DE767123C - Rolled products for high and bridge structures welded by fusion welding - Google Patents

Description

Rolled products for building structures and bridges welded by fusion welding High-quality structural steel, in particular for iron building and bridge building, which is based on the alloy base silicon and manganese, is known and has recently found increased use. Manganese contents of up to 2%, preferably up to 1.5%, are used, while the silicon content is mostly below 1%, preferably below 0.7 %. Steels with higher silicon contents have not been able to establish themselves in practice. Steels with higher alloying additions of manganese and silicon are also known, but these usually have carbon contents above 0.250 / e, while according to the invention the term structural steels is understood to mean steels whose carbon content does not exceed 0.2%.

With thick dimensions, these structural steels have to be alloyed with manganese to a relatively high degree if the required internal yield strength is to be reached. Difficulties start at strengths of about a; up to 30 mm. Steels with a very high manganese content, however, tend to have metallurgical-related defects, inclusions and the like, so that the use of particularly high manganese contents is limited and, in the case of structural steels, hardly goes beyond 1.70; o: manganese. It is also shown that the behavior during welding in the case of pure longan-silicon steels. especially with thick dimensions that. as mentioned above. High-alloy «earth is not very cheap. so that the weld bead bending test shows relatively poor results.

-According to the guidelines of the Deutsche Reichsbahn, which is to be regarded as decisive for the use of St 32 in Germany, the carbon content should not be greater than o.2%, the silicon content a.3 °, 'o, the manganese content i.2 ° / o and the copper content does not exceed 0.5%. For this purpose, either 0.3 % manganese or o, d.% Chromium or 0.2% molybdenum were also permitted.

The use of the St 32 assembled according to these guidelines However, due to various cases of damage to welded buildings and bridges banned from 1938.

The invention relates to the use of a steel with about 0. os to 0.210l0 carbon, 0.83 to 1.8% manganese. 0.3 to 1.0% silicon, 0.1 to 0.30% chromium, the remainder iron with the usual iron components as a material for rolled products over 25 mm thick for buildings and bridges that are welded by fusion or whitening.

Experiments have shown that this type of steel has a sufficiently high yield point, even with large cross-sections, without the need to increase the manganese content beyond the metallurgically permissible level. Above all, however, tests have shown the surprising fact that the welding behavior of these steels that are weakly alloyed with chromium improved significantly compared to the welding behavior of chromium-free steels otherwise of the same composition. This improvement is fully effective in steels that contain more than 1% manganese. It is known of chrome-copper-steel (Union-Baustahl) that it has favorable welding behavior, although chrome contents from about 0.35010 and copper contents of about 0.5010 are possible. - It was not known, however, that in manganese-silicon steels with preferably manganese contents above i%, in which, moreover, copper is only present in the amounts that unintentionally get into the steel. Even a small amount of chromium additions are sufficient to significantly improve the welding properties. It was thus possible to prove that even the addition of 0.110 chromium in manganese-silicon structural steels brings about a decisive improvement in the bending test of the bending test of chromium-free steels that are otherwise of the same composition. With o.-2 to 0.3010 chrome, the result of the weld bead bending test is significantly more favorable: the bending angle at break and the appearance of the cracks in the weld bead.

The use of such steels for the stated purpose was again permitted by the Deutsche Reichsbahn on the basis of official investigations. For the delivery, the rule applies that dimensions over 30 mm thick are to be delivered normalized; Upon request, the regulation of normal annealing up to thicknesses of ..o mm could be waived after passing a special test. In the case of thicknesses of -to mm and more, normal annealing was in any case considered to be not - «- ended.

The following experiments are listed as examples. The following three types of steel were examined: Steel- C - Si 2, 'n Cr We. 0 '0: 0 # 0 , o 1 0.18 or 45 1.32 .- o, 18 o, 48 1 , 25 O, I2 3 o, 19 0.46 1.28 o, 25 Bead bending test at 3o mm sheet thickness. normalized: Steel bending length of the cracks \ r. winl> el ° across the weld bead 1 6o about 185 mm 2 78 - 45 mm 3 9o - 2o mm

Claims (2)

PATE \ TA \ LANGUAGE: i. The use of a steel with about 0.05 to 0.2% carbon, 0.85 to 1.8% manganese, 0.3 to i, o% silicon, o, io to 0.30% chromium, Remaining iron with the usual iron companions as a material for over 23 mm thick Rolled products for buildings and bridges welded by fusion welding. 2. The use of normalizing annealing on rolled products according to claim i, in particular for thicknesses over 30 mm. To distinguish the subject matter of the invention from the state of the art, the following documents were taken into account in the grant procedure: Italian patent specification No. 364 6i9; German Patent No. 486 956; French Patent No. 743 357; Material handbook for steel and iron, 1937, B1. N 4, p. I, paragraphs i and a; Houdremont, »Sonderstahlkunde«, 1935, p.477.