First, the source of tasks
According to the National Steel Standardization Technical Committee [2008] No. 01 "On the release of the National Steel Standards Committee in 2008 the first batch of national standard revision project plan", by the Metallurgical Information Standards Institute jointly drafted the "construction machinery with high strength wear-resistant steel plate" national standard, the project number is "20077255-T-65".
Standard preparation work plan
(1) At the beginning of 2008, the preparatory work of data collection, situation investigation, problem analysis and other drafting standards were carried out in combination with product development, and the national standard (draft) was formed by the end of the year.
(2) In May 2008: issued a standard comment draft - solicit comments from superior standards authorities, production and customer industry representative enterprises and research institutes, according to the summary of feedback, determine the comment (second draft) or (discussion draft).
(3) August 2008: In response to the feedback of the national standard solicitation (second draft), the necessary modification work was carried out to form a comparative analysis of the standard level of similar products at home and abroad and a summary processing table of opinions, necessary data analysis, etc.
(4) September to October 2008: Hold a standard discussion meeting.
(5) The fourth quarter of 2008: according to the opinions of the pre-review committee, revise and form the national standard review draft, and coordinate the convening of the standard review meeting. According to the opinions of the approval meeting, the GBXXXX-200× "High strength wear-resistant steel plate for construction machinery" national standard was submitted for approval.
Second, the purpose of the development of standards
Wear-resistant steel plates are widely used in engineering, mining, construction, agriculture, cement production, ports, power and metallurgy and other mechanical products with particularly bad working conditions and high strength and wear resistance. Such as bulldozers, loaders, excavators, dump trucks and all kinds of mining machinery, grab, stacker and reclaimer, feed bending structure. A major problem that has plagued industry for many years is wear, especially contact with rocks, minerals and other structures subjected to friction, impact, and erosion. According to statistics, in industrially developed countries, the economic loss caused by the wear and tear of machinery and equipment and its parts accounts for about 4% of the gross national economic output value. Therefore, to solve the wear and prolong the service life of mechanical equipment and its components has become the primary issue that industry professionals need to consider in the design, manufacture and use of various mechanical equipment. From the point of view of the national economy, the development of high-strength wear-resistant steel for construction machinery is very necessary, in foreign countries have enterprises to produce high-strength wear-resistant steel and application, such as Japan Sumitomo Corporation, JFE, Sweden SSAB and SWEBOR, Germany Thyssenklub, MITTAL, etc., has produced wear-resistant steel with a wear-resistant life about 4 times higher than ordinary steel. Most of the domestic use of NM360 ~ 400, the international NM400 ~ 550, the annual consumption of 300,000 ~ 600,000 tons.
According to the development of high-strength wear-resistant steel at home and abroad, the standard of high-strength wear-resistant steel should become a more complete universal and serialized standard system. From the current status quo of high-strength wear-resistant steel technology in China, all of them are product technical agreements, and the number is too small. Although some enterprises have formed a series and are developing in the direction of generalization, the whole high-strength wear-resistant steel system is still very imperfect, especially the lack of universal standards. Due to the reasons of management system and operation mechanism, the material development work of enterprises is out of line with the standardization work, resulting in the lag of acceptance standards. This is extremely unfavorable to the standardized production and promotion of high-strength wear-resistant steel. Because the designer believes that the standard material is not mature, the selection of materials has a certain risk, and generally will not be selected, which seriously affects the promotion and use of new materials. The standard of high-strength wear-resistant steel should form a unified system with Chinese characteristics, which will play a key role in improving the standard of high-strength wear-resistant steel in the future and promoting the development and application of high-strength wear-resistant steel. Therefore, in accordance with the requirements of the national recommended standard system, the preparation of a standard system that can fully reflect the development level and needs of China's high-strength wear-resistant steel, and advanced scientific, practical and reasonable, lays a good foundation for the revision and improvement of high-strength wear-resistant steel standards in the future, and will be conducive to the standardized production and promotion of high-strength wear-resistant steel.
The main technical basis for the formulation of standards
The formulation of wear-resistant steel standards started in August 2007, first of all, according to market demand and market research, on the basis of collecting domestic and foreign information, determine the technical route of low-alloy high-strength wear-resistant steel as the standard, from the perspective of science, practicality, cost saving and resources, low alloy high-strength wear-resistant is an inevitable trend. Jinan Steel has developed JAR360F ~ JAR500F export wear-resistant steel, export Bis52J/53J, Bis21J, domestic market JGNM360 ~ JGNM500, B24S, etc. The data collected are mainly: Japan, Germany, Sweden, the United States, Australia and other countries of advanced enterprise standards, focusing on the reference of Germany, Sweden, Japan's wear-resistant steel technical conditions, combined with China's technical situation, and on this basis, to promote domestic wear-resistant steel production enterprises as soon as possible to mature. At present, there is no published national standard at home and abroad, so it is of great significance to formulate this standard.
The traditional wear-resistant steel generally refers to the impact hardening of high manganese steel under the impact load, the main purpose is to have a strong hardening ability after the impact stress in the process of use, but for the impact load is not large, because the work hardening cannot be fully obtained, its hardness and wear resistance can not be improved.
The main contribution of this standard is to break through the traditional concept of high manganese steel, develop low alloy high strength metal materials that are resistant to wear and impact under various operating conditions in the machinery industry, standardize the production of the industry, promote the improvement of the quality level of domestic products, provide resource-saving materials for the machinery industry, reduce the weight and corresponding cost of machinery and equipment.
The main technical content of the standard
1, the determination of the standard name: according to the use of this standard and the design principles of chemical composition, the standard name is: "High strength wear-resistant steel plate for construction machinery".
2. Scope of application:
This standard steel plate is suitable for wear resistant structural components of construction machinery such as mining, construction and agriculture. This standard applies to steel plates with a thickness of 6mm ~ 80mm.
3. Order content
This standard specifies the content of the order and specifies the information that the user must provide to ensure the accuracy of the order and that the product meets the customer's individual requirements and is realized through the ERP system. Therefore, when placing an order, the demander shall provide the following information: a) Standard number;
b) Brand name;
c) Specifications;
d) Size and contour accuracy requirements;
e) Weight;
f) Delivery status;
g) Use;
h) Special requirements.
The grades in this standard are divided into NM300, NM360, NM400, NM450, NM500, NM550 and NM600, which can adapt to the needs of users.
4, the brand representation method
In the existing technical conditions of high-strength wear-resistant steel products of enterprises, their product brands are not standardized. Referring to the standard situation of foreign enterprises and combined with the actual situation in China, for the introduction of high-strength wear-resistant steel brands in China, the current use of more chaotic problems, should adopt the naming method of China's brand, to be unified, to promote the use of general standards in the brand, to promote the development of China's high-strength wear-resistant steel standards, to achieve the generalization and serialization of high-strength wear-resistant steel standards. According to the product characteristics of wear-resistant steel and the user's practice in material selection, the wear-resistant steel grade adopts the combination of Chinese pinyin and Brinell hardness (HB) value. For example, NM450, NM is the first letter of "wear-resistant" Pinyin, and "450" is the Brinell hardness value.
5, size, shape, weight and allowable deviation
The size, shape, weight and allowable deviation of the steel plate comply with the provisions of GB/T709-2006, and the four thickness deviation categories of the standard are available for users to choose.
In order to increase the flexibility of the standard, maximize the requirements of users, and reflect the principle of maximum freedom of the standard, this standard stipulates that other steel plates with deviations in size and shape can be supplied by agreement between the supply and demand parties.
6. Smelting method
This standard specifies the smelting method as converter or electric furnace smelting, with LF off-furnace refining and VD or RH degassing. The main purpose is to determine whether to adopt advanced production methods to achieve user satisfaction according to the specific needs of users.
7. Delivery status
The characteristics of the product determines the delivery status of the product, in order to achieve the ideal comprehensive performance, reasonable delivery status is crucial, wear-resistant steel can be through scientific tempering process, obtain good strength and toughness combination performance, can also improve the hardness value of steel, to achieve the purpose of wear-resistant. This standard specifies the delivery status of hot rolling, controlled rolling, quenching + tempering, etc., according to the design of the grade of wear-resistant steel plate.
8. Chemical composition
The traditional wear-resistant steel used in construction machinery is generally high manganese steel, although high manganese steel has work hardening, but in its use process after the impact stress has a strong hardening ability, so it can only play its role under a large impact load, and for the impact load is not large working conditions, the hardness of the wear resistance can not be improved, and high manganese steel after work hardening, Its yield strength is not high, under the strong action, the workpiece will sometimes crack, it is difficult to achieve the expected service life. Therefore, compared with high manganese steel, in recent years, low alloy wear-resistant steel used to make small and medium-sized mechanical materials is also applied in the field of construction machinery, extending and expanding the use of high manganese steel, has been recognized by the machinery industry, and has become a trend.
(1) C content: The key to the design of this standard chemical composition is whether the hardness of the product can ensure the wear resistance of the material, and the hardenability and hardness of the steel depend on the carbon content. The design characteristics of this standard chemical composition at the same time fully consider the hardness and wear resistance and welding, forming, impact toughness and other factors, the use of lower carbon content, so that the steel through quenching to obtain a higher hardness at the same time, the steel plate has enough plasticity and toughness to meet the comprehensive mechanical properties of construction machinery.
(2) Alloying elements and content: In addition to C, Mn and Si, this standard alloying element also uses Cr, Mo, B and Ni as the main alloying elements. To ensure that the material has good hardenability, hardenability and comprehensive mechanical properties, the main purpose is to improve the wear resistance of the steel. The addition of Ti can play a role in refining grain. This standard focuses on the component design of Japanese, Swedish, German and other enterprise standards.
(3) Control of harmful elements This standard puts forward strict limits on the content of harmful elements P and S. Except NM360 class, other grades are limited to 0.010%.
9. Mechanical properties
Construction machinery high-strength wear-resistant steel products should have high hardness, high toughness, high strength, low carbon and low alloy and other inherent characteristics to ensure the realization of the goal of "high wear resistance, easy processing, saving materials and reducing costs". Referring to Japan, Sweden and other standards, the standard has designed seven wear resistance grades NM300, NM360, NM400, NM450, NM500, NM550 and NM600. Easy for users to select materials. While ensuring high hardness, maintain good impact toughness to resist external impact loads. According to reports, compared with ordinary steel plate, NM360 has not less than twice the wear resistance, NM400 is not less than 2.5 times the wear resistance; NM550 has not less than 4 times the wear resistance. Wear-resistant steel integrates the characteristics of high strength, high hardness, weldability and easy bending together, has excellent mechanical properties and good wear resistance, and can adapt to a variety of mining conditions under different working conditions. The wear-resistant steel formulated by this standard is a great progress in the research of construction machinery materials.
10. Surface quality
GB/T3274 is used for the surface quality in this standard, which has the characteristics of strong operability.
11. Inspection rules
This standard stipulates that the reinspection and acceptance rules of the inspection items shall comply with the provisions of GB/T17505.
