【硬度概述】  

    材料局部抵抗硬物壓入其表面的能力稱為硬度。試驗鋼鐵硬度的最普通方法是用銼刀在工件邊緣上銼擦,由其表面所呈現(xiàn)的擦痕深淺以判定其硬度的高低。這種方法稱為銼試法這種方法不太科學(xué)。用硬度試驗機(jī)來試驗比較準(zhǔn)確,是現(xiàn)代試驗硬度常用的方法。常用的硬度測定方法有布氏硬度、洛氏硬度和維氏硬度等測試方法  

    布氏硬度以HB[N(kgf/mm2)]表示（HBS\HBW）（參照GB/T231－1984），生產(chǎn)中常用布氏硬度法測定經(jīng)退貨、正火和調(diào)質(zhì)得剛健，以及鑄鐵、有色金屬、低合金結(jié)構(gòu)鋼等毛胚或半成品的硬度。

    洛氏硬度可分為HRA、HRB、HRC、HRD四種，它們的測量范圍和應(yīng)用范圍也不同。一般生產(chǎn)中HRC用得最多。壓痕較小，可測較薄得材料和硬得材料和成品件得硬度。  

    維氏硬度以HV表示（參照GB/T4340-1999），測量極薄試樣。  

    一、鋼材的硬度  ：金屬硬度(Hardness)的代號為H。按硬度試驗方法的不同，  

    常規(guī)表示有布氏（HB）、洛氏（HRC）、維氏（HV）、里氏（HL）硬度等，其中以HB及HRC較為常用。  

    HB應(yīng)用范圍較廣，HRC適用于表面高硬度材料，如熱處理硬度等。兩者區(qū)別在于硬度計之測頭不同，布氏硬度計之測頭為鋼球，而洛氏硬度計之測頭為金剛石。  

    HV-適用于顯微鏡分析。維氏硬度(HV)  以120kg以內(nèi)的載荷和頂角為136°的金剛石方形錐壓入器壓入材料表面，用材料壓痕凹坑的表面積除以載荷值，即為維氏硬度值(HV)。  

    HL手提式硬度計，測量方便，利用沖擊球頭沖擊硬度表面后，產(chǎn)生彈跳；利用沖頭在距試樣表面1mm處的回彈速度與沖擊速度的比值計算硬度，公式：里氏硬度HL=1000×VB（回彈速度）/  VA（沖擊速度）。便攜式里氏硬度計用里氏（HL）測量后可以轉(zhuǎn)化為：布氏（HB）、洛氏（HRC）、維氏（HV）、肖氏（HS）硬度?；蛴美锸显碇苯佑貌际希℉B）、洛氏（HRC）、維氏（HV）、里氏（HL）、肖氏（HS）測量硬度值。  

    二、HB  -  布氏硬度：  布氏硬度(HB)一般用于材料較軟的時候，如有色金屬、熱處理之前或退火后的鋼鐵。洛氏硬度(HRC)一般用于硬度較高的材料，如熱處理后的硬度等等。  

    布式硬度(HB)是以一定大小的試驗載荷，將一定直徑的淬硬鋼球或硬質(zhì)合金球壓入被測金屬表面，保持規(guī)定時間，然后卸荷，測量被測表面壓痕直徑。布式硬度值是載荷除以壓痕球形表面積所得的商。一般為：以一定的載荷(一般3000kg)把一定大小(直徑一般為10mm)的淬硬鋼球壓入材料表面，保持一段時間，去載后，負(fù)荷與其壓痕面積之比值，即為布氏硬度值(HB)，單位為公斤力/mm2  (N/mm2)。  

    三、洛式硬度是以壓痕塑性變形深度來確定硬度值指標(biāo)。以0.002毫米作為一個硬度單位。當(dāng)HB>450或者試樣過小時，不能采用布氏硬度試驗而改用洛氏硬度計量。它是用一個頂角120°的金剛石圓錐體或直徑為1.59、3.18mm的鋼球，在一定載荷下壓入被測材料表面，由壓痕的深度求出材料的硬度。根據(jù)試驗材料硬度的不同，分三種不同的標(biāo)度來表示：  

    HRA：是采用60kg載荷和鉆石錐壓入器求得的硬度，用于硬度極高的材料(如硬質(zhì)合金等)。  

    HRB：是采用100kg載荷和直徑1.58mm淬硬的鋼球，求得的硬度，用于硬度較低的材料(如退火鋼、鑄鐵等)。  

    HRC：是采用150kg載荷和鉆石錐壓入器求得的硬度，用于硬度很高的材料(如淬火鋼等)。  

    【另外】  

    1.HRC含意是洛式硬度C標(biāo)尺，  

    2.HRC和HB在生產(chǎn)中的應(yīng)用都很廣泛  

    3.HRC適用范圍HRC  20－－67，相當(dāng)于HB225－－650  

    若硬度高于此范圍則用洛式硬度A標(biāo)尺HRA。  

    若硬度低于此范圍則用洛式硬度B標(biāo)尺HRB。  

    布式硬度上限值HB650,不能高于此值。  

    4.洛氏硬度計C標(biāo)尺之壓頭為頂角120度的金剛石圓錐，試驗載荷為一確定值，中國標(biāo)準(zhǔn)是150公斤力。布氏硬度計之壓頭為淬硬鋼球（HBS)或硬質(zhì)合金球（HBW），試驗載荷隨球直徑不同而不同，從3000到31.25公斤力。  

    5.洛式硬度壓痕很小，測量值有局部性，須測數(shù)點(diǎn)求平均值，適用成品和薄片，歸于無損檢測一類。布式硬度壓痕較大，測量值準(zhǔn)，不適用成品和薄片，一般不歸于無損檢測一類。  

    6.洛式硬度的硬度值是一無名數(shù)，沒有單位。（因此習(xí)慣稱洛式硬度為多少度是不正確的。）  

    布式硬度的硬度值有單位，且和抗拉強(qiáng)度有一定的近似關(guān)系。  

    7.洛式硬度直接在表盤上顯示、也可以數(shù)字顯示，操作方便，快捷直觀，適用于大量生產(chǎn)中。  

    維式硬度需要用顯微鏡測量壓痕直徑，然后查表或計算，操作較繁瑣。  

    8.在一定條件下，HB與HRC可以查表互換。其心算公式可大概記為：1HRC≈1/10HB。  

    硬度試驗是機(jī)械性能試驗中最簡單易行的一種試驗方法。為了能用硬度試驗代替某些機(jī)械性能試驗，生產(chǎn)上需要一個比較準(zhǔn)確的硬度和強(qiáng)度的換算關(guān)系。實(shí)踐證明，金屬材料的各種硬度值之間，硬度值與強(qiáng)度值之間具有近似的相應(yīng)關(guān)系。因為硬度值是由起始塑性變形抗力和繼續(xù)塑性變形抗力決定的，材料的強(qiáng)度越高，塑性變形抗力越高，硬度值也就越高。

Overview of hardness

The ability of a material to resist locally pressing a hard object into its surface is called hardness. The most common way to test the hardness of steel is to use a file on the edge of the workpiece. This method is called filing and it's not very scientific. It is a common method to test hardness with hardness tester. Common hardness measurement methods include brinell hardness, rockwell hardness and vickers hardness

Brinell hardness is expressed as HB[N(KGF /mm2)] (HBS\HBW) (referring to GB/ t231-1984). Brinell hardness method is often used in production to determine the hardness of hair embryo or semi-finished products after return, normalizing, tempering and hardening, as well as cast iron, nonferrous metal, low-alloy structural steel, etc.

Rockwell hardness can be divided into four types: HRA, HRB, HRC and HRD. HRC is most commonly used in production. Small indentation, can measure the hardness of thin and hard materials and finished parts.

Vickers hardness is expressed as HV (reference GB/ t4340-1999) and extremely thin samples are measured.

Hardness of steel: the code name of Hardness of metal is H. Depending on the hardness test method,

Conventional expressions include brinell's (HB), rockwell's (HRC), vickers' (HV), and Richter's (HL) hardness, among which HB and HRC are more commonly used.

HB has a wide range of applications, and HRC is suitable for surface materials with high hardness, such as heat treatment hardness. The difference is that the head of a brinell durometer is a steel ball, while that of a rockwell durometer is a diamond.

HV- is suitable for microscopic analysis. Vickers hardness (HV) is pressed into the surface of the material with a load of less than 120kg and a diamond square cone press with a top Angle of 136°. The surface area of the indentation pit of the material is divided by the load value, which is vickers hardness value (HV).

HL portable durometer, easy to measure, using impact ball head impact hardness surface, resulting in bounce; Hardness was calculated by using the ratio between the springback velocity and impact velocity of the punch at a distance of 1mm from the surface of the sample. The formula was: Richter hardness HL=1000×VB (springback velocity)/VA (impact velocity). Portable Richter hardness tester with Richter (HL) measurement can be converted into: brinell (HB), rockwell (HRC), vickers (HV), shore (HS) hardness. Or the hardness value can be measured directly by brinell's (HB), rockwell's (HRC), vickers' (HV), Richter's (HL) and shore's (HS) by Richter's principle.

2. Hb-brinell hardness: brinell hardness (HB) is generally used when materials are softer, such as nonferrous metals, pre-heat treatment or annealed steel. Rockwell hardness (HRC) is generally used for materials with higher hardness, such as hardness after heat treatment, etc.

Cloth hardness (HB) is to press a certain diameter of hardened steel ball or cemented carbide ball into the surface of the measured metal under a certain size of test load, keep it for a specified time, then unload and measure the indentation diameter of the measured surface. The distribution hardness is the quotient of the load divided by the surface area of the indentation. Generally, a hardened steel ball of a certain size (generally 10mm in diameter) is pressed into the material surface with a certain load (generally 3000kg) and kept for a period of time. After unloading, the ratio of the load to the indentation area is brinell hardness value (HB), which is expressed as kilogram force /mm2 (N/mm2).

Iii. Rockwell hardness is determined by the depth of indentation plastic deformation. Take 0.002 mm as a hardness unit. When HB>450 or samples are too small, brinell hardness test should not be used instead of rockwell hardness measurement. It USES a diamond cone with a top Angle of 120° or a steel ball with diameters of 1.59 and 3.18mm to press into the surface of the measured material under a certain load, and then calculates the hardness of the material by the depth of indentation. According to the hardness of the test material, it can be expressed in three different scales:

HRA: hardness obtained with 60kg load and drill cone presser, used for extremely hard materials (such as cemented carbide, etc.).

HRB: hardness obtained by using 100kg load and 1.58mm diameter hardened steel ball, used for materials with lower hardness (such as annealed steel, cast iron, etc.).

HRC: hardness obtained with 150kg load and drill cone presser, used for materials with high hardness (such as quenched steel, etc.).

"The other"

1.HRC means luo hardness scale C,

2.HRC and HB are widely used in production

3. Applicable scope of HRC: HRC 20--67, equivalent to HB225--650

If the hardness is higher than this range, use luo hardness A scale HRA.

If the hardness is lower than this range, use luo hardness B scale HRB.

The upper limit of cloth hardness is HB650, which cannot be higher than this value.

4. The pressure head of rod C of rockwell durometer is a diamond cone with a top Angle of 120 °. The test load is a definite value. The pressure head of a brinell durometer is a hardened steel ball (HBS) or carbide ball (HBW), and the test load varies with the ball diameter, from 3000 to 31.25 kg.

5. Luo hardness indentation is very small, the measured value is local, need to measure the number of points for the average value, applicable to finished products and flakes, belong to the category of NDT. The cloth hardness indentation is large, the measured value is accurate, not suitable for finished products and flakes, generally does not belong to the category of NDT.

6. The hardness value of luo type hardness is zero, no unit. (so it is not correct to use the term luo hardness.)

The hardness value of the cloth hardness has a unit, and there is a certain approximate relationship with the tensile strength.

7 luo hardness directly on the dial display, can also be digital display, easy to operate, fast and intuitive, suitable for mass production.

D hardness need to use a microscope to measure the indentation diameter, and then look up the table or calculation, the operation is more complicated.

8. Under certain conditions, HB and HRC can be interchanged by table lookup. Its mental formula can be roughly written as: 1HRC≈ 1/10hb.

Hardness test is the most simple and feasible test method in mechanical property test. In order to replace some mechanical property tests with hardness tests, a more accurate conversion between hardness and strength is needed in production. Practice has proved that there is an approximate and corresponding relationship between the hardness values of metal materials and the hardness and strength values. Because the hardness value is determined by the initial plastic deformation resistance and the continuing plastic deformation resistance, the higher the strength of the material, the higher the plastic deformation resistance, the higher the hardness value.