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BS EN 18 steel equivalent ? 4
- Thread starter edison123
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edison123,
Technically, no, 4140 must have 0.15-0.35 Mo. However, 4140 certainly would be an acceptable North American grade to use instead of En 18. The Mo provides additional hardenability, meaning that larger diameter bars or larger parts can be effectively quenched to the same hardness.
Technically, no, 4140 must have 0.15-0.35 Mo. However, 4140 certainly would be an acceptable North American grade to use instead of En 18. The Mo provides additional hardenability, meaning that larger diameter bars or larger parts can be effectively quenched to the same hardness.
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Thx TVP.
The material EN 18 is for a stud bolt in a hydro generator. This anchors the V blocks between the pole coils of the rotor and hence subject to rotational forces.
Will using 4140 instead of EN 18 affect the performance ?
"Most people stop working when they find a job"
The material EN 18 is for a stud bolt in a hydro generator. This anchors the V blocks between the pole coils of the rotor and hence subject to rotational forces.
Will using 4140 instead of EN 18 affect the performance ?
"Most people stop working when they find a job"
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Rolled threads are generally better. The rolling improves the grain structure vs. applied stresses, increases strength via cold working, gives a more rounded thread root for better fatigue resistance, and doesn't waste (cut) material.
CNC-cut threads may give more precise tolerances, especially in larger sizes > 1".
I suggest also reading
Fatigue life of non standard threads
thread725-148865
CNC-cut threads may give more precise tolerances, especially in larger sizes > 1".
I suggest also reading
Fatigue life of non standard threads
thread725-148865
Thread rolling produces a higher quality thread for the following reasons:
1. Improved surface quality (lower surface roughness)
2. Improved strength and hardness due to strain hardening (cold working)
3. Improved fatigue life due to residual compressive stresses when performed after heat treating
4. Somewhat improved fatigue life due to favorable grain flow/orientation when performed prior to heat treating
An excellent journal article on this subject is "The effect of manufacturing processes on the fatigue
lifetime of aeronautical bolts" from Engineering Failure Analysis 8 (2001) 227-235.
1. Improved surface quality (lower surface roughness)
2. Improved strength and hardness due to strain hardening (cold working)
3. Improved fatigue life due to residual compressive stresses when performed after heat treating
4. Somewhat improved fatigue life due to favorable grain flow/orientation when performed prior to heat treating
An excellent journal article on this subject is "The effect of manufacturing processes on the fatigue
lifetime of aeronautical bolts" from Engineering Failure Analysis 8 (2001) 227-235.
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It depends. As noted by TVP, rolling after heat treat (the typical "aerospace" practice, along with using a UNJ thread form) will improve relative fatigue lives, largely due to imparting a residual compressive surface stress that must be overcome before a fatigue crack can inititate/propagate. Heat treat after thread roll will remove those beneficial residual compressive stresses.
If achieving the ultimate attainable fatigue life is not the overriding consideration, then many of the benefits of thread rolling can be obtained by rolling the threads prior to heat treatment (the most common "commercial" fastener practice) without incurring the expense of rolling the material in the heat treated condition, which is typically a job for someone with aerospace threadrolling experience and is more difficult to do with generating unacceptable defects (and is one of the reasons that those aerospace fasteners cost so darn much). Check with your threadroller first to see if he has the experience and equipment to roll material in the heat-treated condition if you decide to have the material rolled in the heat-treated condition.
If achieving the ultimate attainable fatigue life is not the overriding consideration, then many of the benefits of thread rolling can be obtained by rolling the threads prior to heat treatment (the most common "commercial" fastener practice) without incurring the expense of rolling the material in the heat treated condition, which is typically a job for someone with aerospace threadrolling experience and is more difficult to do with generating unacceptable defects (and is one of the reasons that those aerospace fasteners cost so darn much). Check with your threadroller first to see if he has the experience and equipment to roll material in the heat-treated condition if you decide to have the material rolled in the heat-treated condition.
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