Carbon steel does not have one annealing temperature. Grade, delivery condition, section size and the intended result all matter, and supplier instructions can specify different heating and cooling cycles. This chart compares three published instructions for named steel products: hot-rolled 1018/20 bar, Vulcan 1045 bar and Uddeholm UHB 11. It keeps each temperature beside its source and cooling condition so the entries are not mistaken for interchangeable shop recipes.

Carbon Steel Annealing Temperature Chart

The 1018/20 entry is a 1,550–1,650°F range with furnace cooling. The Vulcan 1045 guide gives 800–850°C and says to heat until the section is uniform before furnace cooling. Uddeholm’s UHB 11 sheet describes a different schedule: heat through to about 700°C, furnace cool at 25°C per hour to 600°C, then cool in air. The UHB 11 sheet reports about 170 HB after soft annealing.

Those differences show why the grade and product condition must stay attached to a temperature. A range for hot-rolled 1018/20 bar is not a substitute for a 1045 procedure, and UHB 11 is a supplier-specific carbon-steel product intended primarily for use in its delivered condition. “Annealing” also covers more than one process objective. Soft annealing, stress relief and normalizing use different temperatures and cooling paths.

For a simple lookup, first read the full grade and product form from the material certificate. Then match it to the row’s source. If a drawing calls for C1045 bar and the lot is supplied in a condition described by Vulcan, the 800–850°C row is the closest applicable entry in this comparison. The instruction to heat uniformly and furnace cool remains part of the cycle; choosing only the temperature endpoints discards essential process information.

The Fahrenheit values shown for Vulcan’s 1045 range are converted from the stated Celsius limits and rounded to whole degrees. A conversion does not make that supplier instruction apply to another grade or another manufacturer’s product. Where a supplier specifies a controlled cooling rate, as for UHB 11, preserve it instead of replacing it with a generic “slow cool” description.

Section thickness and shape change how long the core takes to reach temperature. Furnace uniformity, atmosphere, surface condition and previous processing also affect the outcome. The supplier guides do not provide a complete procedure for every part geometry or furnace. Ask the material supplier or qualified heat treater to confirm the cycle when the grade, section, initial condition or required properties differ from the stated application.

Do not use the annealing table to infer tensile strength, hardness or machinability unless the same source reports those results for the same grade and process. Do not use a soft-annealing temperature as a hardening or normalizing setting. After heat treatment, verify the specified property by the method and location required by the drawing, certificate or inspection plan.

A common mistake is treating a familiar grade number as sufficient identification. Product form, condition and supplier specification may change the applicable advice. Another mistake is treating a temperature range as the entire heat-treatment cycle. The source’s hold and cooling requirements are part of the result. Use this comparison to find the relevant supplier document, then follow that document and the part-specific procedure.

For stock identification, keep the supplier name, grade designation, product form, supplied condition and certificate together in the traveler. If those details do not agree with the table row, stop and obtain the applicable written schedule. A temperature copied from a different product page can look plausible while producing an unsuitable structure or hardness.

Sources

Sources: Metal Supermarkets C1018/20 grade summary, Vulcan Engineering Steels 2024 Product Guide, and Uddeholm UHB 11 product data. The table compares the suppliers’ stated conditions and does not merge them into a generic standard.