Metallurgical Principles and Practice of Engineering (PE) Study Guide: Question #2

It Is the Policy of The Minerals, Metals & Materials Society (TMS) to Encourage the Professional Registration of Metallurgical Engineers.
Your company manufactures high-quality steel plate for pressure vessels. You test the material for a variety of physical and chemical properties, and maintain records so that statistical data on the product can be maintained, trends noted and corrective action taken, if required. One of your company's most successful products is low-carbon steel plate used for pressure vessels.

ASTM specification A516 for pressure vessel steel specifies, among other things, the following physical and chemical properties:

Composition, percent, for A516 Grade 60:

For plate 1/2 inch to 2 inches thick

Carbon, max	Silicon	Manganese	Phosphorus, max	Sulfur, max
0.23	0.15-0.40	0.85-1.20	0.035	0.035

Tensile strength 60-80 ksi (60,000-80,000 lbf/in²)
Yield strength minimum 32 ksi
Minimum elongation in 2 inches = 25%

In addition, some purchasers require impact testing of the material. A typical requirement is a Charpy test result of minimum 13 foot-pounds force (ft-lbf) energy absorption at -60°F test temperature. This value is to be the average of three specimens, with minimum energy absorption on any one specimen of 10 ft-lbf.

Seven (7) Charpy tests were run on standard samples from a heat of the steel. The test temperature was -60°F. The energy absorption, (ft-lbf) was as follows for the seven samples.

15, 15, 19, 20, 21, 21, 22.

The mean, median, and standard deviation, (ft-lbf) of the data set are respectively:

(A)	19, 19, 2.67
(B)	19, 20, 2.67
(C)	19, 20, 7.1
(D)	20, 20, 2.67.

The information on this page is maintained by the Nellie Luther (natale@tms.org).

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