Common terms-yield point, specified residual elongation stress and specified non-proportional elongation stress

Yield point (physical yield strength):

Code name: σ s; Unit: MPa (or Newton/mm2)

Introduction: It refers to the ability of metal materials to resist external forces when their deformation (elongation) suddenly increases to a certain extent.

B specified residual elongation stress (yield strength, conditional yield strength):

Code name: σ r; Unit: MPa (or Newton/mm2)

Introduction: It refers to the time when the residual elongation of the gauge reaches the specified value after the metal material is removed from the drawing.

Stress; When the specified value is 0.2%, its code name is σ r0.2.

C specifies the non-proportional elongation stress:

Code name: σ p; Unit: MPa (or Newton/mm2)

Brief introduction: refers to the stress when the non-proportional extension of standard pitch reaches the specified value during the stretching process of metal materials; When the specified value is 0.0 1%, its code is written as σp0.0 1.

Commonly used terms-hardness

Brief introduction: the ability of materials to resist hard objects pressing into their surfaces. According to the different determination methods, hardness is divided into the following categories:

Brinell hardness:

Code name: HBS (determination of hardened steel balls) or HBW (determination of cemented carbide balls), also commonly known as HB;

Unit: None

Introduction: Press the hardened steel ball or cemented carbide ball with a certain diameter into the surface of the material under a certain load, keep it for a specified time, then unload the load, measure the indentation on the surface of the material, and then calculate the hardness according to the formula.

Rockwell hardness:

Code name: HR

Unit: None

Introduction: Press the hardened steel ball or tapered diamond press with the vertex angle of 1200 into the surface of the material under a certain load, and then calculate the hardness according to the depth of the pit on the surface of the material.

Rockwell hardness has many scales, and the common ones are:

A. scale c: code HRC. Used to measure the hardness of hardened and tempered steel and hardened steel with total load of1471n (150kgf), diamond press.

B. Scale A: code HRA, used to measure the hardness of surface hardened steel, carburized steel or cemented carbide, with a total load of 588.4N(60 kgf) and a diamond press.

Class C.B: code HRB, hardness is obtained by using a hardened steel ball press with a total load of 980.7N( 100 kgf) and a diameter of1.588 mm. It is suitable for hardness measurement of soft materials such as nonferrous metals, annealed steel and normalized steel.

Surface Rockwell hardness:

Code name: HR

Unit: None

Introduction: The testing principle is the same as Rockwell hardness. It is suitable for measuring the hardness of carburized and nitrided steel surfaces, and also for measuring the hardness of brand steel plates and non-ferrous metals. This hardness also has many scales:

A. Ruler 15N: code HR 15N, hardness calculated by total load147.1n (15kgf) and diamond press.

B. Ruler 30N: code name HR30N. The hardness is obtained with a total load of 294.2N(30 kgf) and a diamond press.

C.Gauge 45N: code name HR45N. The hardness was obtained with a total load of 44 1.3N(45 kgf) and a diamond press.

D scale 15T: code HR 15T, and hardness obtained by using147.1n (15kgf) total load and 1.588mm diameter hardened steel ball press.

E. Scale 30T: code name HR30T. The hardness was obtained by using a hardened steel ball press with a total load of 294.2N(30 kgf) and a diameter of1.588 mm.

F. Gauge 45T: code HR45T. The hardness was obtained by using a hardened steel ball press with a total load of 294.2N(45 kgf) and a diameter of1.588 mm.

Vickers hardness:

Code name: HV

Unit: None

Brief introduction: under the load of 49.03~980.7N, the square-cone diamond with the diagonal of1360 is pressed into the surface of the blank, and the diagonal length of the indentation is measured after the specified time, and then the hardness is calculated according to the formula. It is suitable for hardness measurement of larger workpieces and deeper surface layers. Vickers hardness still has small load Vickers hardness, and the test load is 1.95438+0 ~ < 49.03N, which is suitable for hardness measurement of thin workpieces, tool surfaces or coatings. Microvickers hardness, test load

Common terms-strength limit (strength)

Code name: σ; Unit: MPa (or Newton/mm2)

Description: It refers to the maximum ability of metal materials to resist external damage. According to the different forms of external forces, forces are divided into:

Compressive strength: code σbc refers to the strength limit when external force is pressure.

Bending strength: code σbb refers to the strength limit when the external force is perpendicular to the axis of the material and bends the material after the action.

Shear strength: code σc refers to the strength limit when the external force is perpendicular to the axis of the material and produces shear effect on the material.

Tensile strength: code: σb, which refers to the strength limit when the external force is tensile force.

Commonly used terms-elastic limit, elongation and area shrinkage

elastic limit

Code name: σ e; Unit: MPa (or Newton/mm2)

Introduction: When the external force (tensile force) of metal material reaches a certain limit, if the external force is removed, its deformation (elongation) will disappear and return to its original state. Elastic limit refers to the ability of metal materials to resist this external force limit.

B elongation (elongation)

Code name: δ; Unit:%

Description: refers to the percentage of elongation of the test bar to the original length when the metal material breaks under the action of external force (tension). According to the different lengths of test bars, the elongation is divided into: the elongation obtained by short test bars, code Δ 5; the standard distance of test bars is equal to the elongation obtained by test bars with 5 times diameter, code Δ 10; and the standard distance of test bars is equal to10 times diameter.

Cesarean section contraction (contraction rate)

Code name: ψ; Unit:%

Brief introduction: It refers to the percentage of the reduced cross-sectional area to the original cross-sectional area when the metal material breaks under the tensile force.

General terms-impact absorption work and impact toughness

Impact absorption work (impact work):

Code name: Ak

Unit: j

Brief introduction: the work absorbed by a material sample with a certain shape and size when it is broken under impact load.

Impact toughness (impact value):

Code name: аk

Unit: Joule/cm2

Introduction: the quotient obtained by dividing the impact absorption work by the cross-sectional area of the bottom of the sample notch.

Note: the impact energy and impact value obtained from Charpy U-notch samples are coded as AkU, respectively; The impact energy and impact value obtained from Charpy V-notch samples are coded as AKV and аkV respectively.