Common terms of the hottest steel II

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Commonly used terms for steel (II)

2, yield strength (0.2)

some metal materials have very low yield point, so it is difficult to measure. Therefore, in order to measure the yield characteristics of materials, it is required to specify the stress when the permanent residual plastic deformation is equal to a certain value (generally 0.2% of the original length), which is called conditional yield strength or yield strength 0.2 for short

3. Tensile strength (b)

the maximum stress value of the material from the beginning to the time of fracture during the tensile process. It indicates the ability of steel to resist fracture. The compressive strength and bending strength are corresponding to the tensile strength

if Pb is the maximum tensile force reached before the material is broken, and fo is the cross-sectional area of the sample, then the tensile strength b= pb/fo (MPA)

11. Host type: portal frame structure 4. Elongation (s)

the percentage of the length of plastic elongation of the material after breaking and the length of the original sample is called elongation or elongation

5. Yield ratio (s/b)

the ratio of yield point (yield strength) to tensile strength of steel. The instantaneous rotation center will be accompanied by sliding, which is called yield ratio. The greater the yield ratio, the higher the reliability of structural parts. Generally, the yield ratio of carbon steel is 0 65, 0 for low alloy structural steel 75 alloy structural steel is 0 86。

6 and for storing microorganisms, hardness

hardness indicates the ability of a material to resist hard objects pressing into its surface. It is one of the important performance indexes of metal materials. Generally, the higher the hardness, the better the wear resistance. Common hardness indicators include Brinell hardness, Rockwell hardness and Vickers hardness

⑴ Brinell hardness (HB)

press a hardened steel ball of a certain size (usually 10mm in diameter) into the material surface with a certain load (usually 3000kg) for a period of time. After the load is removed, the ratio between the load and its indentation area is the Brinell hardness value (HB), and the unit is kilogram force/mm2 (n/mm2)

⑵ Rockwell hardness (HR)

when HB 450 or the sample is too small, the Brinell hardness test cannot be used and the Rockwell hardness measurement is used instead. It uses a diamond cone with a vertex angle of 120 or a steel ball with a diameter of 1.59 and 3.18mm to press into the surface of the tested material under a certain load, and the hardness of the material is calculated from the depth of the indentation. According to the hardness of test materials, there are three different scales:

hra: it is the hardness obtained by using 60kg load and diamond cone indenter, which is used for materials with extremely high hardness (such as cemented carbide)

hrb: the hardness obtained by using 100kg load and 1.58mm diameter hardened steel ball is used for materials with low hardness (such as annealed steel, cast iron, etc.)

hrc: refers to the hardness obtained by using 150kg load and diamond cone press, which is used for materials with high hardness (such as quenched steel)

⑶ Vickers hardness (HV)

with a load within 120kg and a diamond square cone with a vertex angle of 136, press the small thing into the material surface as a big dryer, and divide the surface product of the material indentation pit by the load value, that is, the Vickers hardness value (HV)

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