Maraging steel

 

(57) Abstract:

The invention relates to the field of metallurgy, namely the composition of Maraging high strength steel loaded for critical parts. The technical effect of the invention is to improve the strength, ductility, toughness and resistance to shock loads. Steel contains components in the following ratio, wt.%: carbon from 0.005 to 0.03; Nickel 17,5 - 19, 0mm; cobalt 7,5 - 9,0, molybdenum 4,0 - 5,0; silicon 0.75 to 1.10, which vanadium 0.05 to 0.15; tungsten 0,10 - 0,25; iron - rest. table 2.

The invention relates to the field of metallurgy, namely, to seek Maraging steels containing as the basis of iron, Nickel, cobalt, molybdenum, and silicon, and used for the manufacture of critical parts products, which require enhanced mechanical strength, ductility, toughness and shock resistance to cyclic loads.

Known Maraging steel of the following chemical composition, wt.

Carbon 0,04 0,07

Nickel 8 14

Cobalt 6 10

Molybdenum 3,5 10

Titanium 0,1 1,7

Silicon 1,5 2,5

Iron rest

(and.with. USSR N 952989, class C 22 C 38/14).

This steel is used in the toolbar is stijene high levels of these characteristics have become is a result of aging (heating to a temperature of 500oC, the exposure time 4 to 6 hours), accompanied by a selection of dispersed particles of the hardening intermetallic phases containing iron, molybdenum, Nickel, titanium, silicon.

This steel can be achieved a high level of strengthin2200 MPa. However, the viscosity of steel, if we consider the perspective of its use as a structural material critical parts products experiencing when operating the influence of intensive loads, including shock character, small. So, the values of impact toughness of the steel does not exceed KCV 0,12 0,35 MJ/m2.

As described in the patent and informational literature steels of this type, which can be used as a construction, not instrumental, closest to the technical essence and the achieved result is a steel containing, by weight.

Carbon 0.03

Nickel 15 19

Titanium 0,1 1,0

Silicon 0,55 2,0

Molybdenum 4 10

Cobalt 0,1 5,0

Iron rest

The steel may also contain impurities, wt.

Phosphorus 0.01

Sulfur 0.01

Aluminum-0.15

Manganese 0.10

(and.with. USSR N 282660, class C 22 C 38/14)

Steel 2 in thermally hardened state (stare is>,2= 2060 MPa;

= 7 % ;

= 34%, 14

KCV=0,35 MJ/m2< / BR>
Mechanical properties of this steel for heavy-duty parts are lacking, which hampers the possibility of reducing the overall dimensions of its parts, and therefore of metal products.

The ductility and toughness of steel is also not so high as to guarantee the reliability of the manufactured parts of it with such a complex form of loading, as cyclical shock. A small supply of plasticity and viscosity causes insufficient resistance to cracking impact of fatigue.

The aim of the invention is to improve the strength, ductility, toughness and resistance to shock cyclic loads steel.

To achieve this goal in steel containing carbon, Nickel, cobalt, molybdenum, silicon, and iron, in addition enter vanadium and tungsten, and the content of all of these ingredients should be in the following ratios, wt.

Carbon 0,005 0,03

Nickel 17,5 19,0

Cobalt 7,5 9,0

Molybdenum 4,0 5,0

Silicon 0,75 1,10

Vanadium 0,05 0,15

Tungsten 0,10 0,25

Iron rest

As impurities, the steel can is tvline of the invention, not excluding other options in the scope of the claims, as well as the compositions in proportions of ingredients beyond the boundary values.

The steel was melted in a vacuum induction furnace at a technically clean charge materials. Aging was carried out at a temperature of 490oC, the exposure time 4 hours, cooling in air.

The limits of alloying offer steel are determined by the nature of the influence of ingredients on the phase composition and structural state and achieve new positive properties.

Hardening of the proposed steel with aging is the result of decomposition of the supersaturated solid solution of martensite emitting particles of intermetallic phases containing iron, Nickel, molybdenum, silicon.

The Nickel content within 17,5 19,0% allows on one hand to provide sufficient for a significant hardening of the degree of supersaturation of solid solution, and on the other to keep martensitic structure steel (without residual austenite, which reduces the strength and degrades the stability properties of steel).

Molybdenum and silicon are the main reinforcers steel. Their optimum content in steel is 4,0 5,0% and aging is not so great, and at large, a deterioration of the characteristics of viscosity, plasticity, resistance to shock cyclic loads. In addition, higher contents of molybdenum increases the probability of formation of insoluble phase which may adversely affect the ductility and workability of the steel.

Cobalt in the amount of 7,5 9,0% increases the effect of hardening steel with aging by increasing the volume fraction of the precipitates of the intermetallic phase based on iron, Nickel and molybdenum increases the dispersion of the discharge that has a positive effect on the ductility and toughness.

At a lower content of cobalt does not have the desired effect on strength properties. Thus there is also the danger of formation in the steel of the residual austenite. With more content, although there is an increase in the strength of the steel, at the same time there is a decrease in ductility and resistance to shock cyclic loads.

Alloying steel with vanadium in amounts of 0.05 to 0.15% and tungsten in the amount of 0.10 to 0.25% can significantly improve the ductility, toughness and resistance began to fracture under shock cyclic loading. The specified content of vanadium and tungsten is neobhodimyi positive impact on these properties almost weakly detected, and with a larger effect an additional increase in ductility, toughness, resistance to shock cyclic loads is very small.

The positive influence of vanadium and tungsten is manifested through the grinding of grain and the elimination of the allocation of particles krupchyk phases at the grain boundaries.

In table. 2 shows the characteristic values of strength, ductility, toughness, resistance to shock cyclic loads in comparison with the prototype.

The results obtained indicate that the proposed steel exhibits the required properties only in the inventive combination of ingredients, and declare their ratio (compounds 1 to 5, PL. 1, 2).

Patent and scientific literature began with the inventive combination of ingredients and their ratio, showing positive properties (high strength, ductility, toughness and shock resistance to cyclic loads) not found.

The proposed use of steel as a structural material details of special items, operating under intensive dynamic loads will increase their structural strength, reliability and to reduce overall razmerita, characterized in that it further comprises vanadium and tungsten at the following ratios, wt.

Carbon 0,005 0,03

Nickel 17,5 19,0

Cobalt 7,5 9,0

Molybdenum 4 5

Silicon 0,75 1,1

Vanadium 0,05 0,15

Tungsten 0,1 0,25

Iron Ostalnoe

 

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1 tbl

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