CN112410658B

CN112410658B - Preparation method of high-strength and high-hardness water-atomized prealloyed steel powder

Info

Publication number: CN112410658B
Application number: CN202011015645.4A
Authority: CN
Inventors: 徐从京; 于永亮; 刘增林; 王昌东; 王娟; 张毅; 高慧; 王宁; 孙英庆; 李红刚
Original assignee: Shandong Luyin New Material Technology Co Ltd
Current assignee: Shandong Luyin New Material Technology Co Ltd
Priority date: 2020-09-24
Filing date: 2020-09-24
Publication date: 2021-12-03
Anticipated expiration: 2040-09-24
Also published as: CN112410658A

Abstract

The invention provides a preparation method of high-strength and high-hardness water atomized prealloyed steel powder, which comprises the steps of proportioning, smelting process, atomization, reduction and post-treatment; the high-strength and high-hardness water atomized prealloyed steel powder contains 0.35-0.55% of Mn, 1.30-1.55% of Ni and 1.15-1.40% of Mo. After the high-strength and high-hardness water atomized prealloyed steel powder disclosed by the invention is sintered and hardened, the average sintering hardness reaches 35.0-37.5HRC, and the average transverse breaking strength reaches 1042.6-1109.1 MPa; the compressibility of the prealloyed steel powder reaches 6.69g/cm³Hydrogen loss up to 0.14% and bulk density up to 3.01g/cm³。

Description

Preparation method of high-strength and high-hardness water-atomized prealloyed steel powder

Technical Field

The invention belongs to the field of pre-alloyed steel powder, and particularly relates to a preparation method of high-strength and high-hardness water atomized pre-alloyed steel powder.

Background

The development space of iron-based powder metallurgy products in China is wide, taking the automobile industry as an example, more than 2000 thousands of automobiles are produced in the year in China, but due to the restriction of the technical level, the amount of iron-based powder metallurgy parts used on each automobile in China is less than 5Kg, and the amount of iron-based powder metallurgy parts used on each automobile in developed countries such as Europe, America and the like is 14-19.5 Kg. If each automobile in China increases 9Kg of iron-based powder metallurgy parts, the requirements of at least 18 million tons of steel powder and iron-based powder metallurgy parts are increased every year. Therefore, the improvement of the preparation level of iron and steel powder and iron-based powder metallurgy parts in China has important significance for the development of iron-based powder metallurgy and related industries in China.

The powder metallurgy technique can manufacture a part having a complicated shape with a high dimensional accuracy in a shape extremely close to the shape of a product, and therefore, can greatly reduce cutting costs. Therefore, the powder metallurgy product is used as various machines and parts in various aspects. In recent years, there has been an increasing demand for improving the strength of powder metallurgy products in order to reduce the size and weight of parts. In particular, there is a strong demand for increasing the strength of iron-based powder products.

An iron-based powder compact for powder metallurgy is generally manufactured by the following operations: an alloy powder such as copper powder or graphite powder and a lubricant such as stearic acid or lithium stearate are mixed with an iron-based powder to prepare an iron-based powder mixture, and the mixture is filled in a die and press-molded. Iron-based powders can be classified into iron powders (e.g., pure iron powders) and alloy steel powders according to their components. The high-strength and high-hardness water atomized prealloyed steel powder is prepared by combining sintering and heat treatment (carburizing heat treatment, brightening heat treatment and the like) in the powder metallurgy material processing process into one process, the production process of the material is more effective, and the economic benefit of the product is higher.

Currently, some countries in the united states and europe have successfully developed prealloyed steel powders specifically designed for sinter hardening processes. HoganaasAB, Sweden, Hoeganaes, and Quebec Metal Powder, Canada are internationally well-known Powder manufacturing companies that have successfully developed a variety of sinter-hardening powders. Sinter hardening is gradually becoming a process method for producing high-strength and high-hardness Powder metallurgy iron-based structural parts with low cost, wherein pre-alloyed water atomized steel Powder such as ATOME 4601, ATOME 4701, ATOME 4801 and the like is designed and developed by Quebec Metal Powder Limited company in Canada, FLC-4608 pre-alloyed steel Powder products are developed by Hoeganaes company in America, and the products prepared by adopting the sinter hardening process are already used in a plurality of industries such as electric tools, household appliances, machinery, automobile manufacturing and the like.

At present, the research and application in the aspect are less, more importantly, the process technology and related equipment of the prealloyed steel powder in China are started later, no excellent base powder is used for supporting, the matched process and equipment are not perfected, and the technical development of the prealloyed steel powder with high strength and high hardness is greatly limited. At present, the sintered and hardened prealloyed steel powder used in China is mostly imported from abroad and has high price.

The applicant finds that the existing high-strength and high-hardness water-atomized prealloyed steel powder delays the transformation from austenite to ferrite and cementite by adding alloy elements in the application of sintering hardening materials so as to be beneficial to forming martensite and improving hardenability, but excessive chromium and manganese elements are added in the process; the chromium and manganese elements are easy to oxidize and difficult to reduce in the sintering process, and the oxides are distributed in the grain boundary of the matrix, so that the performance of the matrix material after sintering and hardening is reduced.

Further, the applicant also found that in the preparation process of the high-strength and high-hardness water atomized prealloyed steel powder, the prealloyed raw powder has oxidation phenomena in the water atomization and dehydration drying processes, and the oxide of the prealloyed raw powder is easy to reduce in a conventional reduction state; the chromium and manganese elements are easy to oxidize after being superposed, and the oxides of the chromium and manganese elements are difficult to reduce under the conventional reduction state; the two influence together, which causes high hydrogen loss of the product and seriously restricts the deep application and popularization of the prealloyed steel powder.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a preparation method of high-strength and high-hardness water atomized prealloyed steel powder, which aims to realize the following purposes:

(1) the preparation method of the high-strength and high-hardness water atomized prealloyed steel powder is provided, the defect of high hydrogen loss of the prealloyed steel powder can be effectively overcome, and the deep application and popularization of the prealloyed steel powder are promoted;

(2) the preparation method of the high-strength and high-hardness water-atomized prealloyed steel powder is provided, and the problem that the performance of a base material is reduced after powder is sintered and hardened due to the addition of excessive chromium and manganese elements for improving hardenability is solved;

(3) by adopting the preparation method of the high-strength and high-hardness water atomized prealloyed steel powder, the hardness and strength properties of the prepared prealloyed steel powder after sintering and hardening are improved.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a process for preparing high-strength and-hardness water-atomized prealloyed steel powder includes proportioning raw materials, smelting, atomizing, reduction and post-treating.

1. Ingredients

The selected component content meets the following requirements: the raw materials of high-quality common carbon steel scrap and pig iron are less than 0.50 percent of Mn, less than 0.04 percent of P, less than 0.2 percent of Si, less than 0.04 percent of S, and less than or equal to 0.20 percent of Cr, Ni, Cu and Mo for standby.

The high-quality common carbon steel scrap: the ratio of parts by weight of pig iron is 1-2: 1-2.

The transformation of austenite into ferrite and cementite is delayed by adding alloy elements so as to be beneficial to forming martensite, namely, the hardenability is improved; the increase in hardenability means that more martensite can be obtained at lower cooling rates.

2. Smelting process

The smelting process comprises EBT electric furnace smelting, electric furnace tapping and LF refining furnace smelting.

And smelting in the EBT electric furnace at the temperature of 1500-.

And (3) smelting in the EBT electric furnace, and controlling the carbon content at the end point to be more than or equal to 0.15% when tapping is carried out in the electric furnace.

The EBT electric furnace is smelted, and when the molten steel components of the electric furnace meet the following requirements: less than or equal to 0.28 percent of C, less than or equal to 0.010 percent of P, less than or equal to 0.009 percent of S, less than or equal to 0.13 percent of Mn, less than or equal to 0.03 percent of Si, less than or equal to 0.010 percent of P, less than or equal to 0.07 percent of Cr, Ni, Cu and Mo, and the temperature is raised to 1630-1660 ℃ for electric furnace tapping.

And tapping by the electric furnace, and pouring the electric furnace to enable the molten steel smelted by the EBT electric furnace to flow into a refining ladle.

Tapping by the electric furnace, reserving partial molten steel, and forbidding oxidizing slag from entering a refining ladle.

And smelting in the LF refining furnace, refining in a refining ladle, sampling and detecting under the condition that argon is blown and stirring to ensure that molten steel alloy is uniform, and calculating the addition amount of manganese, nickel and molybdenum according to detection data.

The argon is blown to stir, the pressure of the argon is 0.3-0.5MPa, and the flow rate of the argon is 260 and 350 NL/min.

And smelting in the LF refining furnace, adding ferromanganese (containing 73% of manganese) at the initial stage of refining, and adjusting the manganese content in the molten steel to 0.35-0.55%.

And smelting in the LF refining furnace, adding a nickel plate and ferromolybdenum (containing molybdenum 65%) at the final stage of refining, and adjusting the content of nickel in the molten steel to 1.30-1.55% and the content of molybdenum to 1.15-1.40%.

And adding ferromanganese, a nickel plate and ferromolybdenum, wherein 80% of ferromanganese, nickel plate and ferromolybdenum in parts by weight are added firstly, and after sampling detection, the rest ferromanganese, nickel plate and ferromolybdenum are added according to the contents of Mn, Ni and Mo in molten steel.

Smelting in the LF refining furnace, and during intensified deoxidation, using a silicon-free deoxidizer to ensure rapid whitening slag; the refining time of the white slag is not less than 15 minutes. The white slag refining can reduce the oxygen content of the molten steel, ensure gas-solid inclusions to float to the maximum extent and improve the purity of the molten steel.

And smelting in the LF refining furnace, reducing the pressure of argon gas at the final stage of refining, and blowing argon for not less than 10 minutes to ensure the uniformity of molten steel and the upward floating of part of impurities.

And smelting in the LF refining furnace, and after refining is finished, controlling the molten steel components: the content of C is less than or equal to 0.28, the content of P is less than or equal to 0.010 percent, the content of S is less than or equal to 0.009 percent, the content of Si is less than or equal to 0.03 percent, the content of P is less than or equal to 0.010 percent, the content of Mn is 0.35 to 0.55 percent, the content of Ni is 1.30 to 1.55 percent, the content of Mo is 1.15 to 1.40 percent, and the atomization step is carried out.

The smelting process is an important link for preparing the high-strength and high-hardness water atomized pre-alloyed steel, and on one hand, the purity of molten steel influences the comprehensive performance of a final product; on the other hand, it is determined whether the alloy content can satisfy the predetermined requirements. On the basis of smelting ultrapure molten steel, the required alloy content is achieved through a reasonable alloy adding process.

3. Atomization

The atomization is high-pressure atomization, the spraying included angle of the high-pressure atomization nozzle is 30-50 degrees, and the water pressure is 8-16 MPa.

The prealloyed steel powder prepared after atomization comprises the following components in percentage by weight: the content of C is less than or equal to 0.28 percent, the content of S is less than or equal to 0.009 percent, the content of Si is less than or equal to 0.03 percent, the content of P is less than or equal to 0.01 percent, the content of Mn is 0.35 to 0.55 percent, the content of Ni is 1.30 to 1.55 percent, the content of Mo is 1.15 to 1.40 percent, and the hydrogen loss is less than or equal to 1.67 percent.

4. Reduction of

And the reduction comprises primary fine reduction and secondary fine reduction.

And the reduction is carried out by adopting pure hydrogen.

The primary fine reduction is carried out at the temperature of 925 ℃ and 980 ℃ and the gas flow rate of 70Nm³The material layer thickness is 23-29mm, and the belt speed is 145-185 mm/min.

The primary fine reduction is carried out, the hydrogen loss of the product after reduction is about 0.31 percent, and the compressibility is about 6.64 (g/cm 3).

The secondary fine reduction is carried out at the reduction temperature of 925 ℃ and 980 ℃ and the gas flow rate of 70Nm³The material layer thickness is 23-29mm, and the belt speed is 145-185 mm/min.

And (3) performing secondary fine reduction, wherein the hydrogen loss of the reduced product is about 0.14%, and the compressibility is about 6.69 (g/cm 3).

After the oxygen in the iron powder is removed from the pre-alloyed steel raw powder under a high-temperature reducing atmosphere, the reducing atmosphere becomes a wet atmosphere containing a certain amount of water vapor, and the dew point of the reducing atmosphere is raised, and then the pre-alloyed steel raw powder enters a decarburization area to remove carbon in the iron powder, which is called dry deoxidation and wet decarburization. Because the prealloyed raw powder is oxidized (about 1.6 percent of hydrogen loss) in the water atomization and dehydration drying processes, the oxide is easy to be reduced in the conventional reduction state, and the element is easy to be oxidized and difficult to be reduced in the conventional state because of containing Mn element, in order to achieve the required hydrogen loss content, in the reduction process of the invention, a secondary fine reduction process is adopted, and the product performance is improved through the setting of process parameters such as reduction temperature, gas flow, belt speed, material thickness and the like.

5. Post-treatment

The post-treatment is carried out by crushing, magnetic separation, power or unpowered combination, and then the high-strength and high-hardness water atomized prealloyed steel powder can be prepared.

The performance indexes of the prepared high-strength and high-hardness water atomized prealloyed steel powder are as follows: the content of C is less than or equal to 0.003 percent, the content of S is less than or equal to 0.011 percent, the content of Si is less than or equal to 0.03 percent, the content of P is less than or equal to 0.012 percent, the content of Mn is 0.35-0.55 percent, the content of Ni is 1.30-1.55 percent, the content of Mo is 1.15-1.40 percent, and the hydrogen loss is less than or equal to 0.14 percent.

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

(1) the preparation method of the high-strength and high-hardness water-atomized prealloyed steel powder effectively solves the problem that the performance of a base material is reduced after sintering and hardening due to excessive chromium and manganese elements in raw material components, the average sintering hardness reaches 35.0-37.5HRC after sintering and hardening, and the average transverse breaking strength reaches 1042.6-1109.1 MPa;

(2) the preparation method of the high-strength and high-hardness water atomized prealloyed steel powder effectively overcomes the defect of high hydrogen loss of the prealloyed steel powder, and the compressibility of the prealloyed steel powder reaches 6.69g/cm³The hydrogen loss value reaches 0.14 percent;

(3) the preparation method of the high-strength and high-hardness water atomized prealloyed steel powder has the advantage that the apparent density of the prealloyed steel powder is 3.01g/cm³；

(4) The preparation method of the high-strength and high-hardness water atomized prealloyed steel powder comprises the following steps: +100 mesh 0.6%; +140 mesh 20.4%; +200 mesh 29.6%; +325 mesh 27.9%; the minus 325 meshes are 21.5%, and the later application performance is good;

(5) the preparation method of the high-strength and high-hardness water atomized prealloyed steel powder disclosed by the invention adopts a two-time reduction process, is beneficial to oxygen removal, has a good reduction effect, and effectively improves the performance of the prealloyed steel powder.

Detailed Description

In order to more clearly understand the technical features, objects, and effects of the present invention, specific embodiments of the present invention will now be described.

Example 1

1. Ingredients

The high-quality common carbon steel scrap: the weight ratio of pig iron is 1: 2.

2. smelting process

And smelting in the EBT electric furnace at 1550 ℃.

The EBT electric furnace is smelted, and when the molten steel components of the electric furnace meet the following requirements: less than or equal to 0.28 percent of C, less than or equal to 0.010 percent of P, less than or equal to 0.009 percent of S, less than or equal to 0.13 percent of Mn, less than or equal to 0.03 percent of Si, less than or equal to 0.010 percent of P, less than or equal to 0.07 percent of Cr, Ni, Cu and Mo, and heating to 1630 ℃ for electric furnace tapping.

The argon is blown to stir, the pressure of the argon is 0.3MPa, and the flow of the argon is 260 NL/min.

And smelting in the LF refining furnace, adding ferromanganese (containing 73% of manganese) at the initial stage of refining, and adjusting the manganese content in the molten steel to 0.45%.

And smelting in the LF refining furnace, adding a nickel plate and ferromolybdenum (containing 65% molybdenum) at the final stage of refining, and adjusting the nickel content in the molten steel to 1.43% and the molybdenum content to 1.28%.

And smelting in the LF refining furnace, and after refining is finished, controlling the molten steel components: the content of C is less than or equal to 0.28, the content of P is less than or equal to 0.010 percent, the content of S is less than or equal to 0.009 percent, the content of Si is less than or equal to 0.03 percent, the content of P is less than or equal to 0.010 percent, the content of Mn is 0.35 to 0.55 percent, the content of Ni is 1.30 to 1.55 percent, and the content of Mo is 1.15 to 1.40 percent.

3. Atomization

The atomization is high-pressure atomization, the spraying included angle of the high-pressure atomization nozzle is 30 degrees, and the water pressure is 8 MPa.

The prealloyed steel powder prepared after atomization comprises the following components in percentage by weight: c =0.27%, S =0.008%, Si =0.03%, P =0.01%, Mn =0.45%, Ni =1.43%, Mo =1.30%, and hydrogen loss is 1.69%.

4. Reduction of

And the reduction is carried out by adopting pure hydrogen.

The primary fine reduction is carried out at 945 ℃ and the gas flow is 70Nm³H, material layer thickness of 27mm, belt speed of 180 mm/min.

The hydrogen loss of the product after the primary fine reduction is 0.33 percent, and the compressibility is 6.57 (g/cm)³）。

The secondary fine reduction is carried out at 955 ℃ and 70Nm gas flow³H, the material layer thickness is 23mm, and the belt speed is 180 mm/min.

The secondary fine reduction is carried out, the hydrogen loss of the product after the reduction is 0.17 percent, and the compressibility is 6.61 (g/cm)³）。

5. Post-treatment

And after the post-treatment, crushing, magnetic separation, power or unpowered combination, the high-strength and high-hardness water atomized prealloyed steel powder can be prepared.

The performance indexes of the prepared high-strength and high-hardness water atomized prealloyed steel powder are as follows: c =0.003%, S =0.013%, Si =0.04%, Mn =0.45%, P =0.011%, Ni =1.44%, Mo =1.30%, hydrogen loss =0.16%, and compressibility at room temperature 500MPa is 6.62g/cm³Apparent density of 3.08g/cm³。

The particle size composition is as follows: +100 mesh 0.8%; +140 mesh 20.2%; +200 mesh 29.3%; +325 mesh 28.4%; the minus 325 mesh is 21.3%.

Sintering property test:

the high-strength and high-hardness water-atomized prealloyed steel powder obtained in example 1 was selected as sample 1, and 2 wt% of copper, 0.9 wt% of graphite, and 0.6 wt% of lubricant were added, and the sintered blank was pressed under 600MPa and sintered at 1120 ℃ for 30 minutes under an ammonia decomposition atmosphere. The specific test results are shown in the following table:

example 2

1. Ingredients

The high-quality common carbon steel scrap: the weight ratio of pig iron is 1: 1.

2. smelting process

And smelting in the EBT electric furnace at 1550 ℃.

The EBT electric furnace is smelted, and when the molten steel components of the electric furnace meet the following requirements: less than or equal to 0.28 percent of C, less than or equal to 0.010 percent of P, less than or equal to 0.009 percent of S, less than or equal to 0.13 percent of Mn, less than or equal to 0.03 percent of Si, less than or equal to 0.010 percent of P, less than or equal to 0.07 percent of Cr, Ni, Cu and Mo, and heating to 1650 ℃ for electric furnace tapping.

The argon is blown to stir, the pressure of the argon is 0.35MPa, and the flow of the argon is 300 NL/min.

3. Atomization

The atomization is high-pressure atomization, the injection included angle of the high-pressure atomization nozzle is 47 degrees, and the water pressure is 12 MPa.

The prealloyed steel powder prepared after atomization comprises the following components in percentage by weight: c =0.28%, S =0.009%, Si =0.03%, P =0.01%, Mn = 0.47%, Ni =1.44%, Mo =1.31, and hydrogen loss is 1.67%.

4. Reduction of

And the reduction is carried out by adopting pure hydrogen.

The primary fine reduction is carried out at the reduction temperature of 965 ℃ and the gas flow rate of 70Nm³H, the material layer thickness is 25mm, and the belt speed is 170 mm/min.

The hydrogen loss of the product after primary fine reduction is 0.31 percent, and the compressibility is 6.64 (g/cm)³）。

The secondary fine reduction is carried out at the reduction temperature of 965 ℃ and the gas flow rate of 70Nm³H, the material layer thickness is 25mm, and the belt speed is 170 mm/min.

The secondary fine reduction is carried out, the hydrogen loss of the product after the reduction is 0.14 percent, and the compressibility is 6.69 (g/cm)³）。

5. Post-treatment

Said systemThe performance indexes of the obtained high-strength and high-hardness water atomized prealloyed steel powder are as follows: c =0.003%, S =0.011%, Si =0.03%, Mn =0.48%, P =0.012%, Ni =1.45%, Mo =1.34%, hydrogen loss is 0.14%, and compressibility at room temperature 500MPa is 6.69g/cm³Apparent density of 3.01g/cm³。

The particle size composition is as follows: +100 mesh 0.6%; +140 mesh 20.4%; +200 mesh 29.6%; +325 mesh 27.9%; 325 mesh 21.5%.

Sintering property test:

the high-strength and high-hardness water-atomized prealloyed steel powder obtained in example 2 was selected as sample 2, and 2 wt% of copper, 0.9 wt% of graphite, and 0.6 wt% of lubricant were added to the powder, and the mixture was pressed into a sintered blank under 600MPa, and sintered at 1120 ℃ for 30 minutes under an ammonia decomposition atmosphere. The specific test results are shown in the following table:

example 3

1. Ingredients

2. smelting process

And smelting in the EBT electric furnace at 1550 ℃.

3. Atomization

And atomizing, namely preparing atomized raw powder after high-pressure atomization, material mixing, infiltration, dehydration, drying and screening.

The high-pressure atomization adopts an iron standard solution as an atomized liquid; the iron standard solution is 1 mg/ml iron dissolved in 2% nitric acid.

The high-pressure atomization is carried out, the spray angle of a nozzle is 45 degrees, the atomized liquid pressure is 18MPa, and the flow of the atomized liquid is 275Nm³H, the liquid inlet temperature of the atomized liquid is 25 ℃.

And mixing, namely adding nano silicon carbide and bentonite powder into the material subjected to high-pressure atomization, and uniformly mixing.

The high-pressure atomized material: nano silicon carbide: the weight ratio of the bentonite powder is 22:1: 1.

The particle size of the bentonite powder is 20 mu m.

The particle size of the nano silicon carbide is 50 nm.

And (3) soaking, namely placing the mixed materials in 5% zinc carbonate solution with the volume 2 times that of the mixed materials, and standing for 30 min.

And dehydrating, namely dehydrating the soaked materials by adopting a filter.

And (3) drying, namely drying the dehydrated material at 95 ℃ until the water content is less than 1.5%.

The prealloyed steel powder prepared after atomization comprises the following components in percentage by weight: c =0.26%, S =0.010%, Si =0.03%, P =0.011%, Mn =0.48%, Ni =1.47%, Mo =1.31, and the hydrogen loss is 1.54%.

4. Reduction of

And the reduction is carried out by adopting pure hydrogen.

The primary fine reduction is carried out at the reduction temperature of 965 ℃ and the gas flow rate of 70Nm³H, material layer thickness of 27mm, belt speed of 180 mm/min.

The product after primary fine reduction has hydrogen loss of 0.30 percent and compressibility of 6.60 (g/cm)³）。

The secondary fine reduction is carried out at 970 ℃ and the gas flow rate of 70Nm³H, material layer thickness 23mm, belt speed 185 mm/min.

The secondary fine reduction is carried out, and the product after the reduction is obtainedHydrogen loss 0.15%, compressibility 6.65 (g/cm)³）。

5. Post-treatment

The performance indexes of the prepared high-strength and high-hardness water atomized prealloyed steel powder are as follows: c =0.003%, S =0.008%, Si =0.02%, Mn =0.48%, P =0.010%, Ni =1.47%, Mo =1.31%, hydrogen loss =0.15%, and compressibility at room temperature 500MPa is 6.65g/cm³Loose density =3.02g/cm³。

The particle size composition is as follows: +140 mesh 21.3%; +200 mesh 30.5%; +325 mesh 29.8%; 325 mesh 18.4%.

Sintering property test:

the high-strength and high-hardness water-atomized prealloyed steel powder obtained in example 3 was selected as sample 3, and 2 wt% of copper, 0.9 wt% of graphite, and 0.6 wt% of lubricant were added to the powder, and the mixture was pressed into a sintered blank under a pressure of 600MPa, and sintered at a temperature of 1120 ℃ for 30 minutes under an ammonia decomposition atmosphere. The specific test results are shown in the following table:

example 4

Primary fine reduction temperature selection and optimization test:

based on the characteristics of the prior primary fine reduction process, the hydrogen flow is firstly fixed to be 70Nm³The belt speed is 170mm/min, the thickness is 27mm, and the primary fine reduction temperature is set to be 980 ℃, 970 ℃, 965 ℃, 955 ℃, 945 ℃, 935 ℃ and 925 ℃ for seven groups of data tests, and the test results are shown in the following table:

as can be seen from the table, the reduction effect at 965 ℃ is best, the hydrogen loss content is lowest, and the compressibility can reach the highest value of 6.62g/cm 3.

Meanwhile, the hydrogen loss content of the upper, middle and lower positions of the powder cake blocks is respectively detected at the temperature of 980 ℃, 965 ℃ and 945 ℃, and the result is shown in the following table;

as can be seen from the above table, the difference between the hydrogen loss values at the upper and lower portions was minimal at the reduction temperature of 965 ℃. Because in the high-temperature reduction process, not only complex solid-gas multiphase chemical reaction but also the kinetic problem of reducing the iron oxide by hydrogen exist. The reduction temperature is above 800 ℃, the reaction product layer is not loose, and the gas can participate in the reaction only by diffusing into the ferrite, so that the high temperature is favorable for the reaction speed in the high-temperature reduction process, but the high-temperature agglomeration hinders the diffusion of the reduction atmosphere, and plays a role in inhibiting the reaction. Along with the process that the temperature is increased from 945 ℃ to 965 ℃, the chemical reaction speed is increased, the agglomeration of the powder cakes is gradually enhanced, and the reaction achieves the best effect at 965 ℃. As the temperature is continuously increased, the agglomeration density of the powder cake is higher and higher, and the diffusion in the process plays a decisive role. Therefore, with the increase of the temperature, the reaction is more and more incomplete, the hydrogen loss content is gradually increased, and the compressibility is gradually reduced; meanwhile, due to the fact that the agglomeration of the pressed powder is aggravated due to the overhigh temperature, the crushing difficulty of the pressed powder is increased, the processing hardening degree is improved, and the compressibility of the product is reduced.

All percentages used in the present invention are mass percentages unless otherwise indicated.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of high-strength and high-hardness water atomized prealloyed steel powder is characterized by comprising the steps of proportioning, smelting, atomizing, reducing and post-treating;

the high-strength and high-hardness water atomized prealloyed steel powder contains 0.35-0.55% of Mn, 1.30-1.55% of Ni and 1.15-1.40% of Mo;

the ingredient is prepared from the following components in percentage by weight: high-quality common carbon waste steel and pig iron with Mn content less than 0.50%, P content less than 0.04%, Si content less than 0.2%, S content less than 0.04%, and Cr + Ni + Cu + Mo content less than or equal to 0.20% are used as raw materials;

the smelting process comprises EBT electric furnace smelting, electric furnace tapping and LF refining furnace smelting;

smelting in the EBT electric furnace, and controlling the carbon content at the end point to be more than or equal to 0.15% when tapping steel from the electric furnace; when the molten steel composition in the electric furnace meets the following requirements: less than or equal to 0.28 percent of C, less than or equal to 0.010 percent of P, less than or equal to 0.009 percent of S, less than or equal to 0.13 percent of Mn, less than or equal to 0.03 percent of Si, less than or equal to 0.010 percent of P, less than or equal to 0.07 percent of Cr, Ni, Cu and Mo, and carrying out electric furnace tapping;

tapping by the electric furnace, and making molten steel smelted by the EBT electric furnace flow into a refining ladle;

tapping by the electric furnace, reserving a part of molten steel, and forbidding oxidizing slag from entering a refining ladle;

smelting in the LF refining furnace, adding ferromanganese, and adjusting the manganese content of the molten steel to 0.35-0.55%;

smelting in the LF refining furnace, adding a nickel plate, and adjusting the nickel content of molten steel to 1.30-1.55%;

smelting in the LF refining furnace, adding ferromolybdenum, and adjusting the molybdenum content of molten steel to 1.15-1.40%;

smelting in the LF refining furnace, and during intensified deoxidation, using a silicon-free deoxidizer to ensure rapid whitening slag;

the refining time of the white slag is not less than 15 minutes;

and smelting in the LF refining furnace, and after refining is finished, controlling the molten steel components: the content of C is less than or equal to 0.28 percent, the content of P is less than or equal to 0.010 percent, the content of S is less than or equal to 0.009 percent, the content of Si is less than or equal to 0.03 percent, the content of P is less than or equal to 0.010 percent, the content of Mn is 0.35 to 0.55 percent, the content of Ni is 1.30 to 1.55 percent, and the content of Mo is 1.15 to 1.40 percent;

the prealloyed steel powder prepared by atomization comprises the following components in percentage by weight: the content of C is less than or equal to 0.28 percent, the content of S is less than or equal to 0.009 percent, the content of Si is less than or equal to 0.03 percent, the content of P is less than or equal to 0.01 percent, the content of Mn is 0.35 to 0.55 percent, the content of Ni is 1.30 to 1.55 percent, the content of Mo is 1.15 to 1.40 percent, and the hydrogen loss is less than or equal to 1.67 percent;

the reduction comprises primary fine reduction and secondary fine reduction;

the primary fine reduction is carried out at the reduction temperature of 925-980 ℃, the airflow of 70Nm < 3 >/h, the material layer thickness of 23-29mm and the belt speed of 145-185 mm/min;

the secondary fine reduction is carried out at the reduction temperature of 925-980 ℃, the airflow of 70Nm < 3 >/h, the material layer thickness of 23-29mm and the belt speed of 145-185 mm/min.

2. The method for preparing high-strength and high-hardness water-atomized prealloyed steel powder according to claim 1, wherein the performance indexes of the prepared high-strength and high-hardness water-atomized prealloyed steel powder are as follows: the content of C is less than or equal to 0.003 percent, the content of S is less than or equal to 0.011 percent, the content of Si is less than or equal to 0.03 percent, the content of P is less than or equal to 0.012 percent, the content of Mn is 0.35-0.55 percent, the content of Ni is 1.30-1.55 percent, the content of Mo is 1.15-1.40 percent, and the hydrogen loss is less than or equal to 0.14 percent.