When I first started out as a carbon steel supplier, I’ll admit, I didn’t spend a ton of time thinking about creep properties. Back then, my main focus was getting the right thickness, the right grade, and making sure the steel could hold up to whatever a fabricator or construction team needed for the day. That changed a few years back, when a regular client—someone who builds industrial boilers for power plants—called in a panic. They’d had to pull a batch of carbon steel pipe out of service prematurely; after just two years at 550 degrees Fahrenheit, the pipe had stretched enough to cause leaks. They asked me straight: “What the heck happened to this stuff?” That question pushed me to dig deeper, and now it’s one of the first things I walk customers through before they order anything for high-temperature applications. Carbon Steel
Creep, for anyone who’s new to the term, is that slow, permanent deformation a material goes under when it’s exposed to constant stress—like pressure from inside a pipe, for example—at temperatures below its melting point. For carbon steel, that temperature threshold is roughly 700 degrees Fahrenheit, though it can vary a bit depending on the specific grade. It’s not like a sudden failure, either; creep is a gradual process. You might not notice it at first, but over time, the small stretches add up, leading to cracks, leaks, or even full-on structural collapse. That’s why it’s such a big deal in industries like power generation, oil and gas, chemical processing, and even aerospace—places where equipment runs at high heat for years on end.
Let me break down how carbon steel’s creep works, in plain terms. There are three main stages, right? First, primary creep. That’s the initial phase, where the material deforms quickly at first, then slows down as it starts to work harden. Think of it like bending a paperclip a few times; the first bend is easy, but after that, it gets stiffer, so further bends are slower. The second stage is steady-state creep, and this is where the trouble starts. The rate of deformation here is constant—no speeding up, no slowing down. For carbon steel, this is the phase that takes up most of the equipment’s lifespan, which is why we use it to calculate how long a part will last. The third stage is tertiary creep. Here, the deformation rate spikes, tiny cavities start to form inside the steel, and it’s only a matter of time before it breaks. For that power plant client I mentioned, their pipe had made it past primary creep, was halfway through steady-state, but had hit the point where tertiary kicked in earlier than expected. Turns out, they’d used a lower-grade carbon steel that wasn’t rated for 550 degrees F long-term.
Now, not all carbon steel is the same when it comes to creep. Let’s talk about the grades I supply most often, because that’s what my customers care about. Low-carbon steel, the stuff with less than 0.3% carbon, is actually pretty bad at creep, even at temperatures just above 700 degrees F. It’s soft, so it deforms easily under constant stress. That’s why you don’t see low-carbon steel in boiler tubes or refinery furnaces. Then there’s medium-carbon steel, around 0.3% to 0.5% carbon, which is a step up. It has a bit more strength, so it can handle higher stresses at moderate temperatures. But even medium-carbon steel has its limits—by 800 degrees F, its creep rate starts to jump, and it’s not recommended for continuous use above that. High-carbon steel, over 0.5% carbon, is even stronger at room temp, but its creep behavior is tricky. The higher carbon content can make it more brittle, so when it does start to creep, it’s more likely to fail suddenly instead of deforming gradually. That’s a risk for my customers, so I always warn them about that.
Wait, but there’s a middle ground, right? Carbon steels with small amounts of alloying elements—like manganese, chromium, or molybdenum. I supply a lot of AISI 1020 and AISI 1018, but when a customer needs high-temperature parts, I push A335 P11 or P22. Those are low-alloy carbon steels, with a little chromium and molybdenum added. Those elements form tiny, stable carbides in the steel, which stop the grain boundaries from sliding past each other. That’s the main thing that slows creep down—if the grains can’t move, the material doesn’t deform as fast. I remember one client who tried to cut costs by ordering regular A106 carbon steel for a 600-degree F application. I showed him the creep data for A106: at 600 degrees F, it had a steady-state creep rate of around 0.0001% per hour. That doesn’t sound like much, but over 10 years, that adds up to almost 9% elongation. For a pipe that’s supposed to be within a 1% elongation limit, that’s a disaster. He switched to P11, and the creep rate dropped to 0.00001% per hour—way safer.
Another big factor in creep is stress. It’s not just temperature; the amount of load on the steel matters too. A thin-walled pipe with high internal pressure will creep faster than a thick-walled pipe with the same temperature and lower pressure. I had a fabricator call me last year, saying his steel plates were warping during a long-term pressure test. We checked the numbers, and he’d used a plate with a thinner cross-section than recommended, so the stress on it was too high, even at a temperature that was technically below the creep threshold. That’s why I always work with my customers to calculate the design stress for their application, not just the temperature. If the stress is too high, even “creep-resistant” carbon steel will fail prematurely.
Let me also address a common misconception: some people think creep only happens at super high temperatures, like in jet engines or nuclear reactors. But that’s not true. I’ve seen cases where carbon steel used in structural support for large buildings, exposed to 100-degree F temperatures for 50 years, has shown minor creep deformation. It’s a tiny rate, like 0.0000001% per hour, but over decades, it adds up enough that engineers have to account for it when designing large, long-lasting structures. That’s why I don’t just talk about industrial parts—even construction clients need to know about creep, to make sure their steel will hold up over the life of a building or bridge.
Now, as a supplier, how do I make sure the carbon steel I sell has consistent creep properties? First, I work with mills that adhere to strict quality standards—ASTM A, ASME, those kinds of specs. Those standards test for creep rate and rupture time, so I can tell my customers exactly what they’re getting. For example, if a customer orders A335 P11, I can provide test data that shows its creep rupture strength at 100,000 hours (that’s over 11 years) at different temperatures. That’s non-negotiable for me—no cutting corners on quality. Second, I educate my customers. A lot of fabricators and plant managers don’t have a background in material science, so it’s my job to explain why a certain grade is right for their application, instead of just selling them the cheapest steel on the shelf. I’ll even walk them through creep curves, showing how at 700 degrees F, the creep rate for A106 is 10 times higher than for P11.
I also know that some customers try to mitigate creep by using coatings or heat treatments. Heat treatment, like normalizing or tempering, can affect creep properties a lot. For example, if you temper carbon steel at too high a temperature, you can make the carbides in the steel coarsen, which lets the grains slide more easily, increasing creep rate. I always make sure my customers know that the heat treatment applied to the steel after I supply it can change its creep behavior. If they’re going to do any post-processing, I recommend talking to a material engineer first, because a wrong tempering step can turn a good steel into a creep risk.
Last month, I had a customer in the chemical processing industry reach out, because he was dealing with leaks in his reactor vessels that had been running at 650 degrees F for 8 years. He’d been using standard carbon steel, and the creep had caused the vessels to stretch enough to crack the welds. We worked together to replace them with A387 Grade 11, which is a chromium-molybdenum carbon steel designed specifically for high-temperature pressure vessels. The creep rate for that grade at 650 degrees F is almost a hundred times lower than standard carbon steel, and he’s told me since the replacement, he hasn’t had a single leak. That’s the kind of success story that reminds me why taking the time to understand creep properties matters—for my customers, their equipment, and their bottom line.
If you’re working on a project where carbon steel will be exposed to constant stress at temperatures above 700 degrees F, or even for long-term applications at lower temperatures, you can’t afford to ignore creep properties. Skipping that step can lead to costly downtime, unexpected repairs, or even safety hazards. I’ve seen it too many times, and I don’t want any of my customers to go through that. Whether you’re a fabricator building boiler tubes, a refinery manager replacing pipework, or a construction engineer specifying steel for a high-rise, I’m here to help you choose the right carbon steel for your needs. We can go over your application, run through the temperature and stress specs, and make sure you get steel that will perform for years, not just months. Feel free to reach out and connect to discuss your upcoming projects—let’s make sure your steel is up to the task.
Carbon Steel Pipe/Tube References
- ASM International. (2019). Creep of Carbon and Low-Alloy Steels. ASM Handbook, Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys.
- Garofalo, F. (1965). Fundamentals of Creep and Creep-Rupture in Metals. Macmillan Publishing Company.
- ASTM International. (2021). Standard Specification for Carbon Steel Pipe for High-Temperature Service (ASTM A106/A106M-21).
- Noria Corporation. (2022). Understanding Creep in Carbon Steel Equipment. Industrial Plant Equipment Maintenance Journal.
- British Standards Institution. (2020). BS EN 10216-2: Seamless Steel Tubes for Pressure Purposes – Technical Delivery Conditions – Part 2: Non-Alloy and Alloy Steel Tubes with Specified High-Temperature Properties.
Wuxi Jin Ming Jian De Industry & Trade Co., Ltd.
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