A method for preparing cladding structure boron stainless steel

Abstract

The purpose of the present invention is to provide a method for preparing boron stainless steel with a coating structure, which belongs to the field of neutron absorption materials, and the specific steps are: (1) Preparation of boron stainless steel powder: atomizing the raw materials according to the ratio to prepare boron stainless steel powder; or atomizing the boron stainless steel ingot obtained by casting or forging to prepare boron stainless steel powder; (2) spraying the boron stainless steel powder on a boron-containing substrate by a thermal spraying process to obtain a coating structure. The present invention prepares the boron stainless steel material by atomizing powder making and thermal spraying, avoids the cracking problem of boron stainless steel during hot processing, and the coating of the prepared material can be well combined with the substrate.

Description

Technical Field

[0001] The invention belongs to the field of neutron absorbing materials, and in particular provides a method for preparing boron stainless steel with a cladding structure. Background Art

[0002] Boron stainless steel is a neutron absorbing material, an alloy formed by the uniform dispersion of boron compounds in the stainless steel matrix. It has high strength characteristics and good corrosion resistance and radiation resistance. Boron is the main functional element in boron stainless steel. The higher the boron content, the stronger the neutron absorption ability; however, the solid solubility of boron in steel is very low, which limits the increase of the boron content in boron stainless steel. A large amount of low-melting-point boride eutectics will be formed in high-boron stainless steel, which will seriously split the matrix and greatly weaken the grain boundary strength, resulting in a significant reduction in the plastic toughness of the material, thereby significantly reducing the hot workability of the steel. If the boron content exceeds 2%, it cannot be rolled into shape, making the manufacture and processing of boron stainless steel more difficult.

[0003] The Chinese patent "A high-boron stainless steel neutron absorption material and its preparation method" (publication number CN106378459A) adopts a gas atomization spray powder making-hot isostatic pressing sintering-rolling process to prepare boron stainless steel plates.

[0004] The Chinese patent "A high-boron content austenitic stainless steel and its manufacturing method" (publication number CN102051531A) proposes a method for producing boron stainless steel plates through an ingot casting-forging-rolling process using general equipment.

[0005] The Chinese patent "Boron-containing stainless steel and its manufacturing method" (publication number CN 1681955 A) proposes a method for producing boron stainless steel by rolling after welding the frame.

[0006] The above methods have not been able to fundamentally solve the problem that boron stainless steel has low plasticity and is difficult to increase the boron content. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing boron stainless steel with a cladding structure. The boron stainless steel material is prepared by atomization powder making and thermal spraying, thereby avoiding the cracking problem of the boron stainless steel during hot processing, and the coating of the prepared material can be well combined with the substrate.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing cladding structure boron stainless steel, characterized in that the specific steps are as follows:

[0010] (1) Preparation of boron stainless steel powder: atomizing raw materials according to a ratio to prepare boron stainless steel powder; or atomizing boron stainless steel ingots obtained by casting or forging to prepare boron stainless steel powder;

[0011] (2) Boron stainless steel powder is sprayed onto a boron-containing substrate using a thermal spraying process to obtain a coating structure.

[0012] As the preferred technical solution:

[0013] In step (1), the composition of the boron stainless steel powder is (mass percentage): C: 0.01-0.06%, B: 0.5-6.6% (preferably 3.0-6.6%), Si≤1.0%, Mn: 1.09-2.0%, Ni: 7.0-12.0%, Cr: 23.2-28%, Mo: 0.26-0.32%, Ti: 0.12-0.16%, Gd: 0.01-1.0%, W: 1-12.5%, P≤0.030%, S≤0.025%, N≤0.1%, and the balance is iron and unavoidable impurities.

[0014] The powder making process parameters are: atomizing temperature 1550-1700°C, atomizing medium is argon, liquid guide tube diameter is 4-6mm, and atomizing pressure is 6-10MPa.

[0015] The boron stainless steel powder has a particle size of 45 to 75 μm.

[0016] In step (2), the substrate is made of boron stainless steel with a thickness of 2 to 5 mm.

[0017] The process parameters of the thermal spraying are: air pressure 0.58-0.65 MPa; fuel gas pressure 0.51-0.58 MPa; propane flow rate: 125-145 SLPM; hydrogen flow rate: 30-40 SLPM; nitrogen flow rate: 25-35 SLPM; powder feeding rate: 5-8 rpm; spraying distance: 160-240 mm.

[0018] The thickness of the spray coating is 0.1 to 2 mm.

[0019] Thermal spraying is the main method for preparing metal coatings, especially supersonic flame spraying. Supersonic flame spraying has low flame temperature and high flame velocity, which can greatly reduce the porosity of the coating. Therefore, supersonic flame spraying is a suitable preparation method for cladding structure boron stainless steel coating.

[0020] The beneficial effects of the present invention are:

[0021] The present invention solves the problem that high-boron-content boron stainless steel is difficult to form, and can prepare a neutron absorbing material with an average boron content of more than 2%. The average bonding strength of the prepared coating interface is greater than 60.00 N / mm 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1This is the SEM morphology of the interface of the thermally sprayed boron stainless steel cladding structure in Example 1.

[0023] Figure 2 This is the distribution diagram of boron element at the interface of the thermal sprayed boron stainless steel cladding structure in Example 1.

[0024] Figure 3 This is the cracking condition of the hot-rolled high-boron content boron stainless steel plate of comparative example 1. DETAILED DESCRIPTION

[0025] Example 1

[0026] The composition of boron stainless steel powder is: C: 0.02%, B: 4.8%, Si: 0.7%, Mn: 1.5%, Ni: 10.3%, Cr: 26.0%, Mo: 0.3%, Ti: 0.15%, Gd: 0.8%, W: 1.8%, P≤0.030%, S≤0.025%, N≤0.1%, and the balance is iron and unavoidable impurities.

[0027] The composition of boron stainless steel substrate is:

[0028] C: 0.03%, B: 1.6%, Si: 0.8%, Mn: 1.5%, Ni: 10.0%, Cr: 24.0%, Mo: 0.3%, Ti: 0.15%, Gd: 0.02%, W: 5.0%, P ≤ 0.030%, S ≤ 0.025%, N ≤ 0.1%, and the balance is iron and unavoidable impurities.

[0029] The VIGA equipment is used to melt industrial pure iron, metal chromium, metal nickel, nickel-boron alloy and other raw materials in a crucible according to the proportion and then atomize them to make boron stainless steel powder. The atomization temperature is 1600℃, the atomization medium is argon, the diameter of the liquid guide tube is 6mm, the atomization pressure is 8MPa, and the median particle size of the powder is 70μm.

[0030] Boron stainless steel substrate thickness 3mm, spraying air pressure 0.6MPa, gas pressure 0.55MPa, propane flow: 130SLPM; hydrogen flow: 35SLPM; nitrogen flow: 30SLPM; powder feeding rate: 6rpm; spraying distance: 180mm, single-sided coating thickness 0.5mm. The average boron content of the cladding steel plate is 2.4%, and the average bonding strength of the coating interface is 80.92N / mm 2 .

[0031] Example 2

[0032] The composition of boron stainless steel powder is: C: 0.03%, B: 4.9%, Si: 0.6%, Mn: 1.4%, Ni: 10.0%, Cr: 26.2%, Mo: 0.3%, Ti: 0.16%, Gd: 0.7%, W: 2.2%, P≤0.030%, S≤0.025%, N≤0.1%, and the balance is iron and unavoidable impurities.

[0033] The composition of boron stainless steel substrate is:

[0034] C: 0.03%, B: 1.7%, Si: 0.8%, Mn: 1.3%, Ni: 10.2%, Cr: 24.0%, Mo: 0.3%, Ti: 0.15%, Gd: 0.02%, W: 5.0%, P ≤ 0.030%, S ≤ 0.025%, N ≤ 0.1%, and the balance is iron and unavoidable impurities.

[0035] Boron stainless steel ingots were used as electrodes for gas atomization using EIGA equipment to produce boron stainless steel powder. The atomization temperature was 1650°C, the atomization medium was argon, the diameter of the liquid guide tube was 6mm, the atomization pressure was 8MPa, and the median particle size of the powder was 68μm.

[0036] Boron stainless steel substrate thickness 3mm, spraying air pressure 0.6MPa, gas pressure 0.55MPa, propane flow: 130SLPM; hydrogen flow: 35SLPM; nitrogen flow: 30SLPM; powder feeding rate: 7rpm; spraying distance: 200mm, single-sided coating thickness 0.8mm. The average boron content of the steel plate is 2.81%, and the average bonding strength of the coating interface is 75.84N / mm 2 .

[0037] Example 3

[0038] The composition of boron stainless steel powder is: C: 0.02%, B: 5.1%, Si: 0.6%, Mn: 1.5%, Ni: 10.0%, Cr: 25.7%, Mo: 0.3%, Ti: 0.15%, Gd: 0.8%, W: 2.0%, P≤0.030%, S≤0.025%, N≤0.1%, and the balance is iron and unavoidable impurities.

[0039] The composition of boron stainless steel substrate is:

[0040] C: 0.03%, B: 1.8%, Si: 0.8%, Mn: 1.5%, Ni: 9.8%, Cr: 24.1%, Mo: 0.3%, Ti: 0.14%, Gd: 0.02%, W: 4.9%, P ≤ 0.030%, S ≤ 0.025%, N ≤ 0.1%, and the balance is iron and unavoidable impurities.

[0041] Industrial pure iron, metallic chromium, metallic nickel, nickel-boron alloy and other raw materials are melted in a crucible according to the proportion and then atomized to produce boron stainless steel powder using VIGA equipment. The atomization temperature is 1600℃, the atomization medium is argon, the diameter of the liquid guide tube is 4mm, the atomization pressure is 10MPa, and the median particle size of the powder is 53μm.

[0042] Boron stainless steel substrate thickness 3mm, spraying air pressure 0.6MPa, gas pressure 0.55MPa, propane flow: 130SLPM; hydrogen flow: 35SLPM; nitrogen flow: 30SLPM; powder feeding rate: 6rpm; spraying distance: 200mm, single-sided coating thickness 0.5mm. The average boron content of the steel plate is 2.62%, and the average bonding strength of the coating interface is 82.87N / mm 2 .

[0043] Example 4

[0044] The composition of boron stainless steel powder is: C: 0.02%, B: 4.9%, Si: 0.7%, Mn: 1.4%, Ni: 10.1%, Cr: 26.0%, Mo: 0.3%, Ti: 0.14%, Gd: 0.7%, W: 1.7%, P≤0.030%, S≤0.025%, N≤0.1%, and the balance is iron and unavoidable impurities.

[0045] The composition of boron stainless steel substrate is:

[0046] C: 0.02%, B: 1.7%, Si: 0.9%, Mn: 1.5%, Ni: 10.2%, Cr: 23.6%, Mo: 0.3%, Ti: 0.16%, Gd: 0.03%, W: 5.1%, P ≤ 0.030%, S ≤ 0.025%, N ≤ 0.1%, and the balance is iron and unavoidable impurities.

[0047] Boron stainless steel ingots were used as electrodes for gas atomization using EIGA equipment to produce boron stainless steel powder. The atomization temperature was 1650°C, the atomization medium was argon, the diameter of the liquid guide tube was 4mm, the atomization pressure was 10MPa, and the median particle size of the powder was 48μm.

[0048] Boron stainless steel substrate thickness 3mm, spraying air pressure 0.6MPa, gas pressure 0.55MPa, propane flow: 130SLPM; hydrogen flow: 35SLPM; nitrogen flow: 30SLPM; powder feeding rate: 6rpm; spraying distance: 200mm, single-sided coating thickness 1mm. The average boron content of the steel plate is 2.98%, and the average bonding strength of the coating interface is 62.65N / mm 2 .

[0049] Examples 1 to 4 all obtained tightly bonded coating layers. The morphology and element distribution at the interface of the coating structure of Example 1 are shown in the attached Figure 1 , 2 .

[0050] Comparative Example 1

[0051] When a boron stainless steel ingot with the composition of C: 0.03%, B: 2.5%, Si: 0.8%, Mn: 1.5%, Ni: 10.0%, Cr: 24.0%, Mo: 0.3%, and Ti: 0.15% was directly hot-rolled, severe cracking occurred in the steel plate.

[0052] Comparative Example 2

[0053] Boron stainless steel powder with the composition of C: 0.03%, B: 4.5%, Ni: 10.0%, Cr: 18.0% was sprayed on the 3mm boron stainless steel substrate described in Example 1, with the spraying air pressure of 0.6MPa, the fuel gas pressure of 0.55MPa, the propane flow rate of 130SLPM, the hydrogen flow rate of 35SLPM, the nitrogen flow rate of 30SLPM, the powder feeding rate of 6rpm, the spraying distance of 180mm, and the single-side coating thickness of 1mm. Cracks appeared inside the coating and at the interface of the substrate, and a stable metallurgical bond could not be formed.

[0054] Matters not covered by the present invention are known technologies.

[0055] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing cladding structure boron stainless steel, It is characterized in that The specific steps are as follows: (1) Preparation of boron stainless steel powder: atomizing raw materials according to a ratio to prepare boron stainless steel powder; or atomizing boron stainless steel ingots obtained by casting or forging to prepare boron stainless steel powder; (2) using a thermal spraying process to spray boron stainless steel powder on a boron-containing substrate to obtain a coating structure; in step (1), the composition of the boron stainless steel powder is as follows: C: 0.01-0.06%, B: 0.5-6.6%, Si≤1.0%, Mn: 1.09-2.0%, Ni: 7.0-12.0%, Cr: 23.2-28%, Mo: 0.26-0.32%, Ti: 0.12-0.16%, Gd: 0.01-1.0%, W: 1-12.5%, P≤0.030%, S≤0.025%, N≤0.1%, and the balance is iron and unavoidable impurities.

2. The method for preparing the cladding structure boron stainless steel according to claim 1, Features: The boron content is 3.0 to 6.6 wt.%.

3. The method for preparing the cladding structure boron stainless steel according to claim 1, Features: In step (1), the powder making process parameters are: atomization temperature 1550-1700°C, atomization medium argon, liquid guide tube diameter 4-6mm, and atomization pressure 6-10MPa.

4. The method for preparing the cladding structure boron stainless steel according to claim 1, Features: In step (1), the boron stainless steel powder has a powder particle size of 45 to 75 μm.

5. The method for preparing the cladding structure boron stainless steel according to claim 1, Features: In step (2), the substrate is made of boron stainless steel with a thickness of 2 to 5 mm.

6. The method for preparing the cladding structure boron stainless steel according to claim 1, It is characterized in that In step (2), the process parameters of the thermal spraying are: air pressure 0.58-0.65 MPa; fuel gas pressure 0.51-0.58 MPa; propane flow rate: 125-145 SLPM; hydrogen flow rate: 30-40 SLPM; nitrogen flow rate: 25-35 SLPM; powder feeding rate: 5-8 rpm; spraying distance: 160-240 mm.

7. The method for preparing the cladding structure boron stainless steel according to claim 1, Features: In step (2), the spray coating thickness is 0.1 to 2 mm.

Images