Posted 28 Dec 2010 18:59
Domestic high-speed wire rod production for nearly 30 years, production from the development of hundreds of thousands to more than 50 million t t, the maximum rolling speed from 10m / s up to 120m / s over the control of dimensional accuracy improvement from 0.30mm to 0.10mm, range from 50MPa strength of fluctuations is reduced to 10MPa. At home and abroad in recent years have appeared many new wire production process and technology. Wire rod production of new technology and new technology is divided into two categories: first, through micro-alloying strengthening mechanism or process to strengthen and improve the strength of rod and wire or plastic, such as carbon nanotube technology, ultra-fine grain steel production technology, ultra-fast cooling process, salt treatment process such as wire-line; the second is through process simplification and local process optimization, improve production rhythm, reduce production costs, such as continuous casting and rolling process, hot hot delivery and installation process, technology and the endless rolling process technology such as ultra-short . Which are briefly described below to add carbon nanotubes improved the strength of technology, ultra-fine grain steel production technology, control network ultrafast cooling process of carbon precipitation, salt bath and cooling technology and strip several short process technology and other latest technology and techniques. Nano-materials, also known as ultrafine particulate material, the nano-particles. Out of steel in the steelmaking process or refining process, by adding after the suppression of carbon nanotubes with a certain passivation layer (to prevent its being high temperature oxidation, and increased yield of carbon nanotubes). After fully mixing, the carbon nanotubes uniformly distributed in the steel matrix, the only play the role of dispersion strengthening, but also in the rolling process to prevent austenite grain growth, thus achieving the purpose of fine grain strengthening. Good effect is achieved, add the trace strength of carbon nanotubes made of wire an average of 30 ~ 50MPa. Most widely used of carbon constraints in its manufacturing costs are high, but with the improvement of its manufacturing technology, nano carbon fiber can be expected to improve the strength of steel pipe will be widely used in the future. Nanoparticles can also be used as a catalyst. Smelting process, the catalyst is mainly control the reaction time, improve the reaction efficiency and reaction speed. China's current production of low carbon steel, ferrite grain size is generally ASTMNo.8 ~ 9 level, the grain size is equivalent to 14 ~ 20 m, according to Hall-Petch equation, and now mass-produced carbon structural steel, as long as the grain refinement to less than 5 m, the strength to 400MPa can be increased to more than 200MPa. Grain refinement of low-alloy steel to about 2 m, the intensity can be increased to more than 800MPa. Therefore, to achieve ultrafine grain size is very important, but the key is to explore the refinement of the theory and technology. Ultra fast cooling after rolling (cooling rate of 100 ~ 400 ?/ s), can be quickly through mesh network carbide or ferrite temperature range (700 ~ 900 ?, to avoid generating network organization, significantly improve the drawing processing performance. The ordinary carbon steel, controlled cooling can be rolled out by F + P, B + M, all B, M + F, M and so the whole organization and properties of different composite materials, material yield strength in the range of 463 ~ 933MPa the change in tensile strength in the range 570 ~ 1136MPa changes, the total elongation of 7% in the range of 22% change in yield ratio in the 0.571 ~ 0.927 in the range. The encouraging results indicate the use of ultra fast cooling technology for control of TMCP and cooling path, has a very broad application prospects. Fast cooling technology can improve the wire strength, improve utilization of steel products. As high-speed wire rod rolling, material accumulated strain after strong deformation effects caused by severe temperature, finish rolling temperature up to 900 ~ 1000 ? How to use a continuous wire rolling in large deformation, and cooling after rolling with, to achieve grain refinement and strengthening, is a very pressing issue. In the study presented a new process route: continuous large deformation plus plus ultra fast cooling after rolling mist cooling process after spinning line. This route takes advantage of a continuous wire rod mill of the characteristics of large deformation by the rapid cooling process after rolling wire recrystallization inhibition, and finally through the phase transition of control to achieve the fine grain of the wire. Large deformation by continuous high temperature plus ultra-fast cooling the cold end of the suitable temperature plus the new technical routes, the use of common performance 20MnSi can produce 36mm diameter eligible for the following three high-performance steel. Ultra-fast cooling process can also effectively reduce the secondary carbide in the austenite grain boundary network was precipitated. For example, a large number of bearing steel GCr15 network carbide precipitation when the temperature range of 700 ~ 850 ? the implementation of ultra-fast cooling after rolling, you can make the material quickly through mesh carbide precipitation temperature range to minimize the residence time in this interval, which to avoid carbide precipitation network, received only scattered small carbides. Rapid cooling after rolling, the increase of undercooling, as well as reduce the pellet diameter and refine pearlite pearlite spacing effect. Wire-line molten salt bath treatment directly Ren (the DLP) technology is the first development Nippon Steel, the application main bridge cables variety of wire, high spring steel wire, wire for special purposes such as high-grade wire rope. Rod bath before entering the holding temperature is 800 ~ 850 ? bath temperature is 500 ~ 600 ? salt in the soaking time is about 60s. On both sides with the salt roller, through the rod from the bath, only with the wheel on both sides of contact is the overhead rod travels from the salt bath. Bath cooling line speed wire rod mobile 20m/min. The composition of salt NaNO3 and KNO3, mixed with electric heating molten salt bath quenching lead by simulating the process of isothermal transformation to maximize the proportion of wire sorbite (generally up to 95% to 98%, while Stelmor controlled cooling After the general 80% to 90%). Volatility in terms of performance, DLP also Patented rod close to the rod control is better than cold Stelmor article. The current big drop in steel prices, the plants are actively looking for ways to reduce production costs. Currently, Rod is studying at home and abroad (including profiles, wire, bar) ultra-short short process and the production process of new technology, the long process to replace the traditional production process, the general technical ideas are as follows: 1) short process technology and materials thin slab casting and rolling technology broadly similar, and solidification in continuous casting soft reduction or increase under the weight of equipment, easy to squeeze through the segregation of elements back often gather liquid ****, and cut each tail on cast billet, significantly improve the billet center segregation and center porosity. Process of continuous casting and rolling process production costs are lower than short-traditional technology, efficiency advantages are obvious, and the quality of the production of wire rod is more stable. 2) of the material flow process using liquid-**** ultra-short rolling **** technology, there is liquid in the **** strand, under the state of near-net shape rolling, and through the finishing, production of Rod and cooling products, process greatly simplified production rhythm doubled. A foreign research institutions have taken advantage of the technology end products such as direct production of fasteners.