kv,

    Yes you should be concerned.  AISI 1045 is a plain carbon steel and 4150 is a Cr-Mo steel, and both of these steels are predominately ferrite & pearlite.  (The 4150 can vary from ferrite & pearlite to bainite to martensite depending on heat treatment)  Therefore, these steels will be quite brittle at -130 C.  The 41xx series of AISI steels are actually specifically designed for use in high temperature environments i.e. 600 - 1200 F.  These types of steels undergo a ductile-to-brittle tranisition in their failure mode when operating temperatures start progressing below approx. 40 F.  (This was part of the problem that the Liberty ships of WWI had...some of them literally cracked in half while sitting peirside, in seawater that was close to freezing)  You want a steel that has Nickel added as an alloying addition.  This will lower the ductile-to-brittle transition temperature below your operating temperature.  You could stay with a ferritic steel if you chose one of the NI-Cr-Mo series that had significant enough amounts of Ni, but a better choice might be to go with an austenitic steel.  The standard 300 series migiht have something that would work, you'll have to look at your strength requirements.

regards,

Andy

If your design permits then a conventional stainless steel alloy will be a preferred material.Alternately you could consider LCB grade of steel for low temperature similar to one used in valve castings for cryogenic applications.