From the "Fengshen Wheel" described in the first century AD, to the Swedish engineer Laval designed and manufactured a practical steam turbine in 1882, and nowadays the development of larger capacity and high-parameter steam turbines has been widely used in power stations and navigation. And in large industries. Such an important industry with high technical content and difficulty in manufacturing is often considered to represent the ability and level of equipment manufacturing in a country. Although China's steam turbine development started relatively late, in recent years, the industry's technological progress has been rapid, and the industry competition pattern has undergone profound changes: the development of steam turbine products tends to be high-power, high-efficiency, large-capacity, and intelligent and environmentally friendly. Along with this, it also promotes the development of turbine parts products in the direction of precision, efficiency and energy saving.
China Yangtze Power Corporation (Group) is a traditional power equipment manufacturer with many years of development history, and its tests are particularly severe. Establishing core competitiveness, maintaining stable development of enterprises and effectively improving economic benefits, and adapting the development of enterprises to the needs of the development of the national power industry is a new proposition for the Changdong Group to face challenges in the new era.
Figure 1: The structure of the blade is complex, mostly torsion freeform surfaces (irregularity from the root to the canopy).
"While creating and perfecting the product structure system with new technologies as the core competitiveness, the Group has continuously improved the technological level of steam turbine manufacturing, and has benefited from processing, which has greatly enhanced the core competitiveness of the company." Changdong Group Craftsman Feng Shanqing once said this.
As the core component of the steam turbine, the structure of the blade is particularly complicated, mostly for torsion free-form surface (the irregularity of the profile from the blade root to the canopy), and its processing workload is very large, accounting for almost 1/1 of the total turbine processing capacity. 3, therefore, the quality of the blade processing directly affects the working efficiency and reliability of the turbine. The quality and life of the blade are closely related to the processing method. In other words, the processing method of the blade has a decisive influence on the working quality and production economy of the steam turbine.
Figure 2: The processing of the leaf pages is very large, accounting for almost 1/3 of the total turbine processing.
The five-axis linkage machining center is the most advanced blade processing equipment available. Zhu Aiming of Changdong Group has worked in the field of steam turbine manufacturing for ten years. After using the five-axis linkage machining center, he said with emotion: "The application of the five-axis linkage machining center has greatly reduced the processing of the blade. In the past, we used at least 30 processes to machine the blades with conventional equipment. Today, the five-axis simultaneous machining center can complete all the machining steps of the blade in one setup, eliminating the repeated errors introduced by multiple clamping, processing time. Also shortened to a quarter of the past."
Figure 3: The machining accuracy of the blade root determines the assembly quality of the blade and directly affects the safe operation and efficiency of the turbine.
The upgrading of equipment has revived the vitality of the company, which has also brought new development needs to Changdong Group. The processing content of the blade is mainly the processing of the reference surface, the processing of the steam surface, the processing of the blade root and the processing of the blade crown. There are two main types of processing blanks selected by Changdong Group, namely square blanks and forging blanks. The blade is made of stainless steel and is a difficult material to process. In the middle work of the blade, the roughening of the blank accounts for a large proportion, especially the processing of the blank of the square material, and the rough margin is more than 60%. The good news is that the five-axis simultaneous machining center has excellent high-speed machining performance and has a strong roughing capability. The workpiece blank can be started from square steel until it is processed to the degree of polishing. The problem that can be a headache is that the blade wear is very serious due to the large cutting force during cutting, the large deformation of the cutting, and the high heat generated by the cutting. From blank machining to finished products, it usually takes dozens of tools to participate.
Figure 4: In 2014, Changdong Group publicly implemented the tool procurement tender for the society, and Shangao Tools won the bid. The standard knives of the five-axis linkage machining center at the production site all use Seco knives.
The processing quality of the blade body surface directly affects the working performance of the steam turbine. The machining is mainly based on high-speed cutting. The roughing operation can cut about 60% to 70% of the blank material, so the requirements for the knife are very high. This operation puts the tool under heavy load, and the tool life needs to be predicted during the machining process, and the machining quality of the blade body is maintained by timely changing the tool.
The processing precision of the blade root determines the assembly quality of the blade, and directly affects the safe operation and efficiency of the steam turbine. The requirements for dimensional accuracy and surface roughness are high, which brings certain difficulties to the processing. In order to ensure the tolerance of the blade root, the accuracy of the reference surface must be increased.
Figure 5: Changdong Group Zhu Aiming and Shangao Tool Dong Zhifei.
"In the process of roughing the blade, the tool needs to bear a great load and must have a good life and economical use. For this reason, we chose the MS2500 indexable insert of Seco Tools. In actual production, we On the five-axis linkage machining center, a five-blade milling cutter disc is used for roughing. Under dry cutting conditions, each insert can be indexed at least four times, and the cutting depth can even be indexed by 6~. 8 times. According to Zhu Aiming, the Shangao tool MS2500 indexable inserts stand out in only one round of tool cutting. "The dividends of the company are at the cutting edge. The changes brought by this tool have made us have a deeper understanding of this statement widely circulated by foreign manufacturers."
Figure 6: The blade is the core component of the turbine
The MS2500 insert is a copy milling cutter with strong impact resistance. The chip has a large chip pocket and easy chip output. It is especially suitable for rough machining of difficult materials such as stainless steel. "The round insert design has an innovative variable micro-geometry angle that can cope with the ever-changing material balance in multi-axis blade machining applications. It can effectively improve the machining efficiency of steam turbine blades, reduce vibration and improve chip evacuation control." Tool Dong Zhifei said, "The blade seat is designed with a blade anti-rotation system. This system has been patented. It ensures that the blade does not rotate during processing through four facets, which improves the processing stability and ensures the safety of the process. Turbine blade milling often requires a high tool overhang, so such blade seat design is particularly important." In the field of blade machining, Seco Tools has a wealth of practical experience, which may be overlooked but may be affected The details of the final result are more thoughtful. For example, the insert seat also considers the seal design to avoid the ingress of chips or dirt during processing and to provide high quality machining by maintaining high precision.
Figure 7: Variety of specifications for steam turbine blades processed by Yangtze Power
In 2013, the implementation of the overall relocation and reconstruction project of Changdong Group was completed. The machine shop invested 200 million yuan to upgrade the equipment. The number of CNC machine tools has increased from 18 to 34. The new equipment is all four-axis and five-axis CNC machining centers, and the machine level has reached a new level. In order to ensure the full effectiveness of advanced machine tools, in 2014, Changdong Group publicly implemented tool procurement tenders for the society, requiring tool suppliers to have rich and persuasive practical experience in the design, manufacture and commissioning of tools. In this public bidding event, Seco Tools won the bid.
Figure 8: In addition to blade machining, Seco Tools has the same advantages in turbine block machining. Nie Shihai, the person in charge of the Yangtze River Power, was very touched by this.
In Dong Zhifei's view, Seco Tools was able to successfully win the bid for the Changdong Group. This was not an accident. "From product specialists, tooling system suppliers to today's total machining solution providers, Seco Tools is always guided by the needs of our customers to achieve high efficiency, low cost machining for our customers. Square steel blades for forging and forging With the processing of blades, superalloy blades, rotor slots and turbines, Seco Tools has proven tooling solutions and excellent on-demand service capabilities." In the Changdong Group's technical transformation project, Seco's winning tool varieties There are hundreds of different types and models including milling cutters, three-sided ductile cutters, boring tools, reamers, turning tools and vibration dampers.
High-quality precision engineering requires first-class tools. As far as Seco Tools is concerned, understanding the specific challenges of the power generation industry, with complete milling solutions, years of accumulated expertise can help users reduce processing time and increase productivity, thus maintaining a leading edge in this highly competitive market segment. . "The cooperation with Seco Tools not only allows our new machine tools to be put into production smoothly, but also has a wealth of experience in the field of steam turbine manufacturing," Zhu Aiming concluded.
Figure 9: Changjiang Power has to benefit from processing, which has greatly enhanced the core competitiveness of the company.
Headquartered in Fagersta, Sweden, Seco is committed to developing innovative metal cutting solutions and working closely with customers to fully understand and focus on meeting their needs. We employ more than 5,000 people in 50 countries and enhance the capabilities of our team members through training, development and employee recognition programs, and an open communication environment. Our employees demonstrate three core values ​​– hospitality, family belonging and personal commitment – ​​that define the way we do business and how we interact with our customers, suppliers and other partners. For more information, please visit
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