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3.1 If the desired mechanical properties are as described in 4.1.1 for material identified as Classes P-1 through P-7, or in 4.1.2 for material identified as Classes Q-1 through Q-7, the strength level desired can be based on hardness or the equivalent tensile or yield strength as shown in Tables 1-4. If the desired mechanical properties are as set forth in 4.1.3 for material identified as Classes R-1 through R-6, the strength level is based on yield strength as shown in Tables 5 and 6.
3.2 The user, after determining the mechanical property requirements of the critical section (that carrying the greatest stress) of the part, should select the composition or compositions from Tables 1-6 that fulfills these requirements and is most suitable for processing.
Область применения1.1 This practice covers the selection of steel bars according to section and to the mechanical properties desired in the part to be produced. This is not a specification for the procurement of steel. Applicable procurement specifications are listed in Section 5.
1.2 Several steel compositions intended for various sections and mechanical property requirements are presented in Tables 1-6. The criteria for placing a steel composition in one of the three general class designations, Classes P, Q, and R (described in Section 4) are as follows:
(A) 1 psi = 0.006895 MPa.(B) Minimum as-quenched hardness for obtaining desired hardness after tempering at 800 °F (427 °C) or higher.(C) 1 in. = 25.4 mm. (A) 1 psi = 0.006895 MPa.(B) Minimum as-quenched hardness for obtaining desired hardness after tempering at 800 °F (427 °C) or higher.(C) 1 in. = 25.4 mm.(D) These steels have insufficient hardenability for Class P-4, because of difference in test locations, but are satisfactory for other smaller sizes. (A) 1 psi = 0.006895 MPa.(B) Minimum as-quenched hardness for obtaining desired hardness after tempering at 800 °F (427 °C) or higher.(C) 1 in. = 25.4 mm. (A) 1 psi = 0.006895 MPa.(B) Minimum as-quenched hardness for obtaining desired hardness after tempering at 800 °F (427 °C) or higher.(C) 1 in. = 25.4 mm.(D) These steels have insufficient hardenability for Class Q-4 parts because of different location of test specimens, but are satisfactory for smaller sections.(E) For these steels, the yield to tensile-strength ratio will usually be lower than 80 %. (A) Hot-rolled bars are indicated in table by prefix “HR.”(B) Cold-drawn bars are indicated in table by prefix “CD.” These bars are produced by normal practice in cold-drawing and with no stress relief. Bars cold-finished by turning, grinding, turning and polishing, etc., are not covered under cold-drawn bars, as such cold-finished bars have the properties of hot-rolled bars.(C) Classification of cold-drawn steels by size and yield-strength level in this table is based on yield-strength determinations at 0.2 % offset, or as determined by 0.005 in./in. elongation under load for yield strengths up to 90 000 psi, incl, and by 0.006 in./in. elongation under load for yield strengths above 90 000 psi.(D) 1 psi = 0.006895 MPa.(E) 1 in. = 25.4 mm. (A) Conditions and treatments of bars are indicated in this table by the symbols shown below. Bars cold-finished by turning, grinding, turning and polishing, etc., are not covered, as such bars have the properties of hot-rolled bars. “CD” = Bars produced by normal practice in cold-drawing, and with no stress relief. “CDT” = Cold-drawn bars with subsequent thermal treatment. Heavier than normal drafts may be required.(B) Classification of cold-drawn steels by size and yield-strength level in this table is based on yield-strength determinations at 0.2 % offset or as determined by 0.005 in./in. elongation under load for yield strengths up to 90 000 psi, and by 0.006 in./in. elongation under load for yield strengths above 90 000 psi.(C) 1 psi = 0.006895 MPa.(D) 1 in. = 25.4 mm. (A) 1 in. = 25.4 mm.1.2.1 Classes P and Q should be capable of developing the mechanical properties shown in Tables 1-4 by liquid quenching from a suitable austenitizing temperature, and tempering at 800 °F (427 °C) or higher. A hardness indicated by tests made at a location shown in Fig. 1, A, B, or C, is taken as evidence that a composition is capable of meeting other equivalent mechanical properties shown in the tables. Normal good shop practices are assumed, with control of austenitizing and tempering temperatures, and mild agitation of the part in the quenching bath.
FIG. 1 Locations in Typical Cross Sections of Steel Bars at Which Desired Properties Are Obtained
1.2.2 Class R should be capable of developing the mechanical properties shown in Tables 5 and 6 as hot rolled, by cold drawing, or by cold drawing with additional thermal treatment. The locations for obtaining tension tests are described in 6.2.
1.3 It is not implied that the compositions listed in the tables are the only ones satisfactory for a certain class and mechanical property requirement. Steels with lower alloy contents are often satisfactory through the use of special processing techniques.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.