DE2347078B2 - USE OF A FERRITIC-AUSTENITIC CRNIMON STEEL ALLOY AS A MATERIAL FOR THE MANUFACTURE OF WELDED COMPONENTS - Google Patents

Description

0.002 to below 0.030% C
18.0 to less than 26.0% Cr

4.0 until 8.0% Ni 2.0 until 5.0% Mon 0.08 until 0.25% N 0.20 until 0.80% Si 0.50 until 2.0% Mn 0.10 until 0.50% V

The remainder of iron with the usual impurities caused by the melting process for the production of without post-heat treatment, welded items that are resistant to pitting corrosion and intergranular Corrosion after the Monypcnny-Strauss experiment or boiling in 65% nitric acid and subsequent bending test.

2. Use of a Chmm-nickel-molybdenum-nitrogen-steel alloy according to claim 1, consisting of

0.010 to below 0.030% C

19.0 to less than 26.0% Cr

5.2 to 8% Ni

2.0

0.11

0.20

1.0

0.10

until
until
until
until
until

5%
0.25%
0.80%
2.0%
0.50%

Mon

N
Si
Mn

The remainder is iron and the usual smelting-related impurities for the purpose according to claim 1. 3. Use of a corrosion-resistant, unstabilized, ferritic-austenitic in the state of use Chromium-nickel-molybdenum-nitrogen-steel alloy according to patent application P 22 55 673.6-24, consisting of

0.010 to below 0.030%
19.0 to below 26.0%
5.2 to 8.0%

2.0 to 5.0%

0.11 to 0.25%

0.20 to 0.80%

1.0 to

2.0%

C.
Cr

Ni

Mon

Si

Mn

The remainder is iron with the usual impurities caused by the melting for the purpose according to claim 1. 4. Use according to one of claims 1 to 3 with the proviso that the welded objects Components of chemical apparatus construction, especially heat exchangers that are prone to pitting and their parts are.

The invention relates to the use of a corrosion-resistant, unstabilized, in the state of use ferritic - austenitic chromium - nickel-molybdenum-nitrogen-steel alloy according to patent application P 22 55 673.6-24 for the production of welded objects that are resistant to intergranular corrosion without post-heat treatment, tested according to the Monypenny-Strauss test or after boiling in 65% nitric acid and a subsequent bending test. The steel alloy consists essentially of 0.002 to less than 0.03% C; 18.0 to less than 26.0% Cr; 2.0 to 8.0% Ni; 1.6 to 5% Mo; 0.06 to 0.20% N; up to 0.8% Si; up to 2.0% Mn; The remainder iron with the usual impurities caused by the melting and can optionally contain up to 0.2% Sb, As, Pb, Sn, Al, Ti, Ta, Nb or B, up to 0.5% Zr or V, up to 1% W or Co and up to Contains 2% Cu. With steels of this type, a ductile, crack-free and pore-free welded joint can be produced without post-heat treatment, which in the welded and non-post-heat treated state in particular does not experience any intergranular corrosion attack. The strict standards of either the Monypenny-Strauss test according to DIN 50 914 or the bending test on samples boiled in 65% nitric acid are used as test criteria. The steels described in the main application have, in particular, significantly improved Schwcißeigcnschaftcn in addition to the resistance to intergranular corrosion. At approx. 45 to 55 kp / mm ^{2, the} yield point is sufficiently high so that the steels are particularly suitable for the manufacture of welded components in general and chemical apparatus engineering, in particular for the manufacture of heat exchangers and their parts. The resistance without post-heat treatment is of great importance in the manufacture of welded pipes.

It has now surprisingly been found that within and adjacent to the in the patent application P 22 55 673.6-24 disclosed alloy variants can be found as a special additional property have a high resistance to pitting corrosion. It has been shown, for example, that No pitting could be detected on the water-cooled apparatus components. The use of these steels for the production of welded components for chemical apparatus engineering, in particular for the production of heat exchangers and their parts, is particularly advantageous because there are those made of steel Objects are exposed to media which, in addition to intergranular corrosion, can cause pitting, such as B. Sea water with an elevated temperature. The solutions to be used according to the invention gen consist of

0.010 to under 0.030% C. 19.0 to under 26.0% Cr 5.7 until 8.0% Ni 2.0 until 5.0% Mon 0.11 until 0.25% N 0.20 until 0.80% Si 1.0 until 2.0% Mn

The remainder is iron with the usual impurities caused by the smelting process. This creates a ductile, crack- and

• ejtn · ^

Pure-free welded joint without post-treatment which can be produced in the area of sweat and worm influence zones in the state of use Resistant to pitting resistant without performing any post-heat treatment.! against is intergranular corrosion.

The use of a chromium-nickel-molybdenum-nitrogen-steel alloy is preferably proposed, from

0.010 to under 0.030% C. 19.0 to under 26.0% Cr 5.2 until 8.0% Ni 2.0 until 5.0% Mon 0.11 until 0.25% N 0.20 until 0.80% Si 1.0 until 2.0% Mn 0.10 until 0.50% V

The remainder contains iron and the usual impurities caused by the melting process.
Furthermore, alloys for the production of heat exchangers and dcrcnTcilcn can be used with advantage

0.002 to under 0.030% C. 18.0 to under 26.0% Cr 4.0 until 8.0% Ni 2.0 until 5.0% Mon 0.08 until 0.25% N 0.20 until 0.80% Si 0.50 until 2.0% Mn 0.10 until 0.50% V

exhibit.

1 Γι the following table are different Exemplary embodiments of the steel to be used according to the invention, the preferred compositions and the results with regard to the intergranular corrosion attack and the Illustrate pitting corrosion. The sweat-affected, non-post-heat treatment was tested Area of one welded joint, d. H. the weld, the heat affected zone and the base material.

No. C. Si Mn Cr Ni Mon N V Findings in the sweat Bending affected area attempt after at 5 x 48 h Mony in ENT ₃ penny- cooked Ostrich- rehearse attempt if. if. if. 1 0.012 0.30 1.09 19.8 5.4 3.9 0.12 _ if. if, 2 0.028 0.32 1.78 24.9 6.8 3.24 0.20 - if if. 3 0.020 0.50 1.25 22.4 5.7 3.5 0.14 0.31 if. if. 4th 0.024 0.52 1.76 21.9 5.3 3.4 0.14 0.18 if. 5 0.022 0.45 1.68 22.67 5.44 2.96 0.12 0.10 if. 6th 0.010 0.26 1.04 19.6 4.8 2.7 0.08 0.45 if.

Claims (1)

Patent claims: 1. Use of a corrosion-resistant, unstabilized, ferritic-austenitic in the state of use Chromium - nickel - molybdenum - nitrogen steel - alloy according to patent application P 22 55 673.6-24, consisting of