阅读说明：本技术 一种高密度高强度合金钢及其制备方法 (High-density high-strength alloy steel and preparation method thereof ) 是由 程兴旺 刘安晋 王琳 潘磊 于 2020-06-24 设计创作，主要内容包括：本发明涉及一种高密度高强度合金钢及其制备方法,属于合金钢技术领域。本发明所述合金钢的组成成分及各成分的百分含量如下：Ni 8％～14％,Co 5％～8％,Mo 4％～7％,W 18％～24％,Ti 0.2％～0.6％,Al＜0.2％,余量为Fe及其他不可避免的杂质元素。本发明通过调控所述合金钢的组成成分及各成分的含量,避免了传统冶炼工艺中W、Mo等元素由于高密度、高熔点而产生严重的碳化物偏析以及液相中由于重力而产生的沉积等问题,使该合金钢兼具高致密度、高密度以及高强度；另外,采用传统冶炼工艺制备所述合金钢,工艺成熟,操作简单,易于实现工业化生产。(The invention relates to high-density high-strength alloy steel and a preparation method thereof, belonging to the technical field of alloy steel. The alloy steel comprises the following components in percentage by weight: 8 to 14 percent of Ni, 5 to 8 percent of Co, 4 to 7 percent of Mo, 18 to 24 percent of W, 0.2 to 0.6 percent of Ti, less than 0.2 percent of Al, and the balance of Fe and other inevitable impurity elements. According to the invention, by regulating and controlling the components and the content of each component of the alloy steel, the problems of serious carbide segregation caused by high density and high melting point of elements such as W, Mo and the like in the traditional smelting process and deposition caused by gravity in a liquid phase are avoided, so that the alloy steel has high density, high density and high strength; in addition, the alloy steel is prepared by adopting the traditional smelting process, the process is mature, the operation is simple, and the industrial production is easy to realize.)

1. A high-density high-strength alloy steel is characterized in that: the alloy steel comprises the following components in percentage by mass based on the total mass of the alloy steel as 100 percent: 8 to 14 percent of Ni, 5 to 8 percent of Co, 4 to 7 percent of Mo, 18 to 24 percent of W, 0.2 to 0.6 percent of Ti, less than 0.2 percent of Al, and the balance of Fe and other inevitable impurity elements, wherein the total content of the impurity elements is less than 0.015 percent.

2. A method of manufacturing a high density high strength alloy steel according to claim 1, wherein: the steps of the method are as follows,

(1) smelting

Weighing raw materials of metal simple substances corresponding to metal elements in the alloy steel according to the mass percentage of the components, loading the raw materials into a smelting furnace, vacuumizing until the vacuum degree in the furnace is less than 50Pa, heating to completely melt the raw materials and no bubble overflows on the surface of a molten pool, preserving heat for 30 min-2 h under the conditions that the vacuum degree is less than 1Pa and the temperature is 1600-1700 ℃, and then casting and cooling under vacuum to obtain a steel ingot;

(2) homogenization treatment

Putting the steel ingot into a furnace with the temperature not more than 550 ℃, and then preserving heat at 1100-1250 ℃ for not less than 3h to finish homogenization treatment;

(3) forging

Cogging and forging the homogenized steel ingot at 1050-1250 ℃, wherein the initial forging temperature is 1200-1250 ℃, the final forging temperature is 1000-1050 ℃, the forging deformation of each pass in the forging process is less than or equal to 10 percent, the steel ingot is heated to 1200-1250 ℃ after each pass of forging, and the steel ingot is placed in sand for slow cooling after the forging;

(4) thermal treatment

Firstly, preserving the heat of the forged steel ingot for 0.5 to 2 hours at 900 to 1100 ℃, and then cooling the steel ingot in quenching oil; and then preserving the heat for 3 to 12 hours at the temperature of between 350 and 550 ℃, and then cooling in the air to obtain the high-density high-strength alloy steel.

Technical Field

The invention relates to high-density high-strength alloy steel and a preparation method thereof, belonging to the technical field of alloy steel.

Background

The ultra-high strength steel is a steel grade which is gradually developed for meeting the requirements of the aviation and aerospace industries since the 40 th century, is mainly characterized by high strength and certain toughness, is mainly used for manufacturing important components bearing high stress and large impact load, and has wide application in civil and military fields.

At present, the high-density alloy mainly takes tungsten as a matrix and is an alloy formed by adding a small amount of elements such as Ni, Fe, Cu and the like, and is commonly used as a weight piece, an inertia rotation element, a armor-piercing projectile body, a shielding material and the like in the fields of aerospace and national defense. The alloy contains a large amount of tungsten elements with high melting point, so the alloy is usually prepared by a powder metallurgy process, the strength of the obtained tungsten alloy is usually about 1000MPa, the strength can be improved to more than 1300MPa after large deformation treatment, but the plasticity is obviously reduced. Ultra-high strength steels have good strength and plasticity, but relatively low density, and therefore, there is a need to develop a steel alloy having high density and high strength. The method for improving the density of the alloy steel mainly comprises the step of adding a large amount of high-specific gravity elements such as tungsten, molybdenum and the like. Because tungsten and molybdenum are strong carbides and the brittleness of steel is caused by excessively high content, when a large amount of tungsten and molybdenum elements are added, the main problem is how to enable the steel to still have high strength and certain plasticity.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the high-density high-strength alloy steel and the preparation method thereof, the alloy steel contains a large amount of W, Mo and other high-density elements, and simultaneously does not contain carbon, so that the problems that W, Mo and other elements generate serious carbide segregation due to high density and high melting point in the traditional smelting process and deposit is generated due to gravity in a liquid phase and the like are solved, and the alloy steel has high density, high density and high strength; in addition, the alloy steel is prepared by adopting the traditional smelting process, the process is mature, the operation is simple, and the industrial production is easy to realize.

The purpose of the invention is realized by the following technical scheme.

The high-density high-strength alloy steel comprises the following components in percentage by mass based on 100% of the total mass of the alloy steel: 8 to 14 percent of Ni, 5 to 8 percent of Co, 4 to 7 percent of Mo, 18 to 24 percent of W, 0.2 to 0.6 percent of Ti, less than 0.2 percent of Al, and the balance of Fe and other inevitable impurity elements (such as C, O, N, H, and the total content is less than 0.015 percent).

The preparation method of the high-density high-strength alloy steel comprises the following specific steps:

(1) smelting

Weighing raw materials of metal simple substances corresponding to metal elements in the alloy steel according to the mass percentage of the components, loading the raw materials into a smelting furnace, vacuumizing until the vacuum degree in the furnace is less than 50Pa, heating to completely melt the raw materials and no bubble overflows on the surface of a molten pool, preserving heat for 30 min-2 h under the conditions that the vacuum degree is less than 1Pa and the temperature is 1600-1700 ℃, and then casting and cooling under vacuum to obtain a steel ingot;

(2) homogenization treatment

The steel ingot is put into a furnace with the temperature not more than 550 ℃, and then the temperature is preserved for more than 3 hours at 1100-1250 ℃, so that the homogenization treatment is completed;

(3) forging

Cogging and forging the homogenized steel ingot at 1050-1250 ℃, wherein the initial forging temperature is 1200-1250 ℃, the final forging temperature is 1000-1050 ℃, the forging deformation of each pass in the forging process is less than or equal to 10 percent, the steel ingot is heated to 1200-1250 ℃ after each pass of forging, and the steel ingot is placed in sand for slow cooling after the forging;

(4) thermal treatment

Firstly, preserving the heat of the forged steel ingot for 0.5 to 2 hours at 900 to 1100 ℃, and then cooling the steel ingot in quenching oil; and then preserving the heat for 3 to 12 hours at the temperature of between 350 and 550 ℃, and then cooling in the air to obtain the high-density high-strength alloy steel.

Has the advantages that:

(1) in the alloy steel, W can be partially dissolved in iron to form a solid solution, so that a certain solid solution strengthening effect is achieved, meanwhile, the W and elements such as Fe, Co, Ni and the like can form a B2A type Laves phase with a complex hexagonal lattice structure, and the B2A type Laves phase is dispersed in the alloy steel to achieve an obvious strengthening effect; in the aging process, the W element can prevent a precipitated phase from being precipitated along the prior austenite grain boundary and can also inhibit impurity nucleus nonmetallic inclusion from being segregated in the grain boundary; in addition, the W element also has the functions of improving the tempering resistance of the alloy steel and inhibiting the high-temperature tempering brittleness;

(2) in the alloy steel, Mo is similar to W, and can form a solid solution to generate a solid solution strengthening effect, and simultaneously can form a fine B2A type Laves phase with a (Fe, Co)2Mo structure together with Co, Fe and other elements, and the phase is dispersedly distributed in a matrix to improve the strength of the steel; the Mo element also has the functions of purifying grain boundaries, improving tempering resistance and inhibiting high-temperature tempering brittleness; however, too high a content of Mo lowers the oxidation resistance of the steel, so that the content of Mo does not exceed 7%;

(3) in the alloy steel, the Ni element can improve the hardenability of the alloy steel, generate solid solution strengthening, and simultaneously can obviously improve the toughness and stress corrosion resistance of the alloy steel, so that screw dislocation is not easy to decompose, and the occurrence of cross slip is ensured;

(4) in the alloy steel, Co element can inhibit and delay the recovery of a martensite dislocation substructure, and the high dislocation density of a martensite lath is kept; the Co element can reduce the solid solubility of Mo in martensite to promote the formation of Fe2Mo precipitated phase, promote the complete transformation of austenite into martensite, improve the Ms point and reduce the tendency of transformation of martensite into reverse transformation austenite;

(5) the alloy steel has higher density (the density is more than 9 g/cm) through component design and content regulation and control³) The high strength (the tensile strength is more than or equal to 1400MPa, and the compressive strength is more than or equal to 2300MPa) can still be kept under the condition; and the preparation process of the alloy steel is mature, the industrial production is easy to realize, and the alloy steel has good application prospect.

Detailed Description

The present invention is further illustrated by the following detailed description, wherein the processes are conventional unless otherwise specified, and the starting materials are commercially available from a public source without further specification.