CN112404420B

CN112404420B - A kind of high-strength steel powder for 3D printing, its preparation method, 3D printing method and obtained high-strength steel

Info

Publication number: CN112404420B
Application number: CN202011297333.7A
Authority: CN
Inventors: 李瑞迪; 牛朋达; 袁铁锤; 杨海鸥
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2022-01-04
Anticipated expiration: 2040-11-19
Also published as: CN112404420A

Abstract

The invention discloses high-strength steel powder for 3D printing, a preparation method thereof, a 3D printing method and prepared high-strength steel, wherein the high-strength steel powder for 3D printing comprises, by mass, 0.15% -0.3% of C, 0.4% -0.6% of V, 0.8% -1.2% of Ti, 0.8% -1.5% of Mo, 2.5% -4% of Cr, 10% -12% of Ni, 12% -15% of Co and the balance of Fe. The high-strength steel prepared by the laser additive manufacturing method disclosed by the invention has the tensile strength and the elongation which are far higher than those of other 3D printing metals, and solves the problems that the traditional alloy is low in 3D printing strength, poor in elongation and incapable of improving the tensile property and the elongation at the same time.

Description

High-strength steel powder for 3D printing, preparation method thereof, 3D printing method and prepared high-strength steel

Technical Field

The invention belongs to the technical field of laser additive manufacturing, and particularly relates to high-strength steel powder for 3D printing, a preparation method of the high-strength steel powder, a 3D printing method of the high-strength steel powder and prepared high-strength steel.

Background

In recent years, with the continuous development of high-end fields such as aerospace, rail transit and the like, higher and higher requirements are put forward on the mechanical properties of some key parts. The high-strength steel is used as a structural material with higher specific strength (usually, the tensile strength is greater than 1400MPa, and the yield strength exceeds 1300MPa), and has great potential application in key parts of aerospace, rail transit and the like due to higher elastic modulus, high room-temperature strength, high rigidity modulus and the like. Generally, these parts are processed by conventional forging and casting, which is a serious challenge for preparing some ultra-fine grain structure and complex parts. The laser Additive Manufacturing (AM) technology has irreplaceable advantages for preparing some ultra-fine grain structures and complex parts because of its close near-net-shape forming and high cooling rate.

However, the laser additive manufacturing process is not a simple processing method, and because a high temperature gradient and a high stress gradient exist in a molten pool in the laser additive manufacturing process, metallurgical defects such as thermal cracking deformation and the like are easily generated in the printing process. At present, the strength and plasticity can not be improved simultaneously in the laser additive manufacturing process, the tensile strength in the currently reported additive manufacturing process is usually lower than 1500MPa, the elongation is less than 10%, and the requirements of high-end parts can not be met far away, so that the development of special high-strength steel metal powder for laser additive manufacturing is urgently needed.

Disclosure of Invention

This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.

The present invention has been made in view of the above and/or the problems of low strong plasticity and easy cracking of the existing laser additive manufacturing of steel in the prior art.

It is therefore one of the objects of the present invention to provide a high strength steel powder for 3D printing.

In order to solve the technical problems, the invention provides the following technical scheme: the high-strength steel powder for 3D printing comprises, by mass, 0.15% -0.3% of C, 0.4% -0.6% of V, 0.8% -1.2% of Ti, 0.8% -1.5% of Mo, 2.5% -4% of Cr, 10% -12% of Ni, 12% -15% of Co and the balance Fe.

As a preferred embodiment of the high strength steel powder for 3D printing of the present invention, wherein: the alloy comprises, by mass, 0.2% of C, 0.5% of V, 1.0% of Ti, 1.2% of Mo, 3% of Cr, 11% of Ni, 12.5% of Co and the balance of Fe.

The invention also aims to provide a preparation method of the high-strength steel powder for 3D printing, and the invention provides the following technical scheme: comprises the steps of (a) preparing a mixture of a plurality of raw materials,

preparing metal powder comprising C, V, Ti, Mo, Cr, Ni, Co and Fe according to the mass percent of the alloy powder in the claim 1 or 2;

vacuum melting, namely performing vacuum melting on the prepared metal powder;

and atomizing to prepare powder, wherein the high-strength steel powder for 3D printing is obtained after vacuum melting.

As a preferable aspect of the method for preparing the high strength steel powder for 3D printing of the present invention, wherein: and vacuum melting is carried out, wherein the melting temperature is 1200-1600 ℃, and the pressure in the furnace is 0.4-0.7 MPa.

As a preferable aspect of the method for preparing the high strength steel powder for 3D printing of the present invention, wherein: the atomization powder preparation is carried out by introducing inert gas, and the atomization pressure is 0.5-8 MPa; the inert gas is argon.

The invention further aims to provide a 3D printing method of the high-strength steel powder for 3D printing, wherein the 3D printing is laser coaxial powder feeding printing, and the particle size of the high-strength steel powder for 3D printing is 75-150 mu m.

As a preferable aspect of the 3D printing method of the high strength steel powder for 3D printing of the present invention, wherein: the laser coaxial powder feeding printing is carried out, and the laser power is 800-1500W; the scanning distance is 1-1.5 mm; the laser scanning speed is 8-15 mm/s; the layer thickness was 0.5 mm.

The invention further aims to provide a 3D printing method of the high-strength steel powder for 3D printing, wherein the 3D printing is laser powder bed printing, and the particle size of the high-strength steel powder for 3D printing is 13-50 mu m.

As a preferable aspect of the 3D printing method of the high strength steel powder for 3D printing of the present invention, wherein: printing by the laser powder bed, wherein the laser power is 200-400W; the laser scanning speed is 400-1600 mm/s; the layer thickness is 0.04 mm; the scanning pitch was 0.09 mm.

Another object of the present invention is to provide a high strength steel manufactured by the above 3D printing method, the manufactured high strength steel having cellular martensite/bainite grains, the grains being encapsulated by mesh austenite;

the high-strength steel comprises, by mass percent, C: 0.15% -0.3%; v: 0.4 to 0.6 percent; ti: 0.8 to 1.2 percent; mo: 0.8 to 1.5 percent; cr: 2.5% -4%; ni: 10% -12%; co: 12 to 15 percent; the balance being Fe.

Compared with the prior art, the invention has the following beneficial effects:

the high-strength steel prepared by the invention has cellular martensite/bainite grains, and the grains are wrapped by the mesh austenite, so that the high-strength steel not only has various strong plasticity mechanisms such as phase transformation strengthening, fine grain strengthening, dislocation strengthening, precipitation strengthening and the like in the traditional steel material, but also has a mesh austenite strong plasticizing mechanism on a space structure, and the mesh austenite can induce TRIP and TWIP effects under stress, so that a printed sample has higher strength and plasticity, the tensile strength is more than or equal to 2000, and the elongation is more than or equal to 15%.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise. Wherein:

FIG. 1 is a phase distribution diagram of a sample prepared in example 1 of the present invention.

FIG. 2 is a pictorial representation of a sample prepared in accordance with the present invention; wherein FIG. 2(a) is a pictorial view of a sample prepared in example 1; FIG. 2(b) is a pictorial view of a sample prepared in example 2.

FIG. 3 is a photograph of a gold phase of a sample prepared according to the present invention; wherein, FIG. 3(a) is a gold phase diagram of the sample prepared in example 1; FIG. 3(b) is a gold phase diagram of the sample prepared in example 2.

FIG. 4 is a photograph of the microstructure of a high strength steel manufactured according to the present invention; wherein FIG. 4(a) is a low power plot and FIG. 4(b) is a high power plot of the sample prepared in example 1; fig. 4(c) is a low-power graph of the sample prepared in example 2, and fig. 4(d) is a high-power graph of the sample prepared in example 2.

FIG. 5 is a drawing of a high strength steel manufactured according to the present invention; wherein fig. 5(a) is a drawing of a sample prepared in example 1, and fig. 5(b) is a drawing of a sample prepared in example 2.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described in detail below with reference to examples of the specification.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

Example 1

(1) Preparing metal powder, wherein the metal powder comprises, by mass, 0.2% of C, 0.5% of V, 1.0% of Ti, 1.2% of Mo, 3% of Cr, 11% of Ni, 12.5% of Co and the balance Fe;

(2) vacuum smelting, namely performing vacuum smelting on the prepared metal powder, wherein the smelting temperature is 1500 ℃, and the air pressure in a smelting furnace is 0.5 MPa;

(3) atomizing to prepare powder, wherein after the vacuum melting, the metal molten drops are atomized by adopting argon as a medium, and the atomizing pressure is 4 MPa;

(4) sieving powder, namely sieving and grading the metal powder, and taking alloy powder with the granularity range of 75-150 mu m;

(5) drying treatment, namely drying the screened metal powder at 150 ℃ for 10 hours;

(6)3D prints, carries out the coaxial powder feeding 3D of laser with above-mentioned powder and prints, and the printing parameter is: the laser power is 1200W, the scanning speed is 10mm/s, the scanning interval is 1.2mm, the layer thickness is 0.5mm, and the powder feeding amount is 10 g/min; obtaining high-strength steel; as shown in FIG. 2, FIG. 2(a) is a schematic diagram of a sample prepared in example 1.

As shown in FIG. 1, FIG. 1 is a phase distribution diagram of a sample prepared in example 1 of the present invention. As can be seen from fig. 1, the printed samples were composed of mainly a body-centered cubic martensite phase, an austenite phase, and a close-packed hexagonal martensite phase. Due to the existence of austenite phase, martensite transformation (namely TRIP effect) occurs in the plastic deformation process, so that the printed sample maintains high strength and plasticity.

The tensile strength of the high-strength steel prepared by the laser coaxial powder feeding is up to 2000MPa, and the elongation is up to 22%.

Example 2

(4) sieving powder, namely sieving and grading the metal powder, and taking alloy powder with the granularity range of 15-50 mu m;

(6)3D prints, carries out laser powder bed 3D with above-mentioned powder and prints, and the printing parameter is: the laser power is 300W, the scanning speed is 800mm/s, the scanning distance is 0.09mm, and the layer thickness is 0.04 mm; obtaining high-strength steel; as shown in fig. 2, fig. 2(b) is a physical diagram of the sample prepared in example 2.

The tensile strength of the high-strength steel prepared by the laser coaxial powder feeding is as high as 1800MPa, and the elongation is 15%.

FIG. 3 is a photograph of a gold phase of a sample prepared according to the present invention; wherein, FIG. 3(a) is a gold phase diagram of the sample prepared in example 1; FIG. 3(b) is a gold phase diagram of the sample prepared in example 2. From fig. 3, it can be seen that a typical laser additive manufacturing is characterized by the presence of a significant weld pool topography in the build direction. And the size of a sample molten pool prepared by the laser coaxial powder feeding equipment is far larger than that of a sample prepared by the laser powder bed. And the laser powder bed apparatus was found to produce samples having smaller grain sizes than the laser coaxial powder feed apparatus.

FIG. 4 is a photograph of the microstructure of a high strength steel manufactured according to the present invention; wherein FIG. 4(a) is a low power plot and FIG. 4(b) is a high power plot of the sample prepared in example 1; fig. 4(c) is a low-power graph of the sample prepared in example 2, and fig. 4(d) is a high-power graph of the sample prepared in example 2. It can be seen from fig. 4(a) that the printed sample exhibits a layered structure with austenite distributed at the grain boundaries, martensite distributed within the crystal, and a large amount of cementite in bainite is found in fig. 4(b), which further enhances its tensile strength; in fig. 4(c) a large number of lath-like martensite are found parallel to each other or intersecting at 70.5 °, and the laser powder bed apparatus produced samples with smaller grain size than the laser coaxial powder feeding apparatus.

FIG. 5 is a drawing of a high strength steel manufactured according to the present invention; wherein fig. 5(a) is a drawing of a sample prepared in example 1, and fig. 5(b) is a drawing of a sample prepared in example 2. As can be seen from the figure, the samples after crystal laser additive manufacturing all show higher tensile strength, and meanwhile, still have better plasticity.

Example 3

(1) Preparing metal powder, wherein the metal powder comprises, by mass, 0.2% of C, 0.4% of V, 0.8% of Ti, 0.8% of Mo, 3.5% of Cr, 12% of Ni, 13% of Co and the balance Fe;

(6)3D prints, carries out the coaxial powder feeding 3D of laser with above-mentioned powder and prints, and the printing parameter is: the laser power is 1200W, the scanning speed is 10mm/s, the scanning interval is 1.2mm, the layer thickness is 0.5mm, and the powder feeding amount is 10 g/min; obtaining the high-strength steel.

The tensile strength of the high-strength steel prepared by the laser coaxial powder feeding is up to 1935MPa, and the elongation is up to 19%.

Example 4

(6)3D prints, carries out laser powder bed 3D with above-mentioned powder and prints, and the printing parameter is: the laser power is 300W, the scanning speed is 800mm/s, the scanning distance is 0.09mm, and the layer thickness is 0.04 mm; obtaining the high-strength steel.

The tensile strength of the high-strength steel prepared by the laser coaxial powder feeding is up to 1728MPa, and the elongation is up to 16.2%.

Example 5

(1) Preparing metal powder, wherein the metal powder comprises, by mass, 0.3% of C, 0.6% of V, 1.2% of Ti, 1.5% of Mo, 4% of Cr, 12% of Ni, 15% of Co and the balance Fe;

The tensile strength of the high-strength steel prepared by the laser coaxial powder feeding reaches 2236MPa, and the elongation reaches 14%.

Example 6

(1) Preparing metal powder, wherein the metal powder comprises, by mass, 0.15% of C, 0.4% of V, 0.8% of Ti, 0.8% of Mo, 2.5% of Cr, 10% of Ni, 12% of Co and the balance Fe;

The tensile strength of the high-strength steel prepared by the laser coaxial powder feeding reaches 1832MPa, and the elongation reaches 24%.

Example 7

(1) Preparing metal powder, wherein the metal powder comprises, by mass, 0.1% of C, 0.4% of V, 0.8% of Ti, 0.8% of Mo, 2.5% of Cr, 10% of Ni, 12% of Co and the balance Fe;

The tensile strength of the high-strength steel prepared by the laser coaxial powder feeding reaches 1429MPa, and the elongation reaches 28%.

Example 8

(1) Preparing metal powder, wherein the metal powder comprises, by mass, 0.5% of C, 0.4% of V, 0.8% of Ti, 0.8% of Mo, 2.5% of Cr, 10% of Ni, 12% of Co and the balance Fe;

The tensile strength of the high-strength steel prepared by the laser coaxial powder feeding is 1836MPa, and the elongation is 8%.

The high-strength steel prepared by the invention has cellular martensite/bainite grains, the grains are wrapped by the reticular austenite, the high-strength steel not only has various strong plasticity mechanisms such as phase transformation strengthening, fine grain strengthening, dislocation strengthening, precipitation strengthening and the like in the traditional steel material, but also has a reticular austenite strong plasticizing mechanism on a space structure, and the reticular austenite can induce TRIP and TWIP effects under stress, so that a printed sample has higher strength and plasticity (the tensile strength is more than or equal to 2000 and the elongation is more than or equal to 15%). The high-strength steel prepared by adopting laser additive manufacturing is the steel with the highest metal 3D printing strength so far, the tensile strength and the elongation are far higher than those of other 3D printing metals, and the problems that the traditional alloy 3D printing strength is low, the elongation is poor, and the tensile property and the elongation cannot be improved simultaneously are solved.

It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims

1. A high-strength steel powder for 3D printing, characterized in that: by mass percentage, it comprises: 0.15%-0.3% C, 0.4%-0.6% V, 0.8%-1.2% Ti, 0.8%-1.2% %～1.5% Mo, 2.5%～4% Cr, 10%～12% Ni, 12%～15% Co, and the balance is Fe.

2. The high-strength steel powder for 3D printing according to claim 1, characterized in that: by mass percentage, it comprises: 0.2% C, 0.5% V, 1.0% Ti, 1.2% Mo, 3% Cr, 11% Ni, 12.5% Co, the balance being Fe.

3. A preparation method of high-strength steel powder for 3D printing, characterized in that: comprising,

Prepare metal powder, including C, V, Ti, Mo, Cr, Ni, Co, Fe, according to the mass percentage according to claim 1 or 2;

Vacuum smelting, vacuum smelting the prepared metal powder;

Atomization and pulverization, after the vacuum smelting, atomization and pulverization are performed to obtain high-strength steel powder for 3D printing.

4 . The method for preparing high-strength steel powder for 3D printing according to claim 3 , wherein in the vacuum smelting, the smelting temperature is 1200-1600° C., and the pressure in the furnace is 0.4-0.7 MPa. 5 .

5. The method for preparing high-strength steel powder for 3D printing according to claim 3 or 4, characterized in that: the atomization and powder-making is performed by introducing an inert gas for atomization and powder-making, and the atomization pressure is 0.5-8MPa; the inert gas is argon.

6. A 3D printing method for high-strength steel powder for 3D printing according to claim 1 or 2, characterized in that: the 3D printing is laser coaxial powder feeding printing, and the 3D printing is used for 3D printing. The particle size of the high-strength steel powder is 75 to 150 μm.

7. The 3D printing method of high-strength steel powder for 3D printing according to claim 6, characterized in that: the laser coaxial powder feeding printing, the laser power is 800-1500W; the scanning distance is 1-1.5mm ; The laser scanning speed is 8～15mm/s; the layer thickness is 0.5mm.

8. A 3D printing method for high-strength steel powder for 3D printing according to claim 1 or 2, characterized in that: the 3D printing is laser powder bed printing, and the high-strength steel powder for 3D printing is The particle size of the steel powder is 13 to 50 μm.

9 . The 3D printing method of high-strength steel powder for 3D printing according to claim 8 , wherein: the laser powder bed printing, the laser power is 200-400W; the laser scanning speed is 400-1600mm/s ; The layer thickness is 0.04mm; the scanning spacing is 0.09mm.

10. A high-strength steel prepared by the 3D printing method according to any one of claims 6 to 9, wherein the prepared high-strength steel has cellular martensite/bainite grains, and the The grains are surrounded by reticulated austenite;

The high-strength steel, in terms of mass percentage, includes: C: 0.15% to 0.3%; V: 0.4% to 0.6%; Ti: 0.8% to 1.2%; Mo: 0.8% to 1.5%; Cr: 2.5% to 2.5% 4%; Ni: 10% to 12%; Co: 12% to 15%; the balance is Fe.