Heat Treatment & Its Effect on Alloy Steel Performance

Unlocking the Full Potential of Alloy Steels — Especially DB6 — Through the Science of Heat Treatment

Author

Goel Steel Enterprises
July 07, 2025

At Goel Steel Enterprises, one of the most common questions we receive is:

"Why is heat treatment so important in alloy steels?"

Because it’s the difference between an average-performing material and a high-performing engineering marvel.

In this blog, we’ll explain what heat treatment is, the different types of heat treatment, how it affects various tool and alloy steel grades, and why it's especially critical for DB6, one of our flagship die steel materials.

🔥 What is Heat Treatment?

Heat treatment is a controlled method of heating and cooling metals to alter their internal structure, which in turn changes their mechanical properties like hardness, strength, toughness, and wear resistance.

Just like baking bread transforms dough into something delicious and strong—heat treatment transforms raw steel into high-performance material.

🧪 Why Heat Treatment is Done?

  • ✅ Improve hardness and tensile strength

  • ✅ Enhance wear resistance

  • ✅ Boost toughness (resistance to cracking)

  • ✅ Reduce residual stresses

  • ✅ Improve machinability

  • ✅ Enhance grain structure

🛠️ Types of Heat Treatment Processes

Here’s a breakdown of common heat treatment processes used in alloy and tool steels:

1️⃣ Annealing

  • Purpose: Soften the steel

  • How it works: Steel is slowly heated to ~800–850°C and cooled very slowly, usually in a furnace

  • Effect: Relieves internal stresses, improves ductility, and makes steel easier to machine

  • Common for: EN19, EN24, DB6 (before machining)

2️⃣ Normalizing

  • Purpose: Refine grain structure and make mechanical properties uniform

  • How it works: Steel is heated slightly above its critical temperature (~850–950°C), then cooled in still air

  • Effect: Increases toughness and strength uniformly

  • Common for: Structural alloy steels, forged parts

3️⃣ Hardening

  • Purpose: Increase hardness

  • How it works: Steel is heated to ~800–900°C, then rapidly cooled (quenched) in oil, air, or water

  • Effect: Crystal structure changes to martensite, resulting in high hardness

  • Used in: DB6, H13, D2, EN31

  • 🔥 Hardness increase comes with brittleness — that’s why we temper after this!

4️⃣ Tempering

  • Purpose: Reduce brittleness while maintaining hardness

  • How it works: Steel is reheated to 200–650°C and held at that temperature, then slowly cooled

  • Effect: Restores ductility and toughness lost during hardening

  • Common for: DB6, EN24, H13

5️⃣ Case Hardening

  • Purpose: Create a hard surface with a soft, tough core

  • How it works: Carbon or nitrogen is diffused into the steel surface at high temperature

  • Effect: Increases surface wear resistance while maintaining impact strength inside

  • Used in: EN36, low carbon steels

6️⃣ Stress Relieving

  • Purpose: Minimize internal stresses without major structural changes

  • How it works: Heat to ~500–650°C and cool slowly

  • Effect: Prevents cracking during machining or service

  • Used in: Large die blocks, forged parts

📌  DB6 – Why Heat Treatment is Critical

🔩 What is DB6?

DB6 (DIN 2714 / L6 equivalent) is a hot work tool steel known for:

  • High impact resistance

  • Good toughness

  • Decent wear resistance

At Goel Steel Enterprises, we supply DB6 in:

  • Forged & Machined Blocks

  • Forged & Machined Rounds
    All UT-tested and MTC-certified.

🔥 Heat Treatment for DB6

Step

Temperature Range

Purpose

Annealing

800–850°C

Soften for machining, remove stress

Hardening

850–900°C

Increase core hardness (quenching in oil/air)

Tempering

550–650°C

Balance hardness and toughness

Without proper heat treatment, DB6 may look good on paper, but fail in real-world forging operations. That’s why it’s critical to heat treat it properly for optimum die life and performance.

🔍 Heat Treatment Results – Before vs After

Property

Untreated DB6

Heat-Treated DB6

Hardness

~180–200 HB

~290–320 HB (Annealed) / ~50–54 HRC (Hardened)

Toughness

Low

High

Machinability

Tough

Good (Annealed)

Thermal Stability

Poor

Excellent

Wear Resistance

Moderate

High

📈 What About Other Alloy Grades?

✅ EN19 (4140)

  • After quenching & tempering → High tensile strength

  • Used in shafts, gears, and automotive parts

✅ EN24 (4340)

  • Heat-treated to ~850–1000 MPa

  • Great for aerospace, crankshafts, heavy-duty spindles

✅ EN31

  • Hardened up to ~60 HRC

  • Used in rollers, bearings, precision tooling

✅ H13

  • Tempered for hot work → Withstands thermal shock

  • Ideal for die-casting dies

⚙️ The Goel Steel Advantage

We supply heat-treatment-ready and pre-hardened materials with:

  • 📋 MTC certification

  • 🔍 UT-tested blocks and rounds

  • ⚙️ Pre-machined or raw condition

  • 🧠 Application-based grade recommendations

  • 🧰 Expert support for heat treatment process selection

📏 Need to Compare Hardness?

Use our free hardness conversion tool here:
👉 www.goelsteelenterprises.com/hardness-conversion

💬 Quote of the Day:

“A steel grade’s name doesn't define its power — the right heat treatment does.”

📞 Ready to Order or Consult?

Let’s discuss your next order of heat-treatment-ready steel, including:

  • DB6 (DIN 2714)

  • EN19, EN24, EN31

  • D2, H13, L6

  • Forged rounds, flats

📞 Goel Steel Enterprises
📱 +91-9686477515
🌐 www.goelsteelenterprises.com

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