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SEMI F20-0305 © SEMI 1995, 2005 4 7 Certification 7.1 A certified copy of the material test report shall be provided at the time of shipment. The material test report shall include: 7.1.1 The results of the composition a…

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SEMI F20-0305 © SEMI 1995, 2005 3
6.2.2 The annealing temperature used to achieve the grain size requirements of ¶6.4.1 shall be 982
o
C (1800
o
F)
minimum.
6.3 Composition
6.3.1 Material shall be type 316L stainless steel, as specified in Table I of ASTM A 182/A 182M, ASTM A 240,
ASTM A 269, ASTM A 276, ASTM A 479/A 479M, or ASTM A 632, except where otherwise specified herein.
6.3.2 General purpose grade material shall have a composition per ASTM A 269 and ASTM A 632, with the
exception of limited Sulfur 0.012% maximum.
6.3.3 Additional composition requirements for the high purity and ultra-high purity grades are shown in Table 1.
Table 1 Additional Composition Requirements
Element Range – Wt %
Carbon 0.030 Max
Sulfur 0.010 Max
Manganese 1.5 Max
Copper 0.30 Max
#1
Niobium 0.05 Max
Aluminum 0.01 Max
Calcium 0.02 Max
Titanium 0.02 Max
Selenium 0.02 Max
#1
Agreement may be reached between the supplier and the customer to accept a higher level of copper.
6.3.4 Effects of Sulfur content on welding are significant, as discussed in Appendix 1.
6.3.5 Effects of Copper content on welding are discussed in Appendix 2.
6.3.6 No deviations in material composition from the minimum or maximum values specified in the appropriate
ASTM document or herein shall be allowed without approval by the purchaser.
6.4 Metallurgy
6.4.1 Grain size per ASTM E 112 shall be 5 or finer for hot or cold finished product and tubing of nominal size 3
inches in diameter and smaller, and 3 or finer for material stock greater than 3 inches. These requirements may be
modified as agreed upon between supplier and user. Grain size on flats and squares shall be as agreed upon by the
supplier and the user.
6.4.2 The inclusion content of the material shall be determined from representative samples of the material heat in
accordance with ASTM E 45, Method A, but with ratings based on Plate III. Maximum allowable JK ratings at the
billet stage are shown in Table 2.
Table 2 Maximum JK Inclusion Ratings
General Purpose
Grade High Purity Grade
Ultra-High Purity
Grade
Type
Thin Heavy Thin Heavy Thin Heavy
A 2.5 1.0 2.0 1.0 1.5 1.0
B 2.5 1.0 2.0 1.0 1.0 1.0
C 2.5 1.0 2.0 1.0 1.0 1.0
D 2.5 1.0 2.0 1.0 1.0 1.0
6.4.3 Material shall meet the intergranular corrosion test specified in Practice E of ASTM A 262. This requirement
shall apply in the sensitized condition (1 hour at 677°C [1250°F]).
SEMI F20-0305 © SEMI 1995, 2005 4
7 Certification
7.1 A certified copy of the material test report shall be provided at the time of shipment. The material test report
shall include:
7.1.1 The results of the composition analysis, to include all elements required to be controlled by this specification,
made in accordance with ASTM A 751.
7.1.2 Grain size.
7.1.3 JK ratings of inclusion content.
7.1.4 Mechanical properties.
8 Product Labeling
8.1 Material shall be identified with the following information:
8.1.1 Manufacturer’s name,
8.1.2 Purchaser’s name and order number,
8.1.3 ASTM specification number(s),
8.1.4 This specification number,
8.1.5 Heat number, and
8.1.6 Material type (i.e., 316L).
SEMI F20-0305 © SEMI 1995, 2005 5
APPENDIX 1
THE EFFECTS OF SULFUR ON GTA WELDING OF 316L STAINLESS
STEEL
NOTICE: The material in this appendix is an official part of SEMI F20 and was approved by full letter ballot
procedures.
A1-2 Effects of Sulfur
A1-2.1 AISI Type 316L austenitic stainless steel is the preferred material for components of gas supply systems for
semiconductor fabrication. The composition of 316L specified in Table I of ASTM A 182/A 182M, ASTM A 240,
ASTM A 269, ASTM A 276, ASTM A 479/A 479M, or ASTM A 632, has a maximum of 0.030 percent Sulfur;
however several properties affecting the manufacture and applications of 316L can vary significantly over this range
of Sulfur content. Therefore a lower Sulfur maximum is specified in SEMI F20, as listed in ¶6.3.2 and Table 1 of
¶6.3.3.
A1-2.2 Sulfur has a very low solubility in austenitic stainless steels, thus in these alloys it exists as discrete
inclusions of Manganese Sulfide, with some solubility for Chromium as well as other trace elements. These
inclusions can initiate pits and other defects on electropolished surfaces, increasing in number with increasing Sulfur
content.
A1-2.3 The Manganese Sulfide inclusions improve the machinability of stainless steel; compositions intended for
machining have Sulfur compositions near the 0.030 percent maximum, whereas stainless steels with very low Sulfur
levels require lower feeds and speeds and will cause reduced tool life during machining.
A1-2.4 Sulfur also strongly affects welding of stainless steel; variation of Sulfur from very low contents to the
maximum permitted can increase weld bead penetration by approximately a factor of two for similar weld
parameters.
A1-2.5 The effects of Sulfur are summarized in Table A1-1.
A1-2 Welding Effects of Sulfur
A1-2.1 Two effects are observed on welding with variations in Sulfur level:
A1-2.1.1 As Sulfur is reduced the heat input required for full penetration increases.
A1-2.1.2 As Sulfur is reduced below approximately 0.005 percent there is a marked change in weld pool dynamics,
causing the weld pool to become wider and shallower
2
.
Table A1-1 – Effects of Sulfur on Austenitic Stainless Steels
As Sulfur increases from zero to the 0.030% maximum permitted:
Effects Results
Machinability improves.
– Lower machining costs for machined parts.
Inclusion density increases.
– More pits, stringers, other defects on surface.
– Decreased corrosion resistance, particularly on end grains.
Welding penetration increases.
– Weld settings must be reset when changing lots.
– Problems welding materials with dissimilar Sulfur contents.
2 K. Watanabe and K. Masuda, Effects of Residual and Micro-Alloying Elements on Welding of Stainless Steel; Part 1: Effects on weld pool
behavior by GTAW, IIW Doc. IX-1837-96, International Institute of Welding, 1996, 17 pp. (Literature review).