Material Focus: 17-4 Bolts for Extreme Strength

High strength bolts are one of the main reasons engineers look to specialty materials. 17-4PH bolts often fulfill this demand. In this short newsletter we hope to answer many of your questions surrounding the age-hardened stainless steel we call 17-4PH
How much strength can 17-4PH provide?
17-4PH bolts can provide up to 4 times the strength of stainless 316 fasteners depending on the heat treatment.
Heat treatment: What is it and how do I choose?
Heat treating of the 17-4PH alloy involves a heating and cooling process that enhances its mechanical properties. Different heat treatments (aging processes) provide different levels of strength and hardness.This chart provides a list of the heat treatments (also known as the aged conditions). Beside each heat treatment it also displays the specific strength and hardness they provide. For example, H900 will provide a stronger and harder material than H1150 but also be the most brittle with the least elongation.
What is annealed 17-4PH?
Annealed means that the 17-4PH bolts were not heat treated. This is called 17-4PH Condition A.
Is 17-4PH also useful for high temperature applications?
17-4PH bolts have a maximum usable temperature of about 600°F. In the anneal condition, this maxes out a little lower and should not be used above 572°F.
Can 17-4PH be used for corrosive environments?
17-4PH bolts are typically not used for corrosion like a nickel alloys, however its resistance to common corrosive environments is better than 400 series steel; being most similar to 304 stainless. The heat treating process can also make 17-4PH more susceptible to stress corrosion cracking, which can be a concern in applications where chloride stress corrosion cracking is possible.
So while its not really a very corrosion resistant alloy, it is a stainless steel and will typically corrode in ambient conditions. When high strength and corrosion resistance are needed, there may be more suitable options.
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