Steel melts at about 1,500°C (2,800°F), according to NIST. The exact figure moves a little with the grade, because carbon and other alloying elements make steel melt over a range rather than at one sharp point.
For buildings, the melting point is the less important number. Structural steel loses most of its strength at temperatures far below melting, which ordinary building fires can reach. This guide covers both numbers and what they mean for beams and columns.
The Melting Point of Steel
The National Institute of Standards and Technology states in its FAQs on the NIST WTC Towers Investigation (checked October 2026) that the melting point of steel is about 1,500 degrees Celsius (2,800 degrees Fahrenheit).
Pure iron, steel’s main ingredient, has a sharp melting point. The Los Alamos National Laboratory periodic table entry for iron lists 1,811 kelvins, which is 1,538°C or about 2,800°F. Adding carbon lowers the temperature at which melting starts. That is why cast iron, with 3-5% carbon per the same LANL page, is easier to melt and pour into molds than steel.
| Material or event | °C | °F | Source |
|---|---|---|---|
| Pure iron melts | 1,538 | about 2,800 | LANL (1,811 K) |
| Steel melts (approx.) | about 1,500 | about 2,800 | NIST |
| Normal building and hydrocarbon fires, upper range | up to about 1,100 | up to about 2,000 | NIST |
| Bare steel keeps only about 10% of its strength | 1,000 | about 1,800 | NIST |
| Aluminum alloys melt | 475 to 640 | 900 to 1,200 | NIST |
Unit conversions use °F = °C × 9/5 + 32, and kelvins minus 273.15 for °C. NIST’s figures are rounded as published.
Steel Fails in Fire Long Before It Melts
A steel beam does not need to melt to fail. It needs to get soft enough that it can no longer carry its load. NIST’s FAQ puts it plainly: when bare steel reaches 1,000°C, it softens and its strength drops to roughly 10 percent of its room temperature value. The same page notes that normal building fires can reach about 1,100°C, and that unprotected steel can reach the surrounding air temperature during a long fire.
Steel also loses stiffness as it heats. A hot beam sags more under the same load, and a hot column buckles at a lower load. Steel expands as it heats, too. A long beam that is restrained at its ends can push on the columns, then pull on them as it sags. Heat is not the only issue. The way the frame moves while it heats also matters.
“Jet Fuel Can’t Melt Steel Beams”
This line comes up in almost every search about steel’s melting point, so here is what the investigators actually said. NIST states that in no instance did it report that steel in the World Trade Center towers melted due to the fires. Its finding was that fires reaching about 1,000°C weakened floors and columns where the impacts had knocked the fireproofing off. The floors sagged and pulled the perimeter columns inward until they failed.
The molten metal seen pouring from one tower was, NIST concluded, most likely aluminum from the aircraft, which melts between 475°C and 640°C depending on the alloy. Steel did not melt and did not need to. The important lesson for any steel building is that heat weakens bare steel well before it melts.
How Buildings Protect Steel From Fire
Because bare steel heats quickly, building codes require many steel members to carry a fire-resistance rating, measured in hours. In the US, Chapter 7 of the International Building Code (2021) covers fire-resistance-rated construction. Ratings are established by fire testing under ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials. Its scope includes columns, girders, beams and floor and roof assemblies.
The common ways to get that rating:
- Spray-applied fire-resistive material (SFRM). The gray, fluffy coating seen on beams in commercial buildings. It insulates the steel and slows its temperature rise.
- Intumescent coatings. Thin paint-like films that swell into an insulating char when heated. They are often used where the steel stays visible. Our guide to intumescent paint for steel explains how the thickness is set.
- Board and enclosure systems. Gypsum board or other rated boards boxed around a column or beam.
- Concrete encasement or concrete-filled tubes. Concrete absorbs heat and slows the temperature rise. HSS columns are sometimes filled for this reason. Our steel column guide compares W-shape, HSS and pipe columns.
Heavier sections heat more slowly than light ones, because there is more steel to absorb the same heat. A thick-flanged W14 column will lag behind a light W8 beam in the same fire. That is one reason listed fire-rated designs depend on the specific shape and its weight per foot.
Is Steel Safe to Reuse After a Fire?
Sometimes. Steel that heated, cooled and stayed straight may keep much of its original strength, but that cannot be assumed. The answer depends on the grade, how hot the steel got, how long it stayed hot and whether it distorted. Visibly bent, buckled or twisted members are a red flag. An engineer usually inspects the frame, may take samples for testing, and decides what stays and what is replaced.
Grade matters for that assessment. Most modern wide flange beams are ASTM A992 steel, while older buildings may use earlier grades, and very old ones may use cast or wrought iron. Any decision about fire-damaged structure, and any fire-resistance design, has to be made by a licensed structural engineer working with the local building official.
Melting Point vs Working Temperatures in the Shop
The melting point does matter in fabrication. Welding and cutting depend on melting steel locally. Arc welding fuses the base metal and filler into a small molten pool, and oxy-fuel cutting heats steel until it burns away in a jet of oxygen. Hot rolling, by contrast, shapes steel while it is red-hot but still solid. That is how W-beams get their shape without melting. Our walk-through of the structural steel fabrication process shows where cutting and welding happen in the shop.
Steel Melting Point FAQ
What temperature does steel melt in Fahrenheit?
About 2,800°F, per NIST. The exact range depends on the grade and its carbon content.
Can a house fire melt steel?
No. NIST puts normal building fires at up to about 1,100°C (2,000°F), well below steel’s melting point. A house fire can still heat a bare steel beam enough to lose most of its strength and sag.
At what temperature does steel lose its strength?
Strength falls off gradually as steel heats, not at one point. NIST reports that bare steel at 1,000°C (about 1,800°F) keeps only roughly 10 percent of its room temperature strength.
Does stainless steel melt at a different temperature?
Each grade has its own melting range because its chemistry is different. Check the producer’s data sheet for the exact grade rather than using a general steel figure.
Which melts first, steel or aluminum?
Aluminum, by a wide margin. NIST gives 475 to 640°C for aluminum alloys, against about 1,500°C for steel. That is one reason aluminum framing needs extra care in fire design.
Reference information only, not engineering advice. Disclaimer.