What is the difference between hardness scales?

HRC (Rockwell C) uses a diamond cone indenter with 150 kgf load, suitable for hardened steels (20-70 HRC). HRB (Rockwell B) uses a 1/16" steel ball with 100 kgf, for softer materials (20-100 HRB). HV (Vickers) uses a diamond pyramid with variable load, suitable for all ranges. HB (Brinell) uses a 10 mm carbide ball with 3000 kgf load, best for castings and softer steels.

When should I use which hardness scale?

Use HRC for hardened and tempered steels above ~20 HRC. Use HRB for annealed and softer steels below ~100 HRB. Use HV for thin materials, coatings, case-hardened surfaces, and when a wide range is needed. Use HB for castings, forgings, and when a large test area is acceptable.

Why are hardness conversions approximate?

Different hardness tests use different indenters, loads, and measurement methods. The relationship between scales is not purely mathematical but empirical, based on testing many material samples. ASTM E140 provides accepted conversion tables, but exact conversions depend on the specific material, its condition, and microstructure.

How do I estimate tensile strength from hardness?

For carbon and alloy steels, a common approximation is Rm (MPa) ≈ 3.45 × HB. This is a rough estimate valid for steels in the range of approximately 100-400 HB. For stainless steels, non-ferrous metals, or very hard steels, this relationship does not apply accurately.

What test methods do these scales use?

Rockwell (HRC/HRB): measures depth of indentation under a specific load. Quick and portable. Vickers (HV): measures diagonal of a diamond pyramid indentation under variable load. Very precise, works for all hardness ranges. Brinell (HB): measures diameter of a ball indentation under high load. Good for averaging over larger areas (castings, welds).

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硬度轉換器

在洛氏 HRC、布氏 HB、維氏 HV 與洛氏 HRB 硬度刻度之間進行轉換。基於 ASTM E140 轉換資料並採用線性插值。

ASTM E140 HRC ↔ HB ↔ HV 抗拉強度

結果

HRC（洛氏 C）

—

HRC（洛氏 C）

—

HB（布氏）

—

HV（維氏）

—

HRB（洛氏 B）

—

約略抗拉強度 Rm（鋼材）

—

Rm ≈ 3.45 × HB（約略值，適用於碳鋼與合金鋼）

HRC 範圍（硬化鋼材）

HRC	HV	HB	Rm (MPa)
20	238	228	~787
25	255	243	~838
30	279	266	~918
35	331	311	~1073
40	392	360	~1242
45	458	421	~1452
50	542	484	~1670
55	595	544	~1877
60	697	—	—
65	832	—	—

HRB 範圍（較軟鋼材）

HRB	HV	HB	Rm (MPa)
60	107	105	~362
70	120	118	~407
80	141	138	~476
90	171	166	~573
100	210	202	~697

ℹ️ 注意： 表格條目之間的數值使用線性插值計算。高於 HRC 55 的 HB 數值通常不予測量（材質對於球壓頭而言過硬）。抗拉強度估算僅適用於碳鋼與合金鋼。

洛氏硬度（HRC / HRB）

洛氏測試測量 壓入深度 （相對於預壓下的大負荷）。該方法快速、簡便，且廣泛應用於生產中。

HRC — 鑽石錐（Brale）壓頭，150 kgf 主負荷。範圍：20–70 HRC。適用於硬化鋼材。
HRB — 1/16″ 鋼球，100 kgf 主負荷。範圍：20–100 HRB。適用於較軟鋼材、黃銅、鋁。

維氏硬度（HV）

使用變負荷（1–120 kgf）的鑽石金字塔壓頭。測量 壓痕對角線。適用於從極軟到極硬的所有硬度範圍。

布氏硬度（HB）

使用 10 mm 碳化鎢球與 3000 kgf 負荷（針對鋼材）。測量 壓痕直徑。最適合鑄件等粗晶粒材質。

抗拉強度估算

⚠️ 重要： Rm ≈ 3.45 × HB 的關係為約略值，僅適用於 ~100–400 HB 範圍內的碳鋼與合金鋼。不適用於不鏽鋼、鑄鐵、非鐵金屬或高於 ~55 HRC 的硬化鋼材。

實務範例

範例 — 淬火與回火鋼

已知： 測量硬度 = 45 HRC

根據 ASTM E140 表格：HRC 45 ≈ HV 458 ≈ HB 421

估算抗拉強度：Rm ≈ 3.45 × 421 = ~1452 MPa