{"id":493,"date":"2026-09-28T22:58:18","date_gmt":"2026-09-28T14:58:18","guid":{"rendered":"http:\/\/www.crearventas.com\/blog\/?p=493"},"modified":"2026-09-28T22:58:18","modified_gmt":"2026-09-28T14:58:18","slug":"what-is-the-thermal-conductivity-of-hot-rolled-carbon-steel-46b6-a8ca23","status":"publish","type":"post","link":"http:\/\/www.crearventas.com\/blog\/2026\/09\/28\/what-is-the-thermal-conductivity-of-hot-rolled-carbon-steel-46b6-a8ca23\/","title":{"rendered":"What is the thermal conductivity of hot rolled carbon steel?"},"content":{"rendered":"

If you\u2019ve ever stood near a large hot rolled carbon steel (HRCS) structure as it\u2019s being fabricated or in operation, you\u2019ve probably felt just how much heat that material can move. As someone who\u2019s supplied HRCS to manufacturing, construction, and energy clients for over 12 years, one of the most common questions I get from engineers, project managers, and even machinists is: \u201cWhat\u2019s the thermal conductivity of hot rolled carbon steel, anyway?\u201d It\u2019s not a number you can pull out of thin air\u2014there\u2019s nuance here, from the grade of steel to the temperature it\u2019s at, to how it\u2019s processed, that changes that value. Today, I want to break this down in plain, practical terms, not just textbook jargon, because when you\u2019re choosing steel for a heat exchanger, a furnace part, or a structural beam that will face extreme temperatures, this number isn\u2019t just academic\u2014it\u2019s the difference between a project that works on spec and one that hits snags. Hot Rolled Carbon Steel<\/a><\/p>\n

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First, let\u2019s start with what thermal conductivity actually is, in case you\u2019re new to the term. At its core, it\u2019s a material\u2019s ability to conduct heat. Think of it like a pipe for heat: a high-conductivity material lets heat flow through it quickly, while a low-conductivity one acts more like an insulator. For metals, most of that heat is carried by free electrons zipping through the material\u2019s atomic structure, right alongside lattice vibrations (what we sometimes call phonons). That\u2019s why metals are generally more conductive than, say, wood or plastic.<\/p>\n

Now, hot rolled carbon steel is a specific subset of carbon steel, defined by how it\u2019s made: it\u2019s rolled at temperatures above its recrystallization point\u2014usually around 1,700 to 2,300 degrees Fahrenheit, depending on the grade\u2014then allowed to cool at room temperature, no cold working or special heat treatment afterward. That processing leaves it with a distinct grain structure compared to cold rolled steel, and that grain structure does affect thermal conductivity. But before we get into hot rolled specifics, let\u2019s ground this in the base numbers for carbon steel in general.<\/p>\n

Most standard carbon steels fall into two main categories: low carbon (also called mild steel, with less than 0.3% carbon) and medium carbon (0.3% to 0.6% carbon), with high carbon being above that, up to around 1.0% for common structural grades. For HRCS, the most widely supplied grades are A36 (the workhorse of construction), A572 Grade 50, and 1018 mild steel for machining, along with A516 Grade 70 for pressure vessels and heat-resistant applications. Each of these has a slightly different thermal conductivity, and it changes with temperature, which is a big point most generic charts leave out.<\/p>\n

Let\u2019s get to the numbers, starting with room temperature (around 70\u00b0F, or 21\u00b0C), the point where most people look for specs. For low carbon hot rolled steel\u2014think A36 or 1018\u2014the thermal conductivity at room temperature is roughly 45 to 50 W\/m\u00b7K (watts per meter-kelvin) or about 26 to 29 Btu\/(h\u00b7ft\u00b7\u00b0F) for anyone using imperial units. Medium carbon hot rolled steel, like A572 Grade 50 or 1045, comes in a little lower, at 40 to 45 W\/m\u00b7K, or 23 to 26 Btu\/(h\u00b7ft\u00b7\u00b0F). High carbon HRCS, like 1095, sits around 35 to 40 W\/m\u00b7K, or 20 to 23 Btu\/(h\u00b7ft\u00b7\u00b0F). That drop makes sense, right? As you add more carbon, you introduce more impurities and disruptions in the metal\u2019s atomic structure, which get in the way of those free electrons carrying heat. It\u2019s like adding small rocks to a pipe\u2014they slow the water down, or in this case, the heat.<\/p>\n

But here\u2019s the part that trips up a lot of people: those numbers only apply at room temperature. Thermal conductivity isn\u2019t a fixed value; it changes as temperature rises, which is critical for any application where the steel will be exposed to heat. Let\u2019s talk about what happens when we heat hot rolled carbon steel up to common operating temperatures. Most HRCS starts to soften around 1,000\u00b0F, and by the time it hits 1,500\u00b0F, it\u2019s well into the austenite phase, where its internal structure changes entirely. For low carbon HRCS, its thermal conductivity actually stays pretty steady until about 500\u00b0F, sitting around 47 to 48 W\/m\u00b7K, and then starts to drop gradually, falling to about 30 W\/m\u00b7K at 1,200\u00b0F, and around 20 W\/m\u00b7K by the time it reaches 1,800\u00b0F. Medium carbon HRCS follows a similar trend, just starting at a lower baseline: at 1,000\u00b0F, it\u2019s around 35 W\/m\u00b7K, dropping to 22 W\/m\u00b7K at 1,500\u00b0F.<\/p>\n

What\u2019s interesting here is that this is different from stainless steel, which is often confused with carbon steel for high-heat applications. Stainless steel has a thermal conductivity of only around 16 to 24 W\/m\u00b7K at room temperature, so it\u2019s a worse conductor than even high carbon HRCS. That\u2019s one reason why many heat exchangers and furnace components that need to move heat efficiently are made with hot rolled carbon steel, not stainless.<\/p>\n

Now, you might be wondering: does the hot rolling process itself affect this number? Because that\u2019s a big part of our business\u2014we don\u2019t just sell any steel, we sell hot rolled steel that\u2019s processed to consistent specs. Let\u2019s compare hot rolled vs. cold rolled carbon steel, since that\u2019s a common point of confusion. Cold rolled steel is rolled at room temperature, so it has a finer, more elongated grain structure, and it\u2019s often harder than hot rolled. At room temperature, cold rolled mild steel has a thermal conductivity almost identical to hot rolled mild steel\u2014usually within 1 to 2 W\/m\u00b7K, which is negligible for most industrial applications. The difference only really shows up at very high temperatures, above 1,000\u00b0F, where the cold worked grain structure of cold rolled steel starts to change, making its thermal conductivity slightly lower than hot rolled. For almost all practical purposes, if you\u2019re working below 1,000\u00b0F, the processing (hot vs. cold) doesn\u2019t make a meaningful difference in thermal conductivity\u2014what matters is the carbon content of your HRCS grade.<\/p>\n

But wait\u2014there are other factors that can throw these numbers off, and I\u2019ve seen it happen on jobs. For example, surface condition: if your hot rolled steel has a thick mill scale layer (the dark, oxidized scale that forms on the surface during hot rolling), that oxide layer is a much poorer conductor than the steel itself. Mill scale is mostly iron oxide, which has a thermal conductivity of only around 2 to 3 W\/m\u00b7K at room temperature. So if you\u2019re doing a heat transfer calculation that depends on the steel\u2019s conductivity, you can\u2019t forget about that mill scale\u2014if it\u2019s left on, it will slow heat transfer between the steel and whatever it\u2019s touching, like another pipe or a fluid. That\u2019s why we often tell clients that if mill scale will be in contact with hot surfaces or fluids, they should consider pickling or blasting the surface first.<\/p>\n

Another factor is alloying elements. Most standard hot rolled carbon steel only has small amounts of manganese, silicon, and maybe copper as residual elements, so those don\u2019t affect thermal conductivity much. But if you\u2019re using a specialty HRCS with added chromium, molybdenum, or other alloying elements for high-temperature strength, those will lower the thermal conductivity further. For example, A516 Grade 70, a common hot rolled pressure vessel steel, has a tiny bit of silicon added for strength, so its thermal conductivity at room temp is around 43 W\/m\u00b7K, a bit lower than plain A36. That\u2019s a small difference, but for a pressure vessel holding hot fluid over thousands of cycles, it can add up to slightly more even heat distribution.<\/p>\n

Now, I\u2019ve learned over the years as a supplier that the generic numbers you find online aren\u2019t always tailored to real-world use. For example, I once had a client who was designing a heat treatment oven and used a textbook thermal conductivity number for mild steel that was 55 W\/m\u00b7K\u2014way higher than the actual value for our standard 1018 HRCS. That small error made their heat transfer calculations off by almost 20%, and they almost ordered the wrong size heating elements. That\u2019s why, when we provide specs to clients, we don\u2019t just give a single number\u2014we give a range that\u2019s specific to our hot rolled grades, plus notes on how temperature, surface condition, and processing will change that value.<\/p>\n

Let\u2019s also talk about why this matters for you, the person buying or using hot rolled carbon steel. If you\u2019re building a structural beam, thermal conductivity won\u2019t be your top concern\u2014you\u2019ll care about yield strength and weldability. But if you\u2019re making a component that will be exposed to heat: furnace grates, heat exchanger tubes, boiler parts, even automotive engine components, thermal conductivity is a critical spec. For example, if you\u2019re replacing a stainless steel furnace grate with hot rolled carbon steel, you need to make sure you account for the higher conductivity\u2014so you don\u2019t have to add more insulation than you planned, or adjust the heat output. For a heat exchanger, choosing a low-carbon hot rolled steel with consistent thermal conductivity ensures uniform heating across the entire unit, preventing hot spots that can cause premature failure.<\/p>\n

So, to wrap up the core takeaways about hot rolled carbon steel thermal conductivity: first, it ranges from ~35 W\/m\u00b7K for high carbon grades to ~50 W\/m\u00b7K for low carbon grades at room temperature. Second, it decreases as temperature rises, with the biggest drops happening above 1,000\u00b0F. Third, hot rolling vs. cold rolling barely changes this value for most industrial applications, but mill scale and alloying elements can make a noticeable difference. Fourth, generic online charts are a starting point, but always check a supplier\u2019s specs for the exact HRCS grade you\u2019re using.<\/p>\n

At the end of the day, thermal conductivity is just one of many specs you need to nail when choosing hot rolled carbon steel, but it\u2019s one that\u2019s often overlooked in the design phase. As a hot rolled carbon steel supplier, I\u2019ve worked with hundreds of clients to match the right grade to their application, walking through these details so they don\u2019t run into surprises mid-project. If you\u2019re working on a job where heat transfer is a factor, or you just want to confirm the thermal properties of a hot rolled carbon steel grade you\u2019re using, reach out to our team to get detailed, grade-specific specs tailored to your exact needs. We can also walk through how processing, surface treatment, and operating temperatures will impact performance, so you can make the right choice without guesswork.<\/p>\n

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If you have questions about thermal conductivity, HRCS grades, or need a quote for hot rolled carbon steel for your project, don\u2019t hesitate to get in touch with our team to discuss your requirements. We\u2019re here to help you get the right material for the job, every time.<\/p>\n

Stainless Steel Bar<\/a> References
\nCottrell, A. H. (1967). The Mechanical Properties of Matter. Wiley.
\nASM International. (1992). Properties and Selection: Irons, Steels, and High-Performance Alloys. ASM Handbook, Vol. 1.
\nTaylor, R. P. (2001). Thermal Conductivity of Carbon Steels at Elevated Temperatures. Journal of Heat Transfer.<\/p>\n

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Wuxi Xuanyi Stainless Steel Co., Ltd.<\/a>
Wuxi Xuanyi Stainless Steel Co., Ltd. is one of the most professional hot rolled carbon steel manufacturers and suppliers in China. With abundant experience, we warmly welcome you to wholesale bulk durable hot rolled carbon steel made in China here from our factory. If you have any enquiry about cooperation, please feel free to email us.
Address: Room 1207, Building 11, Shengang Metropolis Plaza, No. 299 Fangcheng Avenue, Xinwu District, Wuxi City,China.
E-mail: jscherryxy@163.com
WebSite: https:\/\/www.xuanyisteel.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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