Stainless steel cast pipe Manufacturers

What are the main elements that affect the corrosion resistance of stainless steel cast pipes?

Stainless steel cast pipes are widely used in petrochemical, heat treatment equipment, metallurgy and high-temperature combustion systems due to their excellent mechanical strength, thermal stability and excellent corrosion resistance. Especially in high temperature, high pressure and strong corrosive environment, the corrosion resistance of materials is one of the core indicators that affect product stability and life.
Wuxi Dongmingguan Special Metal Manufacturing Co., Ltd., located on the shore of the beautiful Taihu Lake, has accumulated a deep technical foundation in the field of heat-resistant, wear-resistant and corrosion-resistant castings with an annual casting capacity of 5,000 tons and advanced process platform. Its high-alloy centrifugal cast pipe series, such as radiation tubes, sinking rollers, paper machine rollers, etc., have been widely used in heat treatment, glass, papermaking, metallurgy and other industries, and are exported to Europe, South America, Japan and other countries and regions.
Chromium (Cr) - the core element for the formation of passivation film
Chromium is the core element that determines the fundamental characteristic of stainless steel "corrosion resistance". Usually, steel with a chromium content of more than 10.5% has the ability to form a stable passivation film. This chromium-rich oxide film can quickly cover the surface of the material and effectively prevent the continued oxidation reaction.
Wuxi Dongmingguan uses high-chromium heat-resistant alloys to ensure that the chromium content is higher than 18% when producing radiation tubes, sinking rollers and other products. Even in high-temperature oxidizing atmospheres or sulfur-containing environments, it can still maintain a stable surface oxide protective film, significantly extending the service life. The compactness and self-healing properties of the passivation film are the key to improving the stability of pipe fittings in highly corrosive media.
Nickel (Ni) - Stabilizes austenite structure and enhances corrosion resistance and toughness
Nickel is an austenite stabilizer that can not only improve corrosion resistance in stainless steel cast pipes, but also significantly improve high-temperature ductility, impact toughness and processability. Especially in media such as hydrogen sulfide and chloride, the higher the nickel content, the better the corrosion resistance.
Wuxi Dongmingguan widely uses alloy systems with a nickel content of 8%-35% in precision casting and centrifugal casting processes. In particular, in high-temperature radiation tubes, heating furnace bottom rollers and other application scenarios, high nickel-chromium alloys (such as HK40, HP, HU, HT and other ASTM A297 standard alloys) are used to ensure that the material has excellent structural stability and corrosion resistance in both oxidizing and reducing atmospheres.
Molybdenum (Mo) - Improves pitting and crevice corrosion resistance
The addition of molybdenum significantly enhances the pitting resistance of stainless steel cast pipes in chloride ion-containing environments (such as seawater and salt spray environments), and is an essential alloying element in marine environments and chemical plants. It resists local corrosion by strengthening the stability of the passivation film.
In cooperation with Japanese and European customers, Dongmingguan added 2%-3% Mo elements to some high-end heat treatment furnace rollers and sinking rollers, significantly improving the service stability of the product in chloride-containing atmospheres or acidic atmospheres, and ensuring that there is no pitting and peeling on the surface during long-term operation.
Silicon (Si) and aluminum (Al) - Improve high-temperature oxidation resistance and carburization resistance
Silicon and aluminum can enhance the oxidation resistance of stainless steel in high-temperature environments, and prevent further oxidation and carbon erosion by forming a dense oxide film. Its role is particularly prominent in products such as heat-treated radiation tubes and high-temperature furnace bottom rollers.
Wuxi Dongmingguan introduces 1.5%-3.0% silicon content in high-alloy castings according to customer customization needs, and simulates and optimizes the organizational evolution of castings in high-temperature atmospheres through simulation software such as ANYCASTING, so that the radiation tubes still maintain a low oxidation rate and good structural integrity above 1000°C.

What are the commonly used casting processes in the manufacture of stainless steel cast pipes?

In high-temperature and high-pressure industrial fields such as petrochemicals, metallurgical heat treatment, and energy-saving equipment, stainless steel cast pipes are widely used due to their excellent high temperature resistance, corrosion resistance, and mechanical strength. In order to meet the high requirements for pipe dimensional accuracy, organizational density, and performance consistency under complex working conditions, the casting process used in the manufacturing process has become a key link in determining quality.
Investment Casting / EPC Lost Foam Casting
Investment casting is a high-precision, near-net-shape casting process, especially suitable for stainless steel castings with complex shapes, precise dimensions and high surface requirements. Dongmingguan can stably produce cast pipe joints, flange sections and customized pipe fittings with complex structures and uniform wall thickness by adopting silica sol process and lost foam (EPC) production line.
Technical advantages:
High surface finish (Ra value can reach within 3.2μm), small subsequent processing volume;
High geometric dimensional accuracy (can be controlled at CT4-6 level);
Can manufacture small batches of multi-variety customized pipe fittings, flexibly respond to customer needs;
The simulation process uses ANYCASTING for flow and solidification analysis to effectively avoid defects such as pores and cold shuts.
Especially in the production of special-shaped cast pipe fittings such as grate bars for waste incinerators and furnace pipe joints for heat treatment, precision casting has become the preferred process due to its mold replication ability and good shape retention.
Centrifugal Casting - The Core Technology of High-alloy Stainless Steel Casting Pipes
Centrifugal casting is a process that uses centrifugal force to shape the molten metal by throwing it toward the inner wall through a high-speed rotating mold. It is widely used to manufacture thick-walled, large-diameter, high-density round tube stainless steel castings. In Dongmingguan's product system, high-end centrifugal castings such as radiant tubes, sinking rollers, and paper machine rollers are typical applications of this process.
Technical advantages:
The metal has high density, almost no shrinkage holes, slag inclusions, and strong anti-penetration performance;
The structure is uniform, the grain is refined, and the creep resistance is good, which is particularly suitable for high-temperature and long-term operation;
The tube wall thickness is controllable, and the inner and outer alloys can be optimized by double-stream casting (such as bimetallic tubes);
It has strong resistance to high-temperature oxidation and thermal fatigue, and is suitable for continuous heating furnaces and radiant tube systems.
At present, Dongmingguan can produce stainless steel centrifugal casting tubes with diameters ranging from 50mm to 1000mm and lengths up to 4000mm, which are widely exported to high-standard markets such as Europe, South America, and Japan. Relying on advanced simulation platforms (ABAQUS, ANYCASTING), the company predicts and analyzes the fluidity, solidification behavior and residual stress distribution of cast pipes, greatly improving the first-time pass rate and service stability of the products.
Resin Sand Molding - A flexible solution for large and non-standard cast pipes
For stainless steel casting pipes with large sizes, special shapes or limited batches, such as large furnace pipe shells, furnace roller bases or connecting sections, resin sand casting is still widely used because of its flexible modeling and strong adaptability.
Technical advantages:
Low cost, short cycle, suitable for small and medium batch orders and engineering trial production;
Castings with large special-shaped pipeline structures or multi-parting surface structures can be manufactured;
The model can be three-dimensionally modeled through CAD and UG, combined with GEOMAGIC CON and 3D scanning equipment for dimensional accuracy comparison and verification.
With its own heat treatment furnace group and machining center, Dongmingguan can carry out various processes such as solid solution treatment, aging treatment, turning, internal and external surface finishing after the resin sand casting pipe is completed, ensuring that the product is delivered in a "usable state".

What is the effect of heat treatment process on the performance of cast pipes?

Stainless steel cast pipes are widely used in high temperature and high pressure working environments such as metallurgy, heat treatment, petrochemical, waste incineration, and electricity. Their performance depends not only on the selected high alloy materials and casting process, but also on the subsequent heat treatment process. Reasonable heat treatment can significantly improve the mechanical properties, organizational stability, thermal fatigue resistance and corrosion resistance of cast pipes, and is the core link for the leap from "qualified products" to "high-quality products".
Organization regulation: heat treatment makes the microstructure more "scientific"
During the casting process, due to uneven cooling speed and alloy element segregation, stainless steel pipes often form defective structures such as coarse grains, dendrite segregation, and carbide networks. Through heat treatment processes such as solution treatment and aging treatment, the organizational state can be significantly improved:
Solution treatment: Heat the cast pipe to 1050~1150℃ and then cool it quickly to promote the full dissolution of carbides and other precipitated phases, and transform the organization into uniform austenite or austenite + δ mixed phase, eliminating cast stress and brittle phase.
Aging treatment/stabilization heat treatment: Keep the heat at a low temperature for several hours to promote the uniform precipitation of beneficial phases such as fine dispersed carbides, and improve creep resistance and thermal fatigue resistance.
In the production of typical high-alloy cast pipes such as radiation tubes, sinking rollers, and furnace bottom rollers, Dongmingguan will accurately match the heat treatment system according to the material type (such as HK40, HP-Nb, HP-MA), and combine simulation analysis software (such as ABAQUS, ANYCASTING) to predict stress changes, thereby optimizing process parameters and achieving a dynamic balance between organization and performance.
Performance improvement: All-round improvement from "hardness" to "toughness"
Different cast pipes face different types of stress tests during use, such as tensile stress at high temperature, thermal fatigue at alternating temperature, pitting in corrosive media, etc. Heat treatment can effectively improve the following properties:
Improved creep resistance: When operating for a long time at high temperature (such as 1000℃), the heat-treated cast pipe can maintain good dimensional stability and organizational stability, and adapt to long-term heat load environments such as petrochemical cracking furnaces and incinerators.
Improved impact toughness: High temperature insulation + rapid cooling can refine the grains and reduce the aggregation of carbides at grain boundaries, thereby improving the impact absorption capacity of cast pipes under complex working conditions.
Enhanced corrosion resistance: Especially for Cr-rich, Ni-rich, and Nb-rich alloys, a dense passivation film and excellent austenite phase are formed after heat treatment, which helps to enhance the surface corrosion resistance and oxidation resistance.
For example, the high-sulfur easy-to-cut centrifugal cast pipes produced by Dongmingguan, in addition to ensuring the mechanical processing performance, heat treatment also needs to take into account the stability of the organization and the resistance to heat corrosion. By optimizing the temperature-time curve, it is ultimately ensured that the product meets the dual standards in terms of mechanical properties and durability.
Release residual stress to ensure dimensional stability and service life
Cast stainless steel pipes inevitably generate internal residual stress during the solidification and cooling process. If this stress is not controlled, it may cause cracking, deformation, and even early failure during use. Through high-temperature tempering or annealing treatment, it can achieve:
Release and homogenization of residual stress;
Control of shape deformation to improve dimensional stability;
Reduce the risk of crack source initiation and increase the overall service life.
Dongmingguan uses a heat treatment furnace for overall heating and slow cooling treatment, and uses a 3D scanner and GEOMAGIC CON software to compare the dimensional changes of cast pipes before and after heating, ensuring that the products can be operated in customer equipment without worries after delivery.
Optimization of surface strengthening and anti-oxidation ability
For cast pipes such as furnace rollers, hot air ducts, incinerator components, etc. that are exposed to high-temperature oxidizing atmospheres for a long time, Dongmingguan can also perform special heat treatments according to customer needs, such as surface aluminizing, chromizing, anti-oxidation layer treatment, etc., to improve surface oxidation resistance and high-temperature gas erosion resistance.