Reference: University of Oslo, Institute of Physics Report Series:. Report 84-09 dated March 12th 1984, "Metallographic tests of steel samples from Alexander L.Kielland, bracing D4 by P.T. Zagierski and Jon Gjønnes.
Two test pieces from the cut-off piece of bracing D4 was in December 1983 examined by mr. P.T.Zagiersky at the Institute of Physics, University of Oslo. Mr. Zagiersky, an expert in material technology from Poland had applied for permanent residentship in Norway. Professor Gjønnes was the superior to mr. Zagiersky.
The one test piece was a rectangular steel sample some distance from the breaking zone to be used as material reference. The position of this "reference piece" in relation to the breaking zone is shown on photo 2.2.1, i.e. the rectangular hole on top of the D4 bracing shown on the photo. The other, "major test piece" was a part of the breaking zone as marked on photo 2.2.2 and shown on photo 2.2.3.
Photo 2.2.1; Position of "reference
piece" on bracing D4 cut-off piece.
Photo 2.2.2; Position of "major test piece"
on Bracing D4 breaking sone.
Photo 2.2.3; "Major test piece" from bracing
D4 breaking zone.
Chemical analyses of both test pieces proved the steel quality to be within the given material specification for Alexander L. Kielland corresponding to the material from other breaking points referred to in the Statoil reports. All test samples, the "reference piece" and seven samples from the "major test piece", ref. photo 2.2.3 were examined by a Reichert MeF3 metalmicroscope at 16-500 magnification. The steel structure of the basic material, "reference piece", is shown in photo 2.2.4. Further examination of selected areas was performed by a JEM 2000A electronmicroscope. Bainitt was found in all the seven samples from the "major test piece" as shown in photo 2.2.5, but not in the "reference piece". Hardness tests further confirmed the identification of bainitt. Twins were found in some of the samples but only on one side of the steel plate as shown in photo 2.2.6.
Photo 2.2.4; Reference piece, basic
material.
Photo 2.2.5; Bainitt.
Photo 2.2.6; Twins.
Discussion:
As stated in the report from Institute of Physics, bainitt was discovered
in all test samples except in the basic material, "reference piece".
Bainitt should not occur in the material. Bainitt is neither mentioned
in the Statoil reports. Bainitt is created by relativly rapid cooling after
heating to above 880 degrees C. Institute of Physics gives in their official
report no explanation why bainitt occurs in the samples from bracing D4
breaking point.
Twins are created by shock force. Twins were only found in some of the samples and only on one side of the steel plate. Some of the samples showed variation in structural alignment. The orientation of subcorn varied and in some instances 90 degrees compared to the rolling direction. Verbally mr. Zagiersky stated his findings were interesting from an explosion point of view, they also differed from findings presented in the Statoil report from other breaking points, however, he could not make an unbias conclussion why bainitt occured in this particular area.
