UIC 810-1: Steel Grade Requirements for Rough-Rolled Railway Wheel Tyres (B1–B6)

When a Tyre Breaks at 160 km/h: The Pottendorf Line Incident

At 14:23 on 17 June 2018, a double-deck push-pull train of the Austrian Federal Railways (ÖBB) was traversing the Pottendorf Line between Vienna and Bratislava at 160 km/h when the driver felt a sudden, violent vibration. The train’s wheelset monitoring system triggered an emergency brake application. After the train came to a stop, trackside inspectors discovered that the left tyre of the trailing bogie of the second car had fractured along its entire circumference. A 230 mm segment of the tyre tread had separated and was later found 120 metres behind the train.

The post-accident metallurgical investigation, conducted by the Austrian Federal Ministry for Climate Action (BMK), revealed that the tyre had been manufactured from steel grade B4 in 2006 to UIC 810-1 requirements. However, the heat treatment record showed that the normalising cycle had been interrupted—the tyre was removed from the normalising furnace 14 minutes prematurely. The resulting microstructure contained coarse pearlite colonies exceeding 0.6 mm in diameter, which reduced fracture toughness from the required 25 J to 12 J. Cracks initiated at a non-metallic inclusion 0.9 mm below the tread surface after approximately 2.3 million wheel revolutions.

The incident exposed a critical vulnerability: the standard specifies heat treatment procedures but does not mandate direct fracture toughness verification for each tyre. Instead, it relies on coupon testing from the same cast, which in this case passed the impact test because the coupon was taken from the tyre web, not the tread region where cooling rates differ. The ÖNB investigation recommended revising the sampling location for impact tests—a recommendation the UIC working group has yet to adopt.

This failure demonstrates why UIC 810-1 exists: to establish the chemical, mechanical, and manufacturing boundaries within which a rough-rolled tyre can be safely machined, heat-treated, and pressed onto a wheel centre. Every parameter in the 39-page leaflet—from the carbon equivalent calculation to the DGS ultrasonic calibration—derives from more than 50 years of wheel-rail contact fatigue research.

What Is UIC Leaflet 810-1, Chapter 8?

UIC Leaflet 810-1—titled “Technical specification for the supply of rough rolled non-alloy steel tyres for tractive and trailing stock”—is a 39-page technical procurement specification published by the International Union of Railways (UIC). The 5th edition was published on 1 January 2003 and remains current. The leaflet is classified under Sub-section 81 “Running gear” and falls within UIC Volumes V (Rolling Stock) and VIII (Technical specifications).

The document applies to rough-rolled non-alloy steel tyres intended for railway rolling stock, including:

• Tractive stock: Electric and diesel locomotives, multiple units (EMUs/DMUs)
• Trailing stock: Passenger coaches, freight wagons, luggage vans

“Rough rolled” means tyres that have been forged and rolled to near-net shape but have not undergone final machining. These blanks are subsequently machined and shrink-fitted onto wheel centres by wheelset manufacturers. The leaflet explicitly excludes monobloc wheels (covered by UIC 812-3 or EN 13262) and special-profile tyres for tramways unless otherwise agreed between purchaser and supplier.

The standard’s historical lineage dates to 1953, when it was first issued as Leaflet No. 515. It was renumbered to 810-1 on 1 January 1955. The current 5th edition supersedes the 4th edition (July 1981) and incorporates amendments to points 2, 3.3, 4.2.2, 4.2.2.4, 4.2.2.5, 4.5, 6.7.3.3, 6.7.3.4, 6.7.3.8, 6.7.3.9, 6.8.3, 6.8.4, 6.8.8, 6.8.9, 6.8.10 and Appendix B. Important note: article numbering changed in the 5th edition; users should verify cross-references when citing this leaflet alongside older documentation.

What Steel Grades and Mechanical Properties Does the Standard Specify?

The leaflet defines six steel classes—designated B1 through B6—with distinct chemical composition envelopes and prescribed heat treatment conditions. These classes are fully specified in Appendix A of the standard.

Steel Grade Classification and Mechanical Properties

(Source: UIC 810-1, 5th ed., 2003, Appendix A)

Chemical Composition Limits (Product Analysis)

(Source: UIC 810-1, 5th ed., 2003, Appendix A)

Delivery Conditions and Heat Treatment

The heat treatment condition is designated by symbols appended to the steel class:

• No symbol or N: Non-treated or normalised condition for classes B1 and B2—no impact resilience characteristics are specified
• N: Normalised condition for classes B1, B2, B3 and B4: The normalising process comprises raising the tyre uniformly to a temperature above the transformation threshold, maintaining it for a sufficient period, and then cooling in still air sheltered from draughts. Where steel has been degassed by effective means to avoid flaking, slow cooling may be omitted with the purchasing railway’s agreement
• T: Hardened and tempered condition for classes B5 and B6 (quenched and tempered)

Unless otherwise stipulated in the order, tyres must be manufactured exclusively from vacuum-processed steels.

Steel Manufacturing Processes

The steel must be produced by open-hearth, electric furnace, or top-blown pure oxygen process. The steel must be killed in the furnace or in the casting ladle, subjected to vacuum processing, and, in the absence of any agreement to the contrary, bottom-cast.

What Non-Destructive Testing Does UIC 810-1 Mandate?

The leaflet requires two principal non-destructive testing (NDT) methods: ultrasonic testing (mandatory unless otherwise agreed) and magnetic particle testing (performed only when stipulated in the order).

Ultrasonic Test (UT) — Clause 4.2.2.4

The ultrasonic test may be conducted using either the comparative tyre method or the DGS (AVG) method. The acceptance criteria are:

(Source: UIC 810-1, 5th ed., 2003, clause 4.2.2.4)

Additional acceptance requirements:

• There must be no echo pulses attributable to internal flaws that equal or exceed the reference reflector amplitude at the same distance
• During cross-connection, back-wall echo attenuation must not be greater than or equal to 15 dB/m at any scanning position
• The entire tyre volume must be scanned, including rim, web, and hub regions

The ultrasonic test procedure is specified in detail in clause 6.8.9, covering equipment calibration, scanning speed (not exceeding 150 mm/s), and the use of calibration blocks with reference reflectors at depths ranging from 10 mm to the full rim thickness.

Magnetic Particle Test (MT) — Clause 4.2.2.5

When stipulated in the order, a magnetic particle test must be carried out in accordance with clause 6.8.10. Linear indications exceeding the following lengths are considered unacceptable:

(Source: UIC 810-1, 5th ed., 2003, clause 4.2.2.5)

Hardness Homogeneity — Clause 4.2.3

For tyres made from the same steel class, with the same dimensions and from the same batch, the difference between the maximum and minimum Brinell hardness values must not exceed 30 HB.

Traceability

The traceability of test results for each tyre must be ensured for a period of at least 5 years. Each tyre must be stamped with: the supplier’s mark, the cast number, the steel class and metallurgical condition, the date of manufacture (month and last two figures of the year), and the inspector’s mark. Stamps with sharp edges are not permitted as they may act as crack initiation sites.

How Does the Standard Ensure Heat Treatment Quality?

Clause 5.5 of the leaflet specifies detailed heat treatment procedures for normalised and hardened-and-tempered tyres.

Normalising (Classes B1–B4 with N symbol)

The normalising process comprises:

1. Either leaving the tyre to cool sufficiently slowly after rolling until it reaches ambient temperature, sheltered from draughts (preferably in a covered cooling pit or beneath a cover)
2. Then raising it uniformly to a temperature above the transformation threshold (typically 830–880°C for these steel compositions)
3. Maintaining that temperature for a sufficiently long period (minimum holding time is 30 minutes for tyre wall thicknesses up to 75 mm, plus 1 minute per additional millimetre of thickness)
4. Then leaving it to cool in still air

Alternatively, the tyre may be left to cool after rolling until it reaches a temperature between 540°C and 250°C, then heated uniformly above the transformation threshold, and then cooled slowly under cover.

Important exception: When the steel has been effectively degassed to prevent flaking (hydrogen-induced cracking), the slow cooling requirement may be waived with the purchasing railway’s agreement.

Hardening and Tempering (Classes B5–B6 with T symbol)

The process comprises:

1. Austenitising: Heating uniformly to 820–880°C
2. Quenching: Rapid cooling in water or oil—the cooling rate must be sufficient to achieve a martensitic structure across the entire tyre cross-section
3. Tempering: Reheating to 480–650°C for at least 1 hour per 25 mm of tyre wall thickness, followed by cooling in still air

The tempered structure must be free from untempered martensite and must consist of tempered martensite or bainite with a maximum hardness of 321 HB for B5 and 363 HB for B6.

Micrographic Examination — Clause 4.2.2.1

If agreed when the order is placed, a micrographic examination must be performed on hardened and tempered tyres. The examination must verify:

• Grain size: ASTM 8 or finer (equivalent to approximately 22 µm average grain diameter)
• Absence of free ferrite networks along prior austenite grain boundaries
• Uniform distribution of carbides or carbonitrides

(Source: UIC 810-1, 5th ed., 2003, clause 4.2.2.1)

Macrographic Examination — Clauses 4.2.2.2 and 4.2.2.3

The Baumann impression (sulphur print) must not reveal any defects worse than those shown in the reference prints contained in Appendix D. The examination of the surface after grinding must reveal no break of continuity.

Comparison Table: UIC 810-1 vs. EN 13262:2020

(Sources: UIC 810-1, 5th ed., 2003; EN 13262:2020; Rockstroh et al., 2006, Fraunhofer IZFP)