Rockwell hardness test basic knowledge
inRockwell hardness test, with poor deep method measuring pressure head produced by the residual indentation depth.Different from rockwell method inbrinell,vickersAnd knoop optical testing method to measure the indentation size.
Under the specified test load, the pressure head through the deeper the sample surface, measured material more soft.Rockwell hardness(HR)通过残留压痕深度以及一些其他因素（见下文）来测定。
inRockwell hardness testThe total test force to put in two steps.This is in order to eliminate the sample surface roughness (for example, a groove on the sample), and because of the indentation depth measurement gap caused by the error of measurement.
In accordance with ISO 6508 standard rockwell hardness test (HR) order
- Step 1 test.
First of all, in the experiment of pre-load pressure head into the sample under test until h0 indentation depth is reached.H0 defined for subsequent permanent indentation depth measurement reference plane (base). - Then, according to the standard definition of the residence time (seconds) impose additional test force, pressure head through the sample at this time until the maximum penetration depth h1.Test the sum of its load and additional test force for total test force (also known as the total force or main load).
- At the end of the residence time, remove the additional test force.head回到起始位置，移动距离为总试验力范围内压痕深度弹性部分的量，然后停留在永久压痕深度h的水平（以0.002或0.001 mm为单位）。这也称为差深（总试验力施加前后压痕深度的差值）。借助永久压痕深度h，根据The ISO 6508Criteria defined in the formula, with reference to the application of rockwell hardness scale, can be calculatedRockwell hardness(HR).
- Rockwell test procedure
Setup test indentation, must ensure that the edge and sample have enough distance, and the test must also have enough distance between indentation.Please see the below must comply with the minimum value.
The advantages and disadvantages of using rockwell hardness test
Rockwell method has the following advantages:
- Without sample preparation, cutting, grinding, embedding)
- Can directly read the hardness value, without optical evaluation (diagonal measurement, and the optical method)
- Is fast (short test period) and the method of economic (without as brinell and vickers and knoop optical method testing machine equipped with sophisticated optical system, so the hardness tester is cost-effective)
- Non-destructive test, the sample can be reused
Rockwell method has the following disadvantages:
- Rockwell method is not always the most accurateHardness testMethods, this is because even a small difference depth measurement error could also lead to big error in calculated hardness value.
- To get meaningful results, must ensure that the test without any dirt or debris (such as scale and coal cinder, foreign bodies, or oil).
- Head has unknown effects on test results, for example, when the head is the wear and tapered tip no longer conform to the requirements of the standard (the standard requirement: can only be used after certification and correction of pressure head, in order to reduce unnecessary influence!).
- With the increase of hardness, material will be more difficult to distinguish.
Rockwell hardness method and application examples
In order to makeThe application range of the rockwell test as widely as possibleHas for rockwell and surface rockwell hardness technology developed several kinds of methods.
The rockwell hardness method difference is:
- Head type (material, shape and size, or the ball diameter);
- The size of the total test force (total force or main load);
- Scale dividing (benchmark for measuring residual indentation depth h h0 for 100 or 130
Unit (depending on the scale, the following applies: 1 E = 0.002 mm or 0.001 mm)).
The resulting rockwell hardness method using five different pressure head of the curvature is 120 degrees (diamond cone or 1/16, 1/8 "diameter, 1/4" and 1/2 "made of tungsten carbide hard metal ball) and six different total test force (15, 30, 45, 60, 100, 150 KGF).
This can lead to according toThe ISO 6508andASTM E18Standard (such as A, B, C, n 30, 15 t) orRockwell test method(e.g., HRA, HRBW, HRC, HR30N, HR15TW) to 30 different kinds of standardizationRockwell scale, each covering different hardness range, therefore covers a variety of materials and application (see table).
Rockwell methodUsually used in the production or quick test in laboratory, also used in other processes, such asJoe, the top hardenability test/Joe) test.
Practice is the most common method of rockwell hardness in HRC.In principle, the spherical head used in soft materialsHardness test, diamond indenter for testing a hard material.Diamond would destroy the softer material or to penetrate it.
This table shows that according toThe ISO 6508To standardize theRockwell hardness methodAnd its application.All of pre-load method for 10 KGF.
| methods | head | The main load (KGF) | application |
|---|---|---|---|
| HRA | Diamond 120 ° | 60 | Surface hardened steel, hard metal and alloy |
| HRBW | 1/16 "balls | 100 | Copper (Cu), no hardening alloy steel (in the United States, also applies to the most about 686 N/mm squared steel) |
| HRC | Diamond 120 ° | 150 | Surface hardened steel, hard metal and alloy |
| HRD | Diamond 120 ° | 100 | Surface hardened steel, hard metal and alloy |
| HREW | 1/8 "balls | 100 | Aluminum (Al) alloy, copper (Cu) |
| HRFW | 1/16 "balls | 60 | Thin soft steel plate |
| HRGW | 1/16 "balls | 150 | Bronze, copper (Cu), cast iron |
| HRHW | 1/8 "balls | 60 | Aluminum (Al), zinc (zinc), lead (Pb) |
| HRKW | 1/8 "balls | 150 | Metal bearings and other very soft or very thin material, including plastic (see ASTM D785 standard) |
| HRLW | Ball 1/4" | 60 | |
| HRMW | Ball 1/4" | 100 | |
| HRPW | Ball 1/4" | 150 | |
| HRRW | 1/2 "ball | 60 | |
| HRSW | 1/2 "ball | 100 | |
| HRVW | 1/2 "ball | 150 |
The following overview display according to the contentASTM E18Standardize allSurface rockwell hardness methodAnd its application.All test of pre-load method for 3 kg.
| methods | head | The main load (KGF) | application |
|---|---|---|---|
| HR15N | Diamond 120 ° | 15 | Surface hardening of the thicker artifacts |
| HR30N | 30 | ||
| HR45N | 45 | ||
| HR15TW | 1/16 "balls | 15 | Sheet metal |
| HR30TW | 30 | ||
| HR45TW | 45 | ||
| HR15WW | 1/8 "balls | 15 | Aluminum (Al), zinc (zinc), lead (Pb), tinplate |
| HR30WW | 30 | ||
| HR45WW | 45 | ||
| HR15XW | Ball 1/4" | 15 | Aluminum (Al), zinc (zinc), lead (Pb), tinplate |
| HR30XW | 30 | ||
| HR45XW | 45 | ||
| HR15YW | 1/2 "ball | 15 | Aluminum (Al), zinc (zinc), lead (Pb), tinplate |
| HR30YW | 30 | ||
| HR45YW | 45 |
