Alloy steel production process

Abstract

The invention relates to the technical field of alloy steel production, and discloses an alloy steel production process which comprises the steps of screening of round steel specifications and quality, furnace entering, heating, dephosphorization, rolling, saw cutting, cooling bed entering, pit entering for slow cooling, finishing and coping and bar finished product inspection and acceptance. The scale on the surface of strip steel or steel is broken and peeled off in the repeated bending process, the surface of round steel becomes smooth and flat, after the scale is removed through the scale breaking process, the rolling force can be effectively reduced, and the rolling process is more stable; the surface of the round steel can be in better contact with a heat treatment medium, so that heat is uniformly transferred into the round steel, more uniform structure transformation of the round steel in the heat treatment process can be ensured, the heat treatment quality is improved, and indentations or scratches on the surface of the round steel caused by residual oxide scales are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of alloy steel production, in particular to an alloy steel production process. Background Art

[0002] Alloy steel is made on the basis of carbon steel. In order to improve the performance of the steel, one or more alloying elements are purposefully added during the smelting process. Alloy steel can achieve very high strength through the strengthening effect of alloying elements. At the same time, reasonable alloy ratio and heat treatment process can enable it to maintain good toughness.

[0003] In the process of alloy steel production, if the scale on the round steel surface cannot be completely removed, it is very easy to cause the surface of the round steel to be uneven. In the subsequent processing, such as rolling or machining, these residual iron oxide scales will form indentations or scratches on the steel surface. The indentations or scratches will make the parts prone to cracks at these stress concentration points when subjected to external forces, which will lead to part failure. Especially for some alloy steel round steels containing alloy elements such as chromium and nickel used in occasions with high corrosion resistance requirements, the residual iron oxide scale on the surface will greatly reduce its corrosion resistance, making it unable to exert its due performance advantages, resulting in low product performance and a large proportion of defective products. To address this problem, we have proposed an alloy steel production process. Summary of the invention

[0004] The purpose of the present invention is to provide a process for producing alloy steel to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: an alloy steel production process, including the selection of round steel specifications and quality, furnace entry, heating, dephosphorization, rolling, sawing, cooling bed, pit slow cooling, finishing and grinding, and finished bar inspection and acceptance;

[0006] S1. In the round steel specification quality screening stage, round steel with a diameter range of 50 mm to 160 mm is selected, wherein Ni≤0.25%, Cu≤0.35%, and Mo≤0.06% in the round steel are used to determine whether the quality of the round steel meets the requirements according to the proportions thereof;

[0007] S2. During the furnace entry, heating and dephosphorization stages, the round steel and billet need to be classified according to their size, weight, shape and surface quality. Different furnace time should be selected according to different categories. The end point control target value of converter smelting steel is: carbon content>0.10%, P<0.015%, and the number of re-blowing times is ≯2 times to ensure C-T coordinated steel tapping. High-pressure water is used for descaling during rolling. The descaling working pressure is set to be not less than 12Mpa. 800 rolling mill is used for descaling rolling to remove the surface iron oxide scale. If the iron oxide scale is not removed cleanly, the steel tapping should be stopped immediately, and the fitter should be arranged to check the nozzle and pressure. Steel can be tapped only after the treatment. For the billet that has been discharged from the furnace, the 800 rolling mill should be notified to use descaling rolling to remove the surface iron oxide scale to avoid defects such as surface pitting caused by the rolling and pressing of the iron oxide scale.

[0008] S3. During the rolling stage, the starting rolling temperature is greater than 1001°C, and the final rolling temperature is greater than 851°C. When the descaling is not clean, the descaling process is used for rolling. When the steel passes through a set of upper and lower rollers, the special design of the rollers will cause the steel to bend and deform. Since the toughness of the iron oxide scale is different from that of the steel matrix, when the steel is bent, the iron oxide scale cannot be deformed synchronously like the steel, resulting in stress concentration inside it. During the continuous bending process, the iron oxide scale will crack due to being unable to withstand these stresses. With the subsequent rolling process, these cracks will gradually expand, and eventually the iron oxide scale will peel off from the surface of the steel. After removing the iron oxide scale, the steel surface is directly exposed to the external environment. After appropriate anti-corrosion treatment (such as painting, galvanizing, etc.), it can better prevent the corrosive medium from contacting the steel matrix, thereby significantly improving the corrosion resistance of the steel.

[0009] S4. During the sawing, cooling bed and slow cooling in the pit, the length of the hot sawing head and tail should be strictly carried out in accordance with the operating procedures. The length can be increased but must not be shorter than the required length. If there is any uncut steel, the sawing length of the corresponding batch should be increased by about 49 to 201 mm. The round steel shall not be cooled by a blower on the cooling bed. After the round steel is produced, it is slow cooled in the slow cooling pit. The slow cooling time is more than 24 hours. After the round steel is produced, the internal structure is in an unstable state;

[0010] S5. During the finishing and grinding stage, do not bend the finished product, do not scratch the surface, clean the ears, scratches, burrs and flash on the surface of the finished product, and inspect the surface quality of the finished product. The scratches, cracks, folds, scars, ears, burrs and flash on the surface must be ground clean, and do not allow products that are not ground clean to leave the factory. For round steel that exceeds the grinding standard range, it must be discarded. The absence of scratches, cracks and other defects on the surface will make the product look smoother and neater, and improve the overall aesthetics of the product;

[0011] S6. During the inspection and acceptance stage of finished bar products, the chemical composition (melting analysis), non-metallic inclusions, end hardenability, flaw detection, surface and size of round steel can improve the quality of the product;

[0012] Preferably, the size of the round steel in the round steel specification quality screening stage is Φ50 to Φ160 mm.

[0013] Preferably, the furnace entry, heating and dephosphorization stages include the following steps:

[0014] S2.1. Use cranes or cranes to transport round steel of different sizes to the raw material area of ​​the converter workshop. Before placing them in the converter, use sandblasting to remove rust. Sandblasting can make the surface of the round steel smoother and cleaner, so as to facilitate subsequent processing.

[0015] S2.2. Adjust the time in the furnace according to the size of the round steel. The time of 150 square cold billet in the furnace shall not be less than 90 minutes, the time of 240 square cold billet in the furnace shall not be less than 149 minutes, the time of 280 square cold billet in the furnace shall not be less than 149 minutes, the time of 300×430 square cold billet in the furnace shall not be less than 239 minutes, and the time of 350×430 square cold billet in the furnace shall not be less than 269 minutes. When the billet is hot-charged, the time in the furnace shall be controlled as follows: the time of 150 square cold billet in the furnace shall not be less than 76 minutes, the time of 240 square billet in the furnace shall not be less than 121 minutes, the time of 280 square billet in the furnace shall not be less than 141 minutes, the time of 300×430 square billet in the furnace shall not be less than 181 minutes, and the time of 350×430 square billet in the furnace shall not be less than 201 minutes, so as to ensure the uniformity of the overall temperature of the billet and prevent the visible yin and yang sides. In the heating process of the billet, "yin and yang sides" is a figurative term. It refers to the obvious temperature difference area on the surface of the billet, just like the billet has two different "sides", one with high temperature and the other with low temperature. Visually, the part with high temperature may be brighter in color (such as bright red), while the part with low temperature is darker in color, such as dark red or close to the original color of the billet, forming a sharp contrast, similar to the difference between yin and yang. The yin and yang surface will cause uneven deformation of the billet in the subsequent processing. For example, in the rolling process, the metal fluidity of the part with high temperature is better and it is easy to deform, while the part with low temperature is difficult to deform, which will cause the billet to have shape defects such as bending and twisting, affecting the dimensional accuracy and appearance quality of the product.

[0016] S2.3. Use a programmable logic controller to count the time from the beginning of the heating process according to a pre-written program. When the heating furnace starts the heating program, the timer of the programmable logic controller starts working at the same time. It can accurately record the passage of every second. Once the time reaches the set 20-minute threshold, the programmable logic controller can automatically trigger the instruction to lower the heating temperature according to the program logic. The timing accuracy of the programmable logic controller can reach the millisecond level, which can meet the requirements for precise time monitoring, and can also resist adverse factors such as electromagnetic interference in industrial environments.

[0017] Preferably, the sandblasting rust removal method in S2.1 is to remove the rust on the surface of the round steel by high-speed spraying of sand particles. This is because impurities such as rust and oil stains will affect the quality of the molten steel during the smelting process and increase the impurity content.

[0018] Preferably, the controller is used in S2.3 because when the accident time is greater than 20 minutes, if the heating temperature is not lowered, the steel billet will continue to absorb heat. For metal materials, when heated at high temperature for a long time, its grains will gradually grow. Once the grains grow to a certain extent, the mechanical properties of the steel billet will be affected, the toughness will be reduced, and the strength will change.

[0019] Preferably, the rolling stage includes:

[0020] S3.1. Use a hand-held grinder to clean the places with sharp angles and burrs on the rolling groove, baffles, guides, rollers, etc. The hand-held grinder is flexible to operate. The purpose of grinding is that if there are sharp angles and burrs on the rolling groove, baffles, guides, rollers, etc., it will directly affect the surface quality of the steel. After grinding, the surface of the rolling groove and other parts will be smoother, which can make the steel receive uniform force during the rolling process, thereby ensuring the dimensional accuracy of the steel;

[0021] When changing rolls and taking over, the roll grooves of the 800 rolling mill should be checked for severe wear and tear, meat loss, etc. Pay special attention to the surface of the pusher to avoid scratches and abrasions on the surface of the red steel, which may cause defects such as discontinuity and shallow folding on the surface of the finished product.

[0022] S3.2. The cutting length of the 400t shear should be carried out according to the operating procedures. When producing large square billets, the 400t shear must cut the head and fishtail defects cleanly. Billets with fishtails will cause deviations in the length after cutting.

[0023] S3.3. During the shift inspection and mid-term shutdown, the wear of the rolling groove should be checked for any serious cracks or meat loss, whether the cooling water pipe nozzle is aligned with the rolling groove, whether the connecting hose is leaking, etc. Check whether the guide is aligned, whether there is iron clamping, wire drawing, guide roller jamming, etc. If any abnormality is found, the machine should be stopped and handled or replaced in time. This method can ensure the safety of production and the continuity of the production process.

[0024] S3.4. During the rolling process, the material shape and size of each rack should be measured every hour, and the red steel surface and size of each rack should be checked by burning wood prints and other methods to ensure that there are no defects such as ears, misaligned rollers, ovals, etc. on the surface of the finished product. Checking the red steel surface and size by burning wood prints and other methods can effectively detect surface defects. Discovering and solving these problems can ensure the surface quality of the finished steel, making it smooth and flat, and meeting the appearance requirements of high-quality products.

[0025] Preferably, the finishing and grinding stage includes: S4, the round steel is put into the pit for slow cooling after coming down from the cooling bed, and the slow cooling time is not less than 24 hours. After the round steel comes down from the cooling bed, it is transferred to the slow cooling pit by lifting equipment (such as a crane). The slow cooling pit is usually an underground or semi-underground structure with a certain depth and capacity, which can accommodate a certain number of round steels. When placing the round steels, try to ensure that the round steels are placed stably and arrange the spacing between the round steels reasonably to ensure uniform cooling effect. If the round steels are placed too closely, it will affect air circulation and cause uneven cooling. Unstable placement may cause poor local contact of the round steels and affect heat transfer. The uniform cooling effect can make the organizational structure of the round steel more uniform and avoid quality problems caused by differences in local cooling rates.

[0026] Preferably, the finishing and grinding stage includes:

[0027] S5.1. Use a hand-held grinder or angle grinder for grinding. These tools use a high-speed rotating grinding wheel to contact the workpiece surface, and use the grinding action of the grinding wheel to remove ears and flash. For larger ears, you can first use a coarse-grained grinding wheel (such as 35-60 mesh) to quickly grind away most of the excess material, and then switch to a fine-grained grinding wheel (such as 109-180 mesh) for fine grinding to make the surface smooth;

[0028] S5.2. Inspectors observe the surface of finished products directly with their naked eyes. Under good lighting conditions, they check for obvious defects on the surface of products, such as scratches, ears, burrs and flash. At the same time, a magnifying glass can be used to improve the accuracy of the inspection. For some relatively small defects, such as slight scratches or small burrs, a magnifying glass can be used to see more clearly. Generally, a magnifying glass with a magnification of 5-10 times can meet most surface quality inspection needs;

[0029] S5.3. Feel the surface of the product to see if there are any defects. For some uneven surfaces, such as scars or folds, you can feel the unevenness of the surface by touching it. When checking the surface quality of metal sheets, you can slide your fingers across the surface of the sheet to detect tiny undulations on the surface, thereby discovering possible defects.

[0030] Preferably, the finished bar product inspection and acceptance stage includes:

[0031] S6.1. Atomic Emission Spectroscopy (AES) is used to detect chemical composition (melting analysis). The detection is carried out by exciting atoms in the round steel sample to emit light with a specific wavelength. The wavelength and intensity of this light are related to the type and content of the element;

[0032] S6.2. Use the energy spectrum analysis method in the electron microscope to detect the content of inclusions. The energy spectrum analysis method can provide high-resolution microscopic morphological images, which can more clearly observe the detailed features of the inclusions. EDS can perform elemental analysis on the inclusions and determine the chemical composition of the inclusions.

[0033] S6.3. Process the round steel into standard specimens, heat them to the specified austenitizing temperature, and then spray quench them at one end. Since the cooling rate gradually decreases from the quenching end to the other end during quenching, the structure and hardness also change accordingly. By measuring the hardness distribution along the length of the specimen, the hardenability of the round steel can be evaluated. The end quenching temperature is 849℃±5℃.

[0034] S6.4. Using ultrasonic flaw detection, when ultrasonic waves propagate in round steel, they will produce reflection, refraction and scattering when encountering defects (such as cracks, pores, etc.). By detecting these changes in ultrasonic waves, the location, size and nature of the defects can be determined;

[0035] S6.5. Inspectors should directly observe the surface of round steel with naked eyes to check whether there are defects such as scratches, folds, ears, burrs and flash. If necessary, auxiliary tools such as magnifying glasses can be used to observe more subtle surface defects;

[0036] S6.6. Use calipers, micrometers, tape measures and other conventional measuring tools to measure the diameter, length and other dimensions of round steel;

[0037] S6.7. Round steel with unqualified surface can be re-grinded and then go to the re-grinding stage. Those that cannot be re-grinded will be scrapped. Round steel with unqualified performance can be salvaged and then heat treated again and go to the re-grinding stage. Round steel with unqualified performance and cannot be salvaged will be reviewed and scrapped.

[0038] Compared with the prior art, the present invention provides an alloy steel production process, which has the following beneficial effects:

[0039] 1. This alloy steel production process uses the rolling force of the roller to make the iron oxide scale on the surface of the strip or steel crack and peel off during repeated bending, so that the surface of the round steel becomes smooth and flat. After removing the iron oxide scale through the descaling process, the rolling force can be effectively reduced, making the rolling process more stable. For round steel that needs to be heat treated, after descaling, the surface of the round steel can better contact with the heat treatment medium, so that the heat is evenly transmitted to the inside of the round steel, which can ensure that the round steel obtains a more uniform organizational transformation during the heat treatment process, improve the quality of the heat treatment, and reduce the occurrence of indentations or scratches on the surface of the round steel caused by residual iron oxide scale.

[0040] 2. The alloy steel production process uses the method of slow cooling in the pit. During the production process of round steel, uneven tissue transformation will produce tissue stress. The slow cooling process can gradually release the tissue stress. When the slow cooling time is greater than 24 hours, the tissue stress can be more fully released to avoid deformation or cracking of the round steel due to tissue stress accumulation during subsequent processing or use.

[0041] 3. The alloy steel production process controls the accident time of the heating furnace to no more than 20 minutes. A shorter accident time helps maintain the uniformity of the internal structure of the steel. During the heating process, the internal structure of the steel will undergo austenitization and other transformations. If the accident time is too long, the temperature difference in different parts of the steel will lead to uneven organizational transformation. Controlling the accident time to no more than 20 minutes is conducive to reducing the occurrence of safety hazards, thereby ensuring the stability of round steel during the production process, thereby improving the safety of round steel during the production process.

[0042] 4. The alloy steel production process adjusts the furnace time according to the size of the round steel to avoid the occurrence of yin-yang surface. When the round steel avoids the yin-yang surface phenomenon, its dimensional accuracy can be better controlled in the subsequent processing process. The round steel without yin-yang surface is heated evenly. Under the action of the rolling roller, the metal flow and deformation of each part are more coordinated, which can effectively improve the dimensional accuracy of the round steel products and meet the needs of high-precision processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the process of the present invention;

[0044] Figure 2 It is a schematic diagram of the specific steps of the present invention. DETAILED DESCRIPTION

[0045] like Figure 1-2 As shown, the present invention provides a technical solution: an alloy steel production process, including the selection of round steel specifications and quality, furnace entry, heating, dephosphorization, rolling, sawing, cooling bed, pit slow cooling, finishing and grinding, and finished bar inspection and acceptance;

[0046] S1. In the round steel specification quality screening stage, round steel with a diameter range of 50 mm to 160 mm is selected, wherein Ni≤0.25%, Cu≤0.35%, and Mo≤0.06% in the round steel are used to determine whether the quality of the round steel meets the requirements according to the proportions thereof;

[0047] S2. During the furnace entry, heating and dephosphorization stages, the round steel and billet need to be classified according to their size, weight, shape and surface quality. Different furnace time should be selected according to different categories. The end point control target value of converter smelting steel is: carbon content>0.10%, P<0.015%, and the number of re-blowing times is ≯2 times to ensure C-T coordinated steel tapping. High-pressure water is used for descaling during rolling. The descaling working pressure is set to be not less than 12Mpa. 800 rolling mill is used for descaling rolling to remove the surface iron oxide scale. If the iron oxide scale is not removed cleanly, the steel tapping should be stopped immediately, and the fitter should be arranged to check the nozzle and pressure. Steel can be tapped only after the treatment. For the billet that has been discharged from the furnace, the 800 rolling mill should be notified to use descaling rolling to remove the surface iron oxide scale to avoid defects such as surface pitting caused by the rolling and pressing of the iron oxide scale.

[0048] S3. During the rolling stage, the starting rolling temperature is greater than 1001°C, and the final rolling temperature is greater than 851°C. When the descaling is not clean, the descaling process is used for rolling. When the steel passes through a set of upper and lower rollers, the special design of the rollers will cause the steel to bend and deform. Since the toughness of the iron oxide scale is different from that of the steel matrix, when the steel is bent, the iron oxide scale cannot be deformed synchronously like the steel, resulting in stress concentration inside it. During the continuous bending process, the iron oxide scale will crack due to being unable to withstand these stresses. With the subsequent rolling process, these cracks will gradually expand, and eventually the iron oxide scale will peel off from the surface of the steel. After removing the iron oxide scale, the steel surface is directly exposed to the external environment. After appropriate anti-corrosion treatment (such as painting, galvanizing, etc.), it can better prevent the corrosive medium from contacting the steel matrix, thereby significantly improving the corrosion resistance of the steel.

[0049] S4. During the sawing, cooling bed and slow cooling in the pit, the length of the hot saw cutting head and tail should be strictly carried out in accordance with the requirements of the operating procedures. The length can be increased but must not be shorter than the required length. If there is any incomplete sawing, the sawing length of the corresponding batch should be increased by about 49 to 201 mm. The round steel shall not be cooled by a blower on the cooling bed. After the round steel is produced, it enters the slow cooling pit for slow cooling. The slow cooling time is greater than 24 hours. After the round steel is produced, the internal structure is in an unstable state. When the slow cooling time is greater than 24 hours, the tissue stress can be more fully released to avoid deformation or cracking of the round steel due to tissue stress accumulation during subsequent processing or use;

[0050] S5. During the finishing and grinding stage, do not bend the finished product, do not scratch the surface, clean the ears, scratches, burrs and flash on the surface of the finished product, and inspect the surface quality of the finished product. The scratches, cracks, folds, scars, ears, burrs and flash on the surface must be ground clean, and do not allow products that are not ground clean to leave the factory. For round steel that exceeds the grinding standard range, it must be discarded. The absence of scratches, cracks and other defects on the surface will make the product look smoother and neater, and improve the overall aesthetics of the product;

[0051] S6. During the inspection and acceptance stage of finished bar products, the chemical composition (melting analysis), non-metallic inclusions, end hardenability, flaw detection, surface and size of round steel can improve the quality of the product;

[0052] During the screening stage of round steel specifications and quality, the size of round steel is Φ50~Φ160mm.

[0053] The following steps are included in the furnace entry, heating and dephosphorization stages:

[0054] S2.1. Use cranes or cranes to transport round steel of different sizes to the raw material area of ​​the converter workshop. Before placing them in the converter, use sandblasting to remove rust. Sandblasting can make the surface of the round steel smoother and cleaner, so as to facilitate subsequent processing.

[0055] S2.2. Adjust the time in the furnace according to the size of the round steel. The time of 150 square cold billet in the furnace shall not be less than 90 minutes, the time of 240 square cold billet in the furnace shall not be less than 149 minutes, the time of 280 square cold billet in the furnace shall not be less than 149 minutes, the time of 300×430 square cold billet in the furnace shall not be less than 239 minutes, and the time of 350×430 square cold billet in the furnace shall not be less than 269 minutes. When the billet is hot-charged, the time in the furnace shall be controlled as follows: the time of 150 square cold billet in the furnace shall not be less than 76 minutes, the time of 240 square billet in the furnace shall not be less than 121 minutes, the time of 280 square billet in the furnace shall not be less than 141 minutes, the time of 300×430 square billet in the furnace shall not be less than 181 minutes, and the time of 350×430 square billet in the furnace shall not be less than 201 minutes, so as to ensure the uniformity of the overall temperature of the billet and prevent the visible yin and yang sides. In the heating process of the billet, "yin and yang sides" is a figurative term. It refers to the obvious temperature difference area on the surface of the billet, just like the billet has two different "sides", one with high temperature and the other with low temperature. Visually, the part with high temperature may be brighter in color (such as bright red), while the part with low temperature is darker in color, such as dark red or close to the original color of the billet, forming a sharp contrast, similar to the difference between yin and yang. The yin and yang surface will cause uneven deformation of the billet in the subsequent processing. During the rolling process, the metal fluidity of the part with high temperature is better and it is easy to deform, while the part with low temperature is difficult to deform, which will cause the billet to have shape defects such as bending and twisting, affecting the dimensional accuracy and appearance quality of the product.

[0056] S2.3. Use a programmable logic controller to count the time from the beginning of the heating process according to a pre-written program. When the heating furnace starts the heating program, the timer of the programmable logic controller starts working at the same time. It can accurately record the passage of every second. Once the time reaches the set 20-minute threshold, the programmable logic controller can automatically trigger the instruction to lower the heating temperature according to the program logic. The timing accuracy of the programmable logic controller can reach the millisecond level, which can meet the requirements for precise time monitoring, and can also resist adverse factors such as electromagnetic interference in industrial environments.

[0057] The sandblasting method used in S2.1 is to remove the rust on the surface of the round steel by spraying sand particles at high speed. This is because impurities such as rust and oil will affect the quality of the molten steel during the smelting process and increase the impurity content.

[0058] The controller is used in S2.3 because when the accident time is greater than 20 minutes, if the heating temperature is not lowered, the steel billet will continue to absorb heat. For metal materials, when heated at high temperature for a long time, its grains will gradually grow. Once the grains grow to a certain extent, the mechanical properties of the steel billet will be affected, the toughness will decrease, and the strength will change.

[0059] The stages of rolling include:

[0060] S4.1. Use a hand-held grinder to clean the places with sharp angles and burrs on the rolling groove, baffles, guides, rollers, etc. The hand-held grinder is flexible to operate. The purpose of grinding is that if there are sharp angles and burrs on the rolling groove, baffles, guides, rollers, etc., it will directly affect the surface quality of the steel. After grinding, the surface of the rolling groove and other parts will be smoother, which can make the steel receive uniform force during the rolling process, thereby ensuring the dimensional accuracy of the steel;

[0061] When changing rolls and taking over, the roll grooves of the 800 rolling mill should be checked for severe wear and tear, meat loss, etc. Pay special attention to the surface of the pusher to avoid scratches and abrasions on the surface of the red steel, which may cause defects such as discontinuity and shallow folding on the surface of the finished product.

[0062] S4.2. The cutting length of the 400t shear should be carried out according to the operating procedures. When producing large square billets, the 400t shear must cut the head and fishtail defects cleanly. Billets with fishtails will cause deviations in the length after cutting.

[0063] S4.3. During the shift inspection and mid-term shutdown, the wear of the rolling groove should be checked for any serious cracks or meat loss, whether the cooling water pipe nozzle is aligned with the rolling groove, whether the connecting hose is leaking, etc. Check whether the guide is aligned, whether there is iron clamping, wire drawing, guide roller jamming, etc. If any abnormality is found, the machine should be stopped and handled or replaced in time. This method can ensure the safety of production and the continuity of the production process.

[0064] S4.4. During the rolling process, the material shape and size of each rack should be measured every hour, and the red steel surface and size of each rack should be checked by burning wood prints and other methods to ensure that there are no defects such as ears, misaligned rollers, ovals, etc. on the surface of the finished product. Checking the red steel surface and size by burning wood prints and other methods can effectively detect surface defects. Discovering and solving these problems can ensure the surface quality of the finished steel, making it smooth and flat, and meeting the appearance requirements of high-quality products.

[0065] The finishing and grinding stage includes: the round steel is put into the pit for slow cooling after coming down from the cooling bed, and the slow cooling time is not less than 24 hours. After the round steel comes down from the cooling bed, it is transferred to the slow cooling pit by lifting equipment (such as a crane). The slow cooling pit is usually an underground or semi-underground structure with a certain depth and capacity, which can accommodate a certain number of round steels. When placing the round steels, try to ensure that the round steels are placed stably and arrange the spacing between the round steels reasonably to ensure uniform cooling effect. If the round steels are placed too closely, it will affect air circulation and cause uneven cooling. Unstable placement may cause poor local contact of the round steels and affect heat transfer. The uniform cooling effect can make the organizational structure of the round steel more uniform and avoid quality problems caused by differences in local cooling rates.

[0066] The finishing and grinding stage includes:

[0067] S5.1. Use a hand-held grinder or angle grinder for grinding. These tools use a high-speed rotating grinding wheel to contact the workpiece surface, and use the grinding action of the grinding wheel to remove ears and flash. For larger ears, you can first use a coarse-grained grinding wheel (such as 35-60 mesh) to quickly grind away most of the excess material, and then switch to a fine-grained grinding wheel (such as 109-180 mesh) for fine grinding to make the surface smooth;

[0068] S5.2. Inspectors observe the surface of finished products directly with their naked eyes. Under good lighting conditions, they check for obvious defects on the surface of products, such as scratches, ears, burrs and flash. At the same time, a magnifying glass can be used to improve the accuracy of the inspection. For some relatively small defects, such as slight scratches or small burrs, a magnifying glass can be used to see more clearly. Generally, a magnifying glass with a magnification of 5-10 times can meet most surface quality inspection needs;

[0069] S5.3. Feel the surface of the product to see if there are any defects. For some uneven surfaces, such as scars or folds, you can feel the unevenness of the surface by touching it. When checking the surface quality of metal sheets, you can slide your fingers across the surface of the sheet to detect tiny undulations on the surface, thereby discovering possible defects.

[0070] The inspection and acceptance stage of finished bar products includes:

[0071] S6.1. Atomic Emission Spectroscopy (AES) is used to detect chemical composition (melting analysis). The detection is carried out by exciting atoms in the round steel sample to emit light with a specific wavelength. The wavelength and intensity of this light are related to the type and content of the element;

[0072] S6.2. Use the energy spectrum analysis method in the electron microscope to detect the content of inclusions. The energy spectrum analysis method can provide high-resolution microscopic morphological images, which can more clearly observe the detailed features of the inclusions. EDS can perform elemental analysis on the inclusions and determine the chemical composition of the inclusions.

[0073] S6.3. Process the round steel into standard specimens, heat them to the specified austenitizing temperature, and then spray quench them at one end. Since the cooling rate gradually decreases from the quenching end to the other end during quenching, the structure and hardness also change accordingly. By measuring the hardness distribution along the length of the specimen, the hardenability of the round steel can be evaluated. The end quenching temperature is 849℃±5℃.

[0074] S6.4. Using ultrasonic flaw detection, when ultrasonic waves propagate in round steel, they will produce reflection, refraction and scattering when encountering defects (such as cracks, pores, etc.). By detecting these changes in ultrasonic waves, the location, size and nature of the defects can be determined;

[0075] S6.5. Inspectors should directly observe the surface of round steel with naked eyes to check whether there are defects such as scratches, folds, ears, burrs and flash. If necessary, auxiliary tools such as magnifying glasses can be used to observe more subtle surface defects;

[0076] S6.6. Use calipers, micrometers, tape measures and other conventional measuring tools to measure the diameter, length and other dimensions of round steel;

[0077] S6.7. Round steel with unqualified surface can be re-grinded and then go to the re-grinding stage. Those that cannot be re-grinded will be scrapped. Round steel with unqualified performance can be salvaged and then heat treated again and go to the re-grinding stage. Round steel with unqualified performance and cannot be salvaged will be reviewed and scrapped.

[0078] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A process for producing alloy steel, characterized in that: It includes the selection of round steel specifications and quality, furnace loading, heating, dephosphorization, rolling, sawing, cooling bed, slow cooling in the pit, finishing and grinding, and finished bar inspection and acceptance; S1. In the round steel specification quality screening stage, round steel with a diameter range of 50 mm to 160 mm is selected, wherein Ni≤0.25%, Cu≤0.35%, and Mo≤0.06% in the round steel are used to determine whether the quality of the round steel meets the requirements according to the proportions thereof; S2. During the furnace entry, heating and dephosphorization stages, the round steel and square billet need to be classified according to their size, weight, shape and surface quality. Different furnace time should be selected according to different categories. The end point control target value of converter smelting steel is: carbon content>0.10%, P<0.015%, and the number of re-blowing times is ≯2 times to ensure C-T coordinated steel tapping. High-pressure water is used for descaling during rolling. The descaling working pressure is set to be not less than 12Mpa. 800 rolling mill is used for descaling rolling to remove the surface iron oxide scale. If the iron oxide scale is not removed cleanly, the steel tapping should be stopped immediately, and the fitter should be arranged to check the nozzle and pressure. Steel can be tapped only after the treatment is completed. For the billets that have been discharged from the furnace, the 800 rolling mill should be notified to use descaling rolling to remove the surface iron oxide scale to avoid the surface pitting defects caused by the rolling and pressing of the iron oxide scale. S3. In the rolling stage, the starting rolling temperature is greater than 1001℃, and the final rolling temperature is greater than 851℃. When the descaling is not clean, the descaling process is used for rolling. When the steel passes through a set of upper and lower rollers, the special design of the rollers will cause the steel to bend and deform. Since the toughness of the iron oxide scale is different from that of the steel matrix, when the steel is bent, the iron oxide scale cannot deform synchronously like the steel, resulting in stress concentration inside it. In the process of continuous bending, the iron oxide scale will crack because it cannot withstand these stresses. With the subsequent rolling process, these cracks will gradually expand, and eventually the iron oxide scale will peel off from the surface of the steel; S4. During the sawing, cooling bed and slow cooling in the pit, the length of the hot sawing head and tail should be strictly carried out in accordance with the operating procedures. The length can be increased but must not be shorter than the required length. If there is any uncut steel, the sawing length of the corresponding batch should be increased by about 49 to 201 mm. The round steel shall not be cooled by a blower on the cooling bed. After the round steel is produced, it is slow cooled in the slow cooling pit. The slow cooling time is more than 24 hours. After the round steel is produced, the internal structure is in an unstable state; S5. During the finishing and grinding stage, do not bend the finished product, do not scratch the surface, clean the ears, scratches, burrs and flash on the surface of the finished product, and inspect the surface quality of the finished product. The scratches, cracks, folds, scars, ears, burrs and flash defects on the surface must be ground clean, and do not allow products that are not ground clean to leave the factory. Round steel that exceeds the grinding standard range must be scrapped; S6. During the inspection and acceptance stage of finished bars, the chemical composition, non-metallic inclusions, end hardenability, flaw detection, surface and dimensions of round steel are checked.

2. The alloy steel production process according to claim 1, characterized in that: In the stage of selecting the round steel specification and quality, the size of the round steel is Φ50 to Φ160 mm.

3. The alloy steel production process according to claim 1, characterized in that: The steps of entering the furnace, heating and dephosphorization are as follows: S2.

1. Use cranes or cranes to transport round steel of different sizes to the raw material area of ​​the converter workshop. Before placing them into the converter, use sandblasting to remove rust. S2.

2. Adjust the furnace time according to the size of round steel. The furnace time of 150 square cold billet shall not be less than 90 minutes, the furnace time of 240 square cold billet shall not be less than 149 minutes, the furnace time of 280 square cold billet shall not be less than 149 minutes, the furnace time of 300×430 square cold billet shall not be less than 239 minutes, and the furnace time of 350×430 square cold billet shall not be less than 269 minutes. When the billet is hot-charged, the furnace time shall be controlled as follows: the furnace time of 150 square cold billet shall not be less than 76 minutes, the furnace time of 240 square shall not be less than 121 minutes, the furnace time of 280 square shall not be less than 141 minutes, the furnace time of 300×430 square shall not be less than 181 minutes, and the furnace time of 350×430 square shall not be less than 201 minutes, so as to ensure the uniform temperature of the whole billet and prevent the visible positive and negative sides; S2.

3. Use a programmable logic controller to count the time from the beginning of the heating process according to a pre-written program. When the heating furnace starts the heating program, the timer of the programmable logic controller starts working at the same time. It can accurately record the passage of every second. Once the time reaches the set 20-minute threshold, the programmable logic controller can automatically trigger the instruction to lower the heating temperature according to the program logic.

4. The alloy steel production process according to claim 3, characterized in that: The sandblasting method used in S2.3 is to remove the rust on the surface of the round steel by high-speed spraying of sand particles. This is because rust and oil impurities will affect the quality of the molten steel during the smelting process and increase the impurity content.

5. The alloy steel production process according to claim 3, characterized in that: The controller is used in S2.3 because when the accident time is greater than 20 minutes, if the heating temperature is not lowered, the steel billet will continue to absorb heat. For metal materials, when heated at high temperature for a long time, its grains will gradually grow. Once the grains grow to a certain extent, the mechanical properties of the steel billet will be affected, the toughness will be reduced, and the strength will change.

6. The alloy steel production process according to claim 1, characterized in that: The rolling stage includes: S3.

1. Use a hand-held grinder to grind the groove, baffle, guide and roller with sharp angles and burrs. The hand-held grinder is flexible to operate. When changing the rolls and taking over the shift, check the 800 mill roll groove to see if there is severe wear and tear. Pay special attention to the surface of the pusher to avoid scratches and abrasions on the red steel surface, which may cause intermittent and superficial folding defects on the surface of the finished product. S3.

2. The shearing length of the 400t shear should be carried out according to the operating procedures. When producing large square billets, the 400t shear must cut the head and fishtail defects cleanly. Billets with fishtails will cause deviations in the length after cutting; S3.

3. During the shift inspection and mid-term stop, the wear of the rolling groove should be checked for any serious cracks or meat loss, whether the cooling water pipe nozzle is aligned with the rolling groove, whether the connecting hose is leaking, whether the guide is aligned, whether there is iron clamping, wire drawing, or guide roller jamming. If any abnormality is found, the machine should be stopped in time for processing or replacement; S3.

4. During the rolling process, the material shape and size of each rack should be measured every hour, and the red steel surface and size of each rack should be checked by burning wood print method to ensure that there are no ears, misaligned rollers, or elliptical defects on the surface of the finished product.

7. The alloy steel production process according to claim 1, characterized in that: The finishing and grinding stage includes: the round steel is put into the pit for slow cooling after coming down from the cooling bed, and the slow cooling time is not less than 24 hours. After the round steel comes down from the cooling bed, it is transferred to the slow cooling pit by lifting equipment. The slow cooling pit is usually an underground or semi-underground structure with a certain depth and capacity, which can accommodate a certain number of round steels. When placing the round steels, try to ensure that the round steels are placed stably, and arrange the spacing between the round steels reasonably to ensure uniform cooling effect.

8. The alloy steel production process according to claim 1, characterized in that: The finishing and grinding stage includes: S5.

1. Use a hand-held grinder or angle grinder for grinding. These tools use a high-speed rotating grinding wheel to contact the workpiece surface, and use the grinding action of the grinding wheel to remove ears and flash. For larger ears, you can first use a coarse-grained grinding wheel to quickly grind away most of the excess material, and then switch to a fine-grained grinding wheel for fine grinding to make the surface smooth; S5.

2. Inspectors observe the surface of finished products directly with their naked eyes. Under good lighting conditions, they check for obvious defects on the surface of products, such as scratches, ears, burrs and flash. At the same time, a magnifying glass can be used to improve the accuracy of the inspection. For some relatively small defects, such as slight scratches or small burrs, a magnifying glass can be used to see more clearly. Generally, a magnifying glass with a magnification of 5-10 times can meet most surface quality inspection needs; S5.

3. Feel the surface of the product to see if there are any defects. For some uneven surfaces, such as scars or folds, you can feel the unevenness of the surface by touching it. When checking the surface quality of metal sheets, you can slide your fingers across the surface of the sheet to detect tiny undulations on the surface, thereby discovering possible defects.

9. The alloy steel production process according to claim 1, characterized in that: The finished bar product inspection and acceptance stage includes: S6.

1. Detection of chemical composition using atomic emission spectroscopy. The detection excites the atoms in the round steel sample to emit light with a specific wavelength. The wavelength and intensity of the light are related to the type and content of the element. S6.

2. Use the energy spectrum analysis method in the electron microscope to detect the content of inclusions. The energy spectrum analysis method can provide high-resolution microscopic morphological images, which can more clearly observe the detailed features of the inclusions. EDS can perform elemental analysis on the inclusions and determine the chemical composition of the inclusions. S6.

3. Process the round steel into standard specimens, heat them to the specified austenitizing temperature, and then spray quench them at one end. Since the cooling rate gradually decreases from the quenching end to the other end during quenching, the structure and hardness also change accordingly. By measuring the hardness distribution along the length of the specimen, the hardenability of the round steel can be evaluated. The end quenching temperature is 849℃±5℃. S6.

4. Using ultrasonic flaw detection, when ultrasonic waves propagate in round steel, they will produce reflection, refraction and scattering phenomena when encountering defects. By detecting these changes of ultrasonic waves, the location, size and nature of the defects can be determined; S6.

5. The inspector directly observes the surface of the round steel with the naked eye to check whether there are scratches, folds, ears, burrs and flash defects. If necessary, a magnifying glass auxiliary tool can be used to observe more subtle surface defects; S6.

6. Use calipers, micrometers, and tape measures to measure the diameter and length of round steel. S6.

7. Round steel with unqualified surface can be re-grinded and then go to the re-grinding stage. Those that cannot be re-grinded will be scrapped. Round steel with unqualified performance can be salvaged and then heat treated again and go to the re-grinding stage. Round steel with unqualified performance and cannot be salvaged will be reviewed and scrapped.

Images