1018 or 1045

[Frank Rathmell]

A local machine shop stocks both 1018 and 1045 steels. Is one a better choice than the other for say a 12 pound Coehorn mortar. If so why.
 
Thanks in advance
Frank

[Cannon Cocker]

1018 is more commonly used to make cannon barrels.  The elasticity and other characteristics make it a good choice.  I don't know what the qualities of 1045 are, but not having ever heard of anyone making a gun out of it I would go with what has been known to be a good choice. 

[GGaskill]

1018 has too little carbon to be hardenable by heat treating while 1045 has enough.  Annealed, both should be OK and not very different.  1045 could be hardened which would make it stronger at the expense of greater brittleness, although one wouldn't need to harden it to the point of brittleness.

1018 is probably easier to work and is strong enough unless you are going to completely engineer your design to minimize weight; not necessary if you are copying an old design.

[Cannon Cocker]

1018 has too little carbon to be hardenable by heat treating while 1045 has enough.  Annealed, both should be OK and not very different.  1045 could be hardened which would make it stronger at the expense of greater brittleness, although one wouldn't need to harden it to the point of brittleness.

1018 is probably easier to work and is strong enough unless you are going to completely engineer your design to minimize weight; not necessary if you are copying an old design.

Most people who make barrels out of 1018 turn the tube, then weld on trunnions into pockets.  Would the carbon in 1045 cause problems with uneven hardness when welding?

[Androclese]

 The wire or rods used in welding 1045 would need to be different from 1018 I do not remember what the numbers are, but its just a matter of using the correct thing for it to weld properly. any supplier will know what you'll need if no one here does.  As to causing local hardness troubles due to welding heat, as long as you cool it as slowly as you can, it should just normalize on its own, do not quench in any way.  1045 has been used for things like Jack Hammer chisels, and Rebar, its forgiving alloy, so I would not dismiss it out of hand, but the 1018-1020 is also excellent, and would not require any specialty welding materials.  How large an overall diameter are you planning ?

[Frank Rathmell]

I bought the 1018 7" dia by 14" long. I am going to build a 12 pound mortar. There wont be any welding. I was considering the 1045 because they had a piece 7x16 that they would of sold me 75 bucks cheaper.

I've never used 1045 before thats why I posted and since no one posted that they have used 1045 of I found no postings about it ,I paid the extra and had a piece 14" of 1018 cut.

Frank

[GGaskill]

Welding would have been a concern for me if you didn't have pre- and post-weld heating capability.