What Does Grade 4.8 Mean
Grade 4.8 screw spikes refer to their mechanical performance classification, where the numerical value represents the tensile strength and the yield ratio. The digit 4 indicates a tensile strength of 400 MPa for the spike material, while 0.8 denotes a yield strength-to-tensile strength ratio of 0.8. This signifies moderate strength combined with excellent ductility, enabling the spike to withstand cyclic loading without fracturing. The grade classification follows the same logic as the bolt grading system, and it defines the load capacity of the fastener.
Materials and Grades
Screw spikes are available in various grades, including 4.6, 4.8, 5.6 and 8.8, and the grade is selected by the load requirement of the application. The raw materials include Q235, 35 steel, 45 steel, 40Mn2 and 20MnSi, and the material is matched to the grade and the required properties. The higher grades provide higher strength for heavy-load service, while the 4.8 grade provides a balance of strength and ductility for general service.
Typical Specifications
Grade 4.8 screw spikes typically feature the following specifications: diameter 16 mm with length 150 mm, and diameter 18 mm with length 180 mm. Different specifications suit varying rail and sleeper types. The hexagonal head design facilitates installation and removal using specialized tools, and the thread form is matched to the sleeper insert.
Application
The screw spike secures the rail to the sleeper, and its threaded design provides a strong pull-out resistance and allows repeated installation and removal. The 4.8 grade suits light and medium-load lines, while higher grades are specified for heavy-load and high-speed service. The spike is installed with the specified torque, and its condition is inspected as part of the track maintenance.
Selection and Customization
Beyond standardized products, customization services are available for non-standard rail components, and buyers can provide drawings or specifications for special requirements. The spike grade, dimensions, thread and surface treatment can be tailored to the application, and the correct selection ensures the fastening performance and the track safety.
Frequently Asked Questions
What does the 4 in grade 4.8 mean? It indicates a tensile strength of 400 MPa for the spike material, according to the mechanical performance classification of the grade.
What does the 0.8 mean? It indicates a yield strength-to-tensile strength ratio of 0.8, giving the spike a defined margin between the yield strength and the ultimate strength.
What are the typical 4.8 spike sizes? Diameter 16 mm with length 150 mm, and diameter 18 mm with length 180 mm. Different specifications suit varying rail and sleeper types.
Why is the 4.8 grade ductile? The grade withstands cyclic loading without fracturing, and the threaded design provides strong pull-out resistance while allowing repeated installation and removal.
What materials are used? Q235, 35 steel, 45 steel, 40Mn2 and 20MnSi, selected by the load requirement of the application. Other grades such as 4.6, 5.6 and 8.8 are also available.
