(2) Good processing performance The cutting wheel manufactured by Shougang's original W6Mo5Cr4V2 is difficult in forging, heat treatment, car and grinding. The injection-infiltrated tungsten carbide cutting wheel base body is made of alloy structural steel, and the process performance is superior to that of high-speed steel. When the splitter wheel is injected, the roughness of the cutting edge surface does not increase, and the amount of deformation is easy to control. For the fastest-wearing cutting wheel blade, in the case of ion injection, more WC can be injected on other parts, such as the bearing neck on both sides, it can not infiltrate WC, in order to facilitate the grinding process after injection. Therefore, the process performance of the injection-infiltrated tungsten carbide cutting wheel is better than that of the original high-speed steel cutting wheel, and the processing cost is low.
(3) The performance price is equivalent to the price of high-injection tungsten carbide splitting wheel and high-speed steel cutting wheel, but the service life is 3 times higher, and the replacement time can be saved, the equipment operation rate can be improved, and the maintenance intensity and cost can be reduced. Bringing great economic benefits to the company.
3 Conclusion The use of high-energy ion-injection WC technology is an important breakthrough in the manufacturing technology of rolled steel wear parts in recent years, and also an important breakthrough in the surface modification technology of mechanical parts. Recently, this technology has been tested on rolled steel guide rolls and guide plates, and has achieved satisfactory results. If high-energy ion-injection WC technology is promoted and applied in the cutting wheel, guide roller, guide plate and other wear-resistant parts of the domestic rolling industry, its economic and social benefits will be considerable.
Cold-rolled hood furnace hydrogen purge process and board surface cleanliness control Jiang Yingwei (Pangzhihua Iron and Steel (Group) Co., Ltd. Cold Rolling Plant, Panzhihua 617022, Sichuan) combines hydrogen purge time and purge volume with rolling oil volatilization rate Matching, better control of the cleanliness of the board.
1 Introduction The all-hydrogenated steel coil has good plasticity, although the tensile strength and yield strength decrease slightly, but the performance is more uniform, while the surface of the strip has less impurities and carbon deposition, the surface is cleaner, and the surface coating can be enhanced. Adhesion reduces corrosion on the surface of the strip.
In the hydrogen annealing process, hydrogen has two effects: one is to heat the cooling of the strip steel and the other is to purify the surface residue of the strip. The surface quality of the strip after annealing (such as residual carbon defects) is closely related to the hydrogen purge process.
The cleanliness of the cold-rolled strip after rolling will not only cause zinc grain defects in the hot-dip galvanizing process, but also affect the surface quality of the carbon ribbon.
Residues with steel plate surface have an important influence on the leveling of the sticky roller and the roller printing. In severe cases, the use of wet flattening cannot be well eliminated. The residue in the wet season of the rainy season will also have a catalyzed effect on the corrosion of the intermediate process of the cold-rolled strip, which will aggravate the formation and development of rust.
2 Factors affecting the cleanliness of the board surface Residues and removal methods of the cold rolled strips (metal clumps mechanical inclusions and oily contaminants) mainly come from the cold rolling process. In the high temperature and high pressure rolling deformation zone, the strip and the roll wear generate a large number of iron powder particles with a diameter of less than 1 Lm. The presence of these iron powder particles enhances the abrasive wear and brings more iron powder. The surface adsorption area is increased, and a large amount of rolling innovation and AC oil, miscellaneous oil and other forms of high molecular polymers are adsorbed to form a large amount of surface residues. Among them, hydrocarbon is the source of residual carbon in the post-process, which can hinder the sintering of iron powder during annealing and the occurrence of residual iron.
Cold-rolled products are generally brightly annealed in a hood furnace without degreasing after cold rolling. To ensure a clean surface and good quality of the strip after annealing, the surface defects caused by the indentation produced in the post-process are prevented. It is necessary to remove the residual emulsion on the surface of the strip before further processing of the cold rolled strip. The usual method is to use a cleaning agent at the end of the rolling mill, electrolytic cleaning off-line or on-line, evaporation degreasing, chemical cleaning, and burning off lubricant residues in the annealing. The cold rolling mill of Panzhihua Iron & Steel Co., Ltd. uses annealing to remove the emulsion.
If the surface of the strip is still annealed with iron powder and other metal scraps or hydraulic oil after annealing, it is easy to leave harmful deposits such as so-called / carbon black 0, / annealing stain edge 0 on the strip surface. When harmful deposits diffuse into the metal matrix, it may be difficult to infiltrate paint, coating materials, and liquid metals. At the same time, the emulsion adhering to the surface of the strip during annealing causes catalytic decomposition of the carbon-containing gas, which causes the CO/CO ratio in the protective atmosphere to be deregulated, resulting in the deposition of carbon at a certain temperature.
The factors affecting the cleanliness of the board are due to the product specification of Panzhihua Cold Rolling Mill being 0125 0mm, spanning 2 process lubrication zones, and only one design rolling oil, all of which rely on changing the rolling oil concentration to meet the lubrication requirements, so The lubricity of the emulsion is high, but the cold rolling mill has no degreasing unit. The rolling oil remaining on the strip surface can only be removed by the annealing process. This requires the emulsion to have good cleaning and combustibility, and is easy to eliminate. No impurities or board marks remain after burning. For the lubricant in the emulsion, a strong washing ability and the ability to accommodate mechanical inclusions and oily dirt are required, but the removal burden of the lower process (annealing) is correspondingly increased. Therefore, in addition to improving the filtration precision of the emulsion, the content of the active oil must be lowered, that is, the saponification value of the rolling oil should not be too high, and the reduction of the active oil content reduces the lubricity of the rolling oil, so the cleaning property, The combustibility and lubricity are contradictory.
When the automobile sheet is cold-rolled, if the saponification value of the rolling liquid is high and the ash content is high, the combustion fluid of the rolling liquid is poor, which often causes carbon coking on the surface of the annealed strip, in the form of dark spots and emulsions. Sticky sand. The emulsion sticking sand is related to the dose of the emulsion remaining on the surface of the strip after rolling. In order to reduce the residual emulsion dose, the concentration should be appropriately reduced. In addition, in order to reduce the hardness of water and improve the anti-corrosion performance of the emulsion, sodium carbonate is often added to the emulsion, but its high content will affect the quality of the cold-rolled sheet surface, such as the generation of dark spots, so it is usually controlled to a few thousandths. concentration.
From the production point of view, the lubricating ability of the emulsion and the surface quality of the strip are opposite. For automotive panels, in addition to considering the viscosity and composition of the emulsion, good washing power and low coking rate and ash are required. The low viscosity of the emulsion makes the surface of the strip brighter, and the higher viscosity makes the surface less lustrous.
In fact, the emulsion which can be completely burned and volatilized during annealing and does not leave coke residue on the surface of the strip steel does not exist. Therefore, measures must be taken to remove the emulsion in the last frame of the continuous rolling mill, such as using a special cleaning agent. Pangang currently uses compressed air to purge, but the effect is not satisfactory.
3 Introduction to the hydrogen blowing process Protection gas composition curve In the typical hood furnace annealing process, the curve of the protective gas composition with time and temperature is shown in Figure 1.
1) Hydrogen concentration 2) Control temperature 3) Core temperature 4) Flue gas concentration 5) Methane concentration can be seen from Figure 1: (1) When heated to the 3h, the flue gas concentration begins to increase greatly, and the coil temperature is At 300 500 e, the concentration of flue gas after the decomposition of the emulsion reaches a peak, which is the evaporation phase of the emulsion, which can be purged with a large flow of hydrogen.
When the coil temperature is 600 620 e, (for 5 5 h before and after), the emulsion is evaporated.
(2) The methane concentration in the furnace atmosphere reaches the maximum value twice, and the first peak peak appears at a heating temperature of about 700 e. The C in the duration of 5 6 h is derived from rolling oil and should be blown off the second one. The peak of the peak appears in the heat-insulating section where the heating is completed. The C in the CH is mainly derived from the steel. In order not to decarburize the steel, the methane generated at this time should not be blown away.
Since the reaction in the chemical reaction equation C 2H is stopped, the CH content in the cooling section is greatly reduced, and the H content is close to 100 after the CH reaches the second peak.
Variations in the dew point of the furnace table After the pre-purge of the furnace space is completed, the dew point is usually measured as 50 e. After the final nitrogen purge, the dew point is usually reached. During the heating of the coil, water and oil are evaporated, and the dew point of the annealing atmosphere is increased to about 30 e. The specific value of the dew point depends on the total oil content, heating rate and hydrogen purging speed of the strip surface. Due to the use of different rolling oils, the cleaning methods of cold rolling vary, and the pre-purging method of the coils used is also different, so there is a large difference in the total amount of emulsion and the amount of water blown away.
During the annealing process, the dew point of the annealing atmosphere is completely controlled by the above factors. When the core temperature is 600 620 e, the oil and gas evaporation is completed, and after the annealing space is purged, the dew point is reduced to about 50 e, and the trace oil and water remaining in the annealing space are less.
If the mill uses different rolling oils, the dew point of the furnace will change differently.
The decarburization mechanism during annealing and at the beginning of cooling is: C and H form methane to remove residual carbon on the strip surface. The decarburization ability of pure hydrogen is strong, and the dew point has little effect on the decarburization ability under pure hydrogen, and has no effect on the formation of methane.
Therefore, pure hydrogen can be used for annealing at a low dew point, which avoids oxidative burning of alloying elements such as Al, Si, Cr, and Ti.
Therefore, annealing in a hood furnace using low dew point total hydrogen as a protective atmosphere can achieve high surface cleanliness and minimize oxidation of alloying elements.
The principle of the hydrogen purge process is established. If the hydrogen purge time and the purge amount match the oil vapor volatilization rate of the rolling oil, the surface cleanliness of the strip is the best, if the surface deposit is not excessive before annealing. The carbon content of the Ford surface can be as low as 1 mg/m. Therefore, a gap-type hydrogen purge should be performed according to the change of the composition in the annealing protective atmosphere, and different hydrogen purge flow rates and corresponding times are selected in different annealing temperature ranges. It is necessary to consider the thickness of the strip (the amount of emulsion residue of the thin material is large), the size of the furnace, the temperature change of the annealing process, and the temperature change when the heating is abnormal. This not only saves hydrogen consumption, but also guarantees the quality of the annealed coil, especially the surface quality.
Therefore, a reasonable hydrogen purge process is to use a small flow purge 3 h before heating, a large flow purge at 4 10 h, and a purge at 14 h. Moreover, it should prevent the hydrogen blowing from ending prematurely, so that a small amount of tar and moisture emulsion remaining on the flange of the furnace is uncleaned, and there will be deposition of decomposition products on the relevant discharge pipe of the furnace or the waste hydrogen/oil burner pipe. Long-term accumulation will affect the normal production.
The improvement of the hydrogen blowing process and the effect of the hydrogen blowing process before the improvement have the following disadvantages: (1) There is almost no difference in the purging process between the carbon steel and the deep drawing steel, but the annealing process is double step annealing and single step annealing, respectively. The evaporation and decomposition processes of the emulsion are also different.
(2) There is no connection between the purge process and the temperature control and strip temperature.
(3) The heating cover has been running for 6 years, and the specific working conditions have changed a lot.
(4) Only the time interval and the flow rate are set, and there is no corresponding relationship with the annealing temperature of the strip steel. Therefore, in the case where the heating capacity of the heating cover is insufficient or there is a failure, the hydrogen purge is in a wasteful or ineffective purge state.
To this end, according to the actual production conditions and equipment conditions, the hydrogen blowing process has been improved.
The 6917t steel coil was processed according to the CQ grade process, and the 7018t steel coil was processed according to the DDQ grade process. The test showed that its oxidation, carbon edge, surface decarburization, surface residual carbon and appearance were normal, and there was no quality problem. No Coke-level phenomenon The new CQ-class process saves about 22m of hydrogen compared to the original process. 5 Conclusion Through process improvement, certain results have been achieved, hydrogen purge is more reasonable, plate quality is good, and hydrogen consumption is greatly reduced for further research and The relationship between strip corrosion in the rainy season lays the foundation.
To improve the cleanliness of the board, further efforts should be made in the following aspects: (1) Improve the control level of the emulsion, that is, monitor the physical and chemical indicators, improve the monitoring means, and ensure good concentration, temperature and rack flow.
(2) Optimize the grinding process of the roll, use the low roughness steel coil level to control the temperature / e strip temperature / e time setting / h flow setting / m roll, strictly control the rack oil leakage, ensure the emulsion system In particular, the device for filtering impurities is working well.
(3) Industrial research on the decomposition characteristics of residual emulsion on the surface of steel strip after rolling at high temperature.
(4) In combination with the wet leveling process of the leveling unit, the impurities accumulated on the surface of the strip are further removed.
(5) Regularly clean the flange of the furnace and the inner wall tar of the inner cover.
(6) Improve the effect of the rolling mill on the strip purging, and consider the equipment improvement.
Li Huxing 1 Friction and lubrication of pressure processing [M] 1 Beijing: Metallurgical Industry Press, 19931 Analysis of the reasons for the effect of regenerative heating furnace Zhou Hongcheng (Nanjing Iron and Steel Group Co., Ltd., Nanjing 035) In the application process of combustion technology, the traditional furnace design theory should also be followed, and the gas should be subjected to more stringent dehydration treatment.
Date of revision: 2002 11 05 1Overview The regenerative heating furnaces that have been put into use in China have three types: built-in channel type with regenerator and heating furnace body, and external storage of regenerator and heating furnace. Channel type, regenerative burner heating furnace. These three types of regenerative heating furnaces are used in three rolling mills of Nanjing Iron and Steel Group Co., Ltd. Among them, the first type of heating furnace has a relatively compact layout, a small footprint, and a low investment, which is suitable for the transformation of the production line where the site is tight. However, its structure is complex, the technical content is high, the construction is difficult, and the oven process is strict. This kind of heating furnace is used in the Nangang Bar Plant. Since the furnace has been put into operation, it has exposed some problems and affected the use effect. Some of them are common problems affecting the use of the regenerative heating furnace.
2 basic conditions Nangang bar plant regenerative heating furnace technical parameters.
The heating furnace body is integrally cast, and the heating section and the soaking section are separated by water beams. The furnace walls on both sides are 1000mm thick, and the air and gas heat storage channels are built in. The regenerator is located under the foundation of the furnace, and there are 16 regenerator cages at the bottom of the furnace. There are 6 sides on the heating section, and there are 2 empty and gas cages in the heating section. 31 sets of nozzles. The heating furnace is provided with two sets of reversing systems, which have two modes of timing/fixing temperature, and the actual production is reversed in a timing mode. Air and gas rolling steel for 8 regenerators in heating section and soaking section
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