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Analysis of the Development and Trends of China's Cast Steel Industry
2020-07-01
Large cast steel parts, due to their large volume and mass, and harsh working conditions, need to withstand high temperature, high pressure, strong impact, strong corrosion, and strong radiation environments, with increasingly high quality requirements. The manufacturing of large cast steel parts is the foundation of national equipment manufacturing and an important indicator of a country's manufacturing development level.
Application Fields
Large cast steel parts are widely used in power plants, petrochemical, metallurgy, shipbuilding, and other equipment and equipment manufacturing industries. Examples include stainless steel main pump casings in nuclear power, turbine cylinders, impellers, blades, upper crowns, and lower rings in hydropower units, cylinder parts in thermal power units, and rolling mill frames, work rolls, large bearing seats in large metallurgical equipment. The manufacturing of these large cast steel parts is directly related to the quality, safety, and progress of key national engineering projects and is of great significance to the national economy and people's livelihood.
Currently, China has made significant progress in the production of large cast steel parts, but product quality still has obvious deficiencies. Although some large cast steel parts can be produced, quality issues are frequently encountered. The technical capability to produce high-end products is still lacking, and some developed countries strictly keep manufacturing technologies of large cast steel parts confidential and even strictly restrict product exports, making large cast steel parts a bottleneck that greatly restricts national economic development.
Characteristics
1. Advantages
1) Cast steel parts have strong metallurgical manufacturing adaptability and variability. Different chemical compositions and microstructure controls can be selected to meet various engineering requirements; different heat treatment processes can be used to select mechanical properties and service performance within a wide range, and they have good weldability and machinability.
2) Cast steel materials have isotropy and strong overall structural integrity, thereby improving engineering reliability. Coupled with advantages such as lightweight design and short delivery time, they have competitive advantages in price and economy.
3) The weight of cast steel parts can vary widely. The lighter ones can be investment castings weighing only a few tens of grams, while large cast steel parts can weigh several tons, tens of tons, or even hundreds of tons.
2. Disadvantages
(1) Uneven microstructure. After liquid metal is poured into the mold, the layer of liquid metal first contacting the mold wall cools fastest and quickly solidifies into finer grains. As the distance from the mold wall increases, the influence of the mold wall weakens, and crystals grow into parallel columnar crystals perpendicular to the mold wall. In the center of the casting, heat dissipation is no longer directional, and crystals can freely grow in all directions until they meet, forming an equiaxed grain zone. Thus, the microstructure inside the casting is uneven, generally with relatively coarse grains.
(2) Porous microstructure. The crystallization of liquid metal proceeds by dendritic growth; the liquid metal between dendrites solidifies last, but it is difficult for the liquid metal to completely fill the spaces between dendrites, causing common porosity in castings. Additionally, if the liquid metal injected into the mold shrinks during cooling and solidification without sufficient compensation, it can form looseness or shrinkage cavities. Graphite in cast iron often appears as large flake, spheroidal, or other shapes, which can also be considered a porous microstructure.
(3) Rough surface. The surface is generally rough and cannot be compared to machined surfaces, and the shapes are more complex.
Development Trends of Large Cast Steel Parts
Current domestic development trends in the cast steel field include the following aspects:
(1) Steel liquid smelting is developing towards high-purity steel liquid technology, strictly controlling the smelting process and the content of S, P, and inclusions. Refining the steel liquid is used to improve steel quality.
(2) In the casting process design, computer simulation technology is used to simulate the pouring and solidification process of castings to optimize casting processes and improve casting quality.
(3) Closely following the transformation and development needs of the mechanical industry equipment field, actively developing new material castings to gradually replace imports and improve the overall production level of Chinese cast steel parts.
(4) Strengthening industrial structure adjustment and optimization to form a reasonable economic scale.
(5) Enhancing technological progress, improving innovation capabilities, and conducting research on materials and manufacturing processes for high-end castings.
(6) Developing green casting technology, improving clean production levels, and enhancing mechanization and intelligent operation levels in post-processing of cast steel production.
Compared with industrially developed countries, China's production of large cast steel parts currently has significant gaps in product variety, process level, quality grade, and manufacturing equipment. Due to the extremely high quality requirements of large cast steel parts, metallurgical technology is developing towards high-purity steel liquid technology, and control technologies for composition uniformity, internal defects, and dimensional accuracy need improvement; production technology of large cast steel parts is developing towards high-end.
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2026-09-05
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