Question for Dave Saxton -- STA61

Warship design and construction, terminology, navigation, hydrodynamics, stability, armor schemes, damage control, etc.
marty1
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Question for Dave Saxton -- STA61

Post by marty1 »

Dave:

Are you familiar with a steel or armor-steel classification STA 61?

Thnx
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Dave Saxton
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Post by Dave Saxton »

I'm sorry, I'm not familar with it, at least not off the top of my head under that designation. Armour materials can have several designations. Today, differing grades of RHA may simply be given a MIL-Spec number. It can be hard to keep track off.

I'm familar with Stahl 61. This is a low alloy construction steel that is a development of ST52, and has been gradually replacing ST52 in off shore oil production equipment in the North Sea since the early 90's.

Since this an armour grade steel, the "61" probably refers to min YTS in metric terms. This is about 85 KSI. There are several armour grade materials with a YTS in this range, including post WWII USN HY80, WWII Italian ER, and WWII German Wh, and more.

I can give you the actual specs and composition for HY80 if that would help. I'll also see what I can find out about STA-61
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Ulrich Rudofsky
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Post by Ulrich Rudofsky »

It may refer to a British Defence Standard for steel http://www.dstan.mod.uk/new.htm

DEF STAN 95-13/Issue 2
Ministry of Defence Defence Standard 95-13 Issue 2 Publication Date 5 January 2001 Armour Plate for ...
... the following: STA 61 dated July 1967 Def Stan 95-13/Issue 1 dated ...
... REQUIREMENTS 8 Steel Manufacture 6 9 Manufacture and Inspection of ...
... Imperfections in Steel Plate, Strip and Wide Flats, Based on ...
... Testing ISO 2604/4 Steel Products for Pressure Purposes - Quality ...
... Manager. 7.5 Steel supplied to this Standard shall comply with ...
http://www.dstan.mod.uk/data/95/013/00000200.pdf • Friday, 2 February 2001, 12:42pm GMT • 110.2k
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Dave Saxton
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Post by Dave Saxton »

The second link posted by Ulrich is really interesting. The chemical composition range specified by the standard is very close to what Tirpitz's Wh tested at. In fact the type 1 material is essentially the same, minus the .17% copper. The chemical composition of the experimental Krupp material tested in 1931 was also essentially the same as the type 1 material in the British STA-61 standard. This 1931 Krupp Cr/Mo Versuchen Stahl did not list any copper. However, there are later research tests conducted were copper is investigated on it's effect on shear strength improvements. That material tested at 95.8kg/mm2 UTS (139 ksi) with the copper. Without the copper, the shear strength was 64 % of the UTS(93kg/mm2). With the copper the shear strength improved to ~75% of the UTS.

The type 2 material has the higher Cr content we see in the early war German tank RHA.

The mechanical property specs are in the ranges expected of the properties of German Wh. Don't take the 16% min elongation spec as typical though. This a minimum acceptable measure, much like the 18% listed in a similar German document from 1935. Typically a material will far exceed the min acceptable spec. An example is HY. Prior to the 1990's, the USN specfied a min 14% elongation for HY. In the 90's the min was raised to 16%. Nevertheless, HY80 will typically test at about 24% in 2-inches, HY100 will be around 22% in 2-inches. One notes that the British specify the elongation measure be transverse in the document, which is in line with German practice.
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Post by marty1 »

Hi Dave & Ulrich:

Thanks for the feedback. I think the material Ulrich found is exactly what I was looking for. The STA61 reference I was referring to comes from British ballistic trials of tungsten rod penetrators – circa-1968 & 1969. This seems to match well with the pdf Ulrich posted.

Excellent work.

Thanks again.
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