Foundries are often called upon to produce special grades of stainless steel. One of the factors which can be controlled is the ferrite content in stainless steel. But which factors determine the amount of ferrite content in stainless steel and how are they controlled? And how is the amount of ferrite determined? But first, what is ferrite?
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ASTM D e1. ASTM A ASTM D ASTM B A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. Scope 1. Methods are described for estimating ferrite content by chemical, magnetic, and metallographic means.
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 practice. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Referenced Documents 2. Terminology 3. This may be formed upon solidication from the molten metal delta ferrite or by transformation from austenite or sigma phase on cooling in the solid state alpha ferrite. Box , N. LeJeune Rd. Current edition approved Mar. Published May Originally published as A — Signicance and Use 4. The ferrite content may be limited by purchase order requirements or by the design construction codes governing the equipment in which the castings will be used.
The quantity of ferrite in the structure is fundamentally a function of the chemical composition of the alloy and its thermal history. Because of segregation, the chemical composition, and, therefore, the ferrite content, may differ from point to point on a casting. Determination of the ferrite content by any of the procedures described in the following practice is subject to varying degrees of imprecision which must be recognized in setting realistic limits on the range of ferrite content specied.
Sources of error include the following: 4. Therefore, the precision of the ferrite content estimated from chemical composition depends on the accuracy of the chemical analysis procedure. These may so alter the magnetic response of the alloy that the indicated ferrite content is quite different from that of the same chemical composition that has undergone different thermal treatment. Also, because the magnets or probes of the various measuring instruments are small, different degrees of surface roughness or surface curvature will vary the magnetic linkage with the material being measured.
Ordering Information 5. NOTE 1—There may be a substantial decrease in the ferrite content of weld deposits after solution heat treatment in comparison with the as-deposited value. General Caution 6. Estimation of Ferrite Content 7. If a comparison is made of ferrite content estimated from a product analysis performed by the purchaser, with that estimated from the heat analysis see 7.
Acceptance Standards 8. Certication 9. The estimates of ferrite content from magnetic measurements S1 or from point counts S2 , or both, if ordered by the purchaser, also shall be reported.
Keywords They shall not apply unless specied in the order, in which event the specied methods of ferrite content estimation shall be employed by the manufacturer before shipment of the castings.
All measurements shall be made on material after the solution heat treatment required by the applicable product specication, or, if any subsequent solution heat treatment is employed, then after the nal solution heat treatment. Measurements may be made either before or after performance of the tension test. If a tension test is not required by the applicable product specication, measurements may be made on a specimen cut from a keel block of a design in Fig. All measurements shall be made on weld deposits as deposited.
When measurements are made on a curved surface the radius of curvature must be greater than 0. Because of errors in chemical analyses, the calculated ratio may differ from the actual composition ratio and, as a result, the ferrite content may be higher or lower than indicated by the central X1. Accordingly, if additional estimates of ferrite content are made by magnetic or metallographic methods, they can be expected to differ from the diagram value. The possible extent of this difference is shown by the broken lines.
Example: If the composition ratio is 1. Similar information is available in Table X1. The gures immediately above and below on the lines U and L indicate the probable upper and lower bounds of the ferrite range that may be expected. Corrected editorially. The American Society for Testing and Materials takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard.
Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every ve years and if not revised, either reapproved or withdrawn.
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Historical Version s - view previous versions of standard. Work Item s - proposed revisions of this standard. More A The ferrite content may be limited by purchase order requirements or by the design construction codes governing the equipment in which the castings will be used.
Low-Ferrite Austenitic Stainless Steel
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