SPECIFICATION FOR THROUGH-THICKNESS TENSION TESTING OF STEEL PLATES FOR SPECIAL APPLICATIONS
(Identical with ASTM Specification A770/A770M-2010 except for editorial correction to Table 2.)
1. Scope
1.1 This specification covers the procedures and acceptance standards for the determination of reduction of area using a unified test specimen whose axis is perpendicular to the rolled surfaces of steel plates 1 in. [25 mm] and greater in thickness. The primary purpose of this testing is to obtain a measure of the resistance of a steel plate to lamellar tearing.
1.2 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.
1.3 This specification is expressed in both inch-pound and SI units. However, unless the order specifies the applicable "M" specification designation (SI units), the material shall be furnished to inch-pound units.
2. Referenced Documents
2.1 ASTM Standards:
- A370 Test Methods and Definitions for Mechanical Testing of Steel Products
3. Ordering Information
3.1 The inquiry and order shall include the following if applicable:
3.1.1 Supplementary requirements that are desired (see S1 through S5).
3.1.2 Special requirements agreed upon between the manufacturer and the purchaser.
4. Tension Tests
4.1 Number of Tests
4.1.1 Two tests shall be required from each plate-as-heat-treated lot. When plates are heat treated individually, two tests shall be required from each plate. The tests shall be representative of the plate in its final condition.
4.1.2 When plates are furnished by the manufacturer in anunheat-treated condition and qualified by heat-treated speci-mens(including normalized,normalized and tempered, andquenched and tempered), two tests shall be required from eachplate-as-rolled.
NoTE 1-The term “plate-as-rolled' refers to the unit plate rolled from a slab or directly from an ingot, It does not refer to the condition of the plate.
4.2 Location of Test Coupons
4.2.1 The term "plate-as-heat-treated lot" refers to all plates of the same nominal thickness in the same heat treated at the same time in the same furnace, or in a different furnace to the same cycle.
4.2.2 Location of Test Coupons—Test coupons shall be taken from each end of each plate tested in accordance with 4.1. The test coupon shall be of sufficient size to provide the required test specimens.
4.3 Orientation of Test Specimens
4.3.1 The longitudinal axis of the reduced section of the test specimen shall be perpendicular to the rolled surface of the plate.
4.4 Preparation of Test Specimens
4.4.1 Attached Prolongations
When required, plate welded prolongations may be attached to the test specimen. The axis of the prolongation shall be in the same direction as the longitudinal axis of the specimen. Shielded metal arc, flux cored arc, or electron-beam welding processes may be used for the attachment.
4.4.2 Standard Test Specimens
4.4.2.1 Three types of standard cylindrical tension test specimens are shown in Fig. 1 and Table 1. For Types 1 and 2 specimens, the length of the reduced section shall be approximately equal to the nominal plate thickness. For Type 3 specimens, the specimen diameter is fixed at 0.500 in. [12.5 mm]. The length of the reduced section should be at least 2D for plates thicker than 2 in. [50 mm] as shown in Fig. 1. For plates less than 1 in. [25 mm] in thickness, use the 0.500-in. [12.5 mm] Type 1 specimen or the 0.500-in. [12.5 mm] Type 2 specimen.
| Specimen Type | |||
|---|---|---|---|
| 1 | 2 | 3 | |
| Plate thickness (t) | 1 ≤ t ≤ 1¼ | 1 < t ≤ 2 | 2 < t |
| Diameter (D) | 0.350 [8.75] | 0.500 [12.5] | 0.500 [12.5] |
| Radius, minimum (R) | ¼ [6] | ⅜ [10] | ⅜ [10] |
| Length of reduced section (A) | 1¾ [45] | 2¼ [60] | 2¼ [60] |
| A See Test Methods and Definitions A370 (Fig. 5 for further details and Fig. 6 for various types of ends). | |||
4.4.2.3 For plates over 1 in. [25 mm] in thickness, a series of sub-size specimens as shown in Fig. 2 and Table 2 may be used. The test specimen type to be used, Type D, Type E, or Type F, is determined by the nominal plate thickness as described in Table 2. A series of two or more Type D specimens may be used to cover the full thickness of the plate. The length of the reduced section (L) as defined in Fig. 2 and specified in Table 2 is the length of the reduced section excluding the fillet radius (R). Within the plate thickness dimension specified for each test specimen type, either the nominal plate thickness or the reduced section length may be used. For all cases, the minimum length of the reduced section shall be not less than 2D. The test specimen volume is minimum length to diameter ratio of the reduced section times πD²/4.
| Specimen Type | ||||||
|---|---|---|---|---|---|---|
| AA | BA | CB | D | E | F | |
| Plate thickness (t) | 2 t [50 t] | 2 t [50 t] | 4¼﹤t [108﹤t] | 1 ≤ t ≤ 1.75 [25 ≤ t ≤ 45] | 1.75﹤t ≤ 2.5 [45 ≤ t ≤ 64] | 2.5﹤t [64﹤t] |
| Diameter (D) | 0.500 [12.5] | 0.500 [12.5] | 0.500 [12.5] | 0.250 [6.25]C ± 0.005 [0.10] | 0.350 [8.75]C ± 0.007 [0.18] | 0.500 [12.5]C ± 10.010 [0.25] |
| Radius, min (R) | 3/8 [10] | 3/8 [10] | 1/16 [2] | Optional | Optional | Optional |
| Length of reduced section, min (A) | t + 0.25 min [t + 6] | 2.25 [60] | t - 1½ [t - 38] | 0.625 [16] | 0.875 [22] | 1.250 [32] |
|
A See Test Methods and Definitions A370 (Fig. 5 for further details and Fig. 6 for various types of ends). B See Test Methods and Definitions A370 (Fig. 6, specimen 3 for further details). C The reduced seclon may have a gracual laper from the ends toward the center, wih the ends not more than 1% laraer in diameter than the certer controlling dimension). |
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5. Acceptance Standards
5.1 Each tension test shall have a minimum reduction of area of 20 %. See 1.1 for explanation of purpose of test. If the reduction of area of one specimen is less than 20 %, a retest shall be permitted. Two additional test specimens may be taken from a location adjacent to the specimen that failed, and both of these additional specimens shall have a reduction of area of 20 % or more.
5.2 Fractures occurring in the prolongation weld or in the fillet radius shall be considered as a "no-test," and an additional specimen shall be tested.
6. Marking
6.1 Plates accepted in accordance with this specification shall be identified by stamping or stenciling "TT" adjacent to the marking required by the applicable product specification.
7. Keywords
7.1 lamellar tearing; special steel-making processes; steel plate; through thickness tension testing
SUPPLEMENTARY REQUIREMENTS
These requirements apply only when specified by the purchaser.
S1. Tensile Strength Requirements
S1.1 The reduction of area may be specified to a minimum value which is subject to agreement between the manufacturer and purchaser.
S2. Yield Strength Requirements
S2.1 The yield strength may be specified to a minimum value which is subject to agreement between the manufacturer and purchaser.
S3. Lamellar Tearing
S3.1 Lamellar tearing is a particular type of cracking that occurs in the through-thickness direction of steel plate. The primary cause of lamellar tearing is a strain induced in the thickness direction resulting from shrinkage of the weld deposit and by the restraint imposed by the component or structure. High restraint increases the possibility of lamellar tearing.
S4. Number of Tests
S4.1 A greater number of tests than indicated in 4.1 may be specified subject to agreement between the manufacturer and purchaser.
S5. Location of Test Coupons
S5.1 Test coupons from locations in addition to those specified in 4.2 may be specified subject to agreement between the manufacturer and purchaser.
APPENDIX
(Nonmandatory Information)
XI. LAMBELLAR TEARING ADJACENT TO WELDS
XI.1 Introduction
Lamellar tearing is not solely confined to highly restrained weldments. Lamellar tearing may also result from loads on the filler surface.
XI.2 Characteristics of Lamellar Tearing
XI.2.1 Lamellar tearing normally occurs in susceptible material underneath the weld, in a direction generally parallel to the plate surface and often slightly outside the heat-affected zone. Lamellar tearing generally has a step-like appearance consisting of a series of parallel terraces (on the fracture surface) and "walls" (cracks normal to the terraces). The tearing may remain completely subsurface or appear at the edge or on the surface.
XI.3 Inclusions
XI.3.1 The step-like fracture characteristic of lamellar tearing is usually considered to result from small elongated nonmetallic inclusions that are randomly present in the metal. Strain in the through-thickness direction can cause individual inclusions to fracture or decohere from the surrounding steel matrix. This initiates the tearing which then links up with adjacent inclusions, creating the step-like fracture appearance.
XI.3.2 A high volume fraction of inclusion content in the steel produces planar regions of lower ductility and strength. The size, shape, distribution, and concentration of these inclusions as well as the properties of the steel matrix determine the susceptibility of the steel to lamellar tearing in the through-thickness direction.
XI.3.3 The nature of nonmetallic inclusions depends on the type of steel and the steelmaking practice. In aluminum-killed steels, inclusions are primarily oxides (alumina). In silicon-killed steels, inclusions are primarily silicates. In both aluminum- and silicon-killed steels with high sulfur, inclusions are primarily sulfides (manganese sulfides). To improve the through-thickness ductility and thus reduce the susceptibility of the steel to lamellar tearing, it is necessary to reduce the level of the nonmetallic inclusions. To provide a high resistance to lamellar tearing may require the use of special steel-making processes that can reduce the oxygen and sulfur contents in the steel to very low levels.
XI.4 Steel Manufacturing Processes
XI.4.1 Special steel-making processes are available for improving the through-thickness ductility. The most common processes include one or a combination of the following: (1) low sulfur practice, (2) desulfurizing additions, (3) vacuum degassing, and (4) vacuum deoxidizing. The steel-making process must be selected for the particular steel type that will improve the through-thickness ductility to varying degrees, depending on the specific needs.
XI.5 Through-Thickness Ductility Requirements
XI.5.1 Susceptibility to lamellar tearing depends on many factors (for example, restraint, welding conditions, etc.); consequently, a specific through-thickness ductility requirement cannot guarantee against lamellar tearing. The most widely accepted method of measuring the material ductility or susceptibility to lamellar tearing is the reduction of area measured on a tension test specimen oriented perpendicular to the rolled surface of a plate.
XI.6 Testing Parameters Affecting Reduction of Area Values
XI.7 Variability of Through-Thickness Ductility
XI.7.1 Through-thickness ductility is not as consistent as longitudinal or transverse ductility. The reduction of area values obtained in the through-thickness direction are subject to substantially greater variability than those obtained in the longitudinal or transverse directions. This scatter is due in part to the inherent variability of the distribution of the nonmetallic inclusions discussed in XI.3. The nonmetallic inclusions are not uniformly distributed throughout the plate and will tend to occur with a higher frequency in the mid-thickness region.
XI.7.2 Test specimens taken from the mid-thickness region will tend to have lower test results because of these factors as discussed in XI.7.1. Because of the effect of inclusions on the fracture process, the appearance of the fractured specimen may be quite different than the classical cup-and-cone fracture typically seen in longitudinal and transverse tension testing. Since there is usually no necking (approximately 0 % reduction of area), the final diameter measurement may require substantial judgment on the part of the test operator.
XI.7.3 Because of the potential variability in the through-thickness reduction of area test results, it is recognized that two tests per plate are not sufficient to fully characterize the through-thickness ductility of a plate. The number of tests and test specimen locations have not been established that would provide a good estimate of the mean and the variability of the through-thickness ductility within a plate. Therefore, an average test requirement is not included in this specification. The intent of this specification is to qualify a plate according to the described testing procedures using only a minimum value determined by the potential variability of the test results. It is expressly recognized that subsequent testing of a steel plate qualified according to this specification may produce test results below the specified acceptance standard.
XI.8 Effects of Test Specimen Size
XI.8.1 Two factors to be considered in the selection of test specimen size are the diameter of the specimen and the ratio of length to diameter. It is generally recognized that there is a specimen size effect, that is, smaller diameter specimens will tend to give higher reduction of area values. It is also accepted that smaller diameter test specimens will tend to give greater variability in the measured reduction of area values. Because these relationships between test specimen diameter and the variability of the test result have not been satisfactorily quantified, no specific test specimen diameter is recommended. The acceptance requirement, however, applies to all test specimen diameters.
XI.8.2 The length-to-diameter ratio (reduced section length/reduced section diameter) is known to affect the values of reduction of area measured in the through-thickness direction. As the length-to-diameter ratio increases, the measured reduction of area decreases. A length-to-diameter ratio of 2:1 is specified in this specification as a compromise between the practical limitations of plate thickness and the desire to have as long a specimen as possible to improve the representativeness of the test result.
