4140 vs 4340
4140 vs 4340
(OP)
I am currently having a discussion about the differences between 4140 and 4340. They seem pretty similar chemically and mechanically, based on the book information I have.
What I am looking for is practical differences that people have gotten through experience. Like one is good for this type of application and one is not.
In the past we seemed to use them depending more on the day of the week then the application so I am trying to get a sense of their usses.
Any help would be appreciated.
What I am looking for is practical differences that people have gotten through experience. Like one is good for this type of application and one is not.
In the past we seemed to use them depending more on the day of the week then the application so I am trying to get a sense of their usses.
Any help would be appreciated.
RE: 4140 vs 4340
4140 / 4340
tensile strength in MPa impact energy in Joules
~1965 (tempered @205C) 15 / 20
~1720 (tempered @315C) 9 / 14
~1020 (temp. @595/650) 93 / 100
This data is for room temperature. 4340 will be MUCH tougher at lower temperatures. 2% Ni shifts the ductile to brittle transition temperature appreciably-- for low carbon steels it would be a delta of ~ 100 degrees F, for medium carbon steels it is less.
Having said all of this, these alloys can be used for many of the same applications. If the application does not require the higher level of fracture toughness (especially at low temperatures) that 4340 offers, then 4140 can be used as a direct replacement, with the caveat that distortion during heat treatment will be higher and thicker sections will not quench to the same hardness. I would caution you against ever saying that an alloy is suitable or unsuitable for a generic appplication without fully understanding the operating environment (forces, temperature, corrosion, etc.). You may want to provide some additional details about the types of components you manufacture, their operating environments, etc. so that we can better answer your question.