Key Advantages and Disadvantages of Q345R Material

Key Advantages and Disadvantages of Q345R Material (Suitable for Surge Tanks/Steam Drums in Batch-type Waste Tire Pyrolysis Equipment)

Q345R is a special low-alloy high-strength steel for boilers and pressure vessels, and also the mainstream material selection for such pyrolysis equipment. Its advantages and disadvantages are all aligned with the core operational requirements of pyrolysis processes—temperature resistance, corrosion resistance, fatigue resistance, economy and processability—boasting an extremely high adaptability. Details are as follows:

I. Core Advantages (Key Properties Adapting to Pyrolysis Conditions)

Excellent Temperature & Pressure Resistance + Thermal Fatigue Resistance, Perfectly Matching Process Fluctuations

It has a long-term service temperature limit of 475℃, far higher than the actual temperature of pyrolysis oil and gas (250-350℃), and features outstanding pressure resistance (yield strength: 345MPa) to withstand the slight positive pressure of the equipment. Meanwhile, it exhibits excellent toughness, which can adapt to the frequent temperature fluctuations of heating and cooling in batch processes, preventing the cracking of tank bodies and welds caused by thermal expansion and contraction with no risk of thermal fatigue failure.

High Strength + Erosion Resistance, Adapting to the Characteristics of Oil and Gas Medium

As a low-alloy steel, it has a much higher mechanical strength than ordinary carbon steel, and can resist the continuous scouring of high-velocity pyrolysis oil and gas (containing trace carbon black and heavy oil). This effectively prevents local thinning of tank bodies, inlet impingement plates and other components, meeting the structural safety requirements for the long-term operation of equipment.

Excellent Weldability, Adapting to Equipment Manufacturing and Installation

It has good weldability with no special welding requirements; a firm connection can be achieved through conventional welding processes, and the weld strength is close to that of the base metal after welding with a low risk of welding defects. It is suitable for the processing and manufacturing of small and medium-sized pressure vessels such as surge tanks and steam drums, reducing the difficulty of production and on-site installation.

Ultra-high Cost Performance, the Economical First Choice for Universal Industrial Application

As a basic mainstream material for pressure vessels, it is far more affordable than 304/316 stainless steel, and requires no complex pre-treatment or post-maintenance. Combined with its comprehensive adaptability to working conditions, it becomes the optimal choice for conventional low-sulfur pyrolysis processes, balancing performance and project costs.

National Standardization, No Barriers to Material Selection and Procurement

Its performance indicators comply with GB 713-2014 Steel Plates for Boilers and Pressure Vessels, a national standard, with stable material quality and sufficient market supply. It is easy to procure and inspect, and complete material certificates and flaw detection reports can be provided, meeting the material selection requirements for equipment safety and compliance.

II. Main Disadvantages (Only for Special Working Conditions, No Impact on Conventional Ones)

Moderate Corrosion Resistance, Susceptible to High-sulfur/High-acidity Media

It can only resist mild corrosion from low-concentration sulfides and acidic components in pyrolysis oil and gas. When processing high-sulfur waste tires, the high content of H₂S in oil and gas will cause slow corrosion of the tank inner wall and welds, which may lead to pitting corrosion and leakage after long-term operation. In such cases, internal anti-corrosion coatings (epoxy resin, polytetrafluoroethylene) must be used as a supplement.

No Intergranular Corrosion Resistance, Requiring Protective Measures After Welding

It is not a stainless steel and has no intergranular corrosion resistance. If welding is carried out in a high-humidity and highly corrosive environment, the welds may become weak points of corrosion without timely anti-corrosion treatment. However, this problem has almost no impact in the dry and high-temperature operating environment of pyrolysis equipment, and only requires thorough cleaning of the welding surfaces during manufacturing.

Strength Attenuation After Long-term High-temperature Service

If it operates continuously at an over-temperature condition above 450℃, its metallographic structure will change gradually, resulting in a slight attenuation of mechanical strength. However, the actual operating temperature of surge tanks/steam drums in pyrolysis equipment is far below this threshold (maximum 350℃), so this disadvantage has no practical impact on the process.

Higher Density Than Stainless Steel, Slightly Heavier Self-weight for the Same Volume

With a density of about 7.85g/cm³, it is the same as ordinary carbon steel and slightly higher than 304 stainless steel (7.93g/cm³, the difference is negligible). The tank body has a slightly heavier self-weight for the same volume and thickness, but surge tanks are small and medium-sized vessels, so this point has no noticeable impact on equipment foundations and installation.

III. Summary of Working Condition Adaptability

Applicable Scenarios

It is the first choice for equipment such as surge tanks, steam drums and pyrolysis furnace cylinders in more than 90% of conventional low-sulfur waste tire pyrolysis processes.

Inapplicable Scenarios

It is not suitable for pure high-sulfur waste tire pyrolysis processes without anti-corrosion measures. For such scenarios, it is necessary to replace it with 304/316 stainless steel or apply a full internal anti-corrosion coating to the Q345R tank body.