CN105088017B - A kind of castable forging kinetic energy tungsten nickel cobalt (alloy) and preparation method of two-phase high density - Google Patents

Abstract

A dual-phase high-density castable kinetic energy tungsten-nickel-cobalt alloy and its preparation method belong to the field of kinetic energy alloys. The chemical composition weight percent of the alloy is: W 35-65%, Ti 0-3%, Al 0-3%, Nb 0-8%, Ta 0-10%, the balance is Ni or Co or NiCo and unavoidable impurity elements and trace elements such as rare earth, etc. The preparation method adopts vacuum induction + vacuum consumable remelting. Compared with the prior art, the present invention has excellent comprehensive performance, high density, high toughness, ultra ^- high strength, ultra ^- high dynamic strength and other excellent performances. The tensile strength reaches above 1300MPa, and the dynamic compressive strength reaches above 1800MPa.

Description

A dual-phase high-density castable forgeable kinetic energy tungsten-nickel-cobalt alloy and its preparation method

technical field

The invention belongs to the technical field of kinetic energy alloys, in particular to a dual-phase high-density castable kinetic energy tungsten-nickel-cobalt alloy (DT790) and its preparation method. The alloy has excellent properties such as high density, high toughness, ultra-high strength, and high dynamic strength. 11.0-15.0g/cm ³ , impact toughness over 80J/cm ² , static tensile strength over 1300MPa, and dynamic compressive strength over 1800MPa.

Background technique

Prior to this, the high-density materials commonly used in the world are mainly tungsten alloys. Due to the high melting point of tungsten, such materials are usually sintered and formed by powder metallurgy. At present, the widely used tungsten alloys in the world include W90, W93, W95 and W97, etc., the density of this kind of material is very high, which can reach 15-18g/cm ³ , but the strength is low and the toughness is poor. The tensile strength of normal sintered state reaches 800-1000MPa, and the elongation reaches 20-30%. To achieve higher strength, it needs to go through large plastic deformation, and its strength can reach about 1400MPa, but the plastic toughness is severely reduced, only about 10%; especially the powder metallurgy process determines that the microstructure of tungsten alloy is tungsten particles + binder phase two-phase structure. Taking the widely used 93W as an example, the approximately spherical tungsten particles are distributed in the W-Ni-Fe binder phase, the structure lacks consistency and continuity, and the mechanical properties are not good under high strain rate loading conditions, which limits a large number of popularization. Application prospects. The strengthening method of tungsten alloy prepared by powder metallurgy liquid phase sintering method can only be deformation strengthening, and the second phase strengthening widely used in metal materials cannot be used. This determines that the mechanical properties of undeformed tungsten alloys are difficult to improve. For large-sized tungsten alloy parts, the requirements for deformation equipment are extremely high, and the deformation is prone to unevenness, which affects the uniformity of the structure. This also determines that the mechanical properties of large-sized tungsten alloys are difficult to improve.

The chemical composition and mechanical properties of several tungsten alloys are shown in Table 1 and Table 2.

Table 1 Rolling properties of high-density tungsten alloy (70W-21Ni-9Fe)

state Deformation Tensile strength MPa Yield strength MPa Elongation% 1 cold rolled 18% 1233 1116 12.5 2 cold rolled 18% 1216 1104 11.9 3 cold rolling 50% 1494 1344 4.3 4 cold rolled 50% 1416 1310 7.2 5 hot rolled 1216 834 11 6 hot rolled 1189 860 twenty three

Table 2 Mechanical properties of high-density tungsten alloy deformation strengthening

Element state Deformation% Tensile strength MPa Elongation% 1 93W-7(Ni,Fe) Rotary forging 18% 1279 7.7 2 91W-9(Ni,Fe) forging 48% 1370 6 3 90W-7Ni-3Fe Rotary forging 17% 1103 13 4 93W-5Ni-2Fe Rotary forging 18% 1199 7.6 5 93W-5Ni-2Fe Envelope Extrusion 80% 1496 3.3 6 93W-7(Ni,Fe) Rotary forging 70% 1430 12 7 90W-7Ni-3Fe Rotary forging + heat treatment 18% 1230 12 8 93W-5Ni-2Fe Rotary forging + heat treatment 18% 1358 5

It is hoped to develop a high-density alloy that can be produced by ordinary forging and casting metallurgical technology, which has the characteristics of castable and forgeable technology, breaks through the limit of the size and strength of tungsten alloy preparation in the past, and has high density, high toughness and ultra-high strength at the same time. Excellent performance such as high strength. Therefore, strengthening elements such as Ti, Al, Nb, etc. are added to the tungsten-nickel solid solution or tungsten-cobalt solid solution to form a strengthening phase γ', etc., and the strength is improved through aging precipitation, such as the invention patent DT730, etc., but limited by the γ' phase forming elements Generally, when the content of tungsten element in this type of alloy is less than 40%, it is difficult to increase the density to more than 12g/ ^cm3 . It is true that when the content of tungsten element is less than 40%, the melting point drops below 1500°C and the solid solution temperature decreases. Below 1050°C, it can have better casting and forging process performance, but in order to further increase the density and kinetic energy, the content of tungsten element must be further increased. When the tungsten element exceeds 38%, the alloy is a dual-phase structure, usually dual-phase tungsten-nickel The casting and forging process performance of the alloy drops sharply, and the conventional process cannot be easily applied, and precise control of the process is required.

It is hoped to develop a dual-phase high-density alloy with a density of 11.0-15.0g/cm ³ , an impact toughness of more than 80J/cm ² , a static tensile strength of more than 1200MPa, and a dynamic compressive strength of more than 1800MPa and its preparation method, so that the density Further improve, realize the production of industrialization at the same time. Therefore, the development of a new concept of dual-phase high tungsten heat-resistant alloys has been put on the scientific research agenda.

Contents of the invention

The purpose of the present invention is to provide a dual-phase high-density castable kinetic energy tungsten-nickel-cobalt alloy and its preparation method, which has excellent comprehensive performance, high density, high toughness, ultra-high strength, ultra-high dynamic strength and other excellent properties, and the density reaches 11.0 -15.0g/cm ³ , impact toughness over 80J/cm ² , static tensile strength over 1200MPa, dynamic compressive strength over 1800MPa, dual-phase high-density castable kinetic energy tungsten-nickel alloy and its preparation method.

Based on the above purpose, the main technical solution of the present invention is that on the basis of tungsten-nickel or tungsten-cobalt single-phase alloy, compared with single-phase tungsten-nickel or tungsten-cobalt alloy, the strengthening method is replaced by W particle reinforcement + Ni4W precipitation composite strengthening instead of single-phase The γ' phase of the kinetic energy alloy is strengthened. For this reason, the W content in the alloy is controlled between 35-65%. At the same time, W and other strengthening elements Ti, Al, Nb, and Ta elements can also be added in combination, and W particles can be used to strengthen +Ni4W Precipitation strengthening and γ' phase composite strengthening to form ultra-high-strength high-density (≥11g/cm ³ ) dual-phase ultra-high-strength kinetic energy alloys, while strictly controlling the ratio of (W+Ta)/Ni and (W+Nb)/ Ni, (W+Ti+Al)/Ni alloy composition ratio, the steel of the present invention can be produced by conventional metallurgical processes, vacuum induction + vacuum self-consumption, and through precisely controlled casting, blanking and forging processes, large Batch and stable industrialized mass production. The chemical composition (weight%) of the alloy is: W 35-65%, others may contain Ti 0-3%, Al0-3% and Nb 0-8%, Ta 0-10%, and the rest are Ni or Co or ( Ni+Co) and other unavoidable impurity elements and trace elements such as rare earth, etc. Compared with the prior art, the present invention has excellent comprehensive performance.

The design basis of the above chemical composition is as follows:

Ni: a matrix element, which ensures good strength and toughness while obtaining high density. Ni can dissolve W in relatively low-melting point metals, making it possible to prepare high-density alloys by smelting. Since there is no density problem in smelting, and the grain can be refined by forging, the second phase can be strengthened by solid solution-precipitation, and it is also the Ni4W strengthening phase, so the mechanical properties can be greatly improved.

Co: matrix element, can be interchanged with Ni, can be used in combination with Ni or alone, can dissolve W in relatively low melting point metals, making it possible to prepare high-density alloys by smelting. However, the solid solubility of W in Co is not as good as that in Ni, so Ni-based or Ni-based NiCo composites are often used to increase the solid solution content of W. Co will promote the precipitation of precipitated phases, and at the same time, in Co-based high-density kinetic energy alloys, Co will form Co4W phases for precipitation strengthening. Therefore, in the present invention, Co can be used alone as a matrix element or combined with Ni.

W: It is the main element to increase the density. It is dissolved in the Ni matrix, which not only increases the density, but also can be strengthened by Ni4W aging precipitation. Theoretically, the higher the W content, the better, but the solid solubility of W in Ni is limited, exceeding 40%. When it exceeds 70%, the powder metallurgy process can only be used because the melting point is too high. If it is too low and less than 35%, the density cannot reach 11.0g/cm ³ . Therefore, within the scope of this patent, the W content is limited 35-65%.

Ta: It is a better element for increasing density, and its effect is equivalent to that of W. However, because Ta is a strategic resource, the price is expensive, and especially the pollution caused by Ta in smelting limits the use of Ta. Therefore, the present invention controls the content of Ta Within 10%.

Ti: Adding a certain amount of Ti will precipitate the γ' phase during the aging process, which can effectively improve the mechanical properties, but too much will seriously reduce the plastic toughness, so the present invention controls it within 3%.

Al: Adding a certain amount of Al will precipitate the γ' phase during the aging process, which can effectively improve the mechanical properties, but too much will seriously reduce the plasticity and toughness, so the present invention controls it within 3%.

Nb: Adding a certain amount of Nb will precipitate the γ' phase during the aging process, which can effectively improve the mechanical properties, but too much will seriously reduce the plasticity and toughness, so the present invention controls it within 8%.

The high-density ultra-high-strength heat-resistant alloy of the present invention is easy to adopt vacuum induction + vacuum self-consumption remelting, and its specific process parameters are as follows:

The ingot opening temperature is 1200-1250°C, and the furnace charging temperature is ≤600°C;

Forging heating temperature: 1150-1180°C, 1120°C ≤ opening forging temperature ≤ 1180°C, 850°C ≤ final forging temperature ≤ 950°C;

Final heat treatment:

Heating to 580-780°C, 5 hours after heat penetration ≤ holding time ≤ 20 hours, air cooling; or carry out secondary aging treatment.

The alloy of the present invention prepared according to the above chemical composition and production method has the advantages of dual-phase structure, high density, high toughness and ultra-high strength, and the specific properties are: the density reaches 11.0-15.0g/cm ³ , the static tensile strength It can reach more than 1200MPa, and the dynamic compressive strength can reach more than 1800MPa. Compared with the prior art, the invention has excellent comprehensive performance, higher strength and density, good dynamic strength, good structure consistency and uniformity, and can be produced by conventional casting and forging processes.

Description of drawings

Fig. 1 is the microstructure diagram of 13# test steel of the present invention.

Figure 2 is the metallographic structure diagram of the single-phase tungsten-nickel-cobalt alloy of the comparison steel.

detailed description

According to the chemical composition range of the dual-phase high-density castable kinetic energy tungsten-nickel-cobalt alloy of the present invention, 25 kilograms of vacuum induction furnaces are used to prepare 15 furnaces of alloy ingots of 20 kilograms, and its specific chemical composition is shown in Table 1.

After the test steel was smelted and cast into steel ingots, the blank was opened at 1180°C, the forging heating temperature was 1170°C, and the final forging temperature was 900°C. The size of the forging test rod is: φ15×2000, 15×15×2000.

After forging, the test bar is first stretched and impacted on the sample blank. Finally, perform aging treatment: aging treatment 700°C×10h, AC. The mechanical properties of the sample blanks can be tested after grinding, as shown in Table 2.

For comparison, the chemical composition and mechanical properties of Comparative Example 93W-7 (Ni, Fe) etc. are listed in Table 1 and Table 2.

As can be seen from Table 1, compared with tungsten alloys such as comparative example 93W-7 (Ni, Fe), the main technical scheme of the present invention is a dual-phase alloy of tungsten-nickel-cobalt structure, and Ta, Ti, Al, Nb elements can be added simultaneously, Form age-strengthened high-density (≥11g/cm ³ ) ultra-high-strength kinetic energy alloys, due to strict (W+Ta)/Ni ratio and (W+Nb)/Ni, (W+Ti+Al)/Ni alloys Composition ratio, the steel of the present invention can be produced by conventional metallurgical technology, vacuum induction + vacuum self-consumption, and ordinary forging technology. Compared with the powder metallurgy method that must be used for tungsten alloys, it is easy to industrialize in large quantities and stability Compared with the single-phase nickel-cobalt-free alloy, the structure of the alloy of the present invention has uniform particle strengthening and continuity, see 1.

It can be seen from Table 2 that compared with the comparative example, the steel grade of the present invention has excellent properties such as high density, high toughness, ultra-high strength, and high dynamic strength, and can be produced by conventional processes. The density reaches 11.0-15.0g/cm ³ The tensile strength reaches above 1200MPa, and the dynamic compressive strength reaches above 1800MPa.

Table 5 embodiment of the present invention and comparative example chemical composition (wt%) comparison table

Table 6 The comparison table of the mechanical properties of the embodiment of the present invention and the comparative example

Claims (2)

1. the castable forging kinetic energy tungsten nickel cobalt (alloy) of a kind of two-phase high density, it is characterised in that chemical component weight % is：W 45- 60%, Ti 1-2%, Al 1-2%, Nb 1-5%, Ta 1-5%, balance of Ni or Co or NiCo and inevitable impurity unit Element and trace element.

2. the preparation method of the castable forging kinetic energy tungsten nickel cobalt (alloy) of a kind of two-phase high density described in a kind of claim 1, using true Empty sensing+vacuum consumable remelting, it is characterised in that the technical parameter controlled in technique is as follows：

1200-1250 DEG C of steel ingot cogging temperature, charging temperature≤600 DEG C；

Forge Heating temperature：1150-1180 DEG C, 1140 DEG C≤starting forging temperature≤1180 DEG C, 900 DEG C≤final forging temperature≤1000 ℃；

Finished heat treatment：

650-780 DEG C is heated to, 5 hours≤soaking time≤20 hour, air cooling after heat penetration；Or carry out secondary ageing treatment.