洛氏硬度計雖然結(jié)構(gòu)簡單，操作方便，但如果長期操作不當(dāng)，檢驗硬度失準，將使產(chǎn)品質(zhì)量受到很大影響，硬度計帶來不佳后果?，F(xiàn)將我們在檢定中常見的幾種誤差及處理方法介紹如下：

    一、人為誤差:

    1、操作人員技術(shù)熟練程度不夠，實踐經(jīng)驗較差，應(yīng)由熟悉操作硬度計的人員使用；

    2、加荷過快，持荷時間短，低硬度的零件硬度偏高，而加荷過慢，持荷時間長，硬度偏低，操作時加荷應(yīng)平整，保持一定加荷時間。

    二、被測零件影響的因素:

    1、不同的表面光潔度在洛氏硬度測試時，表現(xiàn)出不同的影響。表面光潔度愈低，高硬度測試時其硬度愈高，反之硬度越低，有刀痕的粗糙表面，淬火時首先*快冷卻，或很堅硬的表層，硬度值就高。反之，調(diào)質(zhì)件高溫回火時，有刀痕的表層組織先轉(zhuǎn)變，抗回火的能力小，硬度值就低。在測試表面光潔度Δ7以下的零件時，必須使用廢砂輪精磨，再用銼刀銼磨光滑，或用細的手砂輪磨光，然后揩擦干凈；

    2、熱處理零件表面有鹽漬、沙子等物，當(dāng)加負荷時，零件會產(chǎn)生滑移，若有油膩存在，金剛頭壓入時起潤滑作用，減小磨擦，增加壓深。這兩項原因使所測硬度值偏低。零件測試的部位氧化皮蔬松層薄的硬度值降低，氧化皮致密層厚的硬度值增高。對欲測硬度的零件必須去除氧化皮，揩擦干凈，不得有臟物；

    3、斜面(或錐度)、球面及圓柱體零件對硬度測試的誤差較平面大。當(dāng)壓頭壓入這種零件表面時，壓入處四周的抗力比平面小，甚至有偏離、滑移的現(xiàn)象，壓深增大，硬度降低。曲率半徑愈小，斜度愈大，硬度數(shù)值的降低愈顯著。金剛石壓頭也容易損壞。對這類零件要設(shè)計專用工作臺，使工作臺和壓頭同心。

    三、壓頭的影響:

    1、金剛石壓頭不符合技術(shù)要求或是使用一段時間后有磨損，簡單判斷金剛石壓頭是否損壞方法：用金剛石壓頭在光滑玻璃表面來回刮幾下看玻璃表面如沒有刮痕說明壓頭是好的，否則壓頭已經(jīng)損壞。操作者如不能判斷金剛石的好壞，可由計量測試機構(gòu)進行檢定；

    2、鋼球壓頭強度和硬度不夠，容易產(chǎn)生變形。鋼球扳壓扁產(chǎn)生長久變形后呈橢圓，短軸垂直于零件表面時，壓痕淺，示值高；長軸垂直于零件表面時，壓痕加深，示值降低，鋼球允差小0.002mm。

    四、載荷方面:

    1、初負荷：彈簧和主軸、杠桿和百分表之間有摩擦，造成100N的增大或減小。調(diào)整螺絲松曠、調(diào)整移動，頂桿位置不當(dāng)。起始線有差異，引起初負荷不對。如果初負荷不對，應(yīng)調(diào)整彈簧、主軸、杠桿、百分表等處的配合。調(diào)整塊的位置移動合適以后，緊固調(diào)整螺絲，同時要緊固頂桿位置，初負荷的允差應(yīng)小于±2%；

    2、主負荷：杠桿比例不對，吊桿和砝碼的配重有誤差；主軸、杠桿和砝碼有偏斜，均會使主負荷產(chǎn)生誤差。杠桿比不對，應(yīng)進行調(diào)整。刀口有磨損應(yīng)修復(fù)或更換，主軸變形要進行校直。主軸、杠桿和砝碼偏斜應(yīng)撥正。各種標(biāo)尺主負荷的允差小于±0.5%。

    五、硬度計（洛氏硬度計）安置不正。硬度計不處于水平位置，測試硬度時，其值偏低。用水平儀測量水平度，然后墊平硬度計。

    六、零件某一測試部位的表面與工作臺接觸不佳，或支承點不穩(wěn)固，將會產(chǎn)生滑移、滾動、翹起等現(xiàn)象。這不僅使所得結(jié)果不準，還會損壞儀器。

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

1. Human error

1. Operators are not skilled enough and have poor practical experience, so they should be used by those who are familiar with the operation of durometer;

2, too fast loading, short load holding time, low hardness parts hardness on the high side, and too slow loading, long load holding time, low hardness, the operation of loading should be flat, maintain a certain loading time.

Ii. Factors affecting the tested parts:

1. Different surface finishes show different effects in rockwell hardness test. The lower the surface finish, the higher the hardness in the high hardness test, and vice versa, the lower the hardness, the rough surface with knife marks, when quenching * fast cooling first, or very hard surface, the hardness value is high. On the contrary, when tempering at high temperature, the surface structure with knife marks changes first, the resistance to tempering is small, and the hardness value is low. Δ surface finish of the test the following seven parts, must use the grinding wheel finishing grinding, reoccupy file file grinding smooth, or with a hand wheel polishing, then wipe and clean;

2, heat treatment parts surface salt, sand and other things, when the load, the parts will produce slippage, if there is greasy, diamond head into the lubrication, reduce friction, increase the depth of pressure. These two reasons make the hardness measured low. The hardness value of the thin oxide peel pinewood layer decreased and the hardness value of the thick oxide peel dense layer increased. To measure the hardness of the parts must be removed from the oxide skin, wipe clean, no dirt;

3, bevel (or taper), spherical and cylindrical parts of the hardness test error than plane. When pressing a head into the surface of this kind of part, the resistance all round pressing place is smaller than plane, have deviation, the phenomenon of slip even, press deepness increase, hardness decreases. The smaller the radius of curvature, the larger the slope, the more significant the decrease of hardness value. Diamond head is also easily damaged. To this kind of spare parts must design the special work table, causes the work table and the pressure head to be homocentric.

Iii. Impact of head:

1. The diamond indenter does not meet the technical requirements or is worn after being used for a period of time. A simple method to determine whether the diamond indenter is damaged: scrape the glass surface with the diamond indenter for several times to see that the glass surface is good if there is no scratch, otherwise the indenter has been damaged. If the operator cannot judge whether the diamond is good or bad, it can be verified by a measuring and testing institution.

2, steel ball head strength and hardness is not enough, easy to produce deformation. When the short shaft is perpendicular to the surface of the part, the indentation is shallow and the indication value is high. When the long shaft is perpendicular to the surface of the part, the indentation deepens, indicating value decreases, and the tolerance of steel ball is 0.002mm smaller.

Iv. Load:

1. Initial load: there is friction between spring and spindle, lever and dial indicator, resulting in the increase or decrease of 100N. Adjust the screw loose, adjust the movement, the ejector position is improper. The difference of starting line causes wrong initial load. If the initial load is not correct, adjust the spring, spindle, lever, dial indicator, etc. When the position of the adjusting block is moved properly, tighten the adjusting screw and tighten the position of the ejector. The tolerance of initial load should be less than ±2%.

2. Main load: the proportion of lever is wrong, and the balance weight of derrick and weight is wrong; The deviation of spindle, lever and weight will make the main load error. Lever ratio is wrong, should undertake adjusting. Blade wear should be repaired or replaced, spindle deformation to be straightened. The deviation of spindle, lever and weight should be corrected. The tolerance of main load of various scales is less than ±0.5%.

5. Improper placement of hardness tester (rockwell hardness tester). The durometer is not in a horizontal position and its value is low when the hardness is tested. Measure levelness with a leveler and flatten the hardness tester.

Six, the surface of a certain test part and the table contact is not good, or the support point is not stable, will produce sliding, rolling, warping phenomenon. This not only makes the results inaccurate, but also damages the instrument.