Maraging steel and products made from it

 

The invention relates to metallurgy, and in particular to compositions of high strength Maraging steels, as well as products made from them. The steel contains the following components, wt.%: carbon 0,005-0,02; Nickel 15-20,0; cobalt 11,5-13,5; molybdenum 3,5-5,0; titanium 0.5 to 2.0; aluminum of 0.05-1,80; Bor 0,001-0,005; REM 0,001-0,010; iron and inevitable impurities, the ratio of titanium, aluminum and cobalt associated dependency: Ti+Al /Co= 0,08+0,25, aB+REM= 0,005-0,012. The steel may further contain chromium 0.3 to 3.0 mass. %. Products can be made from a steel rod with a diameter up to 100 mm, sheet thickness 1-5 mm or seamless pipe diameters from 24 to 159 mm Steel of this composition and the products have high strength properties, good stampability cold, high plasticity after hardening heat treatment and polishing. 3 C. p. F.-ly, 2 tab.

The invention relates to the field of metallurgy, the composition of high-strength Maraging steels, as well as products made from them, and can be used in the manufacture of rod, sheet or pipe, used in mechanical engineering for high volume products, in particular bellows.

Known Mart,10 - 1.0 Aluminum 0.05 to 0.15 Boron - 0.10 Zirconium - 0.10 Silicon - 0.10
Manganese - 0.10
Calcium - 0.10
Chrome - 0.3 0 or 8.1, and 9.0
The phosphorus - To 0,010
Sulfur - To 0,010
Iron - Rest
(Japan's bid 7-243003 With 22 38/00, publ. 19.09.1995).

The disadvantage of this steel is the low solubility of titanium and aluminum in meloncello solid solution and as a consequence low susceptibility to hardening during aging. At the same time, the high content of molybdenum leads to the formation of excessive discharge edge of the laves phase, which causes embrittlement.

Judging by the values of hardness HRC (47,3 to 55,4), the level of strength of the steel according to this patent is not stable and is characterized by a significant spread of values.

You know the product is cold rolled strip thickness of 3-5 mm, made of Maraging steel of the following composition, %:
Carbon -0.02
Silicon -0,1
Manganese -0,2
Phosphorus -0,01
Sulfur -0,01
Nitrogen -0,01
Nickel - 15 - 25
Cobalt -10
Molybdenum -7,0
Aluminium -

The absence of boron steel affects the surface quality of hot rolled steel due to the presence of a thin surface captivity.

Known for high strength and high viscosity Maraging steel containing, %:
Carbon - <0,05
Cobalt - 9,5 - 15
Molybdenum - 4 - 5,2
Titanium - 0,2 - 1,6
Aluminum - <0,15
Sulfur - <0,05
Steel handle in solid solution when heated to 780-850oC, then subjected to aging. Tensile strength tensile 240-260 kg/mm2, K1C131-150 kg/mm2. (Accepted Japan's bid 4-63145 With 22 38/00 publ. 08.10.1992). In the steel composition contains an insufficient number of elements scavengers, and therefore part of the titanium is involved in the formation of oxides, which leads to decrease in stanoevska and polyremedy. When the content of <0.15% of aluminum is not achieved the desired level of strength.

Known product - high-speed rotor is made of Maraging steel containing, %:
Nickel - 17 - 19
Cobalt - 12 - 13
Molybdenum - 3,5 - 4,5
Titanium - 1,6 - 1,75
Aluminum 0.05 to 0.15
Iron and impurities - Rest
After the heat treatment, the strength of steel is 255-270 kg/mm2.

(Posted application form Apnoti to forming in hot and cold state and a low surface quality (planistat).

Known Maraging steel and made of it products, such as sheets, fasteners, chassis of vehicles, cutting tools, etc. the Steel contains, %:
Carbon, 0.15
Nickel - 14 - 22
Cobalt - 12 - 25
Molybdenum - 0,9 - 4,0
Titanium - 0.4
Zirconium - 0.1
The vanadium - To 2.0
Magnesium - To 0.025
Chrome - 3.0
Aluminum - 0.4
Silicon Up to 1.0
Manganese - 1,0
Tungsten - Up to 2.0
Bor - Up to 0,01
Barely - 1,0
Copper - Up to 6.0
Tantalum - To 4.0
Nitrogen - 0.4
Niobium - 3.0
Iron - Rest
(U.S. patent 3532491 NCI 75-123, publ. 06.10.1970, description, prototype).

Steel contains a high amount of cobalt (12-25%), which significantly increases the cost of it. At the same time, the concentration of molybdenum, titanium sufficient to achieve consistently high level of strength.

For steel in this patent is characterized by a significant variation in mechanical characteristics, which is determined by the change in the amount of residual austenite, for example, for steels of group "a" (PL. 5, U.S. patent 3532491).

The problem to which the invention is directed, is to create a high-strength Maraging steel combining high strength, stampability in a cold state the characteristics of, improving stanoevska in a cold state, increasing plasticity after hardening heat treatment, polyremedy.

This technical result is achieved by the fact that the Maraging steel containing carbon, Nickel, cobalt, molybdenum, titanium, aluminum, boron, iron and inevitable impurities, according to the invention, further comprises REM in the following ratio, wt.%:
Carbon - 0.005 to 0.020
Nickel - 15,0 - 20,0
Cobalt - 11,5 - 13,50
Molybdenum - 3,5 - 5,0
Titanium - 0,5 - 2,0
Aluminum is 0.05 - 1,80
Bor - 0,001 - 0,005
REM - 0,001 - 0,010
Iron and inevitable impurities - Rest
the ratio of titanium, aluminum and cobalt are connected by dependency
0,080.25 andB+REM=0,005-0,012.

The steel may further contain chromium 0.3 to 3.0 wt.%. The technical result is also achieved by the fact that the product is made of Maraging steel of the above composition, including in the form of a rod with a diameter up to 100 mm, sheet thickness 1-5 mm or seamless pipe diameters from 24 to 159 mm

The essence of the invention lies in the fact that became regulated by the ratio of titanium and aluminum, depending on the concentration of cobalt, widestore.net of these elements in solid solution depends on the concentration of cobalt, which in turn determines the efficiency of the hardening phases during subsequent aging, namely the number and dispersion. Depends on the level of strength and ability to polishing (getting a mirror surface), which is crucial from the point of view of ensuring the operational reliability of the products (bellows).

Nickel, cobalt and molybdenum are the traditional elements that form the basis for high-strength Maraging steels. Limits on the content of these elements provide a stable martensitic structure after quenching and selected for the following reasons.

When the content is less than 15% of Nickel decreases the ability to form the martensite during aging hardening intermetallic phase, when the content is more than 20% increases the amount of residual austenite and consequently reduces the level of strength.

The content of cobalt in the range of 11.5 to 13.5% is optimal for the steel, as it provides a relatively high level of strength in combination with high resistance to brittle fracture. When the molybdenum content greater than 5% increases the tendency to form along the grain boundaries of the laves phase, which increases coustical the Introduction of REM in the proposed steel made it possible to carry out more fully the process of deoxidation in the smelting in terms of the need for a carbon content of less than 0.02% at low concentrations of manganese and silicon, and also positively affects the dispersion of the reinforcing phase.

The effect of titanium and aluminum based on their ability to form intermetallic phases during heating martensite structure in the range of 450-520oWith; resulting in increased strength properties. Limits on the titanium content of 0.5-2.0% and aluminum of 0.05-1,80% determined on the basis of the conditions for the combination of high strength and sufficient ductility. The ratio of titanium, aluminum and cobalt in the proposed steel shall be determined by dependence

Compliance with this condition determines the achievement of aggregate properties, such as strength, ability to deformirovaniyu cold and obtaining a mirror surface by polishing. This is due to the influence of cobalt on the change in the solubility of intermetallic phases in the martensite and simultaneously in the process of ordering.

Limits on the total content and REE from 0.05 to 0.12% selected based on their impact on the stampability in quenched condition. These bounds are optimal, as this is achieved the necessary degree of strain hardening nezastroennoe martensite during cold is, the fact is accompanied by the improvement of polyremedy.

Set limits on the content of alloying elements in the proposed steel provide a full range of required operational characteristics due to the formation of a predominantly martensitic structure in the presence of 5-10% residual austenite with the discharge of dispersed intermetallic phases such as Ni3, Ti, Ni3, Al, Fe2, Mo, R-phase (in the presence of chromium).

The optimal particle size Ni3, Ti, Ni3, Al -R-phaseand Fe2Mo -.

If the proposed steel contains chromium in an amount of from 0.3 to 3%, in the structure have an additional small amount of residual austenite, which contributes to the improvement of ductility and toughness at low temperatures.

Examples of carrying out the invention
Experienced steel within the claimed composition, and the prototype was melted in a vacuum induction furnace with a spill of metal molds for ingots weighing 10 kg Chemical composition shown in table 1. The ingots were forged to bars and strips. Heating of ingots for forging a rod with a diameter of 16 mm and a strip thickness of 5 mm was produced when the subject received the product in the form of a sheet thickness of 2 mm

The specimens were examined by standard methods of mechanical tensile properties, formability in cold condition (stampability)1,2(1Reference "Theory" rolling, Pillars A., Talanov A. D. - M., metallurgy, 1982,S. 131;2Shulika N. A. W. Laboratory, 1985, 7,S. 85 -86) was determined by the ability to achieve a mirror surface by mechanical polishing (GOST 2789-77).

The results are given in table 2.

From the comparison of the results of the evaluation of the complex of the performance characteristics shown in the table. 2, it follows that the claimed steel, not inferior strength properties to the prototype (and even better), surpasses it in plasticity, stanoevska and polyremedy.


Claims

1. Maraging steel containing carbon, Nickel, cobalt, molybdenum, titanium, aluminum, boron, iron and unavoidable impurities, characterized in that it further comprises a REM in the following ratio, wt.%:

Carbon 0,005 - 0,02

Nickel 15 - 20,0

Cobalt 11,5 - 13,5

Molybdenum 3,5 - 5,0

Titanium 0,5 - 2,0

Aluminum of 0.05 - 1,80

Bor 0,001 - 0,005

REM 0,001 - 0,010

Iron and inevitable impurities Else

this ://img.russianpatents.com/chr/931.gif">B+REM=0,005-0,012.

2. Maraging steel under item 1, characterized in that it additionally contains chromium 0.3 to 3.0 wt.%.

3. A product made of Maraging steel, characterized in that it is made of steel according to any one of paragraphs.1 and 2.

4. The product under item 3, characterized in that it is made in the form of a rod with a diameter up to 100 mm, sheet thickness 1-5 mm or seamless pipe diameters from 24 to 159 mm

 

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4 ex, 1 tbl

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21 cl, 1 dwg, 9 tbl, 5 ex

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SUBSTANCE: proposed method includes production of steel blank, heating it to temperature above As3, deformation in controllable mode at specific reduction processes and at total reduction of 50-60% followed by controllable cooling; proposed steel has the following composition, mass-%: carbon, 0.05-0.9; manganese, 1.25-1.6; silicon, 0.15-0.30; chromium, 0.01-0.1; nickel, 0.3-0.6; molybdenum, 0.10-0.25; vanadium, 0.03-0.10; aluminum, 0.02-0.05; niobium, 0.01-0.06; copper, 0.2-0.4; calcium, 0.001-0.005; sulfur, 0.0005-0.005; phosphorus, 0.005-0.015; the remainder being iron; preliminary deformation of blanks is performed at temperature of 950-850°C at total reduction of 50-60%; then, blank is cooled down to temperature of 820-760°C at rate of cooling of 15°C/s on controllable cooling unit and final deformation is performed additionally at temperature of 770-740°C to required thickness of skelp at total reduction of 60-76%; further cooling is performed at higher rate of 35-55°C/s to temperature of 530-350°C, after which skelp is cooled in jacket to temperature of 150±20°C and then in the air. New stage of the proposed method makes it possible to manufacture tubes of 1067-1420 mm in diameter at thickness of walls of 24-40 mm which are used for sea gas pipe lines working at pressure of up to 19 Mpa.

EFFECT: enhanced strength, ductility and cold resistance; enhanced operational reliability; increased service life.

2 tbl, 1 ex

FIELD: metallurgy, namely cold resistant steels.

SUBSTANCE: cold resistant steel for machines and apparatuses, namely in gas- and oil production industry operating in condition of cold climate. Such steel contains, mass %: carbon, 0.15 - 0.22; manganese, 0.3 - 0.6; silicon, 0.15 - 0.40; vanadium, 0.08 -0.12; titanium, 0.001 - 0.040; niobium, 0.001 - 0.040; aluminum, 0.03 - 0.06; sulfur, 0.010 - 0.020; phosphorus, 0.010 - 0.020; cerium, 0.005 - 0.05; calcium, 0.001 - 0.01; barium, 0.001 - 0.01; iron, the balance.

EFFECT: improved strength and cold resistance of steel.

5 tbl

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