RU2738033C1 - Martensite-aging steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to corrosion-resistant martensite-aging steels, intended for production of high-loaded parts. Steel is melted in open induction furnace (OIF) with subsequent electroslag remelting (ESR) or vacuum-arc remelting (VAR) and contains components at following ratio, wt. %: carbon to 0.04, silicon to 0.30, manganese to 0.20, chromium 12.0–14.0, nickel 7.5–9.0, molybdenum 0.6–1.0, aluminium 0.3–0.6, titanium 0.3–0.6, vanadium 0.01–0.20, tungsten 0.01–0.20, cerium up to 0.05, magnesium - up to 0.05, the rest - iron and unavoidable impurities, including sulphur - up to 0.025, phosphorus - up to 0.025, copper - up to 0.20, tin - up to 0.001, antimony up to 0.001, arsenic - up to 0.001, lead - up to 0.001, bismuth - up to 0.001.

EFFECT: steel has high strength and corrosion resistance.

2 cl

Description

The invention relates to the field of metallurgy, namely to corrosion-resistant maraging steels, intended for the manufacture of highly loaded parts.

From the prior art, corrosion-resistant maraging steels SU534165A (prototype) and 03X11H10M2T (analogue 1) are known used in the domestic industry. The main disadvantage of the prototype and the analogue is the suboptimal chemical composition that does not provide a sufficiently high strength and corrosion resistance at the same time. Along with this drawback, it should be noted that the chemical composition of the prototype contains selenium, which is a dangerous and toxic element, both in the production of steel and in its subsequent processing and operation.

In addition, steel SU585232 is known (publ. 25.12.1977)

carbon 0.003-0.03 chromium 10.0-14.0 nickel 9.0-14.0 molybdenum 1.0-3.0 titanium 0.7-1.6 vanadium 0.05-0.35 zirconium 0.01-0.10 neodymium 0.003-0.05 calcium 0.02-0.1 lanthanum 0.005-0.08 iron and inevitable impurities rest

The steel is intended for the production of products with large sections with increased ductility and toughness. The disadvantage of this steel is the absence of aluminum in its composition, which is part of the hardening phase Ni ₃ (Ti, Al), which significantly increases the strength properties of steel.

From the prior art, maraging steel 03X11N10M2T (EP678, VNS-17) according to TU 14-1-1540-75 is known

carbon ≤ 0.03 silicon ≤ 0.15 manganese ≤ 0.10 sulfur ≤ 0.010 phosphorus ≤ 0.010 chromium 10.0-11.3 nickel 9.0-10.3 molybdenum 1.8-2.3 titanium 0.7-1.1 aluminum ≤ 0.20 zirconium ≤ 0.03 niobium ≤ 0.15 boron ≤ 0.003 iron and inevitable impurities rest

The disadvantage of this steel is the low content of chromium, which does not provide sufficient corrosion resistance, as well as the increased content of nickel, molybdenum and titanium in quantities that do not allow obtaining a sufficiently high complex of mechanical properties.

Known steel RU2169790S2 (publ. 27.06.2001) - analogue 2

The steel has the following chemical composition (wt%):

carbon 0.01-0.04 silicon 0.10-0.75 manganese 0.10-0.90 chromium 9.5-13.5 nickel 6.0-9.0 cobalt 2.5-7.8 molybdenum 0.8-4.0 vanadium 0.03-0.30 tungsten 0.02-0.30 nitrogen 0.01-0.08 calcium 0.001-0.05 cerium 0.001-0.05 iron and inevitable impurities rest

The steel is intended for the production of brazed-welded structures of power plants, operating at temperatures from -253 to 500 ° C. The disadvantage of this steel is excessive alloying with cobalt, which leads to a significant increase in the cost of steel without providing commensurate advantages in mechanical properties.

Known steel RU2532785С1 (publ. 05/17/2013) - analogue 3

The steel has the following chemical composition (wt%):

carbon ≤ 0.03 silicon 0.05-0.15 manganese 0.05-0.15 chromium 9.3-10.5 nickel 7.0-8.5 cobalt 3.5-7.0 molybdenum 1.2-3.0 vanadium 0.10-0.30 tungsten 0.05-0.20 nitrogen ≤ 0.02 titanium 0.01-0.08 niobium 0.05-0.15 calcium 0.001-0.05 cerium 0.001-0.05 yttrium 0.001-0.05 iron and inevitable impurities rest

The steel is intended for the production of highly loaded elastic metal seals for detachable joints of power plants operating in aggressive environments at temperatures from 20 to 723 K. The disadvantage of this steel, on the one hand, is the insufficient chromium content to ensure corrosion resistance and mechanical properties and the absence of aluminum, and, on the other hand, its excessive alloying with molybdenum and cobalt, which greatly increases the cost of the metal.

Known steel RU2571241С1 (publ. 20.12.2015)

The steel has the following chemical composition (wt%):

carbon ≤ 0.03 chromium 2.0-18.0 nickel 5.0-10.0 molybdenum 0.8-3.0 aluminum 1.0-2.5 titanium ≤ 0.20 cerium ≤ 0.02 yttrium ≤ 0.002 iron and inevitable impurities rest

Steel is intended for the production of products with high hardness and corrosion resistance with sufficient ductility. The disadvantage of this steel is its excessive alloying with aluminum with a low titanium content, which does not satisfy the optimal stoichiometric composition of the hardening phase Ni ₃ (Ti, Al) and, as a consequence, the steel has a lower strength.

Known steel WO2019121879 (publ. 06/27/2019) - analogue 4

The steel has the following chemical composition (wt%):

carbon 0.01-0.05 silicon 0.40-0.80 manganese 0.10-0.50 chromium 12.0-13.0 nickel 9.5-10.5 molybdenum 0.5-1.5 aluminum 0.5-1.5 titanium 0.5-1.5 copper ≤ 0.05 iron rest

The disadvantages of this steel include the absence of small additions of tungsten and vanadium in its composition, which are necessary to protect chromium from binding to carbides. During the heat treatment of such steel, which consists in quenching with subsequent aging, due to the rather high permissible concentration of titanium, in addition to the hardening phase, titanium carbides are released, which worsen the plastic and tough properties of the steel. It should also be noted that the composition of steel according to WO2019121879 (publ. 06/27/2019), according to the description of the invention, was developed for the manufacture of powder materials for their subsequent sintering using selective laser alloying technologies and some other 3D printing technologies, which does not allow assessing the possibility of manufacturing metal products using classical technologies using melting of hot deformation of ingots. Also, the inventors do not provide data on the plastic properties of such a metal, which is a very important characteristic for many products made from maraging steels.

The technical problem to which the present invention is directed is the development of a corrosion-resistant high-strength maraging steel with high strength and increased corrosion resistance.

To achieve this goal, maraging steel is proposed containing carbon, silicon, manganese, chromium, nickel, molybdenum, aluminum, titanium, vanadium and tungsten, cerium and magnesium, the rest of iron and inevitable impurities, including: sulfur, phosphorus, copper, tin, antimony, arsenic, lead and bismuth, characterized in that it contains vanadium, tungsten, cerium and magnesium in the following ratio of components, wt. %:

carbon ≤ 0.04 silicon ≤ 0.30 manganese ≤ 0.20 sulfur ≤ 0.025 phosphorus ≤ 0.025 chromium 12.0-14.0 nickel 7.5-9.0 molybdenum 0.6-1.0 aluminum 0.3-0.6 titanium 0.3-0.6 vanadium 0.01-0.20 tungsten 0.01-0.20 cerium ≤ 0.05 magnesium ≤ 0.05 copper ≤ 0.20 tin ≤ 0.001 antimony ≤ 0.001 arsenic ≤ 0.001 lead ≤ 0.001 bismuth ≤ 0.001 iron rest

The essence of the invention lies in the selection of optimal ratios of the main alloying elements to ensure a complex of physical and mechanical properties, as well as additional alloying of the claimed steel with small amounts of vanadium and tungsten, cerium and magnesium.

In comparison with the steels discussed above, the claimed steel contains a sufficient amount of:

chromium to provide good corrosion resistance;

nickel to provide high toughness and allow the particles of the hardening phase to precipitate during aging;

titanium and aluminum, sufficient to obtain the optimal amount of the hardening phase Ni ₃ (Ti, Al), while ensuring high strength and sufficient ductility;

molybdenum to eliminate temper brittleness of steel, as well as to prevent segregation of the hardening phase along the grain boundaries;

vanadium and tungsten, for the formation of finely dispersed special carbides that protect chromium from binding to Cr ₂₃ C ₆ carbides and thereby improving the resistance of the claimed steel to intergranular corrosion and titanium from the formation of coarse angular inclusions of titanium carbide, improving the ductility of the claimed steel;

cerium and magnesium, the most complete implementation of the deoxidation process during smelting, and also has a positive effect on the dispersion of the strengthening phases.

Also, in the proposed steel, the content of harmful impurities dissolved in the metal is normalized to ensure its purity for non-metallic inclusions and to ensure high quality products.

Examples of implementation of the invention

Experimental steel, within the claimed composition, was smelted in a vacuum induction furnace. We also tested vacuum arc and electroslag remelting, which made it possible to further improve the purity of steel, including non-metallic inclusions. The chemical composition of the experimental heats is shown in Table 1. The results of monitoring the mechanical properties of the proposed steel, as well as its comparison with the prototype and the closest analogs are shown in Table 2. As can be seen from the data provided, the proposed steel has sufficiently high strength properties, surpassing the prototype and some analogues. and at the same time is economically alloyed.

Claims (3)

1. Corrosion-resistant maraging steel containing carbon, silicon, manganese, chromium, nickel, molybdenum, aluminum, titanium, iron and inevitable impurities, including: sulfur, phosphorus, copper, tin, antimony, arsenic, lead and bismuth, characterized in that it is melted in an open induction furnace (OIP) with subsequent electroslag remelting (ESR) or vacuum arc remelting (VAR) and additionally contains vanadium, tungsten, cerium and magnesium in the following ratio of components, wt%: carbon ≤ 0.04 silicon ≤ 0.30 manganese ≤ 0.20 sulfur ≤ 0.025 phosphorus ≤ 0.025 chromium 12.0-14.0 nickel 7.5-9.0 molybdenum 0.6-1.0 aluminum 0.3-0.6 titanium 0.3-0.6 vanadium 0.01-0.20 tungsten 0.01-0.20 cerium ≤ 0.05 magnesium ≤ 0.05 copper ≤ 0.20 tin ≤ 0.001 antimony ≤ 0.001 arsenic ≤ 0.001 lead ≤ 0.001 bismuth ≤ 0.001 iron rest 2. A product made of corrosion-resistant maraging steel, characterized in that it is made of steel according to claim 1.

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