Значение и использование
Ductile vs. Brittle Behavior—Body-centered-cubic or ferritic alloys exhibit a significant transition in behavior when impact tested over a range of temperatures. At temperatures above transition, impact specimens fracture by a ductile (usually microvoid coalescence) mechanism, absorbing relatively large amounts of energy. At lower temperatures, they fracture in a brittle (usually cleavage) manner absorbing appreciably less energy. Within the transition range, the fracture will generally be a mixture of areas of ductile fracture and brittle fracture.
The temperature range of the transition from one type of behavior to the other varies according to the material being tested. This transition behavior may be defined in various ways for specification purposes.
The specification may require a minimum test result for absorbed energy, fracture appearance, lateral expansion, or a combination thereof, at a specified test temperature.
The specification may require the determination of the transition temperature at which either the absorbed energy or fracture appearance attains a specified level when testing is performed over a range of temperatures. Alternatively the specification may require the determination of the fracture appearance transition temperature (FATTn) as the temperature at which the required minimum percentage of shear fracture (n) is obtained.
Further information on the significance of impact testing appears in Annex A5.
1.1 These test methods cover procedures anddefinitions for the mechanical testing of steels, stainless steels,and related alloys. The various mechanical tests herein describedare used to determine properties required in the productspecifications. Variations in testing methods are to be avoided,and standard methods of testing are to be followed to obtainreproducible and comparable results. In those cases in which thetesting requirements for certain products are unique or at variancewith these general procedures, the product specification testingrequirements shall control.
1.2 The following mechanical tests aredescribed:
|Tension||5 to 13|
|Impact||19 to 28|
1.3 Annexes covering details peculiar to certainproducts are appended to these test methods as follows:
|Tubular Products||Annex A2|
|Round Wire Products||Annex A4|
|Significance of Notched-Bar ImpactTesting||Annex A5|
|Converting Percentage Elongation ofRound Specimens to|
Equivalents for Flat Specimens
|Testing Multi-Wire Strand||Annex A7|
|Rounding of Test Data||Annex A8|
|Methods for Testing Steel ReinforcingBars||Annex A9|
|Procedure for Use and Control ofHeat-Cycle Simulation||Annex A10|
1.4 The values stated in inch-pound units are to beregarded as the standard.
1.5 When this document is referenced in a metricproduct specification, the yield and tensile values may bedetermined in inch-pound (ksi) units then converted into SI (MPa)units. The elongation determined in inch-pound gauge lengths of 2or 8 in. may be reported in SI unit gauge lengths of 50 or 200 mm,respectively, as applicable. Conversely, when this document isreferenced in an inch-pound product specification, the yield andtensile values may be determined in SI units then converted intoinch-pound units. The elongation determined in SI unit gaugelengths of 50 or 200 mm may be reported in inch-pound gauge lengthsof 2 or 8 in., respectively, as applicable.
1.6 Attention is directed to ISO/IEC 17025 whenthere may be a need for information on criteria for evaluation oftesting laboratories.
1.7 This standard does notpurport to address all of the safety concerns, if any, associatedwith its use. It is the responsibility of the user of this standardto establish appropriate safety and health practices and determinethe applicability of regulatory limitations prior touse.