如何正确使用洛氏硬度计?

在实际应用中，被测材料的硬度值可以直接从硬度计指示盘上对应的刻度C或B中读取，无需按公式计算。 测试时可选择压头和载荷值、标记符号和有效量程。

  压头和负载应用最常见的组合是：

  A刻度：压头为圆锥形金刚石压头，顶角为120°，总载荷为588.399N。 用于测量硬度较高的金属（如碳化钨等），或当试件为较硬的薄板材料和较薄的表层不宜使用HRC时。

  C标尺：顶角为120°圆锥金刚石压头，总载荷为1471N。 用于测定热硬化钢产品的硬度。 应用范围为HRC20-67。 如果试样硬度低于HRC20，压头会深深压入试样，压头形状不正确造成的误差会增大，因此测量结果不准确。 如果试样硬度高于HRC67，压头压入试样的深度很浅，压头尖端会产生很大的压力，容易损坏压头。

  B标尺：钢球压头，直径1.588mm，总载荷980.665N。 用于测定软或中等硬度的金属和未硬化的钢制品。 应用范围为HRB20-100。 当试样硬度低于HRB20时，大部分情况下开始出现蠕变现象，钢球与试样接触面过大，测量结果不准确。 当硬度高于HRB100时，钢球变形大，压入试件的深度太浅，测量结果不准确。

  洛氏硬度计（HR150A）的使用方法如下：

  1. 准备工作

  使用经过认证的硬度计； 试件厚度大于压痕深度的10倍； 根据试件的形状选择合适的工作台； 选择合适的压头和总载荷值。

  2.测试的具体步骤

  ①将试件放在工作台上，转动手轮使工作台缓慢升高，压头抬高0.6mm。 指示盘的小指针指向“3”，大指针指向标记C和B。（轻轻转动表盘直到对准）。

  ②指针位置对准后，可将加载手柄向前拉，使主要载荷作用于压头。

  ③当指示指针转动明显停止时，可将卸料手柄向后推卸主载荷。

  ④从仪表中读出相应的刻度值。 使用金刚石压头时，根据读数表盘外圈的黑色字进行读数。 使用钢球压头时，根据读数刻度盘内圈上的红色字母读取数值。

  ⑤ 松开手轮，降低工作台后，可将试件稍稍移动，选择新的位置继续试验。

  需要注意的是，两个压痕中心的距离不应小于3mm； 对于同一个试样，最好对不同部位进行不少于3次的试验，这样才能可靠地确定实际情况。

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In practical applications, the hardness value of the tested material can be read directly from the corresponding scale C or B on the hardness tester indicator plate, without calculating according to the formula.  Pressure head and load values, markers and effective ranges can be selected during testing.  

The most common combination of head and load applications is:  

A scale: the indenter is A conical diamond indenter, the apex Angle is 120°, the total load is 588.399N.  HRC is used to measure metals with high hardness (such as tungsten carbide, etc.), or when the specimen is a hard sheet material and a thin surface layer is not suitable for HRC.  

C scale: cone diamond indenter with 120° apex Angle, total load 1471N.  Used for testing the hardness of hot hardening steel products.  The application range is HRC20-67.  If the hardness of the sample is lower than HRC20, the indenter will be deeply pressed into the sample, and the error caused by the incorrect shape of the indenter will increase, so the measurement result is not accurate.  If the hardness of the sample is higher than HRC67, the indenter is pressed into the sample at a shallow depth, and the indenter tip will produce a lot of pressure, which is easy to damage the indenter.  

B scale: steel ball head, diameter 1.588mm, total load 980.665N.  Used for the determination of soft or medium hard metals and unhardened steel products.  The application range is HRB20-100.  When the hardness of the sample is lower than HRB20, creep phenomenon begins to appear in most cases, and the contact surface between the steel ball and the sample is too large, resulting in inaccurate measurement results.  When the hardness is higher than HRB100, the deformation of the steel ball is large, the depth of pressing into the specimen is too shallow, and the measurement result is not accurate.  

Rockwell hardness tester (HR150A) is used as follows:  

1. Preparation  

Use a certified hardness tester;  The specimen thickness is 10 times greater than the indentation depth;  According to the shape of the specimen to choose the appropriate table;  Select the appropriate head and total load value.  

2. Specific steps of the test  

① Place the specimen on the work table, turn the handwheel to make the work table rise slowly, and the pressure head rise 0.6mm.  The small pointer to the dial points to "3" and the large pointer to the markers C and B.  (Gently turn the dial until it is aligned).  

② After the pointer position is aligned, the loading handle can be pulled forward so that the main load is applied to the head.  

When the pointer rotation stops obviously, the unloading handle can be shifted backward to shift the main load.  

④ Read the corresponding scale value from the meter.  When using diamond indenter, read according to the black words on the outer ring of reading dial.  When using the ball indenter, read the value according to the red letter on the inner ring of the reading dial.  

(5) after loosening the handwheel and lowering the workbench, the specimen can be moved slightly to select a new position to continue the test.  

It should be noted that the distance between the two indentation centers should not be less than 3mm;  For the same sample, it is best to test different parts of the test no less than 3 times, so that the actual situation can be reliably determined.