阅读说明：本技术 一种改善铝合金零件表面喷丸强化的方法 (Method for improving shot peening strengthening of surface of aluminum alloy part ) 是由 张韶佳 陈昕 胡方亭 王龙 刘娇婷 于 2021-07-30 设计创作，主要内容包括：本发明属于特种工艺技术领域中的金属材料表面强化技术,一种改善铝合金零件表面喷丸强化的方法。包括设备检查-零件检查-喷丸用压缩空气质量检查-零件的喷丸强化-丸粒残留物检测等步骤实现铝合金零件表面喷丸强化。通过减小喷丸压力、减少喷丸遍数和增加丸粒筛分系统等工艺改进改善,有效解决了丸粒残留问题,保证了零件表面喷丸质量；提出了详细的喷丸零件表面质量理化检测分析方法,从而有效的控制零件表面质量,避免丸粒残留带入的质量问题。(The invention belongs to a metal material surface strengthening technology in the technical field of special processes, and relates to a method for improving shot blasting strengthening of the surface of an aluminum alloy part. The method comprises the steps of equipment inspection, part inspection, compressed air quality inspection for shot blasting, shot peening of the part, shot residue detection and the like to realize the shot peening of the surface of the aluminum alloy part. Through the improvement of the processes of reducing shot blasting pressure, reducing shot blasting times, increasing a shot screening system and the like, the problem of shot residue is effectively solved, and the shot blasting quality on the surface of a part is ensured; a detailed shot blasting part surface quality physicochemical detection analysis method is provided, so that the part surface quality is effectively controlled, and the quality problem caused by shot residue is avoided.)

1. A method for improving shot peening strengthening of the surface of an aluminum alloy part is characterized by comprising the following steps:

step 1, equipment inspection: the nozzle is ensured to be clean and not to be blocked, the glass shots are qualified after being put into a factory, the quantity of the glass shots meets the requirement, and the shot blasting equipment operates normally;

step 2, checking parts: the roughness of the outer surface of the part meets the requirement, and the part has no defects of spots, scratches, bruises, rustiness and the like, and the outer surface of the part is wiped by dipping cotton cloth in 180# gasoline to keep the shot blasting surface clean and free of dirt;

step 3, quality inspection of compressed air for shot blasting: inspecting the compressed air by using a clean and dry mirror or glass with the area not less than 70mm multiplied by 70mm, wherein the compressed air nozzle is vertical to the mirror surface, the nozzle is 203-254 mm away from the mirror surface, the valve is opened to the maximum, and after 15-30S of air blowing, visual inspection is carried out, so that the mirror surface is free from residues of visible oil stains, moisture or solid particles;

and 4, shot peening strengthening of the parts: setting the shot blasting pressure P to be 0.25MPa, setting the part running speed V to be 570mm/min, measuring and adjusting the nozzle distance L to be 180-200 mm, enabling the included angle between a shot flow and the normal line of the surface of a sprayed area of the part to be smaller than 45 degrees, starting a shot screening system, a shot blasting machine dust removal system and a part transmission motor, adding required dry and clean glass rough shots into the shot blasting machine, and ensuring that the part is subjected to shot blasting for 2 times in a free state without external force;

step 5, detecting the pill residues: and (3) cross section metallographic sample preparation is carried out on the test pieces of the parts in the same batch, and detection and analysis are carried out on the pill residue in a scanning electron microscope scanning mode, so that the silicon-rich residue distribution is not detected.

2. A method for improving the surface shot peening strengthening of aluminum alloy parts according to claim 1, wherein the physical and chemical properties of the glass shot are such that the content of SiO2 is not less than 67%, the density is not less than 2.3g/cm3, and the hardness is not less than 500 HV.

3. The method for improving the surface shot blasting reinforcement of the aluminum alloy part according to claim 1, wherein the size specification of the glass shots in the step 1 is 0.19-0.5mm, and the specific detection method adopts a vibration screening method, wherein 25 meshes of screens are required to pass through completely, the residue on a 30-mesh screen is not more than 5%, and the residue on a 120-mesh screen is not more than 5%.

4. The method for improving shot peening strengthening of the surface of aluminum alloy part as claimed in claim 1, wherein in step 1, the glass shot should be ensured to be 250-300kg, and after each two parts are shot peened, the glass shot should be added into the shot peening machine to be 125-150 kg.

5. The method for improving the surface shot peening strengthening of the aluminum alloy part according to claim 1, wherein in the step 2, all sharp points and sharp corners in the part specification peening area are rounded according to a fixed size.

6. The method for improving the surface shot peening strengthening of the aluminum alloy part according to claim 1, wherein the metal part in the step 2 is a LD2 section bar.

7. The method for improving shot peening strengthening of the surface of the aluminum alloy part as claimed in claim 1, wherein in the step 4, a piece of waste steel plate is used for trial peening before the part is formally peened, and the part can be peened only when the glass shot can be normally peened.

8. The method for improving the shot peening strengthening of the surface of the aluminum alloy part according to claim 1, wherein the inner cavity of the metal part is stuffed with cotton cloth for protection treatment in the step 4.

Technical Field

The invention belongs to a metal material surface strengthening technology in the technical field of special processes, and relates to a method for improving shot blasting strengthening of the surface of an aluminum alloy part.

Background

Shot peening is a surface strengthening process. The shot blasting is a process in which shot is ejected by compressed air or a centrifugal shot blasting machine ejects shot onto the surface of a workpiece at a high speed by centrifugal force to strongly impact the surface of the workpiece so as to plastically deform the surface of the workpiece, thereby strengthening the surface and changing the surface state. The pill impacts the metal surface, firstly, the surface of the part is enabled to generate a hardened layer with the depth of 0.1-0.4mm, the resistance of the surface of the part to plastic deformation and fracture is increased, the surface layer generates compressive stress, the fatigue strength of the part is improved, and secondly, the defects on the surface of the part and the damage caused by mechanical processing are reduced, so that the stress concentration is reduced, the fatigue resistance of the part is improved, and the service life of the part is prolonged. The surface of the aluminum alloy part is usually subjected to surface strengthening by glass shot blasting, and the surface of the part is subjected to coverage rate inspection after shot blasting.

The failure analysis data before the shot blasting process is consulted, the failure of part fracture caused by shot residue on the part surface due to unreasonable design of shot blasting process parameters is not proposed, the existing effective patent is consulted, and a detection method for further controlling the shot blasting part surface quality except coverage rate inspection is not proposed.

However, in the failure analysis process for dealing with accidents such as a certain helicopter, the fracture property of a fault part is found to be fatigue, the fracture originates from a stripping block, and the stripping block is also in fatigue, so that the cross section analysis of the crack initiation edge of the stripping block shows that non-conductive inlays rich in Si and O elements exist in discontinuous distribution on the surface of the part, the surface of the part is caused to generate similar micro-cracks, and stress concentration and fracture under the action of stress are caused. The non-conductive silicon-rich inlay was analyzed to be a glass pellet component used for shot blasting. Meanwhile, the distribution and the content of the pill residue can be analyzed by adopting a detection method of preparing a metallographic sample of a cross section of a part and performing surface scanning analysis by amplifying about 100 times under a secondary electron imaging mode of a scanning electron microscope. Therefore, the quality inspection of shot peening on the surface of a part is also becoming increasingly important.

The original shot blasting process design parameters and the production process are as follows: the shot blasting equipment adopts special process equipment independently developed in the 70 s, the shot blasting pressure is 0.4MPa, the nozzle distance L is 180-200 mm, the part running speed V is 570mm/min, the surface is sprayed with JC-03-93 standard glass pill coarse pills (0.19-0.5mm) for 2 times and fine pills (0.05-0.18mm) for 2 times for strengthening, the pills are continuously recycled, and the equipment does not have the function of pill screening.

In order to analyze the main cause of the part fracture, based on the original equipment and process conditions, a large number of comparative tests are carried out to find and summarize the following conclusions.

(1) The method is characterized in that the existing domestic shot blasting process parts with 0.4MPa shot blasting pressure, independently developed shot blasting equipment and 0.05-0.18 and 0.19-0.5 specifications are subjected to shot non-cyclic shot blasting for 2 times of coarse shot blasting and 2 times of fine shot blasting, obvious shot blasting residues exist on the surfaces of the parts in any service state (accident machine, to-life parts and fatigue test qualified parts), and the content of the residues is not obviously changed, so that the method belongs to a common phenomenon;

(2) the shot residue is generated in the shot blasting process, and the surface treatment and the heat treatment only increase the infiltration amount of the shot;

(3) under the condition that other peening parameters of part peening equipment are not changed, the quantity of silicon-rich inserts on the surface of a test piece adopting 0.4MPa peening pressure is obviously more than 0.25MPa peening pressure, which shows that the existing 0.4MPa peening pressure is larger, and the 0.25MPa low peening pressure is more appropriate;

(4) according to the existing 0.4MPa shot blasting pressure, the shot blasting equipment is independently developed, and shot blasting is carried out for 4 times by domestic shot blasting, the appearance of the silicon-rich mosaic can be observed from the sample after each shot blasting, and after the fine shot blasting is started, the content of the silicon-rich mosaic is obviously increased and shows an increasing trend; under the condition that other technical conditions are not changed, domestic pellets are changed into imported pellets AGB70, brand-new pellets are adopted for shot blasting each time, shot blasting is performed for four times, the appearance of the silicon-rich inlay and the appearance similar to micro cracks can be observed on the sample after shot blasting each time, and the content of the silicon-rich inlay presents an increasing trend; tests show that the more times of shot blasting, the more unfavorable the surface appearance of shot blasting;

(5) the surface of the test piece adopting the numerical control shot blasting equipment to blast the shot at the inlet does not generate silicon-rich mosaic, which indicates that the equipment is unreasonable.

In conclusion, the unreasonable shot blasting design parameters and the surface of the part subjected to shot blasting by the improper shot blasting process have glass bead residues, so that the invention provides a method for improving shot blasting strengthening of the surface of the aluminum alloy part and an analysis method for detecting the surface quality of the shot blasting part aiming at the technical problems and findings.

Disclosure of Invention

The invention aims to solve the problem of unreasonable design of the parameters of the existing shot blasting equipment and shot blasting process, and provides an improvement method for shot blasting strengthening of the surface of an aluminum alloy part, which reduces shot blasting pressure, reduces shot blasting times and increases a shot screening system, so as to effectively avoid shot residue after shot blasting.

Technical scheme

A method for improving shot peening strengthening of the surface of an aluminum alloy part comprises the following steps:

step 1, equipment inspection: the nozzle is ensured to be clean and not to be blocked, the glass shots are qualified after being put into a factory, the quantity of the glass shots meets the requirement, and the shot blasting equipment operates normally;

step 2, checking parts: the roughness of the outer surface of the part meets the requirement, and the part has no defects of spots, scratches, bruises, rustiness and the like, and the outer surface of the part is wiped by dipping cotton cloth in 180# gasoline to keep the shot blasting surface clean and free of dirt;

step 3, quality inspection of compressed air for shot blasting: inspecting the compressed air by using a clean and dry mirror or glass with the area not less than 70mm multiplied by 70mm, wherein the compressed air nozzle is vertical to the mirror surface, the nozzle is 203-254 mm away from the mirror surface, the valve is opened to the maximum, and after 15-30S of air blowing, visual inspection is carried out, so that the mirror surface is free from residues of visible oil stains, moisture or solid particles;

and 4, shot peening strengthening of the parts: setting the shot blasting pressure P to be 0.25MPa, setting the part running speed V to be 570mm/min, measuring and adjusting the nozzle distance L to be 180-200 mm, enabling the included angle between a shot flow and the normal line of the surface of a sprayed area of the part to be smaller than 45 degrees, starting a shot screening system, a shot blasting machine dust removal system and a part transmission motor, adding required dry and clean glass rough shots (0.19-0.50 mm) into the shot blasting machine, and ensuring that the part is subjected to shot blasting 2 times under the free state without external force;

step 5, detecting the pill residues: and (3) cross section metallographic sample preparation is carried out on the test pieces of the parts in the same batch, and detection and analysis are carried out on the pill residue in a scanning electron microscope scanning mode, so that the silicon-rich residue distribution is not detected.

Furthermore, the physical and chemical properties of the medium glass pills are such that the content of SiO2 is not less than 67%, the density is not less than 2.3g/cm3, and the hardness is not less than 500 HV.

Further, in the step 1, the size specification of the glass pills is 0.19-0.5mm, and the specific detection method adopts a vibration screening method, wherein 25 meshes of screen mesh are required to pass completely, the residue on a 30-mesh screen mesh is not more than 5%, and the residue on a 120-mesh screen mesh is not more than 5%.

Further, the glass shot in step 1 should be ensured to be 250-300kg, and 125-150kg of glass shot should be added into the shot blasting machine after each shot blasting of two parts, so as to ensure the requirement of continuous shot blasting.

In a further step 2, all sharp and sharp corners in the part specification peening area are rounded according to a fixed size. Preventing damage.

Furthermore, the metal part in the step 2 is specifically an LD2 section bar girder, which is a material used by the current helicopter main blade girder and cannot be changed in a short time due to related factors and the like.

Furthermore, in the step 4, before the formal shot blasting of the parts, a piece of waste steel plate (HRC40-45) is used for trial blasting, and the parts can be blasted only when the glass shots can be normally blasted.

Furthermore, cotton cloth is filled into the inner cavity of the metal part in the step 4 for protection treatment so as to prevent glass shots from entering the inner cavity for shot blasting.

Technical effects

1. The invention effectively solves the problem of shot residue and ensures the shot blasting quality on the surface of the part by improving and improving the processes of reducing shot blasting pressure, reducing shot blasting times, increasing a shot screening system and the like on the original self-developed semi-mechanical shot blasting equipment;

2. the invention provides improper shot blasting process parameters and a process method, shot blasting can leave shot grain inlays on the surface of the part, and serious potential safety hazard is caused to the use of the part, which is not regarded domestically;

3. the invention provides a detailed physicochemical detection and analysis method for shot blasting part surface quality, thereby effectively controlling the part surface quality and avoiding the quality problem caused by shot residue, which is not mentioned at home.

Drawings

FIG. 1 is a schematic view of a shot peening process

Detailed Description

The invention will now be further illustrated with reference to several examples:

the first embodiment is as follows:

1. equipment inspection: the nozzle is clean and is not blocked, the glass shots are qualified after being put into a factory, the quantity of the glass shots meets the requirement, and the shot blasting equipment operates normally;

2. and (3) checking parts: the roughness of the outer surface of the part meets the requirement, and the part has no defects of spots, scratches, bruises, rustiness and the like, and the outer surface of the part is wiped by cotton cloth dipped with 180# gasoline to keep the shot blasting surface clean and free of dirt;

3. quality inspection of compressed air for shot blasting: inspecting the compressed air by using a clean and dry mirror with the area of 70mm multiplied by 70mm, wherein a compressed air nozzle is vertical to the mirror surface, the distance between the nozzle and the mirror surface is 235mmmm, a valve is opened to the maximum, and after 25S blowing, visual inspection is carried out, so that no visible oil stain, moisture or solid particle residues exist on the mirror surface;

4. shot peening of parts: setting the shot blasting pressure P to be 0.25MPa, setting the part running speed V to be 570mm/min, measuring and adjusting the nozzle distance L to be 190mm, enabling the included angle between the shot flow and the normal line of the surface of the sprayed area of the part to be 30 degrees, adding glass coarse shots (0.19-0.50 mm) into the shot blasting machine, starting a shot screening system, a shot blasting machine dust removal system and a part transmission motor, and ensuring that the part is subjected to shot blasting for 2 times in a free state without external force;

5. and (3) detecting the pellet residues: and (3) cross section metallographic sample preparation is carried out on the part along with the furnace test piece, and detection and analysis are carried out on the pill residue in a scanning electron microscope scanning mode, so that the silicon-rich residue distribution is not detected.

Example two:

1. equipment inspection: the nozzle is clean and is not blocked, the glass shots are qualified after being put into a factory, the quantity of the glass shots meets the requirement, and the shot blasting equipment operates normally;

2. and (3) checking parts: the roughness of the outer surface of the part meets the requirement, and the part has no defects of spots, scratches, bruises, rustiness and the like, and the outer surface of the part is wiped by cotton cloth dipped with 180# gasoline to keep the shot blasting surface clean and free of dirt;

3. quality inspection of compressed air for shot blasting: inspecting compressed air by using a clean and dry mirror with the area of 70mm multiplied by 70mm, wherein a compressed air nozzle is vertical to the mirror surface, the distance between the nozzle and the mirror surface is 220mmmm, a valve is opened to the maximum, and after 20S of air blowing, visual inspection is carried out, so that no visible oil stain, moisture or solid particle residues exist on the mirror surface;

4. shot peening of parts: setting the shot blasting pressure P to be 0.25MPa, setting the part running speed V to be 570mm/min, measuring and adjusting the nozzle distance L to be 180mm, enabling the included angle between the shot flow and the normal line of the surface of the sprayed area of the part to be 30 degrees, adding glass coarse shots (0.19-0.50 mm) into the shot blasting machine, starting a shot screening system, a shot blasting machine dust removal system and a part transmission motor, and ensuring that the part is subjected to shot blasting for 2 times in a free state without external force;

5. and (3) detecting the pellet residues: and (3) cross section metallographic sample preparation is carried out on the part along with the furnace test piece, and detection and analysis are carried out on the pill residue in a scanning electron microscope scanning mode, so that the silicon-rich residue distribution is not detected.

Example three:

1. equipment inspection: the nozzle is clean and is not blocked, the glass shots are qualified after being put into a factory, the quantity of the glass shots meets the requirement, and the shot blasting equipment operates normally;

2. and (3) checking parts: the roughness of the outer surface of the part meets the requirement, and the part has no defects of spots, scratches, bruises, rustiness and the like, and the outer surface of the part is wiped by cotton cloth dipped with 180# gasoline to keep the shot blasting surface clean and free of dirt;

3. quality inspection of compressed air for shot blasting: inspecting the compressed air by using a clean and dry mirror with the area of 70mm multiplied by 70mm, wherein a compressed air nozzle is vertical to the mirror surface, the distance between the nozzle and the mirror surface is 240mmmm, a valve is opened to the maximum, and after 28S blowing, visual inspection is carried out, so that no visible oil stain, moisture or solid particle residues exist on the mirror surface;

4. shot peening of parts: setting the shot blasting pressure P to be 0.25MPa, setting the part running speed V to be 570mm/min, measuring and adjusting the nozzle distance L to be 200mm, enabling the included angle between the shot flow and the normal line of the surface of the sprayed area of the part to be 25 degrees, adding glass coarse shots (0.19-0.50 mm) into the shot blasting machine, starting a shot screening system, a shot blasting machine dust removal system and a part transmission motor, and ensuring that the part is subjected to shot blasting for 2 times in a free state without external force;

5. and (3) detecting the pellet residues: and (3) cross section metallographic sample preparation is carried out on the part along with the furnace test piece, and detection and analysis are carried out on the pill residue in a scanning electron microscope scanning mode, so that the silicon-rich residue distribution is not detected.

The invention is also characterized in that the following analysis method is adopted in the failure analysis process:

1. taking accident machine parts as an example, researching the surface residue conditions of parts in different service states under the existing shot blasting parameters and using shot blasting conditions, and analyzing whether the parts belong to individual cases or are common phenomena;

2. researching which process link the pill residue is generated in specifically through the aluminum alloy test blocks in the same batch;

3. through the aluminum alloy test blocks of the same batch, the comparison condition of the residues on the surfaces of the test blocks adopting the same shot under different shot blasting pressures is researched;

4. through the aluminum alloy test blocks in the same batch, the comparison condition of the residues on the surface of the test block shot-blasted in a shot circulation and shot non-circulation mode under the same shot blasting pressure is researched;

5. through the same batch of aluminum alloy test blocks, the comparison condition of residues on the surfaces of the test blocks after shot blasting by adopting pills with different standards and specifications under the condition of the existing process parameters is researched;

6. through the aluminum alloy test blocks in the same batch, the comparison condition of residues on the surfaces of the test blocks after shot blasting of different standards and specifications by adopting a numerical control shot blasting device is researched;

7. and (5) conclusion finding is carried out.

The invention also aims to provide a novel analysis method for detecting residual shot inserts on the surface of the part after shot blasting, thereby solving the problem of a control means for surface quality of the aluminum alloy part after shot blasting strengthening. The invention effectively solves the problem of shot residue and ensures the shot blasting quality on the surface of the part by improving and improving the processes of reducing shot blasting pressure, reducing shot blasting times, increasing a shot screening system and the like on the original self-developed semi-mechanical shot blasting equipment; improper shot blasting process parameters and process methods are provided, shot blasting can leave shot grain inlays on the surface of the part, and serious potential safety hazards are caused to the use of the part, which are not regarded domestically; the detailed shot blasting part surface quality physicochemical detection analysis method is provided, so that the part surface quality is effectively controlled, and the quality problem caused by shot residue is avoided, which is not mentioned at home.