EN 2831-1993 pdf download.Aerospace series-Hydrogen embrittlement of steels -Test by slow bending.
This EN 2831 specifies the test method by slow bending, which is used to assess the hydrogen
embrittlement of steels during chemical or electrolytic surface treatments.
This test is also used to verify the recovery of the initial ductility during de-embrittlement treatments.
It is applicable whenever referenced.
2 Apparatus
Bending test machine with the following characteristics:
— the chucks shall avoid any effects due to clamping in the region 01 cracking,
one of the chucks shall be fixed and the other movable; the fixed chuck shall be fitted with an interchangeable bending block the diameter of which may be between 2 mm and 6 mm (see Figure 1); the movable chuck shall have a deflection rate which can be adjusted between 4°!min and 18°/mm,
— be fitted with a device allowing to measure the angles a0, a and (a2 (see Figure 2 to Figure 4) with
a precision of± 0,5°,
— be fitted with a magnifier of 10 times in order to reveal the occurence of the first crack.
3 Test specimens
They shall:
— be cut from a bar or sheet along the grain direction,
— have the following dimensions:
• length: 180 mm to 200 mm
• width: 15 mm to 20 mm
• thickness: 1,8 mm to4mm
• straightness deflection over the length:< 0,25 mm,
— be machined along the grain direction to a surface roughness Ra ≤ 1.6 tim. then submitted to a stress relief of at least 2 h at 150°C without decarburization.
4 Procedure
Each bending angle (a(,, Ufi, if specified, and a) is determined successively on the same test specimen (see Figure 2 to Figure 4). At least three test specimens shall be used.
The test specimens shall be in the same condition as the parts they represent.
NOTE 1 Test specimens, possibly of a different steel grade, with a higher strength than the pieces may be used. NOTE 2 The fracture angle of the test specimens per bending shall not exceed the deflection angle of the movable chuck.
The diameter of the bending block and the deflection rate of the movable chuck shall be determined according to the material and thickness of the test specimen.
Place the test specimen in the test machine (see Figure 1).
Bend the test specimen under the specified deflection rate of the movable chuck until the first crack occurs in the centre part of the test specimen and measure the bending angles (a0, a0, if specified, and a. Angle a shall be measured within max. 1 h after surface treatment.
5 Expression of results
7 Test report
It shall include the following:
— reference to this standard;
— reference numbers of the test specimens;
— nature of the coating;
— thickness of the coating:
— diameter of the bending block and deflection rate of the movable chuck;
— values of bending angles measured;
— test result.EN 2831-1993 pdf download.