We have a question about paragraph 3.4.3 in AMS 2770H (Heat Treatment of Wrought Aluminum Alloy Parts). In the first sentence it says, "The quenchant temperature shall not exceed the maximum start of quench temperature specified in 3.4.2 by more than 10°F at any time during quenching." Then the second sentence says, "The quenchant temperature shall not increase more than 25°F from the starting temperature as a result of quenching any single load." The two sentences seem to be at odds with each other. Do you know what is intended here?

The paragraphs in AMS 2770H to which you refer may appear to be a bit confusing, but they really aren’t. Here is their interpretation.

1. Paragraph 3.4.2 tells us that the maximum bath temperature at start of quench shall be 90°F or less (ignoring forgings). This should be straightforward.

2. Paragraph 3.4.3 deals with temperature rise and says two things. First, the maximum bath temperature during quenching is 100°F. Second, if you were quenching into a bath at a lower temperature, say 60°F, then you cannot exceed 85°F during quenching (25°F maximum rise from starting temperature). What you are not allowed to do is to quench into a 90°F bath and have a temperature rise over 10°F.