English Views: 0 Author: Eternal Tech Team Publish Time: 2026-09-04 Origin: Site
In the production process of grain-oriented silicon steel, the high-temperature annular annealing furnace is renowned as the "heart" of the entire manufacturing line. This giant equipment, over 60 meters in diameter and capable of holding hundreds of coils of oriented electrical steel simultaneously, undertakes the critical task of high-temperature secondary recrystallization annealing for the steel coils, directly determining the formation of the Goss texture, magnetic properties, and surface quality of the finished product. Under such extreme operating conditions, the coil load‑bearing base—a key component that directly supports 15‑ton‑grade steel coils and endures prolonged exposure to 1200 °C temperatures as well as severe thermal cycling loads—plays a decisive role in the operational efficiency and overall cost of the entire production line, through its material selection and manufacturing process design.
The working conditions in the high-temperature annular furnace for grain‑oriented silicon steel are very harsh. The furnace temperature can reach up to 1300 °C. The steel coil base must support a static load of over 15 tons. It also has to endure alternating stresses from compression and tension during repeated heating and cooling cycles. At the same time, it is exposed to high‑temperature oxidizing gases.
Under such extreme conditions, ordinary carbon steel or low‑alloy steel cannot do the job. 309S heat‑resistant steel (Chinese grades: 0Cr23Ni13 / 06Cr23Ni13) is an ideal choice for this application because of its special alloy design.
309S is a high‑chromium (22.0 %–24.0 %), high‑nickel (12.0 %–15.0 %) austenitic heat‑resistant stainless steel. Its core advantages are as follows:
Excellent high‑temperature oxidation resistance – It can withstand repeated heating up to 980 °C, forming a dense protective chromium oxide scale on the surface during continuous service, which effectively resists attack from high‑temperature oxidizing atmospheres.
Good high‑temperature strength and creep resistance – It exhibits satisfactory creep strength within the common operating temperature range of 600 °C to 900 °C.
Low‑carbon design for improved weldability – As the low‑carbon version of Type 309, with a carbon content ≤ 0.08 %, 309S effectively minimizes carbide precipitation, thereby enhancing weldability.
Good hot workability – It can be forged and hot‑rolled within conventional temperature ranges.
These characteristics make 309S the material of choice for the steel coil base in high‑temperature annular furnaces.
Both are 309S heat-resistant steel. However, the service life and reliability of the bases produced by different manufacturing processes vary greatly. Currently, there are mainly three production routes in the industry: casting, rolling, and forging.
The furnace base plate is produced by direct casting using molten metal, which offers a simple process and relatively low cost. However, the as‑cast structure inevitably contains internal defects such as shrinkage cavities, blowholes, and porosity, along with coarse and non‑uniform grain distribution. Under high‑temperature alternating stresses, cracks tend to initiate at these casting defects and propagate, eventually leading to premature failure. Data indicate that the average service life of cast 0Cr23Ni13 furnace base plates is only 6 to 8 months.
The Japanese rolled SUS309S furnace bottom plates have improved some of their mechanical properties through hot rolling deformation, and their average lifespan has been increased to 2.16 years. However, the rolling process is limited by the plate specifications, and there are limitations when manufacturing large-sized and thick-section bases. Moreover, the streamline distribution and microstructure density of the rolled state are still inferior to those of forging.
Forging is a processing technique that applies pressure to a metal billet to induce plastic deformation. Compared with casting and rolling, forging 309S heat‑resistant steel bases offers irreplaceable advantages:
First, elimination of cast structural defects. During forging, the severe plastic deformation effectively eliminates internal defects such as casting pores and shrinkage porosity, making the material more dense.
Second, grain refinement and optimized flow lines. Forging refines the grains and distributes the metal flow lines along the direction of the stress applied to the base, significantly improving mechanical properties, density, and isotropy.
Third, excellent fatigue resistance. Forgings are free from casting defects, and their fatigue resistance under high‑temperature alternating loads is far superior to that of castings. Studies have shown that under identical test conditions, the fatigue life of forged material can be more than twice that of cast material.
Fourth, longer service life. Based on the above advantages, the average service life of forged 0Cr23Ni13 furnace base plates far exceeds that of cast and rolled products.
For a continuous production facility such as a high‑temperature annular furnace for grain‑oriented silicon steel, every additional month of base life means one less shutdown for replacement, one less interruption of the production line, and a considerable reduction in maintenance costs. The forging process brings not only greater durability, but also greater reliability and greater economy.
From 2025 to 2026, new ideas and improvements around 309S heat‑resistant steel and its uses keep coming. This shows that this material is very important for high‑end industrial equipment.
In December 2025, the 5# and 6# high‑temperature annular furnaces in BaoSteel's green manufacturing project for ultra‑high grade grain‑oriented silicon steel changed their furnace base support design. They replaced 120 furnace bases from "refractory support base + carbon steel bottom plate" to "refractory‑metal composite support base + stainless steel bottom plate". This project involves several key patents, including one on a heating device for the steel coil support plate in silicon steel heat treatment furnaces. This shows that using stainless steel bottom plates in high‑end grain‑oriented silicon steel annular furnaces has moved from testing to real factory use.
In 2026, the new ASTM A473‑2026 standard for stainless steel forgings was released. It gives the latest rules for making 309S and other stainless steel forgings in a standard way. In the same year, Chinese research groups kept applying for many invention patents about how to predict performance and improve processes for austenitic stainless steel.
At the same time, in August 2026, a Chinese steel plant successfully started the first domestically made high‑temperature annular furnace for grain‑oriented silicon steel in a private Chinese silicon steel company. They also improved the design of the steel coil load‑bearing base, using core technology with full local intellectual property, breaking the foreign monopoly on equipment technology. From the start of the design, this project focused on "improving the design of the steel coil load‑bearing base" to balance the temperature and gas flow inside the furnace, so as to ensure stable production of high‑end grain‑oriented silicon steel with low iron loss.
These patent updates and real‑world projects clearly send a message: the steel coil base plates for high‑end grain‑oriented silicon steel high‑temperature annular furnaces are moving towards better performance, longer life, and local production – and this is exactly the core value of forged 309S heat‑resistant steel bases.
If you are planning or operating a high‑temperature annular furnace project for grain‑oriented silicon steel, choosing a forged 309S heat‑resistant steel base means:
The forged structure is dense and free of casting defects, offering a service life far exceeding that of cast products.
Internal defects are eliminated, resulting in more stable performance under 1200 °C high temperatures and thermal cycling loads.
Reduced frequency of shutdowns for replacement, and lower life‑cycle maintenance expenses.
309S corresponds to Chinese grades 0Cr23Ni13 / 06Cr23Ni13, with stable material supply, aligning with the national strategy for localizing high‑end equipment.
Grain‑oriented silicon steel is a core soft magnetic material used in ultra‑high voltage power transmission and transformation, wind power transformers, and new energy electrical equipment. As the key equipment in the production process of grain‑oriented silicon steel, the high‑temperature annular furnace relies on every critical component to determine final product quality and a company's competitiveness.
The 309S forged heat‑resistant steel base, with its excellent high‑temperature properties and the microstructural advantages imparted by the forging process, is becoming the preferred solution for steel coil support plates in high‑end grain‑oriented silicon steel annular furnaces. From patent activities in 2025 to engineering practices in 2026, the industry's technological direction has become clear—forging is the better choice.
As a professional forging manufacturer, Jiangyin Eternal Heavy Industry Co., Ltd. is committed to providing high‑quality 309S forged heat‑resistant steel bases for high‑end grain‑oriented silicon steel high‑temperature annular furnaces. With superior forging techniques and rigorous quality control, we strive to help China's silicon steel industry reach new heights.
