The disc gasket, also known as a conical spring gasket, is an elastic fastening component with a conical disc-shaped geometry. Leveraging its unique advantage of "small clearance, high load capacity," it is widely used in various bolted connection applications and serves as a core foundational component for ensuring reliable connectivity in industrial equipment. Unlike conventional flat or spring washers, this gasket provides stable elastic compensation within limited axial space, effectively counteracting the loss of preload caused by vibration, temperature variations, or material relaxation; thus, it is an indispensable key component in the fastening systems of high-end equipment.
The mainstream standardization system for disc gaskets is centered around German industrial standards; among these, DIN 6796 and DIN 267-26 are the two most widely adopted core standards in the industry and serve as an important reference for selecting components in high-end manufacturing applications in China.
DIN 6796 is a specialized standard specifically designed for disc spring washers used in bolted connections; the version issued in 1987 remains the benchmark specification in the global heavy-duty fastening industry to this day. This standard explicitly specifies that the product is suitable for medium-to high-strength bolts with a grade range of 8.8 to 10.9, ensuring that the washer continues to provide sufficient residual preload even during the flattening phase following bolt tightening. The standard also provides comprehensive, precise dimensional parameters – including inner diameter d1, outer diameter d2, minimum/maximum free height h, and thickness s – for the entire bolt series ranging from M3 to M30. For example, the washer designed for an M6 bolt has an inner diameter of 6.4 mm, an outer diameter of 14 mm, and a thickness of 1.5 mm, thereby fully standardizing the interchangeability requirements across different manufacturers.
DIN 267-26 is a general supplementary standard governing the technical requirements for fasteners; it specifies clear procedures for the permanent deformation test and the elastic test of disc washers (Permanent deformation test: The washer must undergo an initial high-pressure test; the minimum remaining height after the test shall be within the specified range. Elastic test: A specified test load is applied to the washer. After the test load is applied for 2 minutes, the load is released until the washer undergoes a displacement of 20 μm. The residual elastic force resulting from this displacement shall meet the value specified in the standard). These two tests are the core criteria for determining whether a disc washer product meets the requirements.
The design calculation for disc-shaped washers is based on the "force–deformation behavior" principle; its core objective is to obtain an elastic curve that meets the specific operating condition requirements within a limited spatial constraint.
Basic load calculation is the first step in the design process. The axial load calculation formula for conventional disc washers is based on the classical disc spring formula and has been optimized in accordance with the applicable requirements of DIN 6796: F = (4E·t³·h₀) / ((1–μ²)·K₁·D²), where E is the material's modulus of elasticity (for spring steel, E = 2.06*10⁵ MPa), t is the washer thickness, h₀ is the deformation amount under compression, μ is the Poisson's ratio (taken as 0.3), D is the outer diameter of the washer, and K₁ is the diameter ratio correction factor.
During the selection and verification phase, two key verifications must be performed based on specific operating conditions: first, the preload verification – ensuring that the remaining load after the gasket is flattened is no less than 70% of the bolt's rated load, thereby preventing connection loosening during operation; second, the maximum temperature verification – confirming that the operating temperature does not exceed the maximum allowable temperature limit based on the selected material; for gaskets made of conventional spring steel, the long-term operating temperature shall not exceed 200°C.
Below is the DIN6796 series component size and load reference.
The manufacturing of disc-shaped washers involves a high-precision forming process; each step directly determines the final elastic properties and service life of the component.
The first step involves raw material inspection; for conventional operating conditions, spring steel materials such as 65Mn, 50CrVA, and 60Si2Mn are selected; for corrosive environments, 304 or 316 stainless steel is used; and for high-temperature applications up to 700°C, the Inconel 718 nickel-based superalloy is employed. Upon arrival at the facility, the raw materials undergo surface quality inspection, followed by chemical composition analysis and mechanical property testing, ensuring the ultimate product quality.
The second step involves precision stamping forming; the appropriate manufacturing process is selected based on the gasket thickness: for thin gaskets with thickness t ≤ 1.25 mm, a high-speed continuous stamping process is employed to complete both blanking and conical surface forming in a single operation, achieving a production rate of several hundred pieces per minute; for medium-and heavy-duty gaskets with thickness t> 1.25 mm, a single-process precision compression cutting followed by forming using a forming die is adopted.
The third step is the heat treatment process, which is the critical stage determining the elastic properties of the washer. The formed disc-shaped washer undergoes quenching and tempering treatment, with its final hardness being stabilized within the range of 420–490 HV.
The fourth step involves surface treatment – customized surface treatment processes (such as galvanizing, Dacromet coating, or phosphating with blackening) are applied according to customer requirements to enhance the product's rust and corrosion resistance.
To ensure the reliability of disc gaskets, the industry has established a comprehensive testing system covering dimensions, performance, and service life; all products must undergo a full-process inspection before leaving the factory.
4.1 Appearance and Dimensional Inspection: Use an image measurement system to perform a comprehensive inspection of key dimensions—including inner and outer diameters, thickness, and free height—to ensure compliance with the tolerance requirements specified in DIN 6796; simultaneously, conduct a visual inspection using a magnifying glass to examine the surface for any harmful defects such as burrs, cracks, or impact-induced scars; regarding geometric tolerances, measure the coaxiality in accordance with the DIN 6796 standard, ensuring that the coaxiality error does not exceed 2IT12, thereby preventing uneven loading during installation.
4.2 Hardness and mechanical property testing: Use a Vickers hardness tester to determine whether the product's hardness falls within the specified range; then, perform a load–deformation curve test using a force-measuring machine to record the load data throughout the entire process—from the product's free state to its complete flattening—to verify whether it meets the designed elastic characteristics; simultaneously, conduct a permanent deformation test in accordance with DIN 267-26 to measure the residual minimum height under the specified load, ensuring that the residual height deviation remains within the allowable range specified in the standard; this is the core criterion for determining whether the product is conforming.
4.3 Continuous load test: Ten disc-shaped elastic washers shall be alternately fitted onto the bolt, with flat washers used to separate each conical elastic washer from the others. The hardness of the flat washers shall be greater than 500 HV. Apply the test load specified in DIN 267-26 and maintain the specimen at a temperature of 100 °C for 48 h. The disc-shaped elastic washers shall be free of cracks; the reduction in their free height after testing shall not exceed 2% of the value specified in the standard.
4.4 Elasticity Test: Place the disc-shaped washer specimen on the testing apparatus and apply the test load specified in the relevant standard (DIN 267-26). The testing apparatus shall be designed to minimize deformation under the applied load. The surface hardness of the compression plate shall not be less than 60 HRC. After the test load has been applied for 2 minutes, unload the specimen slowly and steadily until a displacement of 20 μm is achieved by the conical elastic washer; this displacement shall be measured using a precise measuring device. The residual elastic force corresponding to a displacement of 20 μm shall equal the value specified in the relevant standard for this specification; any deformation of the testing apparatus shall be appropriately compensated for.
| Application Industries | Typical application site | Core Functions and Roles |
|---|---|---|
| Wind power/New energy | Tower cylinder flange bolts, photovoltaic mounting system fastening, energy storage cabinet assembly connection | Resists outdoor wind, vibration, and temperature fluctuations; maintains long-term bolt preload; reduces high-altitude maintenance and operational tasks. |
| automobile making | Powertrain bolts, chassis connection assembly, new energy vehicle actuator-based braking/thermal management system | Mitigate vehicle vibration and thermal expansion/contraction effects, ensure the reliability of critical connections, and enhance overall vehicle safety rating. |
| rail transit | Track fasteners, carriage suspension system, vehicle structural fastening | Withstands long-term alternating vibration and impact to prevent bolt loosening or detachment, ensuring crane safety. |
| construction machinery | Excavator and crane structural connections; power equipment bolts | Designed for heavy-duty impact loading conditions, preventing bolt failure in critical components and reducing equipment downtime rates. |
| shipbuilding | Ship hull structural bolts, engine base, deck machinery fastening, pipeline flange connections | Resist high-humidity and high-salinity marine corrosive environments as well as marine vibration to ensure the safe and reliable integrity of the ship's structural connections. |
| Power Grid | State Grid transmission tower bolts; substation equipment connections; generator set fastening | Mitigate long-term outdoor wind-induced vibration and temperature variations; maintain the long-term preload on power facility bolts; reduce inspection and maintenance requirements. |
| Construction of buildings and bridges | Steel structure joints and fastening for large-scale bridge projects | Provides continuous preload force for large-scale heavy-duty structures to mitigate the effects of temperature variations and load fluctuations. |
| engineering industry | Bolts for vibration-generating equipment such as motors, pump sets, and gearboxes | Substitutes conventional spring washers to enhance equipment connection stability and extend the fault-free operating cycle. |
| aerospace | Aircraft engine and airframe structural bolted connections | Mitigate the safety risks associated with connection loosening due to extreme temperature fluctuations and high-intensity vibration. |
