DE2342034B2 - Use of a ferritic or ferritic-austenitic steel alloy as a material for the production of objects that are resistant to acid and water mixtures at temperatures of up to 70 degrees C. - Google Patents

Description

The invention relates to the use of a ferritic or ferritic-austenitic steel alloy as a material for the manufacture of objects that are resistant to acid and water mixtures from hydrochloric acid, Nitric acid and water are corrosion resistant up to temperatures of about 70 ° C, in particular against erosive corrosion and pitting corrosion.

For the production of device parts and systems that are used with aggressive media come into contact, for example acids or alkalis, it is known to use austenitic chromium-nickel steel with about 20% chromium, 10% nickel, up to 3% molybdenum, up to 1.50% manganese, up to 2% silicon To use carbon contents of about 0.06 to about 0.08%.

Furthermore, steels with high corrosion resistance and good mechanical strength values have also been proposed, with carbon contents between 0.03 to 0.12%, 24.00 to 28.00% chromium, 4.00 to 6.50% nickel, 0.95 to 12.00% cobalt, 1.95 to 3.00% molybdenum, up to 1.00% silicon, up to 1.50% manganese and up to 0.50% copper, the remainder iron.

Purely austenitic steels are also used for components and apparatus in chemical plant engineering with good corrosion resistance and good weldability recommended, the maximum 0.05% carbon, 16.00 to 28.00% chromium, up to 4.00% copper, 0.50 to 1.20% manganese, up to 5.00% molybdenum, 0.10 to 0.40% Nitrogen, 0.05 to 0.40% niobium, 5.00 to 20.00% nickel, a maximum of 1.00% silicon, the remainder being iron.

In addition, there are also corrosion-resistant steels with a corresponding resistance to them Pitting corrosion has been known to occur when used in an environment with chloride ions a maximum of 0.06% carbon, up to 1.00% silicon, under 2.00% manganese, 20.00 to 35.00% chromium, under 8.00% nickel, 1.00 to 5.00% molybdenum, and 0.30 to Have 1.50% niobium.

Your Zoisatz of niobium or the elements zircon and titanium is of particular importance because the specified resistance to it Pit corrosion to alloying these elements is attributed.

In the Austrian patent 1 46 720 is for the production of objects that special Strength properties, in particular high vibration resistance, must have or are high

The use should have resistance to fragility due to intercostal line corrosion chemically neutral chromium-nickel steel alloys with up to 1% carbon, 6 to 40% chromium, 40.00 to 4.00% nickel and 0.30 to 5.00% silicon, titanium.

Vanadium, molybdenum, manganese or aluminum individually or in groups. Through a Quenching should achieve a structure in the steel with a pronounced magnetic special component will. This does not mean that the steels listed may not be used for any other purpose than this known.

The subject of the invention is the use of a ferritic or ferritic-austenitic Steel alloy as a material for the production of

objects that are corrosion-resistant to acid and water mixtures 5 to 15 percent by weight hydrochloric acid, 20 to 30 percent by weight nitric acid and 55 to 75 percent by weight water up to 70 ⁰ C, in particular against erosive corrosion and pitting

Fractional corrosion and that of a maximum of 0.05% carbon, a maximum of 0.50% silicon, a maximum of 2.00% manganese, over 27.00 to 32.00% chromium, 0.50 to 9.00% Nickel, 3.50 to 5.50% molybdenum, the remainder iron, with the usual accompanying elements.

The steel alloys used according to the invention can additionally contain, individually or together, 0.50 to 4.50% cobalt, 0.02 to 0.15% nitrogen and / or 0.10 to 0.60% titanium.
Steels have proven to be advantageously suitable according to the invention which contain more than 28.00 to 30.00% chromium, 4.00 to 9.00% nickel, 3.50 to 4.50% molybdenum and 2.50 to 3.50% Contains cobalt.

The steels used according to the invention have good mechanical values and show in the test

fung to determine the erosive corrosion in an acids water mixture of 10 percent by weight hydrochloric acid, 25 percent by weight nitric acid and 65 weight percent water at a temperature of 60 ° C practically perfect resistance,

6s The Corresponding to the steels used according to the invention shown:

m 42 634

a) Analysis

A. 0 ^) 28 0.44 1.62 28.36 2.98 4; 88 B. ο, οιβ 03 0.84 27.19 5.14 3.62

Si Mn Cr Ni Mo Co N ₂ Ti

3.29 - -

- 0.051 0.17

b) Mechanical properties: Heating at 1100 "C, holding for 30 minutes, quenching in water

Yield strength, tensile strength, elongation 1 = 5 <J, constriction, impact strength

(kp / ram ² ) (kp / mnj ² ) (% min.) (% min.) (mkp / cm ² )

A 67 ^ 76.4 6 # 7.8 l, ö

B 66.8 79.3 22.0 574

c) Abrasive corrosion in the acid mixture at 60 ° C, determined from 5 χ 48-hour tests

A 0.02 g / m ² h

B .... · 0.03 g / m ² h

Claims (3)

Patent claims: 1. Use of a ferritic or ferritic austenitic steel alloy, consisting of s max.0.05% carbon, max. 0.50% silicon, max. 2.00% manganese, over 27.00 to 32.00% chromium, 0.50 to 9.00% nickel, 3.50 to 5.50% molybdenum, Rest Bisen with the usual accompanying elements as a material for producing articles, the warm up to 70 ⁰ C and acid waters mixtures of 5 to 15 weight percent hydrochloric acid, 20 to 30 CfewfeWsprozent nitric acid and 55 to 75 GewieJitsyiozent water korrosionsbestän *. dig, especially against abrasive corrosion and pitting corrosion. 2. Use of a steel alloy according to claim 1 with the proviso that they are also individually or together 0.50 to 4.50% cobalt, 0 02 to 0.15% nitrogen and / or 0.10 to 0.60% Titanium contains, sir the purpose of claim 1. 3. Use of a steel alloy according to claim 1 with the proviso that it is about 28.00 to 3% chromium, 4.00 to 9.00% nickel, 3.50 to Contains 4 \ 50% molybdenum and 2.50 to 3.50% cobalt, for the purpose of claim 1.