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Steel products mechanical property introduction
1. yield point (σs)
Steel products or test specimen when stretch, when the stress surpasses the limit of elasticity, even if the stress no longer increases, but the steel products or the test specimen still continued to have the obvious plastic deformation, called this phenomenon to submit, but produces submits time the phenomenon minimum stress value is the yield point.
Supposes Ps is the yield point s place external force, Fo is the test specimen sectional area, then yield point σs =Ps/Fo(MPa), MPa is called the megabar to be equal to N (Newton) /mm2, (MPa=106Pa, Pa: Pascal =N/m2)
2. yield strength (σ0.2)
Some metallic material submits the point pole not to be obvious, has the difficulty in the survey, therefore to weigh the material to submit the characteristic, stipulated that has the permanent remaining plastic deformation to be equal to certain value (as original length 0.2% the time stress, is called the condition yield strength or the abbreviation yield strength generally) σ0.2.
3. tensile strength (σb)
The biggest stress value which the material when the stretch process, from starts to have break achieves. It expresses the steel products resistance break ability size. Corresponding also has the compressive strength, the bending strength with the tensile strength and so on.
Before supposing Pb is the material the most high tension which pulls, achieves, Fo is the test specimen cross sectional area, then tensile strength σb= Pb/Fo (MPa).
4. elongation ratio (δs)
Material after abruption, its plastic elongated length and the original sample length's percentage is called the elongation ratio or the elongation ratio.
5. tensile ratio (σs/σb)
The steel products yield point (yield strength) with tensile strength ratio, is called the tensile ratio. The tensile ratio is bigger, constructional detail's reliability is higher, generally the carbon steel tensile ratio is 0.6-0.65, the low-alloy structural steel is 0.65-0.75 alloy structural steel is 0.84-0.86.
6. degree of hardness
Degree of hardness expressed that the material resistance hard object body presses in its superficial ability. It is one of metallic material important performance indices. Generally degree of hardness is higher, the resistance to wear is better. The commonly used degree of hardness target has the Brinell hardness, Luo river degree of hardness and vickers hardness.
⑴Brinell hardness (HB)
Take certain load (of general 3000kg) certain size (diameter generally as 10mm) the hard steel ball presses in the material surface, maintains period of time, after carries, ratio of load and its indentation area, namely for Brinell hardness value (HB), unit for kilogram strength /mm2 (N/mm2).
⑵Luo river degree of hardness (HR)
When HB>450 or the test specimen are too small, cannot use the Brinell hardness experiment to change to the Rockwell tester quantity. It is with a support angle 120° diamond cone or the diameter is 1.59, 3.18mm steel balls, presses under certain load is measured the material surface, extracts the material by the indentation depth degree of hardness. According to the experimental material degree of hardness's difference, divides three kind of different scales to indicate:
HRA: Is uses the 60kg load and drills degree of hardness which the coup-de-poing presses in obtains, uses in the degree of hardness extremely high material (for example hard alloy and so on).
HRB: Is uses the 100kg load and the diameter 1.58mm hard steel ball, obtains degree of hardness, uses in the degree of hardness low material (for example annealed steel, cast iron and so on).
HRC: Is uses the 150kg load and drills degree of hardness which the coup-de-poing presses in obtains, uses in the degree of hardness very high material (for example chilled steel and so on).
⑶Vickers hardness (HV)
Take 120kg in load and support angle as 136° the diamond square shape awl presses in presses in the material surface, divides the load value with the material indentation pit's surface area, namely for vickers hardness value (HV)
