Choice of steel for repairs

Discussion in 'Metal Boat Building' started by richp10, Oct 13, 2018.

  1. richp10
    Joined: Apr 2018
    Posts: 10
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    Location: London

    richp10 Junior Member

    I am looking to repair a steel yacht built in 1992. The original steel used is uncertain but the best information is from the designer: "In those days Grade AH32 mild steel would have been used, these days probably equivalent to AS 3678. You want a yield strength of about 280 n/sqmm ultimate tensile of about 400." The boat was built in the UK but will be repaired in Portugal.

    There are a number of repairs needed including one bit of plate about 4 ft x 2 ft that will be cut in.

    Question: How critical is it to match the steel to the original? I might be able to get Corten - is that a good idea? Any other suggestions on readily available grades of steel which would be suitable?

    Huge thanks (this forum i
     
  2. JosephT
    Joined: Jun 2009
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    Location: Roaring Forties

    JosephT Senior Member

    You have two different types of steel there. Researching into the weld approaches there is a process referred to as "buttering" which applies a layer of nickel or other alloy to improve the weld properties. You're certainly better off discussing details of joining AH32 & AS 3678 with a professional welding forum. Below are some references.

    The Welding Institute: Contact The Welding Institute | TWI Professional http://www.theweldinginstitute.com/contact-us/
    American Welding Society: American Welding Society Forum https://app.aws.org/forum/forum_show.pl

    A seasoned metallurgist and/or welder should be able to point you in the right direction. From what I've read there will be downstream microscopic issues unless you join two different steel types correctly. As with joining any dissimilar metals the areas will also be more prone to corrosion so you'll want to factor corrosion prevention (e.g. proper cleaning and coating of the areas, zinc anode system) after the welds are complete.
     
  3. M&M Ovenden
    Joined: Jan 2006
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    Location: Ottawa

    M&M Ovenden Senior Member

    I think I would stay away from Corten - I'd just try to match the steel as best as possible.
    Mark
     
  4. John mc b
    Joined: Nov 2018
    Posts: 5
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    Location: UK and Spain

    John mc b Junior Member

    Just use ordinary mild steel, don't beat yourself up about corten etc, weld it properly and make sure it is well painted, it will out last you.
     

  5. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Then it was most likely built with standard Grade A steel:

    upload_2018-11-30_10-26-22.png
     
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