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Hardenability

Materials Science · FE Reference Handbook section

Materials Science
4 formulas
10 exam-style examples
~53 min
All Materials Science lectures

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • Hardness: Resistance to penetration. Measured by denting a material under known load and measuring the size of the dent.
  • Hardenability: The "ease" with which hardness can be obtained.
  • JOMINY HARDENABILITY CURVES FOR SIX STEELS
  • The following two graphs show cooling curves for four different positions in the bar.
  • These positions are shown in the following figure.
  • COOLING RATES FOR BARS QUENCHED IN AGITATED WATER
  • COOLING RATES FOR BARS QUENCHED IN AGITATED OIL

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1
Hardenability — Jominy distance to hardness ratio — solve for hardness at distance d — Hardenability

A metallurgist evaluates the hardenability of a steel alloy using Jominy end-quench data. Given surface hardness (HRC0) = 53.5000 HRC; hardness gradient (k) = 11.5000 HRC/in; Jominy distance (d) = 2.4000 in, determine the hardness at distance d (HRC) in HRC.

Given

  • surfacehardness(HRC0)=53.5000HRCsurface hardness (HRC_{0}) = 53.5000 HRC
  • hardnessgradient(k)=11.5000HRC/inhardness gradient (k) = 11.5000 HRC/in
  • Jominydistance(d)=2.4000inJominy distance (d) = 2.4000 in

Find

hardness at distance d (HRC), in HRC

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except HRC is given, so isolate HRC symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for HRC:

    HRC=HRC0−kdHRC = HRC_0 - kd
  3. Step 3 — List the givens: surface hardness (HRC0) = 53.5000 HRC, hardness gradient (k) = 11.5000 HRC/in, Jominy distance (d) = 2.4000 in.

  4. Step 4 — Substitute the given values:

    HRC=HRC0−k2.4000HRC = HRC_0 - k2.4000
  5. Step 5 — Evaluate:

    HRC=25.9000 HRCHRC = 25.9000\ \text{HRC}
  6. Step 6 — Check: returning HRC = 25.9000 HRC to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
HRC=25.9000 HRCHRC = 25.9000\ \text{HRC}

Why the other options are there

  • 51.8000 — kept a factor of two that cancels in the correct rearrangement.
  • 12.9500 — dropped that same factor in the other direction.
  • 28.4900 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 2
Hardenability — Jominy distance to hardness ratio — solve for surface hardness — Hardenability (2)

An engineer selects a steel grade based on its hardenability requirement. Given hardness gradient (k) = 6.5000 HRC/in; Jominy distance (d) = 0.6000 in; hardness at distance d (HRC) = 10.2000 HRC, determine the surface hardness (HRC0) in HRC.

Given

  • hardnessgradient(k)=6.5000HRC/inhardness gradient (k) = 6.5000 HRC/in
  • Jominydistance(d)=0.6000inJominy distance (d) = 0.6000 in
  • hardnessatdistanced(HRC)=10.2000HRChardness at distance d (HRC) = 10.2000 HRC

Find

surface hardness (HRC0), in HRC

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except HRC0 is given, so isolate HRC0 symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for HRC0:

    HRC0=HRC+kdHRC_{0} = HRC + kd
  3. Step 3 — List the givens: hardness gradient (k) = 6.5000 HRC/in, Jominy distance (d) = 0.6000 in, hardness at distance d (HRC) = 10.2000 HRC.

  4. Step 4 — Substitute the given values:

    HRC0=10.2000+k0.6000HRC_{0} = 10.2000 + k0.6000
  5. Step 5 — Evaluate:

    HRC0=14.1000 HRCHRC_{0} = 14.1000\ \text{HRC}
  6. Step 6 — Check: returning HRC0 = 14.1000 HRC to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
HRC0=14.1000 HRCHRC_{0} = 14.1000\ \text{HRC}

Why the other options are there

  • 28.2000 — kept a factor of two that cancels in the correct rearrangement.
  • 7.0500 — dropped that same factor in the other direction.
  • 15.5100 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 3
Hardenability — Jominy distance to hardness ratio — solve for Jominy distance — Hardenability (3)

The hardenability curve shows hardness dropping with distance from the quenched face. Given surface hardness (HRC0) = 54.0000 HRC; hardness gradient (k) = 7.0000 HRC/in; hardness at distance d (HRC) = 15.3000 HRC, determine the Jominy distance (d) in in.

Given

  • surfacehardness(HRC0)=54.0000HRCsurface hardness (HRC_{0}) = 54.0000 HRC
  • hardnessgradient(k)=7.0000HRC/inhardness gradient (k) = 7.0000 HRC/in
  • hardnessatdistanced(HRC)=15.3000HRChardness at distance d (HRC) = 15.3000 HRC

Find

Jominy distance (d), in in

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except d is given, so isolate d symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for d:

    d=HRC0−HRCkd = \dfrac{HRC_0 - HRC}{k}
  3. Step 3 — List the givens: surface hardness (HRC0) = 54.0000 HRC, hardness gradient (k) = 7.0000 HRC/in, hardness at distance d (HRC) = 15.3000 HRC.

  4. Step 4 — Substitute the given values:

    d=HRC0−15.30007.0000d = \dfrac{HRC_0 - 15.3000}{7.0000}
  5. Step 5 — Evaluate:

    d=5.5286 ind = 5.5286\ \text{in}
  6. Step 6 — Check: returning d = 5.5286 in to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
d=5.5286 ind = 5.5286\ \text{in}

Why the other options are there

  • 11.0571 — kept a factor of two that cancels in the correct rearrangement.
  • 2.7643 — dropped that same factor in the other direction.
  • 6.0814 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 4
Hardenability — Jominy distance to hardness ratio — solve for hardness at distance d (case 2) — Hardenability (4)

A metallurgist evaluates the hardenability of a steel alloy using Jominy end-quench data. Given surface hardness (HRC0) = 52.0000 HRC; hardness gradient (k) = 5.0000 HRC/in; Jominy distance (d) = 0.8000 in, determine the hardness at distance d (HRC) in HRC.

Given

  • surfacehardness(HRC0)=52.0000HRCsurface hardness (HRC_{0}) = 52.0000 HRC
  • hardnessgradient(k)=5.0000HRC/inhardness gradient (k) = 5.0000 HRC/in
  • Jominydistance(d)=0.8000inJominy distance (d) = 0.8000 in

Find

hardness at distance d (HRC), in HRC

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except HRC is given, so isolate HRC symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for HRC:

    HRC=HRC0−kdHRC = HRC_0 - kd
  3. Step 3 — List the givens: surface hardness (HRC0) = 52.0000 HRC, hardness gradient (k) = 5.0000 HRC/in, Jominy distance (d) = 0.8000 in.

  4. Step 4 — Substitute the given values:

    HRC=HRC0−k0.8000HRC = HRC_0 - k0.8000
  5. Step 5 — Evaluate:

    HRC=48.0000 HRCHRC = 48.0000\ \text{HRC}
  6. Step 6 — Check: returning HRC = 48.0000 HRC to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
HRC=48.0000 HRCHRC = 48.0000\ \text{HRC}

Why the other options are there

  • 96.0000 — kept a factor of two that cancels in the correct rearrangement.
  • 24.0000 — dropped that same factor in the other direction.
  • 52.8000 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 5
Hardenability — Jominy distance to hardness ratio — solve for surface hardness (case 2) — Hardenability (5)

An engineer selects a steel grade based on its hardenability requirement. Given hardness gradient (k) = 5.5000 HRC/in; Jominy distance (d) = 2.6000 in; hardness at distance d (HRC) = 23.0000 HRC, determine the surface hardness (HRC0) in HRC.

Given

  • hardnessgradient(k)=5.5000HRC/inhardness gradient (k) = 5.5000 HRC/in
  • Jominydistance(d)=2.6000inJominy distance (d) = 2.6000 in
  • hardnessatdistanced(HRC)=23.0000HRChardness at distance d (HRC) = 23.0000 HRC

Find

surface hardness (HRC0), in HRC

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except HRC0 is given, so isolate HRC0 symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for HRC0:

    HRC0=HRC+kdHRC_{0} = HRC + kd
  3. Step 3 — List the givens: hardness gradient (k) = 5.5000 HRC/in, Jominy distance (d) = 2.6000 in, hardness at distance d (HRC) = 23.0000 HRC.

  4. Step 4 — Substitute the given values:

    HRC0=23.0000+k2.6000HRC_{0} = 23.0000 + k2.6000
  5. Step 5 — Evaluate:

    HRC0=37.3000 HRCHRC_{0} = 37.3000\ \text{HRC}
  6. Step 6 — Check: returning HRC0 = 37.3000 HRC to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
HRC0=37.3000 HRCHRC_{0} = 37.3000\ \text{HRC}

Why the other options are there

  • 74.6000 — kept a factor of two that cancels in the correct rearrangement.
  • 18.6500 — dropped that same factor in the other direction.
  • 41.0300 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 6
Hardenability — Jominy distance to hardness ratio — solve for Jominy distance (case 2) — Hardenability (6)

The hardenability curve shows hardness dropping with distance from the quenched face. Given surface hardness (HRC0) = 52.0000 HRC; hardness gradient (k) = 12.0000 HRC/in; hardness at distance d (HRC) = 34.4000 HRC, determine the Jominy distance (d) in in.

Given

  • surfacehardness(HRC0)=52.0000HRCsurface hardness (HRC_{0}) = 52.0000 HRC
  • hardnessgradient(k)=12.0000HRC/inhardness gradient (k) = 12.0000 HRC/in
  • hardnessatdistanced(HRC)=34.4000HRChardness at distance d (HRC) = 34.4000 HRC

Find

Jominy distance (d), in in

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except d is given, so isolate d symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for d:

    d=HRC0−HRCkd = \dfrac{HRC_0 - HRC}{k}
  3. Step 3 — List the givens: surface hardness (HRC0) = 52.0000 HRC, hardness gradient (k) = 12.0000 HRC/in, hardness at distance d (HRC) = 34.4000 HRC.

  4. Step 4 — Substitute the given values:

    d=HRC0−34.400012.0000d = \dfrac{HRC_0 - 34.4000}{12.0000}
  5. Step 5 — Evaluate:

    d=1.4667 ind = 1.4667\ \text{in}
  6. Step 6 — Check: returning d = 1.4667 in to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
d=1.4667 ind = 1.4667\ \text{in}

Why the other options are there

  • 2.9333 — kept a factor of two that cancels in the correct rearrangement.
  • 0.7333 — dropped that same factor in the other direction.
  • 1.6133 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 7
Hardenability — Jominy distance to hardness ratio — solve for hardness at distance d (case 3) — Hardenability (7)

A metallurgist evaluates the hardenability of a steel alloy using Jominy end-quench data. Given surface hardness (HRC0) = 55.5000 HRC; hardness gradient (k) = 4.5000 HRC/in; Jominy distance (d) = 0.6000 in, determine the hardness at distance d (HRC) in HRC.

Given

  • surfacehardness(HRC0)=55.5000HRCsurface hardness (HRC_{0}) = 55.5000 HRC
  • hardnessgradient(k)=4.5000HRC/inhardness gradient (k) = 4.5000 HRC/in
  • Jominydistance(d)=0.6000inJominy distance (d) = 0.6000 in

Find

hardness at distance d (HRC), in HRC

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except HRC is given, so isolate HRC symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for HRC:

    HRC=HRC0−kdHRC = HRC_0 - kd
  3. Step 3 — List the givens: surface hardness (HRC0) = 55.5000 HRC, hardness gradient (k) = 4.5000 HRC/in, Jominy distance (d) = 0.6000 in.

  4. Step 4 — Substitute the given values:

    HRC=HRC0−k0.6000HRC = HRC_0 - k0.6000
  5. Step 5 — Evaluate:

    HRC=52.8000 HRCHRC = 52.8000\ \text{HRC}
  6. Step 6 — Check: returning HRC = 52.8000 HRC to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
HRC=52.8000 HRCHRC = 52.8000\ \text{HRC}

Why the other options are there

  • 105.6 — kept a factor of two that cancels in the correct rearrangement.
  • 26.4000 — dropped that same factor in the other direction.
  • 58.0800 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 8
Hardenability — Jominy distance to hardness ratio — solve for surface hardness (case 3) — Hardenability (8)

An engineer selects a steel grade based on its hardenability requirement. Given hardness gradient (k) = 5.0000 HRC/in; Jominy distance (d) = 1.8000 in; hardness at distance d (HRC) = 40.4000 HRC, determine the surface hardness (HRC0) in HRC.

Given

  • hardnessgradient(k)=5.0000HRC/inhardness gradient (k) = 5.0000 HRC/in
  • Jominydistance(d)=1.8000inJominy distance (d) = 1.8000 in
  • hardnessatdistanced(HRC)=40.4000HRChardness at distance d (HRC) = 40.4000 HRC

Find

surface hardness (HRC0), in HRC

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except HRC0 is given, so isolate HRC0 symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for HRC0:

    HRC0=HRC+kdHRC_{0} = HRC + kd
  3. Step 3 — List the givens: hardness gradient (k) = 5.0000 HRC/in, Jominy distance (d) = 1.8000 in, hardness at distance d (HRC) = 40.4000 HRC.

  4. Step 4 — Substitute the given values:

    HRC0=40.4000+k1.8000HRC_{0} = 40.4000 + k1.8000
  5. Step 5 — Evaluate:

    HRC0=49.4000 HRCHRC_{0} = 49.4000\ \text{HRC}
  6. Step 6 — Check: returning HRC0 = 49.4000 HRC to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
HRC0=49.4000 HRCHRC_{0} = 49.4000\ \text{HRC}

Why the other options are there

  • 98.8000 — kept a factor of two that cancels in the correct rearrangement.
  • 24.7000 — dropped that same factor in the other direction.
  • 54.3400 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 9
Hardenability — Jominy distance to hardness ratio — solve for Jominy distance (case 3) — Hardenability (9)

The hardenability curve shows hardness dropping with distance from the quenched face. Given surface hardness (HRC0) = 61.5000 HRC; hardness gradient (k) = 5.0000 HRC/in; hardness at distance d (HRC) = 30.6000 HRC, determine the Jominy distance (d) in in.

Given

  • surfacehardness(HRC0)=61.5000HRCsurface hardness (HRC_{0}) = 61.5000 HRC
  • hardnessgradient(k)=5.0000HRC/inhardness gradient (k) = 5.0000 HRC/in
  • hardnessatdistanced(HRC)=30.6000HRChardness at distance d (HRC) = 30.6000 HRC

Find

Jominy distance (d), in in

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except d is given, so isolate d symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for d:

    d=HRC0−HRCkd = \dfrac{HRC_0 - HRC}{k}
  3. Step 3 — List the givens: surface hardness (HRC0) = 61.5000 HRC, hardness gradient (k) = 5.0000 HRC/in, hardness at distance d (HRC) = 30.6000 HRC.

  4. Step 4 — Substitute the given values:

    d=HRC0−30.60005.0000d = \dfrac{HRC_0 - 30.6000}{5.0000}
  5. Step 5 — Evaluate:

    d=6.1800 ind = 6.1800\ \text{in}
  6. Step 6 — Check: returning d = 6.1800 in to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
d=6.1800 ind = 6.1800\ \text{in}

Why the other options are there

  • 12.3600 — kept a factor of two that cancels in the correct rearrangement.
  • 3.0900 — dropped that same factor in the other direction.
  • 6.7980 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

Example 10
Hardenability — Jominy distance to hardness ratio — solve for hardness at distance d (case 4) — Hardenability (10)

A metallurgist evaluates the hardenability of a steel alloy using Jominy end-quench data. Given surface hardness (HRC0) = 60.5000 HRC; hardness gradient (k) = 8.5000 HRC/in; Jominy distance (d) = 2.2000 in, determine the hardness at distance d (HRC) in HRC.

Given

  • surfacehardness(HRC0)=60.5000HRCsurface hardness (HRC_{0}) = 60.5000 HRC
  • hardnessgradient(k)=8.5000HRC/inhardness gradient (k) = 8.5000 HRC/in
  • Jominydistance(d)=2.2000inJominy distance (d) = 2.2000 in

Find

hardness at distance d (HRC), in HRC

Start with the thinking

  • The governing relation printed in this handbook section is Hardenability — Jominy distance to hardness ratio.
  • Everything except HRC is given, so isolate HRC symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Hardenability describes how hardness decreases with distance from the quenched end in a Jominy test.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HRC=HRC0−k dHRC = HRC_0 - k \, d
  2. Step 2 — Rearrange symbolically for HRC:

    HRC=HRC0−kdHRC = HRC_0 - kd
  3. Step 3 — List the givens: surface hardness (HRC0) = 60.5000 HRC, hardness gradient (k) = 8.5000 HRC/in, Jominy distance (d) = 2.2000 in.

  4. Step 4 — Substitute the given values:

    HRC=HRC0−k2.2000HRC = HRC_0 - k2.2000
  5. Step 5 — Evaluate:

    HRC=41.8000 HRCHRC = 41.8000\ \text{HRC}
  6. Step 6 — Check: returning HRC = 41.8000 HRC to

    HRC=HRC0−k dHRC = HRC_0 - k \, d

    reproduces the given quantities, and both sides carry the same units.

Answer:
HRC=41.8000 HRCHRC = 41.8000\ \text{HRC}

Why the other options are there

  • 83.6000 — kept a factor of two that cancels in the correct rearrangement.
  • 20.9000 — dropped that same factor in the other direction.
  • 45.9800 — rounded an intermediate value before the final step.

Reference: FE Handbook — Hardenability

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