阅读说明：本技术 一种复杂曲面封闭内腔零件热处理工艺方法 (Heat treatment process method for complex curved surface closed inner cavity part ) 是由 娄志强 孔德权 杨屹 刘谨怡 于 2018-08-27 设计创作，主要内容包括：本发明提供一种复杂曲面封闭内腔零件热处理工艺方法,零件内腔涂刷热处理保护涂料；去应力回火；零件内腔底部接通气管；外表面涂热处理保护涂料；用通气管向内腔充氩气保护；预热；等温淬火；回火。本发明满足了大型复杂曲面封闭内腔零件热处理时氧化、脱碳及热处理变形要求,与真空热处理工艺相比,具有生产成本低、效率高、热处理变形小等优点。(The invention provides a heat treatment process method for a part with a complex curved surface and a closed inner cavity, wherein the inner cavity of the part is coated with a heat treatment protective coating; stress relief tempering; the bottom of the inner cavity of the part is communicated with an air pipe; coating heat treatment protective paint on the outer surface; filling argon into the inner cavity by using a vent pipe for protection; preheating; isothermal quenching; and (6) tempering. The invention meets the requirements of oxidation, decarburization and heat treatment deformation during heat treatment of large-scale complex curved surface closed inner cavity parts, and has the advantages of low production cost, high efficiency, small heat treatment deformation and the like compared with a vacuum heat treatment process.)

1. A heat treatment process method for a part with a complex curved surface and a closed inner cavity is characterized by comprising the following steps:

coating heat treatment protective paint on the inner cavity of the part;

stress relief tempering;

the bottom of the inner cavity of the part is communicated with an air pipe;

coating heat treatment protective paint on the outer surface;

filling argon into the inner cavity by using a vent pipe for protection;

preheating;

isothermal quenching;

and (6) tempering.

2. The heat treatment process method for the part with the complex curved surface and the closed inner cavity according to claim 1, wherein the stress relief tempering comprises the following steps: heating to 680 deg.C, keeping the temperature for 100-120 min, and cooling in air.

3. The heat treatment process method for the part with the complex curved surface and the closed inner cavity according to claim 1, wherein the preheating comprises the following steps: heating to 650 ℃, and keeping the temperature for 100-120 minutes.

4. The heat treatment process method for the part with the complex curved surface and the closed inner cavity according to claim 1, wherein the isothermal quenching comprises the following steps: the temperature is preserved for 120 minutes in an electric furnace at 900 ℃, and then the steel plate is transferred into a nitrate tank at 180 ℃ and 220 ℃ to be cooled for 60 minutes for isothermal quenching.

5. The heat treatment process for the part with the complex curved surface and the closed inner cavity as claimed in claim 1, wherein the tempering is carried out by heating to 250-300 ℃, keeping the temperature for 180 minutes and cooling in air.

Technical Field

The invention relates to the technical field of heat treatment, in particular to a heat treatment method for a part with a closed inner cavity of a complex curved surface.

Background

During heat treatment of a workpiece, the most common defects are oxidation, decarburization and heat treatment distortion.

Oxidation is the process by which iron on the steel surface interacts with oxygen, oxidizing gases, oxidizing impurities in the heating medium to form iron oxide. Oxidation of steel is a chemical reaction, and after an oxide film appears on the surface of steel, the rate of oxidation depends mainly on the diffusion rate of oxygen and iron atoms through the oxide film. With the increase of the heating temperature, the diffusion speed of atoms increasesThe oxidation rate of steel is greatly increased, especially at 570 ℃ or higher, and the formed oxidation film is mainly FeO, is not compact and has a loose structure, so that oxygen easily penetrates through the formed surface oxidation film to continue the oxidation reaction with iron. Therefore, when FeO is present in the oxide film, the oxidation rate of the steel is greatly accelerated, and the oxide layer is gradually thickened. The oxide film is made of relatively dense Fe below 570 DEG C₃0₄The oxidation film on the surface of the workpiece has compact structure, is firmly combined with the substrate, and is difficult to continuously permeate oxygen atoms, so the oxidation speed is relatively slow. Due to the formation of the iron scale, the size of the workpiece is reduced, the surface finish is reduced, and the cooling speed during quenching is also seriously influenced, so that soft spots and insufficient hardness are generated on the surface of the workpiece.

Decarburization is that carbon in the surface layer of steel is oxidized to lower the carbon content in the surface layer of steel, and the higher the heating temperature of steel is, the more the carbon content of steel is (particularly, when there are high contents of elements such as silicon, phase, and aluminum), the more decarburization the steel becomes. Because of the high diffusion rate of carbon, the decarburization rate of the steel is always greater than the oxidation rate thereof, and a decarburized layer of a certain thickness is always present below the oxidized layer of the steel. The carbon content of the surface layer of the steel is reduced due to decarburization, so that the hardness of the surface layer of the steel is insufficient after quenching, the fatigue strength is reduced, and surface cracks are easily formed during quenching of the steel.

The heat treatment deformation refers to a certain deformation of the workpiece caused by the influence of structural stress and thermal stress in the heating and cooling processes of the workpiece, and is one of the inevitable defects of the heat treatment.

In order to prevent oxidation and decarburization and control heat treatment deformation, protective atmosphere heat treatment and vacuum heat treatment production are often adopted according to the technical requirements of workpieces, but through actual heat treatment production, the heat treatment process methods cannot simultaneously meet the heat treatment quality control requirements of large-scale complex curved surface closed inner cavity parts.

Disclosure of Invention

The invention provides a heat treatment process method, and aims to control oxidation, decarburization and heat treatment deformation of a large ultrahigh-strength steel complex curved surface closed inner cavity part during heat treatment.

In order to achieve the purpose, the invention adopts the technical scheme that:

a heat treatment process method of a part with a complex curved surface and a closed inner cavity,

1) coating heat treatment protective paint on the inner cavity of the part;

2) stress relief tempering;

3) the bottom of the inner cavity of the part is communicated with an air pipe;

4) coating heat treatment protective paint on the outer surface;

5) filling argon into the inner cavity by using a vent pipe for protection;

6) preheating;

7) isothermal quenching;

8) and (6) tempering.

The stress relief tempering: heating to 680 deg.C, keeping the temperature for 100-120 min, and cooling in air.

Preheating: heating to 650 ℃, and keeping the temperature for 100-120 minutes.

And (3) isothermal quenching: the temperature is preserved for 120 minutes in an electric furnace at 900 ℃, and then the steel plate is transferred into a nitrate tank at 180 ℃ and 220 ℃ to be cooled for 60 minutes for isothermal quenching.

The tempering is carried out, the tempering is carried out after the heating is carried out to the temperature of 250-300 ℃, the heat preservation is carried out for 180 minutes, and the air cooling is carried out.

The invention has the beneficial effects that:

the invention meets the requirements of oxidation, decarburization and heat treatment deformation during heat treatment of large-scale complex curved surface closed inner cavity parts, and has the advantages of low production cost, high efficiency, small heat treatment deformation and the like compared with a vacuum heat treatment process.

Detailed Description

The present invention will be further described with reference to the following examples.

The invention relates to a heat treatment process method for a part with a complex curved surface and a closed inner cavity, which comprises the following steps:

and (3) checking parts: and (5) checking the size and the quality of the inner surface and the outer surface of the part.

Brushing paint: the upper and lower inner cavities are coated with heat treatment protective paint.

Welding: welding the upper and lower parts, welding a vent pipe with the diameter of 10 multiplied by 1.0mm at the bottom end, and performing the step 5) within 120 minutes after welding.

And (3) inflation protection: high-purity argon is filled into the inner cavity by utilizing a vent pipe with the diameter of phi 10 multiplied by 1.0 mm.

Stress relief tempering: heating to 680 deg.C, keeping the temperature for 100-120 min, and cooling in air.

Quenching: heating to 650 ℃, preserving heat for 100-.

And (3) cooling: cooling in water of 30-60 deg.C.

Washing in water at 60 deg.c for 60 min, air cooling and drying.

Tempering: heating to 250-300 deg.C, tempering, holding the temp for 180 min, and air cooling.

And (4) checking: and testing the hardness, the deformation and the decarburization control requirement.