Q960E and Q690E are both star products in the domestic high-strength low-alloy structural steel system, with the "E" grade ensuring reliable impact toughness at -40℃. However, the nearly 40% gap in yield strength divides them into two distinct tracks-ultra-high-strength and high-strength. Beyond the basic performance differences, the two steels also show significant disparities in technical barriers, industrial chain layout, market competition patterns, and future development directions. This analysis explores their core differences and industrial value from a more macro and forward-looking perspective.
Technical Barriers: From Production Thresholds to Quality Control Difficulties
The technical gap between Q960E and Q690E runs through the entire process from smelting to post-processing, and the former has built a higher technical moat to balance ultra-high strength and material stability.
- Q960E: Breaking Through the Limits of Strength-Toughness BalanceThe biggest technical challenge of Q960E lies in avoiding brittle fracture while achieving a yield strength of 960MPa. In smelting, it must adopt dual processes of converter smelting and VD vacuum degassing, strictly controlling the total content of phosphorus and sulfur below 0.035% to produce "ultra-pure steel". During the heat treatment stage, it needs precise quenching at 900 - 950℃ and low-temperature tempering at 200 - 300℃. Even a temperature fluctuation of ±20℃ may lead to uneven microstructure and reduced toughness. In terms of welding, its preheating temperature must be strictly controlled at 150 - 200℃, and the heat input is limited to 15 - 25kJ/cm. Once the parameters are exceeded, the heat-affected zone is prone to softening, resulting in a strength loss of more than 10%. At present, only a handful of large steel mills such as Baowu Group and Wuyang Iron and Steel can stably mass-produce Q960E.
- Q690E: Optimizing Stability Under Mature ProcessesQ690E takes a route of balancing performance and process simplicity. It can meet the strength requirements either by the TMCP thermo-mechanical control process or the conventional quenching and tempering process. Its carbon equivalent is controlled below 0.47%, which avoids the problem of cold cracks during welding without extremely strict preheating operations. In terms of production equipment, most medium-sized steel mills can achieve stable production using three-roll limited mandrel continuous rolling pipe units. The key technical focus is on controlling dimensional accuracy-the outer diameter tolerance can be maintained within ±0.5%, and the wall thickness tolerance within ±5%, which is easier to achieve compared with Q960E's requirement of controlling the austenite grain size to 5 - 8μm. At present, dozens of domestic steel mills including Angang and Tianjin Steel Pipe have the capacity for large-scale production of Q690E.
Industrial Chain and Market Layout: Niche High-End vs Mass Popularization
The differences in technical thresholds directly shape the distinct industrial chain roles and market supply-demand patterns of the two steels.
- Q960E: High-Value Niche Market with Concentrated DemandQ960E targets the high-end segment of the industrial chain, with an annual domestic demand of only about 150,000 tons, which is less than 20% of Q690E. Its downstream customers are highly concentrated in leading enterprises in heavy equipment manufacturing, such as Sany Heavy Industry and Zoomlion. For example, the ZAT12000H all-terrain crane uses 28mm-thick Q960E steel plates for its main boom, achieving a weight reduction of 15 tons. In the market, its price is as high as 18,000 - 22,000 yuan/ton, about 2.5 times that of Q690E. The supply cycle is as long as 20 - 30 days, and many products are customized according to the special requirements of equipment, such as adjusting the alloy ratio to enhance bulletproof performance for light armored vehicles.
- Q690E: Mass Market with Diversified Demand ScenariosQ690E is a backbone product in the high-strength steel market, with an annual domestic production capacity of about 800,000 tons. Its downstream demand covers a wide range of fields such as engineering machinery, wind power, coal mining, and marine engineering. For instance, it is used in the hydraulic supports of coal mines, which can increase the working resistance to more than 10,000kN and extend the service life by 3 - 5 times. In the 100-meter-level wind power towers, its application proportion has exceeded 60%. The market price of Q690E is stable at 11,000 - 13,000 yuan/ton, and the supply cycle is only 7 - 14 days. A large number of medium-sized steel mills can produce it, and the product specifications are standardized, which can meet the needs of large-scale engineering construction.
Practical Application Cases: Complementation Rather Than Competition
In many large-scale projects, Q960E and Q690E are not mutually exclusive alternatives but often used in combination to achieve the optimal balance of performance and cost.
- In Super High-Rise Buildings: The 1000-meter-level skyscraper's giant supporting columns adopt Q960E to reduce the cross-sectional area of the columns and save floor space. However, for the connecting parts and secondary stress-bearing structures, Q690E is used for heterogeneous steel welding. This combination not only ensures the overall structural strength but also reduces the project cost by more than 15%.
- In Heavy Machinery: In the boom system of a large-tonnage crane, the main stress-bearing section adopts Q960E to achieve lightweighting and improve lifting efficiency. The auxiliary sections such as the boom tail and connecting brackets use Q690E. According to the test data of Zoomlion, this mixed application can reduce the overall weight of the boom by 10% while reducing the manufacturing cost by 20% compared with using Q960E entirely.
- In Marine Engineering: The pressure hulls and key load-bearing structures of deep-sea drilling platforms use Q960E to withstand ultra-high pressure in deep seas. For conventional structures such as deck railings and auxiliary pipelines, Q690E is selected. Its excellent corrosion resistance can meet the marine working environment, and at the same time, it lowers the overall procurement cost of the platform.
Future Development Trends: Divergent Paths Driven by Demand
Driven by policies such as the "dual carbon" strategy and the upgrading of the equipment manufacturing industry, the development directions of Q960E and Q690E will become increasingly divergent.
- Q960E: Toward More Extreme Performance and SpecializationThe future R&D focus of Q960E will be on extreme environment adaptation and functional upgrading. For example, developing a version resistant to low-temperature brittle fracture at -60℃ for polar scientific research equipment; or adding corrosion-resistant alloy elements to meet the working conditions of acidic oil and gas fields. At the same time, it will try to enter emerging fields such as aerospace launch brackets and deep-sea robot frames. With the popularization of hydrogen reduction smelting technology, its carbon emissions are expected to be reduced by 40%, which will enhance its competitiveness in high-end equipment fields.
- Q690E: Toward Large-Scale, Low-Cost, and Green DevelopmentQ690E will focus on expanding application scenarios and reducing costs. It is expected that by 2030, its annual domestic demand will exceed 1.2 million tons, of which the offshore wind power field will account for 35%. Steel mills will further promote the TMCP process to replace the traditional quenching and tempering process, reducing the production energy consumption by more than 20%. In addition, the integration of digital twin technology will shorten the product customization cycle from 30 days to 7 days, which can better meet the personalized needs of different industries such as bridges and high-speed rail bogies.
What are the main reasons for the large price gap between Q960E and Q690E?
The price gap stems from differences in production costs and market positioning. Q960E requires complex processes like vacuum degassing and precise heat treatment, with strict control over alloy proportions, leading to high production costs. It targets the niche high-end market with small demand and customized production. In contrast, Q690E adopts mature and simple production processes such as TMCP, which reduces costs significantly. It caters to the mass market with large demand and standardized products. These factors result in Q960E being roughly 2.5 times more expensive than Q690E.
In which scenarios can Q690E not be replaced by Q960E, and why?
Q690E is irreplaceable in large-scale general heavy-duty projects that prioritize cost-effectiveness. For example, in the production of a large number of hydraulic supports in coal mines and ordinary wind power tower flanges, the use of Q690E can meet the strength requirements. Replacing it with Q960E would not significantly improve the equipment performance but would increase the project cost by more than twice. Additionally, Q690E has better ductility and simpler welding processes, making it more suitable for components that require large-scale welding and certain plastic deformation.
What technical breakthroughs are needed for Q960E to be more widely used?
Two key technical breakthroughs are essential. First, optimizing the welding process to reduce its dependence on high-precision equipment, such as developing special welding materials to lower the preheating temperature, thereby reducing the construction difficulty. Second, reducing production costs through technological innovation, such as applying continuous casting and rolling integrated technology to shorten the production process. Moreover, improving the stability of batch production to reduce the performance fluctuation rate of products can also promote its application in more general equipment fields.
What impacts will the development of new materials such as carbon fiber have on Q960E and Q690E?
The impact will be different. Carbon fiber materials may squeeze Q960E's market share in some high-end lightweight scenarios like small special aircraft due to their lighter weight. However, Q960E still has advantages in cost and impact resistance, so it will remain dominant in heavy equipment such as cranes. For Q690E, the impact is minimal. Because in large-scale engineering fields such as coal mining and bridges, carbon fiber is too expensive and difficult to maintain, while Q690E has the advantages of mature processes and low maintenance costs, which are irreplaceable in these fields.
Why can only a few steel mills produce Q960E stably?
Stable production of Q960E requires extremely high technical and equipment capabilities. It needs advanced equipment such as vacuum degassing furnaces and precision heat treatment lines to ensure the purity of the steel and the uniformity of the microstructure. Meanwhile, technicians must master precise process parameters. A slight deviation in quenching temperature or alloy ratio will lead to unqualified products. These high thresholds require large-scale investment and long-term technical accumulation, which are difficult for small and medium-sized steel mills to achieve, so only a few leading enterprises can stably produce Q960E.