an extremely fine-grained and homogeneous microstructure. They are also called QT bars. QT steel bars are characterized by high strength and good ductility.
We can provide you Quenched and Tempered Bars of grades such as SAE4140, etc.
For details contact Mr Apurv Gupta on +91 9004064570.
Lesser‑Known Insights
1. Microstructure Benefits
When heat treated correctly, 4140 steel’s tempered martensite microstructure minimises internal stresses, reducing the likelihood of unexpected warping during CNC machining or under fluctuating loads. This property is particularly valuable in industries such as aerospace and oil & gas, where component failure risk must be near zero.
2. Stability During Further Processing
Unlike many hardened steels, properly tempered 4140 remains dimensionally stable during nitriding, induction hardening, or stress relieving. This makes it a go‑to choice for precision, high‑load components that require post‑heat‑treatment surface enhancements without distortion.
Frequently Asked Questions
1. What are Hardened and Tempered 4140 Steel Bars?
Hardened and tempered 4140 steel bars are medium-carbon alloy steel bars that have undergone a heat treatment process to enhance hardness, strength, and wear resistance. The steel grade 4140 contains chromium, molybdenum, and manganese, making it suitable for high‑stress industrial applications.
2. What is the hardness of Hardened 4140 Steel Bars?
Typically, hardened and tempered 4140 steel bars achieve a hardness range of 28–32 HRC (Rockwell C), depending on the tempering temperature and specific heat treatment.
3. What are the key properties of 4140 Hardened and Tempered Steel Bars?
1) High tensile strength (850–1000 MPa typical) 2) Excellent fatigue resistance 3) Good toughness 4) High wear resistance 5) Better machinability compared to many other hardened steels
4. What are the common applications of Hardened 4140 Steel Bars?
4140 heat-treated steel bars are widely used in Hydraulic shafts, Gears & pinions, Crankshafts, Tool holders, Drill collars, Automotive and aerospace components
5. How is the hardening and tempering process done for 4140 steel?
The process includes: A) Austenitizing at ~840–875°C B) Quenching in oil or polymer to increase hardness C) Tempering at 540–680°C to adjust hardness and improve toughness
6. Can Hardened 4140 Steel Bars be machined?
Yes, they can be machined, but their machinability decreases as hardness increases. Using carbide tooling and proper cutting speeds is recommended.
7. Is 4140 hardened steel weldable?
4140 steel can be welded, but it requires preheating (150–260°C) and post‑weld heat treatment to avoid cracking and maintain mechanical properties.
8. What International standards and specifications apply to Hardened 4140 Steel Bars?
Common standards include: A) ASTM A29 / A322 (for hot rolled bars) B) ASTM A331 (for cold finished bars) C) DIN 42CrMo4 D) SAE 4140
9. How do Hardened & Tempered 4140 Steel Bars compare to 4340 steel?
4140: More economical, good balance of strength and toughness 4340: Higher nickel content, better ultra‑high‑strength capabilities, better fatigue life in extreme conditions
10. Where can I buy Hardened and Tempered 4140 Steel Bars?
If you have a requirement of 20000 kg of SAE4140 hardened and tempered steel per order, contact Mr Apurv Gupta on +91 9004064570.