CN116024405A - Processing technology of carbon tool steel - Google Patents
Processing technology of carbon tool steel Download PDFInfo
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- CN116024405A CN116024405A CN202211482697.1A CN202211482697A CN116024405A CN 116024405 A CN116024405 A CN 116024405A CN 202211482697 A CN202211482697 A CN 202211482697A CN 116024405 A CN116024405 A CN 116024405A
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Abstract
The invention relates to a processing technology of carbon tool steel, which comprises the following steps: preparing raw materials; stress relief annealing; acid washing; softening and annealing; rolling; spheroidizing annealing; pulling and straightening; slitting and slitting longitudinally; packaging and warehousing. The beneficial effects of the invention are as follows: the method has the advantages that the oxide skin attached to the surface layer of the material is effectively removed, the decarburization problem of the surface layer of the material in the subsequent high-temperature softening annealing and spheroidizing annealing is prevented, the strength of the material is effectively reduced, the edge stress generated by the reverse coiling in the pickling process is eliminated, the quality problems of edge cracking, strip breakage and unstable rolling thickness tolerance are avoided in the subsequent rolling, the temperature rise and the heat preservation time of each stage and the temperature of each stage are effectively controlled, the upper, middle and lower regions of the carbon steel strip in the hearth and the outer, middle and inner rings of the carbon steel coil are uniformly heated, the metallographic structure in the material tends to be consistent, the quality of the produced product is stable, the toughness is high, and the production yield is improved.
Description
Technical Field
The invention relates to the technical field of strip steel production and processing, in particular to a processing technology of carbon tool steel.
Background
Sk5 is known as carbon tool steel, which has high hardness and wear resistance after quenching and tempering, but has low hot hardness, poor hardenability, very easy deformation, low plasticity and strength. Sk5 can be used as various tools that require higher hardness and wear resistance.
The quality of the produced carbon tool steel strip is not stable enough under the influence of the existing processing technology of the steel strip, and unqualified products with surface decarburization, poor toughness and uneven internal structure are easy to appear in the production process, so that the whole production yield is low.
Disclosure of Invention
The invention aims to provide a processing technology of carbon tool steel, which solves the problems in the prior art.
The technical scheme for solving the technical problems is as follows: a processing technology of carbon tool steel comprises the following steps:
firstly, preparing raw materials, selecting a hot rolled coil with the brand number of SK-5M, and performing longitudinal shearing and slitting;
transferring the hot rolled coiled plate to a hood-type annealing furnace, firstly raising the temperature to 320 ℃ at full speed, preserving heat for 2 hours, then raising the temperature to 780-820 ℃ at full speed, preserving heat for 10-12 hours, after finishing, carrying out hood-changing air cooling on the annealing furnace, reducing the temperature of the annealing furnace to 320 ℃, and then adopting water cooling to reduce the temperature to 100 ℃, and discharging to obtain the destressing annealed coiled plate;
step three, pickling, namely pickling the stress annealing coiled plate to obtain a pickled coiled plate;
transferring the pickled coiled plate to a hood-type annealing furnace, firstly raising the temperature to 320 ℃ at full speed, preserving heat for 2 hours, then raising the temperature to 730-780 ℃ at full speed, preserving heat for 14 hours, cooling to 650 ℃ along with the furnace, changing the hood of the annealing furnace, cooling the annealing furnace to 320 ℃, and then cooling to 100 ℃ by adopting water cooling, and discharging the softened annealed coiled plate;
fifthly, rolling, namely conveying the softened and annealed coiled plate to a rolling mill production line for multi-pass rolling to obtain a rolled coiled plate;
transferring the rolled coiled plate to a hood-type annealing furnace, heating to 320 ℃ at full speed, preserving heat for 2 hours, heating to 680 ℃ at full speed, preserving heat for 2 hours, then heating, preserving heat and cooling with a furnace for a plurality of reciprocating periods, cooling to 650 ℃ with the furnace, performing hood-changing air cooling to reduce the temperature to 320 ℃, and finally reducing the temperature of the annealing furnace to 80 ℃ in a water cooling mode, and discharging to obtain the spheroidized annealed coiled plate;
step seven, straightening and pulling, namely moving the spheroidizing annealed coiled plate into a straightening and pulling unit for flattening and straightening;
step eight, slitting by longitudinal shearing, namely transferring the spheroidizing annealed rolled plate to a slitting machine for slitting by longitudinal shearing to prepare a slit rolled plate;
and step nine, packaging and warehousing, namely packaging the split coiled plates by using a packaging machine and then counting and warehousing.
The beneficial effects of the invention are as follows:
1. the stress relief annealing is carried out before the acid cleaning, so that the problems of high rapid cooling strength of the head and the tail of the hot rolled coil, easy breakage and uncoiling scratch during the acid cleaning uncoiling are solved, the internal stress of the material is fully released while the surface layer of the material is not subjected to high-temperature decarburization, the acid cleaning procedure is arranged after the stress relief annealing, the oxide skin attached to the surface layer of the material is effectively removed, the decarburization problem of the surface layer of the material in the subsequent high-temperature softening annealing and spheroidizing annealing is prevented, and the smooth proceeding of the subsequent rolling work is facilitated;
2. the softening annealing is arranged after the pickling, the temperature and the heat preservation time of each stage are controlled in the softening annealing process, the strength of the material is effectively reduced, the edge stress generated by the back coiling in the pickling process is eliminated, and the quality problems of edge cracking, strip breakage and unstable rolling thickness tolerance are avoided in the subsequent rolling;
3. when the rolled coil is subjected to spheroidizing annealing, the whole spheroidizing annealing process is divided into a plurality of reciprocating periods, the temperature rise and the heat preservation time of each stage and the temperature of each stage are effectively controlled, the upper, middle and lower regions of the carbon steel strip in the hearth and the outer, middle and inner rings of the carbon steel coil are heated uniformly, the metallographic structures in the materials tend to be consistent, and therefore the produced product has stable quality and high strength and toughness, and the production yield is improved.
On the basis of the technical scheme, the invention can be improved as follows.
In the second, fourth and sixth steps, a detonation test is needed before the temperature rise during annealing to ensure the purity of the hydrogen in the methanol cracking furnace, and the difference between the actual temperature value and the process temperature value is less than 10 ℃ in the whole temperature rise and heat preservation process.
The adoption of the further scheme has the beneficial effects that the heat treatment environment is ensured, the quality of the carbon steel during heat treatment is ensured not to cause quality problems due to environmental temperature difference, and the stability of the quality of the head, middle and tail of the annealed coil plate can be effectively ensured.
Further, in the step three, when pickling is performed, the negative difference of the thicknesses of the stress relief annealed rolled sheet before and after pickling is less than 0.15mm, the number of pickling tanks is two, the number of passivating tanks is one, the number of neutralizing tanks is one, the pickling concentrations of the two pickling tanks are respectively 18-22%, 15-18%, the acid liquid levels in the two pickling tanks are 380-420 mm, the acid liquid temperature is 50-70 ℃, the PH value of the neutralizing tank is 11-13, the PH value of the passivating tank is 7-8, the temperature value of the passivating tank is 40-50 ℃, and the cleaning speed of a pickling production line is 5-15 m/min.
The further scheme has the beneficial effects that oxide skin generated in the softening annealing process of the hot rolled coil can be effectively removed, and the influence on subsequent processing is avoided.
Further, rolling oil is used as a cooling lubricant in the fifth step, the oil temperature is controlled to be 40+/-2 ℃, the thickness of the multi-pass rolling is reduced, and the final thickness tolerance is controlled to be +/-0.002 mm.
The beneficial effect of adopting above-mentioned further scheme is, the rolling oil of the oil temperature of about 40 ℃ can be when rolling to soften the annealed coiled sheet and cool down to the inside tissue of softened annealed coiled sheet influences little, guarantees the quality.
Further, the reciprocating cycle of spheroidizing annealing in the step six is as follows: after the annealing furnace is kept at 680 ℃ for 2 hours, the annealing furnace is heated to 750 ℃ at full speed and kept for 4 hours, and then is cooled to 720 ℃ and kept for 2 hours along with the furnace.
The technical scheme has the beneficial effects that the upper, middle and lower areas of the carbon steel strip in the hearth and the outer, middle and inner rings of the carbon steel coil are heated uniformly, and the metallographic structures in the materials tend to be consistent.
Further, the elongation of the drawing and leveling machine set in the step seven is set to be 1.0% -1.7%.
In the eighth step, before slitting, the hardness of the finish rolled coil is detected by a universal tester and a hardness tester, the qualified range of the hardness value of the finish rolled coil is HV170 to HV250, metallographic detection is performed on the finish rolled spheroidizing annealed coil with qualified hardness value, and the finish rolled spheroidizing annealed coil with qualified metallographic detection is put on the slitting machine.
The adoption of the further scheme has the beneficial effects that the parameter values in the production process can be timely adjusted according to the detection data, whether the sequence production is performed or not can be judged in advance, and the production quality of the finished product is ensured.
Drawings
FIG. 1 is a flow chart of a process for machining carbon tool steel according to the present invention;
FIG. 2 is a graph of a stress relief anneal process according to the present invention;
FIG. 3 is a graph of a softening annealing process in accordance with the present invention;
FIG. 4 is a diagram showing a spheroidizing annealing process according to the present invention;
FIG. 5 is a diagram showing a metallographic examination after spheroidizing annealing according to the present invention.
Detailed Description
The principles and features of the present invention are described below with reference to the drawings, the examples are illustrated for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention.
As shown in fig. 1, a process for machining carbon tool steel comprises the following steps:
step one, preparing raw materials, and selecting a spring steel hot-rolled coil with the brand number of SK-5M, wherein the chemical components (refer to JIS G3311-2004) of the hot-rolled coil with the brand number of SK-5M are as follows: c is 0.80 to 0.90, si is less than or equal to 0.35, mn is less than or equal to 0.50, P: let 0.030, S: less than or equal to 0.030, cr: less than or equal to 0.30, less than or equal to 0.25 for Ni and less than or equal to 0.25 for Cu; the requirements of the mechanical properties of the SK-5M hot rolled coil are as follows: tensile strength is equal to or less than 1050MPa; the metallographic requirements of the SK-5M hot rolled coil are as follows: ferrite + pearlite structure, decarburized layer, when the thickness is >5mm, allowed decarburization +. 1%t, where t is the thickness of the hot rolled steel sheet, when the thickness +.5 mm, allowed decarburization <50 μm, band structure <2 grade, inclusion fine system <2 grade, in this example, the thickness of the hot rolled sheet with brand SK-5M is selected to be 2.3mm, and the thickness of the finished product is 1.0.+ -. 0.03mm; the allowable deviation of the thickness of the hot rolled coil is in accordance with the specification of GB/T709, the convexity requirement is less than or equal to 60 mu m, the surface of the hot rolled coil cannot be provided with bubbles, cracks, scars, skin tilting, pulling cracks and inclusions, the hot rolled coil cannot be layered, and the surface of the hot rolled coil cannot be provided with slight pits and local deep pits, small bubbles, slight scratches and roller indentations within the half thickness tolerance range; the edges of the hot rolled coiled plates are neat and have no saw tooth shape;
transferring the hot rolled coiled plate to a hood-type annealing furnace, firstly raising the temperature to 320 ℃ at full speed, preserving heat for 2 hours, then raising the temperature to 780-820 ℃ at full speed, preserving heat for 10-12 hours, after finishing, carrying out hood-changing air cooling on the annealing furnace, reducing the temperature of the annealing furnace to 320 ℃, then adopting water cooling to reduce the temperature to 100 ℃, and discharging to obtain the destressing annealed coiled plate, and referring to the figure 2;
step three, pickling, namely pickling the stress annealing coiled plate to obtain a pickled coiled plate;
when pickling is carried out, the negative difference of the thicknesses of the stress-relief annealed rolled plate before and after pickling is less than 0.15mm, the number of pickling tanks is two, the number of passivation tanks is one, the number of neutralization tanks is one, the pickling concentrations of the two pickling tanks are respectively 18-22%, 15-18%, the acid liquid levels in the two pickling tanks are 380-420 mm, the acid liquid temperature is 50-70 ℃, the PH value of the neutralization tanks is 11-13, the PH value of the passivation tanks is 7-8, the temperature value of the passivation tanks is 40-50 ℃, and the cleaning speed of a pickling production line is 5-15 m/min;
transferring the pickled coiled plate to a hood-type annealing furnace, firstly raising the temperature to 320 ℃ at full speed, preserving heat for 2 hours, then raising the temperature to 730-780 ℃ at full speed, preserving heat for 14 hours, cooling to 650 ℃ along with the furnace, changing the hood of the annealing furnace, cooling the annealing furnace to 320 ℃, cooling the temperature to 100 ℃ by adopting water cooling, and discharging the annealed coiled plate to obtain the softened annealed coiled plate, which is shown in the figure 3;
fifthly, rolling, namely conveying the softened and annealed coiled plate to a rolling mill production line for multi-pass rolling to obtain a rolled coiled plate;
the rolling oil is used as a cooling lubricant, the oil temperature is controlled to be 40+/-2 ℃, the thickness of the multi-pass rolling is reduced, and the final thickness tolerance is controlled to be +/-0.002 mm;
transferring the rolled coiled plate to a hood-type annealing furnace, heating to 320 ℃ at full speed, preserving heat for 2 hours, heating to 680 ℃ at full speed, preserving heat for 2 hours, then heating, preserving heat and cooling with a furnace for a plurality of reciprocating periods, cooling to 650 ℃ with the furnace, performing hood-changing air cooling to reduce the temperature to 320 ℃, and finally reducing the temperature of the annealing furnace to 80 ℃ in a water cooling mode, and discharging to obtain the spheroidized annealed coiled plate;
the reciprocation period of spheroidizing annealing is: after the annealing furnace is kept at 680 ℃ for 2 hours, the annealing furnace is fully heated to 750 ℃ and kept for 4 hours, and then is cooled to 720 ℃ and kept for 2 hours along with the furnace, as shown in the figure 4;
step seven, straightening and withdrawal, namely moving the spheroidizing annealed rolled plate into a straightening and withdrawal unit for flattening and straightening, wherein the elongation of the straightening and withdrawal unit is set to be 1.0% -1.7%;
step eight, slitting by longitudinal shearing, namely transferring the spheroidizing annealed rolled plate to a slitting machine for slitting by longitudinal shearing to prepare a slit rolled plate;
and step nine, packaging and warehousing, namely packaging the split coiled plates by using a packaging machine and then counting and warehousing.
In the invention, the specific operation flows of stress relief annealing, acid washing, softening annealing, rolling, spheroidizing annealing and slitting are formulated according to the processing technology characteristics of the carbon tool steel plate, so that the stable product quality is effectively controlled and produced, and the product performance meeting the requirements of customers is effectively controlled.
In the stress relief annealing, softening annealing and spheroidizing annealing, a detonating test is required before the temperature is raised, so that the purity of hydrogen in the ammonia decomposing furnace is ensured; in the whole heating and heat preservation process, the difference between the actual temperature value and the process temperature value is less than 10 ℃, the actual temperature value is measured by a thermocouple, the frequency of detection is 1 time/1 hour, and in addition, a heat preservation platform can be properly added in the heating process so as to meet the theoretical speed-up.
In the whole production process, the secondary detection is needed, wherein the primary detection is the stock inspection, namely the thickness and width dimensions of the selected hot rolled material are ensured to meet the requirements of a planned finished product, the chemical composition, mechanical property and organization structure of the material are required to meet the standard requirements of SK-5M hot rolled material, the surface of the hot rolled coil cannot be provided with bubbles, cracks, scars, skin lifting, pulling cracks and inclusions, the plate cannot be layered, the surface is allowed to be provided with slight pits and local deep pits, small bubbles, slight scratches and roller indentations within the half thickness tolerance range, and the edges of the coil are tidy and free of saw teeth.
Secondly, before slitting by longitudinal shearing after spheroidizing annealing, detecting the hardness of the spheroidizing annealed rolled plate by a universal tester and a hardness tester, wherein the qualification range of the hardness value of the spheroidizing annealed rolled plate is HV170-250; a spheroidizing annealed rolled sheet having a satisfactory hardness value is subjected to metallographic examination, and a finish rolled sheet having a satisfactory metallographic examination is put on a small slitter, and the metallographic examination is defined in accordance with JIS G3311-2004, with reference to FIG. 5.
The surface of the rolled coiled plate obtained during rolling has no skin tilting, pits, yellow rust, water rust, scratches, flat plate shape and no napping and broken edges at the edge;
the surface of the split coiled plate obtained by shearing the split strips has no skin tilting, pits, water rust, scratches, yellow rust, embossing, flat plate shape and broken edges at the edge;
when longitudinal shearing slitting is carried out, rust-preventive oil needs to be sprayed on the slitting coiled plate electrostatically.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (7)
1. A process for machining carbon tool steel, which is characterized by comprising the following steps:
firstly, preparing raw materials, selecting a hot rolled coil with the brand number of SK-5M, and performing longitudinal shearing and slitting;
transferring the hot rolled coiled plate to a hood-type annealing furnace, firstly raising the temperature to 320 ℃ at full speed, preserving heat for 2 hours, then raising the temperature to 780-820 ℃ at full speed, preserving heat for 10-12 hours, after finishing, carrying out hood-changing air cooling on the annealing furnace, reducing the temperature of the annealing furnace to 320 ℃, and then adopting water cooling to reduce the temperature to 100 ℃, and discharging to obtain the destressing annealed coiled plate;
step three, pickling, namely pickling the stress annealing coiled plate to obtain a pickled coiled plate;
transferring the pickled coiled plate to a hood-type annealing furnace, firstly raising the temperature to 320 ℃ at full speed, preserving heat for 2 hours, then raising the temperature to 730-780 ℃ at full speed, preserving heat for 14 hours, cooling to 650 ℃ along with the furnace, changing the hood of the annealing furnace, cooling the annealing furnace to 320 ℃, and then cooling to 100 ℃ by adopting water cooling, and discharging the softened annealed coiled plate;
fifthly, rolling, namely conveying the softened and annealed coiled plate to a rolling mill production line for multi-pass rolling to obtain a rolled coiled plate;
transferring the rolled coiled plate to a hood-type annealing furnace, heating to 320 ℃ at full speed, preserving heat for 2 hours, heating to 680 ℃ at full speed, preserving heat for 2 hours, then heating, preserving heat and cooling with a furnace for a plurality of reciprocating periods, cooling to 650 ℃ with the furnace, performing hood-changing air cooling to reduce the temperature to 320 ℃, and finally reducing the temperature of the annealing furnace to 80 ℃ in a water cooling mode, and discharging to obtain the spheroidized annealed coiled plate;
step seven, straightening and pulling, namely moving the spheroidizing annealed coiled plate into a straightening and pulling unit for flattening and straightening;
step eight, slitting by longitudinal shearing, namely transferring the spheroidizing annealed rolled plate to a slitting machine for slitting by longitudinal shearing to prepare a slit rolled plate;
and step nine, packaging and warehousing, namely packaging the split coiled plates by using a packaging machine and then counting and warehousing.
2. The process for machining carbon tool steel according to claim 1, wherein in the second, fourth and sixth steps, a detonating test is required before heating during annealing to ensure the purity of hydrogen in the methanol cracking furnace, and the difference between the actual temperature value and the process temperature value is less than 10 ℃ during the whole heating and heat preservation processes.
3. The process according to claim 1, wherein in the third step, when pickling is performed, the negative difference between the thicknesses of the stress relief annealed rolled sheet before and after pickling is less than 0.15mm, the number of pickling tanks is two, the number of passivation tanks is one, the number of neutralization tanks is one, the pickling concentrations of the two pickling tanks are respectively 18% to 22%, 15% to 18%, the acid liquid levels in the two pickling tanks are 380mm to 420mm, the acid liquid temperature is 50 ℃ to 70 ℃, the PH value of the neutralization tank is 11 to 13, the PH value of the passivation tank is 7 to 8, the temperature value of the passivation tank is 40 ℃ to 50 ℃, and the cleaning speed of the pickling line is 5m/min to 15m/min.
4. The process of claim 1, wherein the rolling oil is used as a cooling lubricant in the fifth step, the oil temperature is controlled to be 40+ -2 ℃, the thickness of the multi-pass rolling is decreased, and the final thickness tolerance is controlled to be + -0.002 mm.
5. The process for producing a carbon tool steel according to claim 1, wherein the reciprocating cycle of the spheroidizing annealing in the step six is: after the annealing furnace is kept at 680 ℃ for 2 hours, the annealing furnace is heated to 750 ℃ at full speed and kept for 4 hours, and then is cooled to 720 ℃ and kept for 2 hours along with the furnace.
6. The process for producing a carbon tool steel according to claim 1, wherein the elongation of the drawing and leveling unit in the seventh step is set to 1.0% -1.7%.
7. The process according to claim 1, wherein in the eighth step, before slitting, the hardness of the finish rolled coil is detected by a universal tester and a hardness tester, the hardness value of the finish rolled coil is qualified in the range from HV170 to HV250, the finish rolled spheroidizing annealed coil with qualified hardness value is subjected to metallographic detection, and the finish rolled spheroidizing annealed coil with qualified metallographic detection is put into the slitting machine.
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