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[标准解读]ASTM A388大型锻件超声检测标准操作方法

热度 2已有 666 次阅读2019-3-25 22:10 |个人分类:理论学习| A388

问题1:首次使用A388标准时候,如何使用?
问题2:使用底面反射法时候,如何进行检测灵敏度设定及验收标准参考?
答:该标准是美标体系中碳钢锻件的检测方法核心标准,包括了直射波、斜射波技术。该标准对锻件的直射波检测灵敏度、验收标准没有详细说明,看完了标准也不知道怎么检测。实际上该标准必须和A788,S20一起使用,除非设计或者合同有详细的要求。
S20. Ultrasonic Examination
S20.1 Ultrasonic examination of forgings shall be carried
out in accordance with Practice A 388/A 388M.
S20.2 Unless otherwise agreed upon between the manufac￾turer and the purchaser, acceptance levels BR or DA shall be
specified for the longitudinal wave examination and level S for
shear wave examination.
Level BR—Longitudinal Wave
S20.2.1 The back reflection method of tuning shall be used
in accordance with Practice A 388/A 388M.
S20.2.2 In addition to the reportable conditions of the
Recording Section of Practice A 388/A 388M, indications
exceeding the resultant back reflection shall be recorded.
S20.2.3 The following conditions are subject to rejection, or
repair if applicable.
S20.2.3.1 Complete loss of back reflection accompanied by
an indication of a discontinuity. For this purpose, a back
reflection less than 5 % of full screen height shall be consid￾ered complete loss of back reflection.
S20.2.3.2 An indication equal in amplitude to that of the
back reflection established in an indication-free portion of the
forging.

Level DA—Longitudinal Wave
S20.2.4 Reference blocks of acoustically similar metal shall
be used for calibration. Blocks shall meet one of the following
requirements:
S20.2.4.1 A comparison of the back reflections between
equivalent thicknesses of the reference block material and the
actual forging to be tested, without change in instrument
setting shall not show a variation in excess of 25 %.
S20.2.4.2 The reference blocks shall be manufactured from
steel that is similar in chemistry and processing history to the
production forging being tested. The reference blocks shall be
fabricated in accordance with the procedures of Practice E 428.
S20.2.4.3 For test sections up to and including 12 in. (300
nm) thick, the reference blocks shall contain a 1⁄4 in. (6.5 mm)
diameter flat-bottom hole; for over 12 in. (300 mm) up to and
including 18 in. (300 to 455 mm), the hole diameter shall be 3⁄8
in. (9.5 mm); and for over 18 in. (455 mm), it shall be 1⁄2 in.
(13 mm).
S20.2.4.4 A distance-amplitude correction curve shall be
established for the proper grade of steel and specified hole size.
S20.2.4.5 A forging containing one or more indications
equal in amplitude to that of the applicable reference hole,
when properly corrected for distance, is subject to rejection, or
repair if applicable.
Level S–Shear Wave
S20.2.5 Calibration notches, calibration reference, and
method of scanning shall be in accordance with Practice
A 388/A 388M. Unless otherwise agreed upon, a 60° V-notch
shall be used.
S20.2.6 A forging containing a discontinuity which results
in an indication exceeding the amplitude of the reference line
is subject to rejection.
S20.2.7 The report of the ultrasonic examination shall be in
compliance with Practice A 388/A 388M.
S20.2.8 Additional nondestructive examination or trepanning may be employed to resolve questions of interpretation of
ultrasonic indications. The manufacturer shall accept responsibility for injurious conditions which will not be removed in
final machining.
S21. Additional Test Coupon Heat Treatment
S21.1 When subcritical heat treatment, applied to a completed forging during subsequent fabrication, may affect the
mechanical properties of the forging, then coupons for the
mechanical testing required by the product specification shall
be given a laboratory heat treatment which simulates the
anticipated subcritical heat treatment.
S21.2 The purchaser shall specify the required heat treatment temperature range, minimum time at temperature, and the
rates of heating and cooling.
S21.3 The required number of test coupons shall be taken
from the forging location described in the product specification.
S21.4 The test specimens shall meet the minimum mechanical test requirements of the product specification, as well as
those of any additional tests agreed upon between producer and
purchaser, after completion of the test coupon heat treatment.
S21.5 The forgings supplied in accordance with this supplementary requirement shall be marked in accordance with
17.1.7.
S21.6 The material test reports shall include the heat treatment of the as delivered material and the results of the
mechanical tests from the test coupons subjected to the
purchaser specified heat treatments which represent fabrication.
S22. Ultrasonic Examination from Bore Surface
S22.1 Bored cylindrical forgings shall be examined from the
bored surface in accordance with Test Method A 939. The
acceptance criteria shall be agreed upon between the purchaser
and the producer.

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