What is metal hardness

Relationships between hardness numbers

The hardness of a metal is its property of resisting plastic deformation during the contact action of a standard tip body on the surface layers of the material.

Hardness testing is the main method for assessing the quality of heat treatment of a product.

Determination of hardness using the Brinell method . The method is based on inserting a steel ball into a flat surface under load. The hardness number HB is determined by the ratio of the load to the spherical surface of the indentation.

The Rockwell (HR) method is based on statically pressing a tip into the test surface under a certain load. Steel balls are used as tips for materials with hardness up to 450 HR. In this case, the hardness is designated as HRB . When using a diamond cone, hardness is designated as HRA or HRC (depending on load).

Vickers hardness (HV) is determined by statically pressing a diamond tetrahedral pyramid into the test surface. During the test, the indentation is measured with an accuracy of 0.001 mm using a microscope, which is an integral part of the Vickers instrument.

Shor's method . The essence of this method is to determine the hardness of the sample material by the height of the rebound of the striker falling onto the surface of the test body from a certain height. Hardness is assessed in conventional units proportional to the height of the striker's rebound.

HRC hardness numbers for some parts and tools

Parts and tools HRC hardness number

Hinged bolt heads, hex nuts, clamping handles	3338
Hinge screw heads, setscrew ends and heads, hinge axes, clamping and removable strips, screw heads with internal hex holes, drive chuck pin	3540
Round nut splines	3642
Gears, keys, clamps, crackers for machine grooves	4045
Spring and retaining rings, tension wedges	4550
Self-tapping screws, turning centers, eccentrics, mushroom supports and support plates, mounting pins, collets	5060
Installation nuts, locknuts, blockers for machine grooves, circular eccentrics, eccentric cams, clamps for dividing devices, replaceable jaws for vices and chucks, gear wheels	5660
Working surfaces of gauges - plugs and staples	5664
Copiers, carbon rollers	5863
Jig bushings, rotating bushings for boring bars	6064

Table of relationships between hardness numbers according to Brinell, Rockwell, Vickers, Shore

RockwellBrinellVickers (HV)Shore HRCHRAHRBPrint diameter HB

65	84,5	—	2,34	688	940	96
64	83,5	—	2,37	670	912	94
63	83	—	2,39	659	867	93
62	82,5	—	2,42	643	846	92
61	82	—	2,45	627	818	91
60	81,5	—	2,47	616	—	—
59	81	—	2,5	601	756	86
58	80,5	—	2,54	582	704	83
57	80	—	2,56	573	693	—
56	79	—	2,6	555	653	79,5
55	79	—	2,61	551	644	—
54	78,5	—	2,65	534	618	76,5
53	78	—	2,68	522	594	—
52	77,5	—	2,71	510	578	—
51	76	—	2,75

Source: http://tekhnar.ru/materialy/tverdost.html

Hardness of metals. Metal hardness table

In order for parts and mechanisms to serve for a long time and reliably, the materials from which they are made must meet the necessary operating conditions. That is why it is important to control the permissible values ​​of their main mechanical parameters. Mechanical properties include hardness, strength, impact strength, and ductility. The hardness of metals is a primary structural characteristic.

Concept

The hardness of metals and alloys is the property of a material to create resistance when another body penetrates its surface layers, which does not deform or collapse under accompanying loads (indenter). Determined for the purpose of:

• obtaining information about acceptable design features and operational capabilities;
• state analysis under the influence of time;
• monitoring the results of temperature treatment.

The strength and aging resistance of the surface partly depend on this indicator. Both the source material and finished parts are examined.

Research options

The indicator is a value called the hardness number. There are various methods for measuring the hardness of metals. The most accurate studies involve the use of various types of calculations, indenters and corresponding hardness testers:

1. Brinell: the essence of the apparatus is pressing a ball into the metal or alloy being tested, calculating the diameter of the indentation and subsequent mathematical calculation of the mechanical parameter.
2. Rockwell: Uses a ball or diamond cone tip. The value is displayed on a scale or determined by calculation.
3. Vickers: The most accurate measurement of metal hardness using a diamond pyramid tip.

To determine parametric correspondences between indicators of different measurement methods for the same material, there are special formulas and tables.

Factors that determine the measurement option

In laboratory conditions, if the necessary range of equipment is available, the choice of research method is carried out depending on certain characteristics of the workpiece.

1. Approximate value of the mechanical parameter. For structural steels and materials with low hardness up to 450-650 HB, the Brinell method is used; for tool, alloy steels and other alloys - Rockwell; for hard alloys – Vickers.
2. Dimensions of the test sample. Particularly small and thin parts are examined using a Vickers hardness tester.
3. The thickness of the metal at the measurement location, in particular the cemented or nitrided layer.

All requirements and compliance are documented by GOST.

Features of the Brinell technique

Hardness testing of metals and alloys using a Brinell hardness tester is carried out with the following features:

1. Indenter - a ball made of alloy steel or tungsten carbide alloy with a diameter of 1, 2, 2.5, 5 or 10 mm (GOST 3722-81).
2. Duration of static indentation: for cast iron and steel - 10-15 s, for non-ferrous alloys - 30, a duration of 60 s is also possible, and in some cases - 120 and 180 s.
3. Limit value of the mechanical parameter: 450 HB when measured with a steel ball; 650 HB when using carbide.
4. Possible loads. Using the weights included in the kit, the actual deformation force on the test sample is adjusted. Their minimum permissible values: 153.2, 187.5, 250 N; maximum – 9807, 14710, 29420 N (GOST 23677-79).

Using formulas, depending on the diameter of the selected ball and the material being tested, the corresponding permissible indentation force can be calculated.

Alloy type	Mathematical load calculation
Steel, nickel and titanium alloys	30D2
Cast iron	10D2, 30D2
Copper and copper alloys	5D2, 10D2, 30D2
Light metals and alloys	2.5D2, 5D2, 10D2, 15D2
Lead, tin	1D2

Example notation:

400HB10/1500/20, where 400HB is the Brinell hardness of the metal; 10 – ball diameter, 10 mm; 1500 – static load, 1500 kgf; 20 – period of indentation, 20 s.

To establish accurate figures, it is rational to examine the same sample in several places, and determine the overall result by finding the average value of the obtained ones.

Determination of hardness using the Brinell method

The research process proceeds in the following sequence:

1. Checking the part for compliance with the requirements (GOST 9012-59, GOST 2789).
2. Checking the health of the device.
3. Selecting the required ball, determining the possible force, installing weights for its formation, and the period of indentation.
4. Starting the hardness tester and deforming the sample.
5. Measuring the diameter of the recess.
6. Empirical calculation.

HB=F/A,

where F – load, kgf or N; A – print area, mm2.

НВ=(0.102*F)/(π*D*h),

where D is the diameter of the ball, mm; h – indentation depth, mm.

The hardness of metals measured by this method has an empirical connection with the calculation of strength parameters. The method is accurate, especially for soft alloys. It is fundamental in systems for determining the values ​​of this mechanical property.

Features of the Rockwell technique

This measurement method was invented in the 20s of the 20th century, and is more automated than the previous one. Used for harder materials. Its main characteristics (GOST 9013-59; GOST 23677-79):

1. Availability of a primary load of 10 kgf.
2. Holding period: 10-60 s.
3. Limit values ​​of possible indicators: HRA: 20-88; HRB: 20-100; HRC: 20-70.
4. The number is visualized on the dial of the hardness tester and can also be calculated arithmetically.
5. Scales and indenters. There are 11 different scales depending on the type of indenter and the maximum permissible static load. The most common in use: A, B and C.

A: diamond cone tip, apex angle 120˚, total permissible static influence force – 60 kgf, HRA; Thin products, mainly rolled products, are being studied.

C: also a diamond cone, designed for a maximum force of 150 kgf, HRC, suitable for hard and hardened materials.

B: 1.588 mm ball, made of hardened steel or hard tungsten carbide, 100 kgf, HRB, used to evaluate the hardness of annealed products.

A ball-shaped tip (1.588 mm) is applicable for Rockwell scales B, F, G. There are also scales E, H, K, for which a ball with a diameter of 3.175 mm is used (GOST 9013-59).

The number of tests performed with a Rockwell hardness tester on one area is limited by the size of the part. A repeat test is allowed at a distance of 3-4 diameters from the previous place of deformation. The thickness of the tested product is also regulated. It should be no less than the tip penetration depth increased by 10 times.

Example notation:

50HRC is the Rockwell hardness of a metal, measured using a diamond tip, its number is 50.

Rockwell Study Design

Measuring metal hardness is more simplified than for the Brinell method.

1. Assessment of the dimensions and surface characteristics of the part.
2. Checking the health of the device.
3. Determination of tip type and permissible load.
4. Sample installation.
5. Implementation of a primary force on the material of 10 kgf.
6. Exercising full appropriate effort.
7. Reading the resulting number on the dial scale.

A mathematical calculation is also possible to accurately determine the mechanical parameter.

Provided that a diamond cone is used with a load of 60 or 150 kgf:

HR=100-((Hh)/0.002;

when performing a test with a ball under a force of 100 kgf:

HR=130-((Hh)/0.002,

where h is the penetration depth of the indenter at a primary force of 10 kgf; H – indenter penetration depth at full load; 0.002 is a coefficient that regulates the amount of movement of the tip when the hardness number changes by 1 unit.

Rockwell's method is simple, but not accurate enough. At the same time, it allows the measurement of mechanical properties for hard metals and alloys.

Characteristics of the Vickers technique

Determining the hardness of metals using this method is the simplest and most accurate. The hardness tester works by pressing a diamond pyramidal tip into the sample.

Key Features:

1. Indenter: diamond pyramid with apex angle 136°.
2. Maximum permissible load: for alloy cast iron and steel - 5-100 kgf; for copper alloys - 2.5-50 kgf; for aluminum and alloys based on it - 1-100 kgf.
3. Static load holding period: from 10 to 15 s.
4. Test materials: steel and non-ferrous metals with a hardness of more than 450-500 HB, including products after chemical-thermal treatment.

Example notation:

700HV20/15,

where 700HV is the Vickers hardness number; 20 – load, 20 kgf; 15 – period of static force, 15 s.

Vickers study sequence

The procedure is extremely simplified.

1. Checking the sample and equipment. Particular attention is paid to the surface of the part.
2. Selection of permissible force.
3. Installation of the test material.
4. Putting the hardness tester into operation.
5. Reading the result on the dial.

The mathematical calculation for this method is as follows:

HV=1.8544*(F/d2),

where F – load, kgf; d – average value of the print diagonal lengths, mm.

It allows you to measure high hardness of metals, thin and small parts, while providing highly accurate results.

Ways to switch between scales

Having determined the diameter of the print using special equipment, you can use tables to determine the hardness. The metal hardness table is a proven assistant in calculating this mechanical parameter. Thus, if the Brinell value is known, the corresponding Vickers or Rockwell number can be easily determined.

Example of some match values:

Print diameter, mm	Research method
Brinell	Rockwell	Vickers
A	C	B
3,90	241	62,8	24,0	99,8	242
4,09	218	60,8	20,3	96,7	218
4,20	206	59,6	17,9	94,6	206
4,99	143	49,8	—	77,6	143

The metal hardness table is compiled on the basis of experimental data and is highly accurate. There are also graphical dependences of Brinell hardness on the carbon content in an iron-carbon alloy. So, in accordance with such dependencies, for steel with an amount of carbon in the composition equal to 0.2%, it is 130 HB.

Sample requirements

In accordance with the requirements of GOSTs, the tested parts must meet the following characteristics:

1. The workpiece must be flat, lie firmly on the hardness tester table, its edges must be smooth or carefully processed.
2. The surface should have minimal roughness. Must be sanded and cleaned, including using chemical compounds. At the same time, during machining processes, it is important to prevent the formation of work hardening and an increase in the temperature of the treated layer.
3. The part must comply with the selected method for determining hardness using parametric properties.

Fulfillment of primary requirements is a prerequisite for measurement accuracy.

The hardness of metals is an important fundamental mechanical property that determines some of their other mechanical and technological features, the results of previous processing processes, the influence of temporary factors, and possible operating conditions. The choice of research methodology depends on the approximate characteristics of the sample, its parameters and chemical composition.

Source: https://FB.ru/article/269317/tverdost-metallov-tablitsa-tverdosti-metallov

Metal hardness measurement

The hardness of steel is one of the most important mechanical properties of steel. Generally speaking, the hardness of a material is not an intrinsic property of it.

Therefore, it cannot be given an accurate and unambiguous definition based on the fundamental units of measurement - mass, length and time. Therefore, hardness measurement is the result of a specific measurement procedure - the hardness measurement method.

many definitions of the concept of “hardness” as there are methods for measuring hardness .

The oldest method for measuring hardness

The hardness of materials has long been assessed by their resistance to scratching or cutting. For example, material B scratches material C, but does not scratch material A. And, conversely, material A scratches material B only slightly, but material B very strongly. Thus, the relative hardness of minerals is still assessed using the Mohs mineralogical scale, which was introduced by the German Mohs back in 1811. According to the Mohs scale, diamond has a maximum hardness of 10, and talc has a minimum hardness of 1.

A practical method for measuring hardness

In practice, a similar method of measuring hardness is often used using a special set of files, each of which is thermally hardened to a certain hardness - from low to high. Such a set of six files is shown in the figure below.

Figure - Set of files for measuring the hardness of metals

If the file slides over the material without forming any mark, then this material is considered harder than the file; if the mark remains, it is considered less hard. This relative method of measuring hardness is limited in practical use and does not provide accurate numerical data or scales, especially for modern metals and materials.

What is hardness?

Hardness testing is applied to most materials, especially metals. The very concept of “hardness” has many definitions - from physicists, metallurgists and mechanical engineers. In mineralogy, hardness is the resistance to scratching by another substance, and in metallurgy, it is the ability of a material to resist plastic deformation.

The most commonly used definition of hardness of metals is: “The resistance of a metal to local plastic deformation that occurs when a harder body, such as the tip (indenter) of a testing device, is introduced into it.”

However, hardness can also have other manifestations such as stiffness, resistance to scratching, abrasion or cutting. The hardness of a metal gives it the ability to resist irreversible deformation—bending, breaking, or changing shape.

The greater the hardness of the metal, the greater its resistance to irreversible, for example, plastic deformation. This variety of manifestations of hardness also gives rise to a variety of methods for measuring it.

Hardness measurement using static indentation methods

To measure hardness, the most commonly used methods are static pressing of a ball, diamond cone or diamond pyramid into the material. These methods include: - Brinell method according to GOST 9012-59) - steel ball; - Rockwell method according to GOST 9013-59) - diamond cone; - Super-Rockwell method according to GOST 22975-78 - steel ball or diamond cone; - method Vickers according to GOST 2999-75 – diamond pyramid;

- microhardness testing method according to GOST 9450-75 - diamond pyramid.

Scratch hardness measurement

This is the oldest method for measuring hardness. This principle is the basis for the Mohs scratch testing of materials, which is used for minerals. In addition, GOST 21318-75 defines a method for measuring the microhardness of a material by scratching it - making a groove - with special diamond pyramids.

Impact imprint method according to GOST 18661-73

It is used for massive parts and structures when other methods cannot be used. Hardness is measured using a special device. A standard block of known hardness is placed in the device. The device is installed on the surface of the part being examined. When a hammer hits the top of the striker, a ball with a diameter of 10 mm is pressed simultaneously into the part and into the standard. By comparing the dimples on the part and the sample, the hardness of the part material is judged.

Method of elastic rebound of the striker (Shor method) according to GOST 23273-78

A special device is used - a scleroscope, inside which a striker with a diamond tip falls freely. Hardness measurement is carried out based on the rebound height of the striker.

Electromagnetic method for measuring steel hardness

This method is based on the dependence of the magnetic characteristics of steel on its structure. Since each steel structure corresponds to a certain hardness, a certain relationship can be established between the magnetic characteristics and hardness. These are less precise than mechanical methods and require a lot of experience to use. They are used for mass testing of the hardness of similar parts.

Ultrasonic method for measuring steel hardness

This method of hardness measurement is called the ultrasonic contact impedance method. The diamond pyramid is pressed against the test sample under constant force and elastic vibrations are excited. The lower the hardness of the sample, the more the indenter presses through its surface. Used to measure hardness in hard-to-reach places.

Source: http://otlivka.info/articles/%D0%B8%D0%B7%D0%BC%D0%B5%D1%80%D0%B5%D0%BD%D0%B8%D0%B5-% D1%82%D0%B2%D0%B5%D1%80%D0%B4%D0%BE%D1%81%D1%82%D0%B8-%D0%BC%D0%B5%D1%82%D0 %B0%D0%BB%D0%BB%D0%BE%D0%B2/

Hardness tests

CONTENT

Hardness is the property of a material to resist elastic and plastic deformation or destruction when another, harder body that does not receive residual deformation - an indenter - is introduced into the surface layer of the material.

Methods for determining hardness depending on the temporary nature of the application of load and measuring the resistance to indentation of the indenter are divided into:

• static
• dynamic
• kinetic

The most common are static methods, in which the load is applied to the indenter smoothly and gradually, and the holding time under load is regulated by standards for the corresponding methods.

In dynamic methods for determining hardness, the indenter acts on the sample with a certain kinetic energy expended on elastic recoil and/or the formation of an indent; dynamic hardness is often also called the hardness of the material upon impact. Impact hardness characterizes the resistance to penetration not only on the surface of the sample, but also in a certain volume of the material.

Kinetic methods for determining hardness are based on continuous recording of the process of indentation of the indenter with recording of the diagram “load on the indenter - depth of penetration of the indenter. The peculiarity of this approach is to record the entire kinetics of the process of elastoplastic deformation of the material during indentation of the indenter, and not just the final test result, as with other methods.

Based on the principle of load application, methods for determining hardness can be divided into indentation, rebound, scratching and cutting methods.

Indentation methods are the most common. Hardness in this case is defined as the resistance that the test body provides to the penetration of a harder indenter and primarily reflects the resistance of the surface layers of the material to plastic deformation.

Rebound methods are based on measuring hardness by the height of the rebound of the striker falling onto the test surface. In this case, hardness primarily reflects resistance to elastic deformation. Rebound hardness testing is widely used to control the quality of mill rolls, large products and structures using portable instruments.

Method for measuring hardness by scratching

In scratching and cutting methods, hardness is defined as the material's resistance to scratching or cutting, respectively. The scratching method was developed by Mohs at the beginning of the 19th century; they were given a scale of mineral hardness based on the ability of one to scratch the surface of another. This ten-point scale (from talc No. 1 to diamond No. 10) is used in mineralogy, as well as for assessing the hardness of technical ceramics and single crystals.

When determining hardness by all methods (except microhardness), the integral value of the material’s hardness (averaged for all structural components) is measured.

Hardness values ​​cannot be unambiguously translated into values ​​of other mechanical properties of the material. However, determining hardness is an effective way to compare materials of the same type with each other and control their quality.

Brinell hardness test

The Brinell hardness measurement method is regulated by GOST 9012.

When determining hardness by this method, a steel ball of a certain diameter D is pressed into the test sample under the action of a load P applied perpendicular to the surface of the sample for a certain time. After removing the load, the diameter of the indentation d is measured. The Brinell hardness number is designated by the letters HB and is determined by dividing the load P by the surface area of ​​the spherical imprint F.

For convenience, there are tables of Brinell hardness numbers and dependence on the ball diameter D, indent diameter d and load P.

Polished (Ra 

Source: https://HeatTreatment.ru/ispytaniya-na-tverdost

What is hardness and how to measure it?

Hardness is the property of a material to resist penetration of an indenter into its surface.

How is hardness measured?

There are two main ways to display the hardness of materials:

• in kilogram-force per square millimeter (kgf/mm2);
• may be designated by the letters HB (HBW), HRB, HRC, HV, HA, HD, HC, HOO, etc.

What methods can be used to measure hardness?

Currently, many methods have been developed for determining the hardness of metals, such as:

• measurement of hardness by indentation under the influence of a static load (according to the Brinell, Rockwell, Super-Rockwell, Vickers, M.S. Drozd, Hertz, Ludvik method, Shore monotron, Brinell press);
• hardness measurement by dynamic indentation (according to the Martel, Poldi method, Nikolaev's vertical impact tester, Schopper and Bauman's spring device, Walzel's pendulum impact tester, Shore's scleroscope, Herbert's pendulum, Kuznetsov's pendulum sclerometer);
• microhardness measurement by static indentation (using the method of Lips, Egorov, Khrushchev, Skvortsov, Alekhin, Ternovsky, Shorshorov, Berkovich, Knoop, Peters, Emerson, Zeiss-Hahnemann microhardness tester, etc.);
• hardness measurement by scratching (Barba file, Mohs, Martens, Hankins device, Bierbaum microcharacterizer, O'Neill sclerometer, Grigorovich, Berkovich).

Among all these methods, the most popular is the method of introducing an indenter under the influence of a static load. The main methods for measuring hardness are: Brinell, Rockwell, Vickers, Shora.

Hardness Testing Requirements

The most common method of measuring hardness has the following requirements:

• the measuring device must be reliable in design, easy to use, universal and applicable to all solids without exception, and the hardness measurement operation itself must be simple and fast;
• regardless of the amount of force applied or energy expended, the hardness value for a homogeneous body at a constant temperature must be a material constant;
• the surface of the sample and the method of its fastening must ensure reliable fixation and do not allow the sample to shift relative to the axis of application of the load;
• hardness must have a completely definite and clear physical meaning, and the correct dimension characterizing the resistance of the material to plastic deformation.

How to calculate the hardness of a material?

The higher the hardness, the higher the load required to determine its hardness. The more accurate the method, the higher the requirements for preparing the test surface of the material. Accordingly, we need to select a method for determining hardness that gives a minimum error with minimal damage to the surface and minimal costs for preparing the surface for testing.

How is the hardness of steel measured?

The most common way to determine the hardness of steel is to introduce an indenter under the influence of a static load using the Brinell, Rockwell, and Vickers methods (see Table 1). And each method has its own hardness measurement scale.

Table 1

Name of the devicePrinciple of operation and tip shapeExample of scale designationFormula for calculating hardnessIndenterScaleDesignation

Brinell device	Indentation of a hardened steel ball with a diameter of 1.25; 2.5; 5 or 10 mm, etc., with loads in the range from 1 to 62.5 kgf or from 62.5 to 3000 kgf into the flat surface of the test body	Carbide spherical indenter ⌀2.5 and force 187.5 kgf	HB(w)	HB(w) 2.5/187.5	Hardness is calculated along the diagonal of the print as the load divided by the surface area of ​​the print:, kgf/mm2
Rockwell and Super-Rockwell device

Source: https://metrotest.ru/article/tverdost

Rockwell hardness

The hardness of materials is an integrating indicator of their mechanical properties. There is an empirical correspondence between the hardness value and a number of mechanical properties (for example, compressive, tensile or bending strength).

With the development of mechanical engineering, the need arose to have general methods for measuring hardness. At the beginning of the 20th century, Professor Ludwig developed the theoretical part of the method for determining hardness with a diamond cone. In 1919, Hugh and Stanley Rockwell patented a hydromechanical device, which was named the Rockwell hardness tester.

The relevance of this device is caused by the need to use non-destructive methods of hardness control in the bearing industry. The existing Brinell (HB) method is based on measuring the indentation area of ​​a 10 mm diameter ball.

The imprint is formed using a ball of hardened steel or tungsten carbide, which is pressed into the sample with a certain force. The Brinell method is used to determine the hardness of non-ferrous metals or low-alloy steels and is not applicable to hardened steel samples.

 This is due to the fact that the working load is 3000 kgf. The ball is deformed, so the Brinell method cannot be considered a non-destructive testing method.

Rockwell hardness test method

Hardness is a characteristic of a material that is opposite to plasticity, the ability of a material to “flow” under load. The Rockwell hardness measurement technique is intended for non-destructive testing of the hardness of the least ductile materials - steels and their alloys.

The versatility of the method lies in the presence of three hardness scales, which are calibrated for measurement under one of three loads (60, 100 and 150 kgf) to work with one of the measuring heads.

A diamond cone with an angle of 120° and an apex radius of 0.2 mm or a hardened ball with a diameter of 1/16“ (1.588 mm) is used as the working body of the measuring head.

The method is based on recording the direct measurement of the depth of penetration of a solid body by a measuring head (indenter) into the sample material. The depth of the indentation characterizes the ability of the material to resist external influences without forming a roll of displaced metal around the indenter.

The Rockwell hardness unit is a dimensionless value, which is expressed in conventional units up to 100. The displacement of the indenter by 0.002 was taken as a unit of hardness.

Metal hardness according to Rockwell: table

The table was created for a visual comparison of the Rockwell and Brinell methods.

According to Rockwell	According to Brinell
HRACone 120° load. 60 kgf	HRCone 120° loaded 150 kgf	HRB Ball Ø 1.58 mm load. 100 kgf	Diameter of printsmm	HBball Ø 10 mmload. 3000 kgf
84,5	65	—	2,34	688
83,5	64	—	2,37	670
83	63	—	2,39	659
82,5	62	—	2,42	643
82	61	—	2,45	627
81,5	60	—	2,47	616
81	59	—	2,5	601
80,5	58	—	2,54	582
80	57	—	2,56	573
79	56	—	2,6	555
79	55	—	2,61	551
78,5	54	—	2,65	534
78	53	—	2,68	522
77,5	52	—	2,71	510
76	51	—	2,75

Source: https://www.equipnet.ru/articles/tech/tech_54357.html

How to determine the hardness of a metal at home - Metals, equipment, instructions

Mechanical engineering parts and mechanisms, as well as tools intended for their processing, have a set of mechanical characteristics. Hardness plays a significant role among the characteristics. The hardness of metals clearly shows:

• wear resistance of metal;
• possibility of processing by cutting, grinding;
• resistance to local pressure;
• ability to cut other materials and others.

Hardness of metals

In practice, it has been proven that most of the mechanical properties of metals directly depend on their hardness.

Hardness concept

The hardness of a material is its resistance to destruction when a harder material is introduced into the outer layer. In other words, the ability to resist deforming forces (elastic or plastic deformation).

The hardness of metals is determined by introducing a solid body called an indenter into a sample. The role of the indenter is performed by: a metal ball of high hardness; diamond cone or pyramid.

After exposure to the indenter, an imprint remains on the surface of the test sample or part, the size of which determines the hardness. In practice, kinematic, dynamic, and static methods of measuring hardness are used.

The kinematic method is based on the compilation of a diagram based on continuously recorded readings that change as the tool is pressed into the sample. Here the kinematics of the entire process is traced, and not just the final result.

The dynamic method is as follows. The measuring tool acts on the part. The reverse reaction allows you to calculate the expended kinetic energy. This method allows you to test the hardness of not only the surface, but also a certain volume of metal.

Static methods are non-destructive methods that allow you to determine the properties of metals. The methods are based on smooth indentation and subsequent holding for some time. The parameters are regulated by methods and standards.

The applied load can be applied:

• pressing;
• scratching;
• cutting;
• rebound

Machine-building enterprises currently use the Brinell, Rockwell, Vickers methods, as well as the microhardness method, to determine the hardness of materials.

Based on the tests carried out, a table is compiled indicating the materials, the applied loads and the results obtained.

Hardness Units

Each method of measuring the resistance of a metal to plastic deformation has its own methodology, as well as units of measurement.

The hardness of soft metals is measured using the Brinell method. Non-ferrous metals (copper, aluminum, magnesium, lead, tin) and alloys based on them, cast iron (except for white) and annealed steel are subjected to this method.

Brinell hardness is determined by indentation of a hardened, polished ball made of ShKh15 ball bearing steel. The circumference of the ball depends on the material being tested. For hard materials - all types of steel and cast iron - 10 mm, for softer materials - 1 - 2 - 2.5 - 5 mm. Required load applied to the ball:

• iron alloys – 30 kgf/mm2;
• copper and nickel – 10 kgf/mm2;
• aluminum and magnesium – 5 kgf/mm2.

The unit of hardness measurement is a numerical value followed by a numerical index HB. For example, 200 NV.

Rockwell hardness is determined by the difference in applied loads to the part. First, a preliminary load is applied, and then a general load, at which the indenter is introduced into the sample and held.

A pyramid (cone) of diamond or a ball of tungsten carbide (hardened steel) is introduced into the test sample. After removing the load, the depth of the indentation is measured.

The unit of measurement for hardness is conventional units. It is generally accepted that one is the amount of axial displacement of the cone, equal to 2 μm. The hardness designation is marked with three letters HR (A, B, C) and a numerical value. The third letter in the marking indicates the scale.

The technique reflects the type of indenter and the load applied to it.

Scale type	Tool	Applied load, kgf
A	Diamond cone with 120° apex angle	50-60
IN	1/16" ball	90-100
WITH	Diamond cone with 120° apex angle	140-150

Basically, measurement scales A and C are used. For example, the hardness of steel is HRC 2632, HRB 2529, HRA 7075.

Products of small thickness or parts with a thin, hard surface layer are measured by Vickers hardness. The blade used is a regular tetrahedral pyramid with an apex angle of 136°. The display of hardness values ​​is as follows: 220 HV.

Hardness measurement using the Shore method is carried out by measuring the rebound height of a fallen striker. Indicated by numbers and letters, for example, 90 HSD.

Microhardness is determined when it is necessary to obtain the values ​​of small parts, thin coatings, or individual alloy structures. The measurement is made by measuring the imprint of a tip of a certain shape. The value notation looks like this:

Н□ 0.195 = 2800, where

□ — tip shape;

0.196 — tip load, N;

2800 – numerical value of hardness, N/mm2.

Hardness of base metals and alloys

The hardness value is measured on finished parts sent for assembly. Control is carried out for compliance with the drawing and technological process. Tables of hardness values ​​have already been compiled for all basic materials, both in the initial state and after heat treatment.

Non-ferrous metals

The Brinell hardness of copper is 35 HB, the values ​​of brass are 42-60 HB units, depending on its brand. For aluminum, the hardness is in the range of 15-20 HB, and for duralumin it is already 70 HB.

Black metals

The Rockwell hardness of cast iron SCH20 HRC 22, which corresponds to 220 HB. Steel: tool – 640-700 HB, stainless steel – 250 HB.

To convert from one measurement system to another, tables are used. The values ​​in them are not true, because they are derived imperially. Not the full volume is presented in the table.

HB	H.V.	H.R.C.	HRA	HSD
228	240	20	60.7	36
260	275	24	62.5	40
280	295	29	65	44
320	340	34.5	67.5	49
360	380	39	70	54
415	440	44.5	73	61
450	480	47	74.5	64
480	520	50	76	68
500	540	52	77	73
535	580	54	78	78

Hardness values, even if produced by the same method, depend on the applied load. The lower the load, the higher the readings.

Hardness measurement methods

All methods for determining the hardness of metals use mechanical action on the test sample - indentation of an indenter. But this does not destroy the sample.

The Brinell hardness method was the first to be standardized in materials science. The principle of testing samples is described above. It is subject to GOST 9012. But you can calculate the value using the formula if you accurately measure the imprint on the sample:

HB=2P/(πD*√(D2-d2),

• where P – applied load, kgf;
• D – ball circumference, mm;
• d – circumference of the imprint, mm. The ball is selected relative to the thickness of the sample. The load is pre-calculated from accepted standards for the relevant materials: iron alloys - 30D2; copper and its alloys - 10D2; babbits, lead bronze - 2.5D2.

Symbol of the test principle

Download GOST 9012-59

Schematically, the Rockwell research method is depicted as follows according to GOST 9013.

  How to cut tempered glass at home

Rockwell hardness test method

The final applied load is equal to the sum of the initial load and that required for the test. The device indicator shows the difference in penetration depth between the initial load and the test load h –h0.

Download GOST 9013-59

The Vickers method is regulated by GOST 2999. It is schematically depicted as follows.

Vickers method

Mathematical formula for calculation: HV=0.189*P/d2 MPaHV=1.854*P/d2 kgf/mm2

The applied load varies from 9.8 N (1 kgf) to 980 N (100 kgf). The values ​​are determined from the tables relative to the measured print d.

Shore method

The Mohs hardness of metals and alloys can be measured by scratching. Mohs at one time proposed making scratches on the surface of an object with a harder mineral. He classified known minerals by hardness into 10 positions. The first is occupied by talc, and the last by diamond.

After measurement using one method, transfer to another system is very conditional. Clear values ​​exist only in the Brinell and Rockwell hardness ratios, since machine-building enterprises widely use them. The dependence can be observed when the diameter of the ball changes.

d, mm	HB	HRA	H.R.C.	HRB
2,3	712	85,1	66,4	—
2,5	601	81,1	59,3	—
3,0	415	72,6	43,8	—
3,5	302	66,7	32,5	—
4,0	229	61,8	22	98,2
5,0	143	—	—	77,4
5,2	131	—	—	72,4

As can be seen from the table, increasing the diameter of the ball significantly reduces the readings of the device. Therefore, machine-building enterprises prefer to use measuring instruments with the same type of indenter size.

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Source: https://spb-metalloobrabotka.com/kak-opredelit-tverdost-metalla-v-domashnih-usloviyah/

How to determine the hardness of a metal - Metalworker's Handbook

Mechanical engineering parts and mechanisms, as well as tools intended for their processing, have a set of mechanical characteristics. Hardness plays a significant role among the characteristics. The hardness of metals clearly shows:

• wear resistance of metal;
• possibility of processing by cutting, grinding;
• resistance to local pressure;
• ability to cut other materials and others.

Hardness of metals

In practice, it has been proven that most of the mechanical properties of metals directly depend on their hardness.

Hardness of metals

Mechanical engineering parts and mechanisms, as well as tools intended for their processing, have a set of mechanical characteristics. Hardness plays a significant role among the characteristics. The hardness of metals clearly shows:

• wear resistance of metal;
• possibility of processing by cutting, grinding;
• resistance to local pressure;
• ability to cut other materials and others.

Hardness of metals

In practice, it has been proven that most of the mechanical properties of metals directly depend on their hardness.

How to test the hardness of metal - the main secrets

When it comes to metals, an important indicator is its hardness. A factor of this kind plays a significant role in the choice of whether or not to use a particular metal in production for the manufacture of products for a specific purpose. It is worth understanding this issue in more detail, which requires testing the hardness of metal in the production line of various industries.

What is metal hardness

This concept refers to a characteristic closely related to metals and their alloys. This is the ability to resist damage when the top layer is synchronized with a harder metal. Based on this knowledge, various equipment and parts are manufactured that play a role in the durability of objects, structures, machines, and tools. Simply put, resistance to deformation. You can check this parameter in different ways.

Methods for testing metal hardness

Experts distinguish several options for checking characteristics:

• According to the Brinnell method, a steel ball takes part in the verification process. It is pressed under great pressure into a metal surface. Then a special magnifying glass comes into effect, and with its help the specialist measures the diameter of the hole. Hardness is determined from tabular data. This method is the first method for determining the nature of the metal. This is how soft alloys are measured.
• Rockwell's technique involves impacting a metal surface with a diamond cone. A special press is used to measure the hardness of soft, colored, thin Me. It is not considered very accurate, although it is successfully used for the study of hard alloys.
• Similar actions to the previous one are included in the Vikxer method, which involves turning to a diamond pyramid, only the angle of the top is not 120, but 136 degrees. The load is carried out strictly perpendicular to the metal and increases slowly. Refers to high-precision methods.
• Shore's method involves the presence of a striker with a diamond-coated tip. It falls from a specific height onto the surface of the material being tested. Hardness is measured by the height of the striker's rebound. This methodology is distinguished by a large scatter of readings; for the most part it is used to measure curved objects and large parts.

At home, the indicator is also measured, but you should not expect high accuracy. When you turn to professionals, you can get a highly accurate result, and this is a crucial moment. Some conduct home education to determine this value, using an ordinary bottle and scratching it with a metal object, for example, a knife blade. Metal of 62 units easily scratches glass, which cannot be said about 56 units.

What does the hardness of the metal indicate, what does it give

The question arises as to why this parameter needs to be measured at all. The characteristics of metals are important to those involved in the steel heat treatment industry. The conclusion about the mechanical properties of the weld is also obtained by studying the heat-affected surface.

The feasibility of the research being carried out is also predetermined by the intention of manufacturers to obtain high-strength products so that they can withstand different operating conditions, temperature changes, and ensure reliability. The hardness of a metal product is a primary structural characteristic.

Research is carried out with the following objectives.

• Analyze the state of the material under the influence of time.
•  Obtain knowledge of likely destructive consequences to improve operational capabilities.
• Monitor the results obtained as part of the temperature treatment.

According to the information acquired during the experiments, it is possible to determine the resistance to abrasion and wear of the source material.

Conclusion

To carry out the analysis, certain conditions are imposed on the material being tested. In particular, the workpiece is selected to be even. It should fit tightly to the hardness tester, with carefully processed edges. As a result, fundamental mechanical quality is achieved, which plays a role in the production of high-quality products.

Specialists use the results obtained during the study, compare them with previously known analysis, and this is a lot of work that helps determine the production method. Information is necessary for mechanical engineering, metalworking, and metallurgical enterprises. The concept of “hardness” is associated with elasticity, plasticity, and strength, although there is no direct connection between mechanical qualities.

It is important to turn to professionals to perform such work; the home method is only suitable for tasks of hardening knives.

Source: http://rosgranitsa.ru/stroitelstvo/raznoe-2/kak-proverit-tverdost-metalla-glavnye-sekrety/

How is the hardness of a metal measured?

The hardness of a metal is its property of resisting plastic deformation during the contact action of a standard tip body on the surface layers of the material.

Hardness testing is the main method for assessing the quality of heat treatment of a product.

Determination of hardness using the Brinell method . The method is based on inserting a steel ball into a flat surface under load. The hardness number HB is determined by the ratio of the load to the spherical surface of the indentation.

The Rockwell (HR) method is based on statically pressing a tip into the test surface under a certain load. Steel balls are used as tips for materials with hardness up to 450 HR. In this case, the hardness is designated as HRB . When using a diamond cone, hardness is designated as HRA or HRC (depending on load).

Vickers hardness (HV) is determined by statically pressing a diamond tetrahedral pyramid into the test surface. During the test, the indentation is measured with an accuracy of 0.001 mm using a microscope, which is an integral part of the Vickers instrument.

Shor's method . The essence of this method is to determine the hardness of the sample material by the height of the rebound of the striker falling onto the surface of the test body from a certain height. Hardness is assessed in conventional units proportional to the height of the striker's rebound.

Methods for determining metal hardness

Hardness is the ability of a metal to resist the penetration of another, harder body into it.

The hardness of a metal is a very important characteristic, since it is closely related to such basic characteristics of metals and alloys as strength, wear resistance, etc.

Currently, there are many ways to determine the hardness of metals. Let's look at some of them that are most widely used in industry.

Determination of hardness by indentation of a steel ball (Brinell method)

The steel ball, made from hardened ball bearing steel, is pressed into the metal surface under force.

Using a special magnifying glass, the diameter of the hole is measured. The HE hardness value is determined from the tables attached to the device.

For testing, a special Brinell type press is used, the appearance of which is shown in the figure.

Steel ball is fixed in a mandrel2.

The sample under study is placed on the stage 1 and raised to the ball by the steering wheel 4.

When the motor 5 the weights of the press 3 are lowered and press the steel ball into the sample.

For steel, the hardness value determined by this method is related to the tensile strength ratio, which is sometimes used in practice:

Determination of hardness by the depth of indentation of a diamond cone (Rockwell method)

A diamond cone with an apex angle of 120° is pressed into the metal with a preliminary constant load of 10 kg, and then with a shelf load of 60 or 150 kg.

For testing, a special press is used, the appearance of which is shown in Fig. 25.

The diamond cone is mounted in a mandrel 4.

The sample is installed on table 3 and raised using steering wheel 2 to a load of 10 kg.

Handle 1 releases weights 6 , which create a force to press the cone into the metal. Depth of indentation, i.e. hardness value, indicated by indicator 5.

The hardness values ​​by this method are determined by the difference in the depth of indentation of the diamond cone under the action of full and preliminary loads.

The harder the metal, the less depth the diamond penetrates when pressed, the higher the hardness number will be.

The standard load for this method is 150 kg.

Hardness is designated H RC . In some cases, for example, when measuring hardness on a thin sample or when measuring the hardness of the surface layer of a metal, a load of up to 60 kg is applied.

Hardness measurement of soft materials

The same device can be used to measure the hardness of soft materials (non-ferrous metals, annealed steel).

In this case, a hardened steel ball with a diameter of 1.59 mm (1/16") is used. The standard load is 100 kg, and the hardness value is indicated by the HRB index.

Determination of hardness by dynamic indentation of a ball

When changing the hardness of massive parts and structures , when the devices described above cannot be used, use a portable device shown in the figure:

A reference sample 1 is placed into the device. When the device is struck with a hammer, a special ball 2 makes imprints on the object under study and on the reference sample, the hardness of which is known.

By comparing the values ​​of the diameters of the holes of the sample and the part according to the tables, the hardness of the part is determined.

Determination of hardness by the elastic recoil method

In cases where it is impossible to use indentation methods, so as not to spoil the surface of the product, a device is used that determines the hardness of the metal using the elastic recoil method.

The figure shows the appearance of the device:

A striker of a certain weight falls onto the metal from a constant height and bounces off . Hardness is judged by the magnitude of the rebound. The greater the hardness, the greater the rebound of the striker.

The productivity of this test method is very high (several hundred measurements per hour). However, it can only be used to compare the hardness of products made from the same metal or from metals that have the same elastic properties.

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Source: http://www.Conatem.ru/tehnologiya_metallov/metody-opredeleniya-tverdosti-metalla.html