洛氏硬度計(jì)雖然結(jié)構(gòu)簡(jiǎn)單，操作方便，但如果長(zhǎng)時(shí)間操作不當(dāng)，測(cè)試硬度會(huì)不準(zhǔn)確，極大地影響產(chǎn)品質(zhì)量，帶來(lái)不良后果。 下面我們就來(lái)介紹一下驗(yàn)證中的幾種常見(jiàn)錯(cuò)誤及處理方法

  1. 人為錯(cuò)誤。

  （1）操作人員技術(shù)水平不夠，實(shí)踐經(jīng)驗(yàn)差，應(yīng)由熟悉硬度計(jì)的人員使用；  (2)加載太快，加載保持時(shí)間短，低硬度零件硬度高，加載太慢，加載保持時(shí)間長(zhǎng)，硬度低。 運(yùn)行時(shí)裝料應(yīng)平整，并保持一定的裝料時(shí)間。

  2、影響被測(cè)零件的因素。

  (1)不同的表面光潔度對(duì)洛氏硬度試驗(yàn)的影響不同。 表面光潔度越低，高硬度試驗(yàn)的硬度就越高，反之，硬度越低，有刀痕的粗糙表面，淬火時(shí)冷卻最快，或者很硬的表面，硬度值就越高。 反之，調(diào)質(zhì)件在高溫回火時(shí)，帶刀痕的表面組織首先發(fā)生轉(zhuǎn)變，抗回火能力小，硬度值低。 測(cè)試表面光潔度在△7以下的零件時(shí)，必須用廢砂輪進(jìn)行精磨，然后用銼刀銼平，或用細(xì)手砂輪打磨，然后擦干凈。

  (2)熱處理件表面有鹽漬、砂粒等。 當(dāng)負(fù)載增加時(shí)，零件會(huì)滑動(dòng)。 如果有油膩，金剛頭在壓入時(shí)會(huì)潤(rùn)滑，減少摩擦，增加壓入深度。 這兩個(gè)原因使得測(cè)得的硬度值偏低。 被測(cè)零件的薄氧化皮層和植物松層的硬度值降低，而厚氧化皮層的硬度值增加。 待測(cè)硬度的零件，必須去除氧化皮，擦拭干凈，不得有污垢。

  （3）傾斜（或錐度）、球面和圓柱形零件的硬度測(cè)試誤差比平面要大。 當(dāng)壓頭壓入此類零件表面時(shí)，壓痕處周圍阻力小于平面，甚至出現(xiàn)跑偏、打滑現(xiàn)象，壓痕深度增加，硬度降低。 曲率半徑越小，斜率越大，硬度值下降越明顯。 金剛石壓頭也容易損壞。 對(duì)于此類零件，應(yīng)設(shè)計(jì)專用工作臺(tái)，使工作臺(tái)與壓頭同心。

  三是壓頭的影響。

  (1)金剛石壓頭不符合技術(shù)要求或使用一段時(shí)間后磨損。 如果操作者無(wú)法判斷鉆石的質(zhì)量，可以通過(guò)計(jì)量檢測(cè)機(jī)構(gòu)進(jìn)行驗(yàn)證。

  (2)鋼球壓頭強(qiáng)度和硬度不夠，容易變形。 當(dāng)鋼球被壓扁并產(chǎn)生永久變形時(shí)，它就變成了一個(gè)橢圓。 短軸與零件表面垂直時(shí)，壓痕淺，示值高； 當(dāng)長(zhǎng)軸垂直于零件表面時(shí)，壓痕加深，示值減小，鋼球公差小0.002mma

  第四，負(fù)載。

  (1)初荷：彈簧與主軸、杠桿與百分表之間有摩擦，產(chǎn)生100N的增減。 調(diào)整螺釘松動(dòng)，調(diào)整塊移動(dòng)，頂桿位置不當(dāng)。 起跑線不同，導(dǎo)致初始加載不正確。 如果初始載荷不正確，應(yīng)調(diào)整彈簧、主軸、杠桿、百分表等的配合。 調(diào)整塊位置移動(dòng)正常后，擰緊調(diào)整螺釘，同時(shí)擰緊頂桿位置。 初始負(fù)載的公差應(yīng)小于±2%。

  （2主載荷；如果第二個(gè)杠桿比例正確，則拉桿配重和重物有誤差；如果主軸、杠桿和重物歪斜，會(huì)導(dǎo)致主 魚(yú)負(fù)荷。杠桿比不正確，應(yīng)調(diào)整，刀口磨損，應(yīng)修理或更換，并矯正主軸變形。主軸偏斜， 應(yīng)校正杠桿和重量，各種秤的主要載荷之差小于0.5%。

  5、硬度計(jì)放置不當(dāng)。

  硬度計(jì)不在水平位置，測(cè)試硬度時(shí)其數(shù)值偏低。 使用水平儀測(cè)量水平度，然后將硬度計(jì)壓平。

  6、零件某試驗(yàn)件表面與工作臺(tái)接觸不良，或支撐點(diǎn)不穩(wěn)定：

  這會(huì)導(dǎo)致打滑、滾動(dòng)、翹曲等，不僅會(huì)使結(jié)果不準(zhǔn)確，還會(huì)損壞儀器。 應(yīng)根據(jù)零件的幾何形狀設(shè)計(jì)合適的工作臺(tái)。

  10、周圍環(huán)境的影響。

  工廠生產(chǎn)中使用的硬度計(jì)經(jīng)常會(huì)因周圍環(huán)境而受到振動(dòng)的影響，導(dǎo)致儀器結(jié)構(gòu)松動(dòng)，顯示值不穩(wěn)定。 硬度計(jì)應(yīng)安裝在無(wú)振動(dòng)或遠(yuǎn)離振動(dòng)源的地方。

英斯特力儀器是一家集研發(fā)、生產(chǎn)及銷售于一體的 影像測(cè)量?jī)x，拉力試驗(yàn)機(jī), 硬度計(jì) ,探傷儀, 粗糙度儀, 測(cè)厚儀, 金相設(shè)備廠家, 致力于為客戶提供更好的檢測(cè)儀器。

Although rockwell hardness tester is simple in structure and easy to operate, if it is operated improperly for a long time, the quality of products will be greatly affected, resulting in adverse consequences.  Now we are in the verification of several common errors and processing methods are introduced as follows  

First, human error.  

(1) Operators are not skilled enough and have poor practical experience, so they should be used by those familiar with the hardness tester;  (2) charging too fast, holding time is short, the hardness of parts with low hardness is high, and the loading is too slow, holding time is long, and the hardness is low. The loading should be smooth during operation, and the loading time should be maintained.  

Second, the factors affecting the measured parts.  

(1) Different surface finish in rockwell hardness test, show different effects.  The lower the surface finish, the higher the hardness of the high hardness test, on the contrary, the lower the hardness, the rough surface with knife marks, the first fastest cooling when quenching, or very hard surface, the hardness value is high.  On the contrary, when tempering parts at high temperature, the surface tissue with knife marks changes first, and the ability to resist tempering is small, and the hardness value is low.  When testing parts with a surface finish below △7, it is necessary to use a waste grinding wheel for fine grinding and then smooth them with a file or smooth them with a fine hand grinding wheel and wipe them clean.  

(2) The surface of heat treatment parts with salt, sand and other things, when loading, parts will slip, if there is grease, diamond head pressure when the lubrication effect, reduce friction, increase the pressure depth.  These two reasons cause the measured hardness value to be low.  The hardness value of the thin oxide peel pine layer decreases and the hardness value of the thick oxide peel dense layer increases.  To measure the hardness of the parts must remove the oxide skin, wipe clean, no dirt.  

(3) The incline (or taper), spherical and cylindrical parts of the hardness test error is larger than the plane.  When the pressure head is pressed into the surface of this part, the resistance around the pressure is smaller than the plane, and there is even deviation and slippage, and the depth of the pressure increases, and the hardness decreases.  The smaller the radius of curvature is, the larger the slope is, the more significant the hardness value decreases.  Diamond indenter is also vulnerable to damage.  To this kind of parts to design a special table, so that the table and pressure head concentric.  

Three, the impact of the head.  

(1) The diamond indenter does not meet the technical requirements or is worn after a period of use. If the operator cannot judge the quality of the diamond, it can be verified by the metrological testing institution.  

(2) Steel ball head strength and hardness is not enough, easy to produce deformation.  The steel ball is elliptical after the permanent deformation caused by flattening. When the short axis is perpendicular to the surface of the parts, the indentation is shallow and the value is high.  When the long axis is perpendicular to the surface of the parts, the indentation deepens, the indication value decreases, and the ball tolerance is 0.002mmA smaller  

Four, load.  

(1) Initial load: spring and spindle, lever and dial indicator.  There is friction between them, causing 100N to go up or down.  The adjusting screw is loose, the adjusting block moves, and the push rod position is improper.  The starting line is different, resulting in incorrect initial load.  If the initial load is not correct, should adjust the spring, spindle, lever, dial indicator, etc.  Tighten the adjusting screw and push rod after the adjusting block is moved properly. The allowance of initial load should be less than 2%.  

(2 main load;  Two lever proportion is not correct, product bar and weight balance error;  Deflection of spindle, lever and weight can cause errors in the main fish load.  If the rod ratio is not correct, it should be adjusted.  Knife-edge wear should be repaired or replaced, and spindle deformation should be straightened.  Spindle, lever and weight deflection should be adjusted.  The modal difference of the main load of all scales is less than 0.5% of soil.  

Five, hardness tester placement is not straight.  

The hardness tester is not in a horizontal position and its value is low when testing hardness.  Measure the levelness with a level, then line a level hardness tester.  

Six, parts of a test part of the surface and the table is not good contact, or the support point is not stable: industry  

This will cause slippage, rolling, warping and other phenomena, which will not only make the results not accurate but also damage the instrument.  A suitable worktable shall be designed according to the geometry of the parts.  

10. The influence of the surrounding environment.  

The hardness tester used in factory production is often affected by the vibration of the surrounding environment, resulting in loose instrument structure and unstable display value.  The durometer should be installed in a place without vibration or far from the source.