Rail spikes are essential railway fasteners used to secure steel rails to sleepers or base plates, maintaining the correct gauge and ensuring track stability. The steel grade of a railroad spike determines its strength, toughness, wear resistance and corrosion behavior. This article explains the common steel grades used for dog spikes and screw spikes, and how to select the correct grade for a railway project.
Common Steel Grades for Railroad Spikes
The most widely used steel grades for railroad spikes are carbon structural steels such as Q235 and 45#, together with 55# and other carbon steels. Q235 provides a minimum yield strength of 235 MPa and is the economical standard for general track fastening. 45# carbon steel offers a tensile strength of about 600 MPa and better wear resistance, making it suitable for heavier duty spikes. For screw spikes, the raw material is usually Q235, 35 steel or 45 steel, with 40Mn2 and 20MnSi used for special applications. All grades can be supplied according to GB, AREMA, ASTM, BS or UIC requirements.
Dog Spike Steel Grades
Dog spikes, also called cut track spikes, are chisel-shaped fasteners with a flat-edged point and a head resembling a dog head. They are primarily used to fasten rails to wooden sleepers, with the wedge-shaped tip driven across the grain into the tie. Common dog spike materials are Q235, 45# and 55# carbon steel. The steel must combine sufficient hardness to be driven into wood without bending, with enough toughness to avoid fracture under impact loading. Common sizes include 5/8 x 6 inch and 9/16 x 5-1/2 inch, typically packed in 50 lb, 100 lb or 200 lb kegs.
Screw Spike Steel Grades and Mechanical Classes
Screw spikes are threaded fasteners installed by rotation, providing higher pull-out resistance than driven spikes. They are commonly used in railway turnouts and on concrete sleepers with plastic dowels. The mechanical grade of a screw spike defines its tensile and yield strength:
| Grade | Material | Tensile strength | Yield strength | Elongation |
|---|---|---|---|---|
| 4.6 | Q235 | ≥400 MPa | ≥240 MPa | ≥22% |
| 4.8 | Q235 | ≥400 MPa | ≥320 MPa | ≥14% |
| 5.6 | 35# | ≥500 MPa | ≥300 MPa | ≥20% |
| 8.8 | 45# | ≥800 MPa | ≥640 MPa | ≥12% |
The mechanical properties follow the classification system of ISO 898-1, and series-type sleeper screws such as Ss5, Ss8, Ss25 and Ss36 are supplied according to UIC 864-1. Surface treatments include plain oiled finish, black paint, color paint, zinc plating and hot-dip galvanizing.
How to Select the Steel Grade and Common Misconceptions
Select the steel grade according to the sleeper type, rail weight, axle load, climate and applicable standard. For wooden sleepers with light to medium traffic, Q235 dog spikes are economical and reliable. For heavy-haul lines and turnouts, 45# or higher strength screw spikes are recommended. In cold regions, steel with good low-temperature toughness is required, and in coastal or humid regions, hot-dip galvanized or stainless steel spikes are preferred to resist corrosion. Always confirm the grade and mechanical requirements with the project specification before ordering.
Quality and Inspection
Quality spikes are manufactured from high-quality alloy steels with controlled chemical composition and heat treatment. Key quality checks include tensile and yield strength tests, hardness measurement, cold bending tests at 90 degrees without cracks, and dimensional inspection of the head, shank and thread. For screw spikes, the thread profile and pitch are checked with gauges, and the surface finish is inspected for defects. Reliable suppliers provide mill test certificates and follow international standards to ensure consistent quality.
A common misconception is that a higher steel grade is always better. In fact, the grade must match the sleeper and the fastening system; an overly hard spike may crack or be difficult to drive into wooden sleepers. Another misconception is that all spikes with the same diameter have the same strength; the grade determines the mechanical properties. Some also believe that surface coating is only cosmetic. Coating is a real corrosion protection measure that significantly affects service life. Finally, dog spikes and screw spikes are not interchangeable, because they rely on completely different fastening principles.
Frequently Asked Questions
What grade of steel is a railroad spike? Railroad spikes are commonly made of Q235, 45# and 55# carbon steel, with alloy steels such as 40Mn2 used for special screw spike applications.
What is the difference between a dog spike and a screw spike? dog spike is driven into the wooden tie and grips by friction, while a screw spike is threaded and rotated into a pre-bored hole for higher pull-out resistance.
What are the common sizes of dog spikes? Common sizes include 5/8 x 6 inch and 9/16 x 5-1/2 inch, packed in 50 lb, 100 lb or 200 lb kegs.
What does grade 5.6 mean for a screw spike? Grade 5.6 means a tensile strength of at least 500 MPa and a yield strength of at least 300 MPa, per the ISO 898-1 classification.
Can railroad spikes be made of stainless steel? Yes, stainless steel spikes are available for highly corrosive environments such as coastal lines and chemical plants.
What standards apply to railroad spikes? Common standards include GB, AREMA, ASTM, BS and UIC, and products can be made to customer drawings or samples.
