What is shot peening?

September 5, 2024

What is Shot Peening?

Shot peening is a surface treatment technology that improves the performance of a workpiece by shooting hard particles (called “shots”) at the surface of the workpiece at high speed. This technology is widely used in metal processing, automobile manufacturing, aerospace and other fields. Its main purpose is to improve the physical properties of the workpiece, such as strength, wear resistance and surface quality, by impacting the workpiece surface with particles.

Principle

The basic principle of shot peening is to generate a compressive stress layer by impacting the workpiece surface with high-speed particles, thereby offsetting the tensile stress that may appear on the surface and improving the fatigue strength of the material. The high-speed impact of the particles causes plastic deformation of the surface layer of the material. This deformation not only improves the surface quality, but also improves the mechanical properties of the material. After shot peening, the surface cracks and defects of the material will be effectively reduced, and the durability will be further improved.

Material

The material of the shot peening media is diverse, and different materials are suitable for different processing requirements:

• Steel shot: high hardness, often used to process metal materials, can effectively remove surface oxide layers and dirt.
• Stainless steel shot: corrosion-resistant, suitable for use in occasions with high environmental requirements.
• Ceramic shot: high hardness, often used to remove surface dirt and improve surface quality, suitable for occasions with high precision requirements.
• Glass shot: softer, suitable for fine surface treatment, such as removing minor surface defects.

Note: When the surface cannot tolerate iron contamination, stainless steel shot, ceramic shot or glass shot should be considered.

History of Shot Peening

The development of shot peening technology reflects the progress of industrial manufacturing technology. From the initial manual operation to modern automated equipment, shot peening technology has been widely used and continuously improved in various fields.

Early development

The origin of shot peening technology can be traced back to the early 19th century, when shot peening was mainly used for strengthening metal parts. Early shot peening equipment was usually manually operated and less efficient, but it laid the foundation for later technological development.

Modernization process

• Early 20th century: With the advancement of industrialization, shot peening technology gradually matured. The emergence of automated shot peening equipment greatly improved processing efficiency and consistency, making shot peening technology widely used.
• Technological innovation: In the mid-20th century, shot peening technology underwent a series of innovations, including improvements in materials and equipment, making the shot peening process more precise. The emergence of new shot peening media and shot peening equipment has improved the treatment effect and production efficiency of shot peening.

Important Milestones

• Patent application: Patent application for shot peening technology marks the formalization and standardization of technology, which promotes the development and application of shot peening technology.
• Industry standards: For example, SAE’s standards for shot peening standardize the shot peening process and provide unified operating guidelines for all walks of life.

What are The Shot Peening Equipment?

There are many types of shot peening equipment to meet different surface treatment needs. From pneumatic shot peening machines to fully automatic shot peening systems, the choice of equipment depends on the specific application scenario and treatment requirements. The types and configurations of shot peening equipment mainly include the following:

1. Shot peening machine

Shot peening machines are the core equipment for shot peening. These devices are used to control the flow, speed and direction of particles to ensure the desired treatment effect. Operating parameters such as pressure, speed, particle size and shape have an important impact on the shot peening effect. According to different structures and applications, they can be divided into the following types:

• Pneumatic shot peening machine: Use compressed air to spray balls at high speed onto the surface of the workpiece, suitable for the treatment of small and media-sized parts. Pneumatic shot peening machines are simple to operate and easy to maintain, but the processing efficiency is relatively low.
• Centrifugal shot peening machine: The shot is projected onto the surface of the workpiece by centrifugal force, which is suitable for mass production and processing of large workpieces. The centrifugal shot peening machine has uniform processing and high efficiency, and is suitable for occasions that require fine processing.
• Drum shot peening machine: The workpiece is placed in the drum and processed by the shot peening device. The drum shot peening machine is suitable for processing irregularly shaped parts, especially for automotive parts and small metal parts.
• Hanging shot peening machine: The workpiece is suspended in the shot peening room by a hanging device and processed by the shot peening equipment. It is suitable for processing large or heavy workpieces, such as mechanical parts and structural parts.
• Shot peening room: An enclosed space equipped with a shot peening machine to accommodate workpieces and shot peening equipment. The shot peening room can effectively control the particle scattering during the shot peening process and keep the working environment clean.

2. Key components of shot peening machine

• Nozzle: The nozzle is responsible for accelerating and ejecting the shot onto the surface of the workpiece. The design and material of the nozzle directly affect the efficiency and effect of shot peening.
• Shot conveying system: Conveys the shots to the nozzle, including components such as hoppers and conveying pipes.
• Recovery system: Collects the shots scattered during the shot peening process and puts them back into use to improve material utilization and reduce costs.
• Control system: Used to adjust the operating parameters of the shot peening machine, such as pressure, speed and spray angle, to ensure the consistency and controllability of the treatment effect.

Can It be Automated?

The shot peening process can be manual or automated. The specific operation method depends on the type of shot peening equipment, the processing requirements of the workpiece, and the scale of production.

Manual operation

• Manual shot peening: In some small-scale production or special workpiece processing, it may be necessary to manually operate the shot peening machine. In this case, the operator needs to manually adjust the settings of the shot peening machine and control the direction and range of the shot peening. Manual shot peening is suitable for situations where there are special requirements for the treatment effect, such as repairing small parts or performing fine surface treatment.
• Manual assistance: Even in an automated shot peening system, manual operation is still necessary. The operator needs to regularly check the operating status of the equipment and perform maintenance and cleaning work to ensure the smooth progress of the shot peening process.

Automated operation

• Fully automatic shot peening machine: Modern shot peening equipment is increasingly using automated control systems that can automatically complete various steps of the shot peening process, including workpiece conveying, shot peening and recycling. Fully automatic shot peening machines can improve production efficiency, ensure consistency of treatment effects, and reduce the need for human intervention.
• Robotic shot peening system: In some complex shot peening needs, industrial robots are used for shot peening operations. Robotic shot peening systems can accurately control the angle and position of the shot peening, and are suitable for processing workpieces with complex shapes or high precision requirements.
• Intelligent shot peening system: Shot peening systems that combine artificial intelligence and data analysis technology can monitor and adjust the parameters of the shot peening process in real time to optimize the treatment effect. These systems can automatically detect and adjust problems in the shot peening process, reduce human intervention, and improve production efficiency and quality.

 

Although modern shot peening equipment is increasingly using automation technology, manual operation and monitoring are still an important part of ensuring the smooth progress of the shot peening process. Whether it is manual operation or automated shot peening system, understanding the function and operation method of the equipment is essential to achieve the best treatment effect.

How to Measure Shot Peening Effect?

Measuring the effect of shot peening usually requires evaluation from the following perspectives:

• Surface hardness: Through shot peening, the hardness of the material surface should be significantly improved, which can be measured using a hardness meter.
• Surface roughness: The surface morphology and roughness of the material will change after shot peening, which can be evaluated using a surface roughness meter.
• Depth of compressive stress layer: Shot peening will form a compressive stress layer on the surface of the material. The depth of compressive stress can be measured through X-ray diffraction or microhardness testing.

It is worth mentioning that John Almen invented a standardized method for measuring the effectiveness of shot peening, called the Almen test. This method evaluates the effect of compressive stress by using a special test piece (Almen test piece) and recording the amount of bending caused by shot peening.

The specific steps are as follows:

1. Almen test piece: It is a standard thickness steel piece that is tested during the shot peening process.
2. Measurement of bending: After shot peening, the test piece will bend to a certain extent, and the bending degree is measured with a special measuring tool (Almen arc height meter).
3. Arc height indicates strength: The measured bending amount is called arc height, which indicates the intensity of compressive stress on the material surface caused by shot peening. The larger the arc height, the stronger the applied compressive stress.
4. Control the shot peening effect: The Almen test can effectively control the shot peening effect and ensure processing consistency and quality. It is widely used in quality control in aerospace, automobile and other fields.

• Fatigue strength: Shot peening can improve the fatigue strength of the material, which can be determined through fatigue testing.
• Surface morphology: Use a scanning electron microscope (SEM) to observe the surface microstructure to analyze whether the surface achieves the desired effect.

Shot Peening Application Scenarios

Shot peening technology plays a significant role in improving material performance and surface quality, and is widely used in many fields.

Effect

• Enhance fatigue strength: Shot peening forms a compressive stress layer through impact, which significantly improves the fatigue resistance of the material and reduces the occurrence of cracks. This type of processing is particularly important in demanding fields such as aerospace and automotive manufacturing.
• Improved wear resistance: Shot peening increases the surface hardness of the material, thereby enhancing wear resistance. This effect is crucial for high-wear components such as machinery and tools.
• Improve surface quality: Shot peening can remove surface impurities, improve the finish of the workpiece, improve the appearance, and make it more beautiful.

Application scenarios

• Automobile manufacturing: Used for surface treatment of engine parts, transmission systems and other components to improve their service life and reliability. For example, shot peening can effectively improve the fatigue resistance of engine components and reduce failure rates.
• Aerospace: Shot peening technology plays an important role in the processing of key components such as aircraft engines and fuselage structures. Shot peening enhances the strength and durability of these components, ensuring their reliability in extreme environments.
• Construction engineering: Used for anti-corrosion treatment of steel structures to improve their durability. In construction projects, shot blasting can effectively prevent corrosion of steel structures and extend their service life.
• Metal processing: Used to remove oxide layers, welding spatter, etc. from metal surfaces to improve the cleanliness and quality of metal surfaces.
• Medical devices: Shot peening improves biocompatibility and durability of implants. Through shot peening, the surface of the implant is smoother, which helps improve the integration with the body’s tissues.
• Mechanical equipment: Used for the maintenance and repair of large mechanical equipment. Shot blasting can improve the working efficiency and service life of the equipment.

The Difference Between Shot Blasting and Sand Blasting

Shot peening and sandblasting are both surface treatment technologies. The principles of the two are similar. They both use compressed air as power to spray a high-speed projectile stream onto the surface of the part and change the physical properties of the material surface through high-speed impact. However, they have technical details and There are some differences in application.

Different media used:

• Sandblasting: There are various types of sand blasting media, including sand, glass beads, ceramic beads, etc. It is suitable for cleaning large areas, and the effect is relatively rough.
• Shot peening: Shot peening mostly uses hard steel shots, stainless steel shots, ceramic beads, etc., which are suitable for strengthening treatment. The process requirements are high and the treatment effect is fine and uniform.

Different purposes and effects:

• Sand blasting: Mainly used to remove surface rust and dirt, improve surface roughness, and is suitable for cleaning and pretreatment.
• Shot peening: Used to enhance the fatigue strength and wear resistance of materials, and improve material performance by forming a compressive stress layer.

Applicable materials are different:

• Sandblasting: By choosing the appropriate size and hardness of the sandblasting material, it can be applied to a variety of materials: metal, glass, stone, plastic and composite materials, wood, etc.
• Shot peening: Thin plate workpieces cannot be processed, otherwise the workpiece will be easily deformed. It can only be used to remove oxide scale and rust on media and large metal products with a thickness of not less than 2mm or which do not require accurate size and contours, as well as castings and forgings, molding sand and old paint film. Widely used in high carbon steel, stainless steel, aluminum alloy, titanium alloy, magnesium alloy, brass, copper alloy and plastic.

The Future Development Trend of Shot Peening

The future development of shot peening technology will focus on technological innovation and changes in market demand.

Technological Innovation

• Intelligent shot peening system: Future shot peening technology will combine artificial intelligence and automation technology to improve the accuracy and efficiency of shot peening. The intelligent shot peening system can monitor and adjust processing parameters in real time to optimize the processing effect.
• Environmentally friendly shot peening technology: Develop low-pollution, low-noise shot peening technology to meet modern environmental protection requirements. Environmentally friendly shot peening technology will reduce the impact on the environment and improve the safety of the working environment.

Market Demand

• High-end industrial applications: The demand for shot peening technology in high-end fields such as aerospace and medical equipment will continue to grow. These areas have extremely high requirements on material performance and surface quality, and shot peening technology can meet these strict requirements.
• Miniaturization and precision: The market demand for small and precision shot peening equipment has increased to accommodate finer surface treatment requirements. For example, small shot peening equipment can handle complex micro-parts and meet the needs of high-precision processing.

Cross-industry applications

Shot peening technology will be more integrated into emerging industries, such as 3D printing and nanotechnology. These emerging industries have increasingly higher requirements for surface treatment, and the application of shot peening technology will further expand its fields and improve product quality and performance.

Shot peening technology, like a fine craftsman, carefully carves each workpiece with high-speed particles, improving their pressure resistance and overall performance. Whether it is in the solid treatment of aircraft engines or in the improvement of wear resistance of automobile parts, shot peening is quietly changing many invisible details in our lives. As technology continues to advance, it is becoming more and more Smart, eco-friendly and precise. In the future, we can expect shot peening technology to work its magic in more areas, from high-end manufacturing to emerging technologies, where it will continue to bring us higher quality and longer service life. Shot peening is not only the “invisible hero” of industry, but will also continue to create a more perfect future for us.