What Is a Grade 5.6 Screw Spike
The railway screw spike is a critical fastener in railway track systems, primarily used to secure rails firmly to wooden or concrete sleepers. The spike features a square or hexagonal head design, facilitating quick installation with specialized tools while ensuring track stability and safety. The grade number 5.6 means a minimum tensile strength of 500 MPa and a minimum yield strength of 300 MPa, calculated as 500 times 0.6. This grade is a common choice for secondary lines, sidings, and standard freight track where moderate holding power is required.
Material Selection
Grade 5.6 screw spikes are typically manufactured from medium carbon steel such as 35# steel, which reaches the required strength after hot forming and heat treatment. Lower carbon steel such as Q235 is more commonly used for grade 4.6 fasteners, where the tensile requirement is 400 MPa. For grade 8.8 and above, 45# steel or alloy steel is used. The material choice must always match the strength class, because the grade guarantees are based on the actual mechanical properties of the finished product.
Mechanical Properties
For grade 5.6, the tensile strength is at least 500 MPa and the yield strength is at least 300 MPa, with a minimum elongation of 20 percent. The spike must pass a 90 degree cold bending test without cracking. Higher grades in the same product family reach 800 MPa for grade 8.8 and 1000 MPa for grade 10.9, with correspondingly higher yield strength and lower elongation. All mechanical properties are verified by testing samples from each production batch.
Specification
Common types for concrete sleeper fastening include the Ss5-150, Ss8-140, Ss8-150, Ss8-160, Ss23-160, Ss25-165, and Ss35-161 screw spikes, together with the V20-135, V23-115, V23-135, V23-155, V23-215, and V26-115 types. The reference standards are ISO 898-1 for mechanical properties, UIC864-1 for sleeper screws, and NF F500-50 for French railway fasteners. Custom types can be manufactured according to customer drawings.
Surface Options
Available surfaces include plain oiled, oxide black, zinc plating, hot-dip galvanizing, wax, bitumen, Dacromet, and sherardizing. Plain oiled and black finishes are economical choices for dry environments, while galvanizing and Dacromet protect against corrosion in humid and coastal areas. The surface is selected together with the strength grade to match the service conditions of the line.
Frequently Asked Questions
What does grade 5.6 mean for a screw spike? Grade 5.6 means a minimum tensile strength of 500 MPa and a minimum yield strength of 300 MPa.
Which steel is used for grade 5.6 spikes? Medium carbon steel such as 35# steel is typical, while Q235 is more common for grade 4.6 fasteners.
Can Q235 meet the grade 5.6 requirement? Q235 is normally used for grade 4.6; grade 5.6 requires medium carbon steel that reaches 500 MPa after heat treatment.
What standards apply to screw spikes? ISO 898-1, UIC864-1, and NF F500-50 are the reference standards for material and mechanical requirements.
What surfaces are available? Plain oiled, oxide black, zinc, hot-dip galvanized, Dacromet, and sherardized surfaces are available.
