Production • Processing • Handling
Having in mind that the tabulated tensile values are too high (compared with the yield strength values), they are the most challenging to achieve for testing.
Te 85per cent and
90 per cent reference lines are plotted in the graphs.
EN 10314 As the above ratios of Rp0,2
/ Rm ,
Fig. 3. Relationship between design-values and mechanical properties (A387-22-2).
In Fig. 1 the requirements according ASME are included as solid lines. In Fig. 2 the design values according ASME II-D, Table U and Table Y-1 are shown as a function of the testing temperature. It comes clear that the ratio Rp0,2
/ Rm is
characteristic for a given steel, by way of example, for steel grade A387-22-2 this typically is between 0.65 and 0.85. Fig. 3 shows for the SA 387-22-2 the relation of , calculated both with the design values and
Rp0,2 / Rm
the recently measured values of our production. Te large difference between the data population and the curve calculated with the design values is obvious. In terms of the related Rp02
, the design values
according Table Y-1 are much lower than the measured yield-strength data points, whereas for the tensile strength the design values, according to Table U, is much too high, compared to the tested values. We plotted a 85 per cent (dotted) and a 90 per cent (solid) line to better visualise different acceptance criteria levels. Tis indicates a certain misfit according the tabulated design values and the mechanical properties of the examined steel grades. Furthermore, the ratio Rp0,2
/Rm calculated
with the design values of Table U and Y-1 leads to extremely low value of about 0.45, which is more typical for an A516-60 than an A387-22-2.
Tis all may raise reasonable doubts, that the tabulated design values should be used as acceptance criteria. Te graph in Fig. 4 highlight for SA387-22- 2 the measured hot tensile test values versus calculation limits of ASME II-D, Tables U and Y-1 in a temperature range up to 550°C
calculated with the tabulated values do not fit with the long term experience of one the most experienced plate mill, ways have to be found in order
to specify acceptance criteria in order to guarantee a safe product with excellent properties. Some of the specification writers understand the
above described issue, specifying values, which fit more with the modern steels. An appropriate statistical method for calculation of the minimum hot tensile or yield strength is given by EN 103143
. Using this method will leads
to curves, which are less or equal 85 per cent of the values listed in table U of ASME II-D. Te same method is used to determine the
derivation of minimum values of proof strength included in the harmonised European standard for flat products made of steels for pressure purposes (EN10028-3). In the graphs we plot the curve, resulting from EN 10314, into the measured data, in order to enable the reader to compare them with the calculation limits of ASME II-D, Table U. We can now see that the graph fits well with the 85 per cent level.
Fig. 4. Steel grade A387-22-2, Hot Tensile Test Values versus Calculation Limits of ASME II-D, Tables U and Y-1.
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