CS257877B1 - Martensitic-Bueteniticeles with Increased Resistance to Selective Types of Corrosion and Brittle Violation - Google Patents

Abstract

Martensitic-austenitic steel with increased resistance to selective corrosion and brittle fracture, also suitable for making welds and hardfacing, contains by weight 0.005 to 0.045% carbon, 12.5 to 17.5% chromium, 0.001 to 0.35% silicon, 2.00 to 6.50% nickel, 0.01 to 0.30% manganese, 0.0005 to 0.015% phosphorus, 0.0005 to 0.015% sulfur, 0.0001 to 0.15% oxygen, 0.001 to 0.30% nitrogen, 0.4 to 2.0% molybdenum, 0.0001 to 0.005% arsenic, 0.0001 to 0.005% antimony, 0.0001 to 0.005% tin, 0.00001 to 0.005% bismuth, 0.00001 to 0.01% selenium, 0.00001 to 0.003% boron, 0.001 to 0.005% magnesium, while the sum of silicon and phosphorus does not exceed 0.3%, sulfur and selenium 0.015%, antimony, arsenic, tin and bismuth 0.02%, carbon and nitrogen 0.05% and the hydrogen content is up to 1 cm3 per 100 g of steel.

Description

The invention relates to martensitic-austenitic steel with increased resistance to selective types of corrosion and brittle failure, in particular to intercrystalline and point corrosion, corrosion cracking, which steel is also suitable for welding and welding. It is intended for applications where high demands are placed on thermal influences and mechanical and corrosive stresses in environments causing intergranular corrosion and intergranular corrosion cracking, chloride corrosion cracking and other selective types of corrosion.

Known, commercially produced, wrought, cast and welded, carbon-reduced martensitic-austenitic steels exhibit, at the prescribed content of the alloy elements, in relation to the carbon content and, where appropriate, the carbon content. % nitrogen or at a carbon content of up to 0.05 wt. good corrosion resistance. However, if these steels are exposed to temperatures in the range of 350-650 ° C for an extended period of time, they will have an increased sensitivity to intergranular corrosion or corrosion. to intercrystalline corrosion cracking due to the precipitation of chromium carbides.

K intercrystal, resp. the interphase nature of the attack and the fragile failure, they may also occur as a result of segregation of some impurities at the grain boundaries. These steels, welds and welds contain relatively high amount of impurities - phosphorus, sulfur, oxygen, antimony, arsenic, lead etc.

- are also subject to corrosion cracking, spot and crevice corrosion. Higher impurities

- phosphorus, sulfur, as well as nitrogen, copper, chromium in steels with normal carbon contents, increase the tendency to brittle failure.

These drawbacks are largely eliminated by martensitic-austenitic steel with increased resistance to selective types of corrosion and brittle failure, also suitable for the production of welds and welds according to the invention, characterized in that the steel contains from 0.005 to 0.045% carbon, , 50 to 17.50% chromium, from 2.00 to 6.50% nickel, from 0.001 to 0.35% silicon, from 0.01 to 0.30% manganese, from 0.0005 to 0.015% phosphorus, from 0.0005 to 0.015% sulfur, from 0.0001 to 0.15% oxygen, from 0.001 to 0.030% nitrogen, from 0.4 to 2.0% molybdenum, from 0.001 to 0.035% copper, from 0.001 to 0.007% aluminum , from 0.0001 to 0.005% arsenic, from 0.0001 to 0.005% antimony, from 0.0001 to 0.005% tin, from 0.00001 to 0.005% bismuth, from 0.00001 to 0.01% selenium, from 0 , 00001 to 0,003% of boron, from 0,001 to 0,005% of magnesium, not exceeding 0,3% by weight of silicon and phosphorus, 0,0150% of sulfur and selenium, 0,06% of antimony, arsenic, tin and bismuth, carbon and a nitrogen of 0.05% and up to 1 ci / hydrogen per 100 g of steel.

The martensitic-austenitic steels according to the invention and the welds and welds made therefrom are characterized by increased resistance to various selective types of corrosion, especially in heat-affected environments and in environments causing intergranular corrosion and corrosion cracking, such as chloride environments.

The invention is further elucidated by way of examples of steel compositions. Reducing the amount of accompanying elements is achieved by selecting suitable master alloys, metallurgical and technological processes. The contents of carbon, chromium, nickel and molybdenum, respectively. and some other elements are selected in relation to the required mechanical characteristics to the corrosion stress to be considered. The content of the individual elements is given in percent by weight.

Example 1

Steel in composition: carbon

0.029% of silicon chromium nickel

0.15% 0.1%

15.7%

5.4 »sulfur phosphorus molybdenum oxygen

0.005% 0.006% 1.50% 0.007%

nitrogen 0.019% copper 0.01% of aluminum 0.005% arsenic 0.004% antimony 0.005% of tin 0.005% bismuth 0.0005% selenium 0.0005% magnesium 0.0009% boron 0.001% irons up to 100% hydrogen 0,6 cn? :

has high resistance to brittle failure.

Thermally affected areas of welded joints are not susceptible to intergranular corrosion. The susceptibility to point corrosion and corrosion cracking is more than 2 orders of magnitude less than the previously known steels with 16 S chromium and 6% nickel.

Example 2

Steel composition: carbon 0,03% of manganese 0.18% silicon 0.09% ohromu 13.8% nickel 4.9% phosphorus 0.006% open 0.004% molybdenum 0.9% of oxygen 0.005% nitrogen 0.020% copper 0.01% of aluminum 0.006% arsenic 0.004% antimony 0,004 t of tin 0.005% bismuth 0.0007 « selenium 0.0005 « magnesium 0.0005% boron 0.002% irons up to 100% hydrogen 0,9 ci? :

It is resistant to intergranular corrosion, limited to corrosion cracking, point corrosion and brittle failure.

The steels according to the invention can be used in particular in the chemical industry and power engineering wherever increased demands are placed on the corrosion resistance of total and selective types of corrosion attack and on the reliability and safety of operation and the long life of the equipment.

Claims (1)

Martensitic-austenitic steel with increased resistance to selective types of corrosion and brittle failure, also suitable for welding and cladding, characterized in that it contains from 0.005 to 0.045% carbon, from 12.50 to 17.50% chromium, by weight 2.00 to 6.50% nickel, from 0.001 to 0.35% silicon, from 0.01 to 0.30% manganese, from 0.0005 to 0.015% phosphorus, from 0.0005 to 0.015% sulfur, from 0 0001 to 0.15% oxygen, from 0.001 to 0.030% nitrogen, from 0.4 to 2.0% molybdenum, from 0.001 to 0.035% copper, from 0.001 to 0.007% aluminum, from 0.0001 to 0.005% arsenic from 0.0001 to 0.005% antimony, from 0.0001 to 0.005% tin, from 0.00001 to 0.005% bismuth, from 0.00001 to 0.01% selenium, from 0.00001 to 0.003% boron, from 0.001 to 0.005 % of magnesium, not exceeding 0,3% of silicon and phosphorus, of sulfur and selenium 0,015%, of antimony, arsenic, tin and bismuth 0,02%, of carbon and nitrogen of 0,05% by mass, and up to 1 cm cm of hydrogen per 100 g of steel.