硬度是材料機械性能重要指標之一，而硬度試驗是判斷材料或產品零件質量的一種手段。所謂硬度，就是材料在一定條件下抵抗另一本身不發生殘余變形物體壓入能力。抵抗能力愈大，則硬度愈高，反之則硬度愈低。在機械性能試驗中，測量硬度是一種最容易、最經濟、最迅速的方法，也是生產過程中檢查產品質量的措施之一，由于金屬等材料硬度與其他機械性能有相互對應關系，因此，大多數金屬材料可通過測定硬度近似地推算出其他機械性能，如強度、疲勞、蠕變、磨損和內損等。所以硬度計被廣為應用。

一、顯微硬度計工作原理和組成

顯微硬度計是近年來常用測量硬度的設備。測量硬度是通過升降顯微硬度計的調焦機構、測量顯微鏡、加荷機構，正確選擇負荷、加荷速度進行全自動加卸試驗力及正確控制試驗力保持時間，通過顯微硬度計光學放大，測出在一定試驗力下金剛石角錐體壓頭壓入被測物后所殘留壓痕的對角線長度，來求出被測物硬度值。

二、顯微硬度計的正確使用

由于顯微硬度試驗往往是對很小的試樣（如針尖)，或試樣上很小的特定部位（如金相組織）進行硬度測定，而這些情況難以用人眼來進行觀察和判定，而且顯微硬度試驗后所得壓痕非常小，這也是難以人眼來尋找，更不用說進行壓痕對角線長度的測量，所以非得用顯微鏡才能進行工作。正確使用顯微硬度計，除了正確選擇負荷、加荷速度、保荷時間外，測量顯微鏡使用的正確與否是十分重要的。現就如何正確使用顯微硬度計作簡要介紹。

1.負荷的選擇

為確切得到被測對象的真實硬度，必須選擇恰當負荷。選擇負荷應考慮以下幾個原則:

(1)在測定薄片或表面層硬度時，要根據壓頭壓入深度和試件或表面層厚度選擇負荷。因為一般試件或表面層厚度是知道的，而被測部位硬度或硬度范圍也應是可知道的，基于壓頭壓入試樣時擠壓應力在深度上涉及范圍接近于壓入深度的10倍，為避免底層硬度的影響，壓頭壓入深度應小于試件或表面層的十分之一。

(2)對試樣剖面測定硬度時，應根據壓痕對角線長度和剖面寬度選擇負荷。基于壓頭壓入試樣時產生的擠壓應力區域最大可從壓痕中心擴展到4倍對角線的距離。為避免相鄰區域不同硬度或空間對被測部位硬度影響，所以壓痕中心離開邊緣的距離應不小于壓痕對角線長度的2.5倍，即壓痕對角線長度為試件或表面層剖面寬度的五分之一。

(3)當測定晶粒、相、類雜物等時，應遵守以上兩個原則來選擇負荷，壓頭壓入深度不大于其厚

度的1/10，壓痕的對角線長度應不大于其面積的1/5.

(4)測定試件(零件、表面層、材料)平均硬度時，在試件表面尺寸及厚度允許的前提下，應盡

量選擇大負荷，以免試件材料組織硬度不均勻影響試件硬度測定的正確性。

(5)為保證測量精確度，在情況允許時，應選擇大負荷，一般應使壓痕對角線長度大于20μ m。

(6)考慮到試件表面冷加工時產生的擠壓應力硬化層的影響，在選擇負荷時應在情況許可的情況

下選擇大負荷。

2.測量顯微鏡的正確使用

(1)尋找像平面

1)針尖試樣應采用“光點找像法”。

一般顯微硬度計測量顯微鏡物方視場只有0.25~0.35mm,在此視場范圍外區域，在測量顯微鏡目鏡視場內，眼睛是看不見的。而針尖類試樣項尖往往小于0.1mm,所以在安裝調節試樣時，很難把此頂尖調節在視場內:如果此頂尖在視場周圍而不在視場內，則在升降工作臺進行調節時不小心就會把物鏡鏡片頂壞，即使不頂壞物鏡，找像也很困難，為解決這個問題，提出“光點找像法”方法。開啟測量顯微鏡的照明燈泡，這時在物鏡下面工作臺，上就有一個圓光斑，把針尖試樣垂直于工作臺安裝在此光斑的中心，升高工作臺，使此針尖的頂尖離開物鏡約1mm,這時眼睛觀察頂尖部位，調節工作臺.上的兩個測微絲桿，使物鏡下照明光點在前后左右對稱分布在此頂尖上(這-步驟必須仔細),隨后緩慢調節升降機構，這時在目鏡視場中即會看到-一個光亮點，這就是此頂尖上的反射光點，再進一步調節升降即可找到此針尖的像。

(3)當測定晶粒、相、類雜物等時，應遵守以上兩個原則來選擇負荷，壓頭壓入深度不大于其厚度的1/10，壓痕的對角線長度應不大于其面積的1/5.

(4)測定試件(零件、表面層、材料)平均硬度時，在試件表面尺寸及厚度允許的前提下，應盡量選擇大負荷，以免試件材料組織硬度不均勻影響試件硬度測定的正確性。

(5)為保證測量精確度，在情況允許時，應選擇大負荷，一般應使壓痕對角線長度大于20μ m。

(6)考慮到試件表面冷加工時產生的擠壓應力硬化層的影響，在選擇負荷時應在情況許可的情況下選擇大負荷。

2.測量顯微鏡的正確使用

(1)尋找像平面

1)針尖試樣應采用“光點找像法”。

一般顯微硬度計測量顯微鏡物方視場只有0.25~0.35mm,在此視場范圍外區域，在測量顯微鏡目鏡視場內，眼睛是看不見的。而針尖類試樣項尖往往小于0.1mm,所以在安裝調節試樣時，很難把此頂尖調節在視場內:如果此頂尖在視場周圍而不在視場內，則在升降工作臺進行調節時不小心就會把物鏡鏡片頂壞，即使不頂壞物鏡，找像也很困難，為解決這個問題，提出“光點找像法”方法。開啟測量顯微鏡的照明燈泡，這時在物鏡下面工作臺，上就有一個圓光斑，把針尖試樣垂直于工作臺安裝在此光斑的中心，升高工作臺，使此針尖的頂尖離開物鏡約1mm,這時眼睛觀察頂尖部位，調節工作臺.上的兩個測微絲桿，使物鏡下照明光點在前后左右對稱分布在此頂尖上(這-步驟必須仔細),隨后緩慢調節升降機構，這時在目鏡視場中即會看到-一個光亮點，這就是此頂尖上的反射光點，再進一步調節升降即可找到此針尖的像。

2)表面光潔度很高的試樣( 如顯微硬度塊)應采用邊緣找像法.

顯微硬度試驗中，試樣表面光潔度一般都是很高的，往往是鏡面，表面上沒有明顯觀察特征，而顯微硬度計中所有高倍測量顯微鏡的景深都是非常小的，只有1~7μm，所以在調焦找像平面時，對于缺乏經驗的操作者是很困難的，甚至會碰壞物鏡，所以操作者有的留用表面殘留痕跡來找像平面，但有時往往無殘留痕跡時，建議采用邊緣找像法。即按上述同樣方法使用照明光點(約為0.5~-.1mm)的中心對準試樣表面輪廓邊緣，則在且鏡視場內看到半亮半暗的交界處即為此輪廓邊緣，隨后進-步調節升降即可找到此表面邊緣的像。

(2)調節照明

為防止傾斜照明對壓痕對角線長瘦測量精確度的影響，要調節照明光源，使壓痕處在視場中心時按兩對角線區域分的四個區間亮度一致，通過觀察測微目鏡視場內壓痕像的清晰程度，可將照明光源經上、下、前、后、左、右方向稍稍移動，直至觀察到壓痕像最明亮，沒有陰影為止:移動工作臺微分筒將壓痕像前、后、左、右移動，測微目鏡視場內均應明亮,沒有陰影的壓痕像為好。

(3) 視度歸正

我們知道測量顯微鏡測壓痕時，是把壓痕經物鏡放大后，成像在目鏡前分劃板上，進行瞄準測量。由于人眼視差異(如正常眼、近視眼、遠視眼)，作為放大鏡作用的目鏡必須放在各種不同位置，才能對分劃板的刻線作清楚觀察(即刻線這時為最“細”),這個步驟(調節目鏡相對于分劃板距離)稱為視度歸正，不然會影響測量正確性。

(4)壓痕位置的校正

通過試驗力載荷在測微目鏡視場看到的壓痕像，若其偏移視場中心較大，則需要進行壓痕位置校正，通過物鏡座幾個調整螺釘反復調整，直到在測微目鏡視場內壓痕像居中為止此.G調整]D個螺釘時不要移動工作臺)并相互鎖緊。

(5)調焦

為找到正確成像位置，應注意要調節使壓痕邊緣清晰，而不是壓痕對角線或對角線交點清晰.我們需要測量的是這個四棱角錐體坑表面棱形的對角線長度。為幫助操作者掌握這一步驟，這里提出“視差判別法”，當用分劃板刻線或十字交點對準壓痕對角線頂尖時，人眼相對于目鏡左右移動，這時如調焦不正確，即壓痕邊緣象不完全落在分劃板上，則會發現此邊緣相對于分劃線會左右移動。這說明調焦不正確，如人眼相對目鏡的位置不一致，則一定存在測量誤差，此時應進一步調焦， 直至此邊緣相對分劃線在人眼晃動時無相對位置才為正確。

三掌握正確的測量方法

1、旋轉測量目鏡，使分劃板的移動方向和待測壓痕對角線方向平行，這樣可避免兩者夾角對測量精確度的影響。如兩者來角為C實際長度為，EO則測得長度d’: d/osc, 而且對于用十字線交點瞄準壓痕對角線頂朱覽當兩者有一交角時載會造成其對角線- -端頂尖對準十字線交點時，另一端頂尖則不能對準。

2、測量壓痕對角線長度，在瞄準時必須瞄準壓痕對角線的兩端頂尖,不必考慮壓痕棱形四邊情況。這對于分劃板上刻線是直線的情況是不成問題的，而對于分劃板上刻線是十字線，瞄準壓痕棱邊還是對角線頂尖的爭論時常發生，為統一各種 分劃線的瞄準，所以確定了這- -原則，這樣也可解決棱邊多種多樣復雜情況下的瞄準問題.

3、測量中應注意的幾個問題

(1)機械式測微機構測量目鏡，測量時應單向轉動測微手輪，消除空回對測量的影響..

(2)對于同時測定型的測微目鏡，操作者應注意兩塊分劃板刻線重合時，測微讀數零位是否正確，如不正確，應規正微分簡或測量后加以讀數修正。

(3)對數字式測微目鏡，在每次開機后應使兩塊分劃板刻線重合，然后按按“清零鍵" 使讀數清零。

(4)當壓痕兩條對角線長度不等時，應測量兩條對角線長度并取其平均值. 

(5)在旋轉測量顯微目鏡使其分劃板的移動方向和壓痕待測對角線平行后，可在此對角線垂直方向.上移動工作臺，使對角線落在分劃板十字線交點移動的軌跡上，但在用此交點進行瞄準時，則應轉動測微目鏡的手輪，而不應移動工作臺。

(6)操作人員應嚴格訓練，經常以標準顯微硬度塊校驗自已的瞄準精確度.

英斯特力儀器是一家集研發、生產及銷售于一體的 影像測量儀，拉力試驗機, 硬度計 ,探傷儀, 粗糙度儀, 測厚儀, 金相設備廠家, 致力于為客戶提供更好的檢測儀器。

Hardness is one of the important indexes of material mechanical properties, and hardness test is a means to judge the quality of material or product parts.  The so-called hardness, is the material under certain conditions to resist another itself does not occur residual deformation of the object pressed into the ability.  The higher the resistance, the higher the hardness, vice versa.  In mechanical properties test, hardness measurement is one of the most easy way, the most economical, most quickly, is also one of the measures to check the quality of the products in the process of production, such as metal material hardness and other mechanical properties have a corresponding relation between each other, therefore, most metal materials can be approximately calculated by measuring hardness other mechanical properties,  Such as strength, fatigue, creep, wear and internal loss, etc.  So the hardness tester is widely used.  

First, micro hardness tester working principle and composition  

Microhardness tester is commonly used to measure hardness equipment in recent years.  Measuring hardness is through the platform of microhardness meter focusing mechanism, measuring microscope, load, correct selection of load and the loading speed for automatic unloading test force and control test force to keep time correctly, by microhardness meter optical amplifier, measured under a certain test force diamond pyramid head pressing into the material being tested by the residual indentation diagonal length,  To figure out the hardness of the object being measured.  

Two, the correct use of microhardness tester  

Because microhardness test is often on a small sample (tip), or on a specific part of the small sample hardness measurement, such as microstructure, and the situation is difficult to choose and employ persons eye for observation and judgement, and micro hardness test after the indentation is very small, it is also difficult to the human eye to look for, not to mention the indentation diagonal length measurement,  So you have to work with a microscope.  In order to use microhardness tester correctly, it is very important to choose the correct load, loading speed and holding time.  This paper introduces how to use microhardness tester correctly.  

1. Load selection  

In order to obtain the true hardness of the tested object, the appropriate load must be selected.  The following principles should be considered in the selection of load:  

(1) When determining the hardness of thin section or surface layer, the load should be selected according to the depth of the indenter and the thickness of the specimen or surface layer.  Because general specimens or know, is the thickness of surface layer and the measured parts hardness or hardness range should be know, based on the pressure head into sample extrusion stress in depth range close to 10 times the depth of press in, to avoid the influence of hardness, depth of head pressure should be less than one over ten of the specimen or surface layer.  

(2) When determining the hardness of the sample profile, the load should be selected according to the diagonal length of the indentation and the width of the profile.  Based on the indenter pressed into the sample, the compressive stress region can extend from the center of the indentation to a maximum distance of 4 times the diagonal.  In order to avoid the influence of different hardness or space in adjacent areas on the hardness of the measured part, the distance between the indentation center and the edge should not be less than 2.5 times the length of the indentation diagonal, that is, the length of the indentation diagonal is 1/5 of the width of the specimen or surface layer profile.  

(3) When determining grain, phase, sundry, etc., the above two principles should be followed to select the load, the depth of the head is not greater than its thickness  

Degree of 1/10, the length of the diagonal indentation should not be greater than 1/5 of its area.  

(4) When measuring the average hardness of the specimen (parts, surface layer, material), the surface size and thickness of the specimen should be used under the premise of allowing  

Large load is selected to avoid the uneven hardness of specimen material structure affecting the accuracy of hardness measurement.  

(5) in order to ensure the accuracy of measurement, when the situation allows, should choose a large load, generally should make the indentation diagonal length greater than 20μ m.  

(6) Considering the influence of the extrusion stress hardening layer on the surface of the specimen during cold processing, the load selection should be under the condition that conditions permit  

Under select large load.  

2. Proper use of measuring microscope  

(1) Find the image plane  

1) Tip sample should adopt "light spot image finding method".  

General microhardness tester measuring microscope object square field of view is only 0.25~0.35mm, in this field outside the area, in the field of view of the measuring microscope eyepiece, the eye is invisible.  And needlepoint class sample items are often less than 0.1 mm, so when installing a control sample, it is difficult to adjust the top in the field: if the top around the field and not in the field, when making adjustment in the platform will not carefully the objective lens very bad, if not the top bad objective, find like is hard, in order to solve this problem, the "spot to find like method" is proposed.  Turn on the lighting bulb of the measuring microscope, then there is a round spot on the table below the objective lens, install the tip sample perpendicular to the table in the center of the spot, raise the table, make the tip tip leave the objective lens about 1mm, then observe the top part of the eye, adjust the table.  The two on the micrometer screw, make objective under illumination light spot on the left and right sides is symmetrical distribution in the top before and after (this step must be carefully), then slowly adjust the lifting mechanism, then will see in the eyepiece - a light point, this is the reflection on the top spot, further adjust the lift can find like this tip.  

(3) when determining grain, phase, sundry, etc., should comply with the above two principles to choose the load, the depth of the head is not greater than 1/10 of its thickness, the diagonal length of the indentation should not be greater than 1/5 of its area.  

(4) When measuring the average hardness of specimens (parts, surface layer and materials), under the premise of allowing the surface size and thickness of specimens, large load should be selected as far as possible, so as to avoid the uneven hardness of specimen material structure affecting the accuracy of hardness measurement of specimens.  

(5) in order to ensure the accuracy of measurement, when the situation allows, should choose a large load, generally should make the indentation diagonal length greater than 20μ m.  

(6) Considering the influence of the extrusion stress hardening layer on the surface of the specimen during cold working, large load should be selected if the situation permits.  

2. Proper use of measuring microscope  

(1) Find the image plane  

1) Tip sample should adopt "light spot image finding method".  

General microhardness tester measuring microscope object square field of view is only 0.25~0.35mm, in this field outside the area, in the field of view of the measuring microscope eyepiece, the eye is invisible.  And needlepoint class sample items are often less than 0.1 mm, so when installing a control sample, it is difficult to adjust the top in the field: if the top around the field and not in the field, when making adjustment in the platform will not carefully the objective lens very bad, if not the top bad objective, find like is hard, in order to solve this problem, the "spot to find like method" is proposed.  Turn on the lighting bulb of the measuring microscope, then there is a round spot on the table below the objective lens, install the tip sample perpendicular to the table in the center of the spot, raise the table, make the tip tip leave the objective lens about 1mm, then observe the top part of the eye, adjust the table.  The two on the micrometer screw, make objective under illumination light spot on the left and right sides is symmetrical distribution in the top before and after (this step must be carefully), then slowly adjust the lifting mechanism, then will see in the eyepiece - a light point, this is the reflection on the top spot, further adjust the lift can find like this tip.  

2) the sample with high surface finish (such as microhardness blocks) should use edge image finding method.  

Microhardness test, sample surface roughness are generally not very high, often is a mirror, on the surface, no obvious observation characteristics, and all at high magnification in the microhardness meter measuring microscope depth of field is very small, only 1 ~ 7 microns, when focusing find like plane so, for lack of experience of the operator is very difficult, even damaged lens,  Therefore, the operator sometimes retains the surface traces to find the image plane, but sometimes there is no residual trace, it is recommended to use the edge image method.  That is, the center of the lighting spot (about 0.5~ -1.1mm) is aligned with the contour edge of the sample surface in the same way, and the semi-bright and semi-dark junction is seen in the mirror field of view, which is the contour edge, and then step-adjust the rise and fall can find the image of the surface edge.  

(2) Adjust lighting  

To prevent oblique illumination influence on the measurement accuracy of indentation diagonal long thin, to adjust the lighting light source, the indentation in the field of center according to the two points of the four diagonal area range of brightness is consistent, by observing the micrometer eyepiece in creasing like clear degree, lighting light source can be the up, down, forward, backward, left and right direction slightly move, until the observed indentation like the bright,  Until there is no shadow: the differential cylinder of the moving table moves the indentation image forward, back, left and right, and the field of view of the micrometer eyepiece should be bright and the indentation image without shadow is better.  

(3) Visual alignment  

As we know, when measuring indentation with a measuring microscope, the indentation is magnified by an objective lens and imaged on the demarcation plate in front of the eyepiece for sighting measurement.  Due to the human eye visual differences (such as normal eyes, myopia, farsightedness), as a magnifying glass effect of ocular must be put in different position, clear the scribed line of reticle to observe (immediate line at this time as the "thin"), the step (adjust the eyepiece) relative to the reticle distance is called the visibility reformed, or it will affect the accuracy of measurement.  

(4) correction of indentation position  

If the indentation image seen in the field of view of the micrometer eyepiece by test force is loaded with a large offset field center, the indentation position needs to be corrected. The indentation position needs to be adjusted repeatedly through several adjustment screws of the objective seat until the indentation image is centered in the field of view of the micrometer eyepiece.  Do not move table when adjusting D screws) and lock each other.  

(5) focus  

In order to find the correct imaging position, care should be taken to adjust the indentation edge clear, not the indentation diagonal or diagonal intersection point clear.  What we need to measure is the diagonal length of the pyramid on the surface of the pit.  To help operator to master this step, "parallax discriminant method" is put forward here, with reticle scribed line or cross intersection point on the indentation diagonal top, moving around eye relative to the eyepiece, at this time as the focus is not correct, the indentation like edge is not completely on the reticle, will find this edge relative to the points and lines can move around.  This indicates that the focusing is not correct. If the position of the eye relative to the eyepiece is inconsistent, there must be measurement error. At this time, the focus should be further focused until the edge relative marking has no relative position when the eye shakes.  

Master the correct measurement method  

1. Rotate the measuring eyepiece so that the movement direction of the demarcation plate is parallel to the diagonal direction of the indentation to be measured, so as to avoid the influence of the Angle between the two on the measurement accuracy.  If the Angle of the two is C and the actual length is, EO will measure the length D ': D/osC, and for the intersection point of the crosshead to aim at the top of the indentation diagonal. When the two have an intersection Angle, the diagonal tip will be aligned with the intersection point of the crosshead, and the other end of the tip can not be aligned.  

2, measurement of the indentation diagonal length, when aiming at the indentation diagonal must be aimed at both ends of the top, do not have to consider the indentation prism quadrilateral situation.  This line is a straight line on the reticle is not a problem, for the reticle is scribed line on the reticle, targeting indentation edge or diagonal of the top debate frequently occurred, to unify various points crossed the aim, so make sure the principles, which can solve the edge varied aimed at problems under complex conditions.  

3. Several problems should be paid attention to in measurement  

(1) Mechanical micrometer mechanism measuring eyepiece, measurement should be unidirectional rotation micrometer handwheel, eliminate the impact of air loop on measurement..  

(2) For the micrometer eyepiece of simultaneous measurement, the operator should pay attention to whether the zero of the micrometer reading is correct when the two marking lines coincide. If not, it should be normalized and simplified or corrected after measurement.  

(3) for the digital micrometer eyepiece, after each boot should make the two marking board lines coincide, and then press the "reset key" to clear the reading.  

(4) when the indentation of two diagonal length is not equal, the length of the two diagonal should be measured and take the average value.  

(5) After rotating the measuring microscope eyepiece so that the movement direction of the demarcating plate is parallel to the indentation diagonal to be measured, the diagonal can be perpendicular to it.  Move the table so that the diagonal line falls on the track of the crossing point of the demarcation board, but when aiming with this crossing point, turn the handwheel of the micrometer eyepiece and do not move the table.  

(6) Operators should be trained strictly and often check their aiming accuracy with standard microhardness blocks.