阅读说明：本技术 一种sk85碳素工具钢 (SK85 carbon tool steel ) 是由 宁立峥 雷启文 周成戈 何茂华 于 2021-07-22 设计创作，主要内容包括：本发明涉及一种SK85碳素工具钢的加工工艺,包括如下步骤：选取牌号为SK85的热轧卷板,通过罩式退火炉进行去应力退火,制得热轧应力释放退火卷板；将退火卷板进行酸洗,并制得酸洗卷板；将酸洗通过罩式退火炉进行软化退火。本发明的有益效果是：防止碳素含量热轧板在加工中材料表面擦伤及酸洗卷取中的边部应力集中产生裂纹,轧制到成品尺寸后安排球化退火,让冷轧后的材料被轧制破碎、拉长的片状珠光体晶粒重组,转变成均匀分布的粒状或球状珠光体组织,适合于后续精冲工序的正常进行,并为冲制的零件作好淬火前的组织准备,能够稳定产品质量、提高制品的耐用度,生产的弹性零部件力值更加稳定、衰减小,使用寿命成倍提升。(The invention relates to a processing technology of SK85 carbon tool steel, which comprises the following steps: selecting a hot-rolled coil with the mark SK85, and performing stress relief annealing through a hood-type annealing furnace to obtain a hot-rolled stress release annealed coil; pickling the annealed coil to obtain a pickled coil; and (4) softening and annealing the acid washing through a hood-type annealing furnace. The invention has the beneficial effects that: the method has the advantages that the surface of the hot rolled plate with carbon content is prevented from being scratched in the processing process and the edge stress concentration in the acid pickling coiling process is prevented from generating cracks, spheroidizing annealing is arranged after the hot rolled plate is rolled to the size of a finished product, the cold rolled material is rolled and crushed, elongated flaky pearlite grains are recombined and are converted into uniformly distributed granular or spherical pearlite structures, the method is suitable for normal operation of a subsequent fine blanking process, the structure preparation before quenching is made for punched parts, the product quality can be stabilized, the durability of the products is improved, the force value of the produced elastic parts is more stable, the attenuation is reduced, and the service life is prolonged exponentially.)

1. A processing technology of SK85 carbon tool steel is characterized by comprising the following steps:

step one, selecting a hot-rolled coil with the mark number of SK 85;

step two, stress relief annealing;

step three, acid washing;

step four, softening and annealing;

step five, rolling;

step six, spheroidizing annealing;

step seven, slitting and splitting;

and step eight, packaging and warehousing.

2. The processing technology of SK85 carbon tool steel as claimed in claim 1, wherein in the stress relief annealing, the annealing furnace is first heated to 320 ℃ at full speed, and then kept warm for 2h after heating to 320 ℃; secondly, after the annealing furnace is subjected to heat preservation for 2 hours at the temperature of 320 ℃, heating the annealing furnace to 650 ℃ at full speed, and preserving heat for 10 to 12 hours after heating to 650 ℃; thirdly, after the annealing furnace is insulated for 10 to 12 hours at the temperature of 650 ℃, hood replacement air cooling is carried out on the annealing furnace, and the temperature of the annealing furnace is reduced to 320 ℃; fourthly, after the temperature of the annealing furnace is reduced to 320 ℃, the temperature of the annealing furnace is reduced to 100 ℃ from 320 ℃ by adopting a water cooling mode.

3. The processing technology of SK85 carbon tool steel as claimed in claim 2, wherein in the stress relief annealing, a detonation test is required before the temperature rise to ensure the purity of hydrogen in the methanol cracking furnace; in the whole temperature rising and preserving process, the difference value between the actual temperature value and the process temperature value is less than 10 ℃.

4. The processing technology of SK85 carbon tool steel as claimed in claim 1, wherein during pickling, the negative difference between the thickness of the stress-relieved annealed coil 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 18% to 22% and 15% to 18%, the acid positions 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 15 m/min.

5. The processing technology of SK85 carbon tool steel as claimed in claim 1, wherein in the softening annealing, the annealing furnace is first heated to 320 ℃ at full speed, and after heating to 320 ℃, the temperature is kept for 2 h; secondly, keeping the temperature of the annealing furnace at 320 ℃ for 2h, then raising the speed of the annealing furnace to 680 ℃ at full speed, and keeping the temperature for 2h after raising the temperature to 680 ℃; thirdly, after the annealing furnace is kept at the temperature of 680 ℃ for 2 hours, heating the annealing furnace to 730 ℃ at full speed, and keeping the temperature for 14 hours after the temperature is raised to 730 ℃; fourthly, the annealing furnace is cooled to 650 ℃ along with the furnace after heat preservation is carried out for 14h at the temperature of 730 ℃; fifthly, cooling the annealing furnace to 650 ℃ along with the furnace, then performing cover replacement air cooling on the annealing furnace, and reducing the temperature of the annealing furnace to 320 ℃; and sixthly, reducing the temperature of the annealing furnace to 320 ℃, and discharging the product from the annealing furnace from 320 ℃ to 100 ℃ by adopting a water cooling mode.

6. The processing technology of SK85 carbon tool steel as claimed in claim 5, wherein during the softening annealing, before the temperature rise, detonation test is required to ensure the purity of hydrogen in the methanol cracking furnace; in the whole temperature rising and preserving process, the difference value between the actual temperature value and the process temperature value is less than 10 ℃.

7. The processing technology of SK85 carbon tool steel as claimed in claim 1, wherein in spheroidizing annealing, the annealing furnace is first heated to 320 ℃ at full speed, and after heating to 320 ℃, the temperature is kept for 2 h; secondly, keeping the temperature of the annealing furnace at 320 ℃ for 2h, then raising the speed of the annealing furnace to 680 ℃ at full speed, and keeping the temperature for 2h after raising the temperature to 680 ℃; thirdly, keeping the temperature of the annealing furnace at 680 ℃ for 2h, heating the annealing furnace to 750 ℃ at full speed, and keeping the temperature for 4h after heating to 750 ℃; fourthly, after the annealing furnace is kept at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the annealing furnace is kept at the temperature of 720 ℃ for 2 hours; fifthly, after the annealing furnace is subjected to heat preservation at the temperature of 720 ℃ for 2 hours, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; sixthly, after the annealing furnace is subjected to heat preservation at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the heat preservation is carried out at the temperature of 720 ℃ for 2 hours; seventh; after the annealing furnace is subjected to heat preservation at the temperature of 720 ℃ for 2 hours, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; eighthly, after the annealing furnace is kept at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the annealing furnace is kept at the temperature of 720 ℃ for 2 hours; ninth, after the annealing furnace is subjected to heat preservation for 2 hours at the temperature of 720 ℃, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; tenthly, keeping the temperature of the annealing furnace at 750 ℃ for 4h, and cooling to 650 ℃ along with the furnace; eleventh, after the temperature of the annealing furnace is reduced to 650 ℃ in a furnace cooling mode, cover changing and air cooling are carried out on the annealing furnace, and the temperature of the annealing furnace is reduced to 320 ℃; twelfth, after the temperature of the furnace is reduced to 320 ℃, the temperature of the annealing furnace is reduced from 320 ℃ to 80 ℃ by adopting a water cooling mode.

8. The processing technology of SK85 carbon tool steel as claimed in claim 7, wherein during spheroidizing annealing, detonating test is required before temperature rise to ensure the purity of hydrogen in methanol cracking furnace; in the whole temperature rising and preserving process, the difference value between the actual temperature value and the process temperature value is less than 10 ℃.

9. The processing technology of the SK85 carbon tool steel as claimed in claim 1, wherein before slitting, the hardness of the finish rolled sheet is detected by a universal tester and a hardness tester, and the qualified range of the hardness value of the finish rolled sheet is HV170 to HV 250; and performing metallographic detection on the finish rolling spheroidizing annealed coil with qualified hardness value, and putting the finish rolling spheroidizing annealed coil with qualified metallographic detection on a small slitting machine.

Technical Field

The invention relates to the technical field of strip steel production and processing, in particular to SK85 carbon tool steel.

Background

It is known that strip steel is a narrow and long steel sheet produced to suit the needs of different industrial sectors. The width of the glass is generally within 300mm, but with economic development, the width is not limited. The steel strip is supplied in a coiled manner, has the advantages of high dimensional precision, good surface quality, convenient processing, material saving and the like, and is widely used for producing blanks of cold-formed steel, bicycle frames, rims, clamps, gaskets, spring pieces, saw blades, blades and automobile fine blanking parts.

With the development of the automobile industry, higher requirements are provided for some important structural parts, particularly, the carbon structural steel and the high, medium and low carbon alloy steel cannot meet the requirements on higher tensile strength on the premise of ensuring the light weight of parts, and are also suitable for fine die bending and cold forming without cracking, either the yield ratio does not meet the standard as the structural part is unsafe, or the strength does not meet the standard and the thickness of the part needs to be increased, so that the weight of the parts is greatly increased, and the requirements on vehicle light weight are not met. However, in order to meet the requirement in the industry, thick hot rolling raw materials are often adopted, the internal structure of the material is changed through large rolling reduction, and an annealing process is assisted to meet the requirement that the finished material is suitable for fine blanking production. However, domestic and foreign high-strength yield series steel grades basically belong to fine grain structural steel, internal grains are seriously crushed after rolling under high reduction, abnormal poor coarse grain structures are often generated after annealing, and the production of fine-blanking parts is very unfavorable. Therefore, a method for processing a high-strength structural steel for cold forming is produced.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a high-strength structural steel processing technology which can stabilize the size of a fine blanking part, improve the product quality, has high tensile strength, certain hardness and heat treatment process characteristics, reduces the weight of a structural part and is suitable for bending production of a fine blanking die.

The technical scheme for solving the technical problems is as follows: a processing technology of SK85 carbon tool steel comprises the following steps:

step one, selecting a carbon tool steel hot-rolled coil plate with the mark number of SK 85;

step two, stress relief annealing;

step three, acid washing;

step four, softening and annealing;

step five, rolling;

step six, spheroidizing annealing;

step seven, slitting and splitting;

and step eight, packaging and warehousing.

The invention has the beneficial effects that: by carrying out stress relief annealing before pickling, improve the quick cold intensity of the head, the tail of hot-rolled coil finish rolling back and be on the high side, easy disconnected area and open a book the scotch problem when pickling is opened a book, divide into a plurality of stages with whole stress relief annealing process, and the effectual temperature and the heat preservation time of controlling each stage well, guarantee that the material top layer can not let the material internal stress obtain fully releasing because of high temperature decarbonization simultaneously, arrange the pickling process behind stress relief annealing, effectively detach the adnexed cinder in material top layer, prevent the material top layer decarbonization problem in follow-up high temperature softening annealing and balling annealing from taking place, also be favorable to going on smoothly of follow-up rolling work. The softening annealing is arranged after the acid washing, the temperature and the heat preservation time of each stage are well controlled in the softening annealing process, the strength of the material is effectively reduced, the edge stress generated by reverse coiling in the acid washing process is eliminated, and the quality problems of edge cracking, strip breakage and unstable rolling thickness tolerance in the subsequent rolling are avoided. And 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 steel strip in the hearth and the outer, middle and inner rings of the steel coil are heated uniformly, the metallographic structures in the material tend to be consistent, so that the quality of the produced product is stable, the product qualification rate is improved, and the labor productivity is improved.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, during stress relief annealing, firstly, heating the annealing furnace to 320 ℃ at full speed, and preserving heat for 2 hours after heating to 320 ℃; secondly, after the annealing furnace is subjected to heat preservation for 2 hours at the temperature of 320 ℃, heating the annealing furnace to 650 ℃ at full speed, and preserving heat for 10 to 12 hours after heating to 650 ℃; thirdly, after the annealing furnace is insulated for 10 to 12 hours at the temperature of 650 ℃, hood replacement air cooling is carried out on the annealing furnace, and the temperature of the annealing furnace is reduced to 320 ℃; fourthly, after the temperature of the annealing furnace is reduced to 320 ℃, the temperature of the annealing furnace is reduced to 100 ℃ from 320 ℃ by adopting a water cooling mode.

Further: during stress relief annealing, a detonation test is required before temperature rise is carried out, and the purity of hydrogen in the methanol cracking furnace is ensured; in the whole temperature rising and preserving process, the difference value between the actual temperature value and the process temperature value is less than 10 ℃.

The adoption of the further beneficial effects is as follows: the stability of the quality of the stress-relief annealed coil can be effectively ensured.

Further: and during softening annealing, heating the annealing furnace to 320 ℃ at full speed, preserving heat for 2h after heating to 320 ℃, preserving heat for 2h at the temperature of 320 ℃, heating the annealing furnace to 730 ℃ at full speed, preserving heat for 14h after heating to 730 ℃, cooling to 650 ℃ along with the furnace after heat preservation is finished, exchanging covers and air cooling the annealing furnace after cooling to 650 ℃ along with the furnace, reducing the temperature of the annealing furnace to 320 ℃, and then discharging the annealing furnace from 320 ℃ to 100 ℃ by adopting a water cooling mode.

Further: during softening annealing, a detonation test is required before temperature rise is carried out, and the purity of hydrogen in the methanol cracking furnace is ensured; in the whole temperature rising and preserving process, the difference value between the actual temperature value and the process temperature value is less than 10 ℃.

The adoption of the further beneficial effects is as follows: the quality stability of the softening annealing coiled plate can be effectively ensured.

Further: during acid cleaning, the negative difference of the thicknesses of the stress-relief annealed coil before and after acid cleaning is less than 0.15mm, the number of the acid cleaning tanks is two, the number of the passivating tanks is one, the number of the neutralizing tanks is one, the acid cleaning concentrations of the two acid cleaning tanks are respectively 18% -22% and 15% -18%, the acid positions in the two acid cleaning tanks are 380 mm-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 an acid cleaning production line is 5-15 m/min.

The adoption of the further beneficial effects is as follows: the oxide skin generated in the softening and annealing process of the hot-rolled coil can be effectively removed, and the subsequent processing is prevented from being influenced.

Further, during spheroidizing annealing, firstly, heating the annealing furnace to 320 ℃ at full speed, and preserving heat for 2 hours after heating to 320 ℃; secondly, keeping the temperature of the annealing furnace at 320 ℃ for 2h, then raising the speed of the annealing furnace to 680 ℃ at full speed, and keeping the temperature for 2h after raising the temperature to 680 ℃; thirdly, keeping the temperature of the annealing furnace at 680 ℃ for 2h, heating the annealing furnace to 750 ℃ at full speed, and keeping the temperature for 4h after heating to 750 ℃; fourthly, after the annealing furnace is kept at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the annealing furnace is kept at the temperature of 720 ℃ for 2 hours; fifthly, after the annealing furnace is subjected to heat preservation at the temperature of 720 ℃ for 2 hours, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; sixthly, after the annealing furnace is subjected to heat preservation at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the heat preservation is carried out at the temperature of 720 ℃ for 2 hours; seventh; after the annealing furnace is subjected to heat preservation at the temperature of 720 ℃ for 2 hours, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; eighthly, after the annealing furnace is kept at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the annealing furnace is kept at the temperature of 720 ℃ for 2 hours; ninth, after the annealing furnace is subjected to heat preservation for 2 hours at the temperature of 720 ℃, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; tenthly, keeping the temperature of the annealing furnace at 750 ℃ for 4h, and cooling to 650 ℃ along with the furnace; eleventh, after the temperature of the annealing furnace is reduced to 650 ℃ in a furnace cooling mode, cover changing and air cooling are carried out on the annealing furnace, and the temperature of the annealing furnace is reduced to 320 ℃; twelfth, after the temperature of the furnace is reduced to 320 ℃, the temperature of the annealing furnace is reduced from 320 ℃ to 80 ℃ by adopting a water cooling mode.

Furthermore, in spheroidizing annealing, a detonation test is required before temperature rise is carried out, so that the purity of hydrogen in the ammonia decomposition furnace is ensured; in the whole temperature rising and preserving process, the difference value between the actual temperature value and the process temperature value is less than 10 ℃.

The adoption of the further beneficial effects is as follows: the quality stability of the spheroidizing annealed coil plate can be effectively ensured.

Further, before slitting and splitting, a universal testing machine and a hardness tester are used for detecting the hardness of the rolled coil, and the qualified range of the hardness of the rolled coil is HV 170-HV 250; and performing metallographic detection on the coiled plate with qualified hardness value, and putting the rolled coiled plate which is subjected to decarburization depth detection and metallographic detection according to JIS G3311-2004 into a small slitting machine.

The adoption of the further beneficial effects is as follows: parameter values in the production process can be adjusted in time according to the detection data, whether sequence conversion production is carried out or not is judged in advance, and the production quality of finished products is ensured.

Drawings

FIG. 1 is a graph of stress relief annealing in the machining process of SK85 carbon tool steel according to the invention;

FIG. 2 is a graph of softening annealing in the machining process of SK85 carbon tool steel according to the invention;

FIG. 3 is a graph of spheroidizing annealing in the machining process of the SK85 carbon tool steel;

FIG. 4 is a metallographic phase diagram of a metallographic phase detection in a machining process of the SK85 carbon tool steel.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

A processing technology of SK85 carbon tool steel comprises the following steps:

preparing raw materials, and selecting a spring steel hot-rolled coil with the mark of SK85, wherein the chemical composition (according to JIS G3311-2004) of the hot-rolled coil of SK85 requires that: 0.80 to 0.90 of C, less than or equal to 0.35 of Si, less than or equal to 0.50 of Mn, P: 0.030,. S: ≦ 0.030, Cr: is less than or equal to 0.30, Ni is less than or equal to 0.25, and Cu is less than or equal to 0.25; the requirements of the mechanical properties of the hot rolled coil of SK85 are as follows: the tensile strength is less than or equal to 1050 MPa; the requirements of the metallographic phase of the hot-rolled coil of SK85 are: ferrite plus pearlite structure and a decarburized layer, wherein when the thickness is greater than 5mm, the allowable decarburization is less than or equal to 1% t, wherein t is the thickness of a hot rolled steel plate, when the thickness is less than or equal to 5mm, the allowable decarburization is less than 50 μm, the banded structure is less than 2 grade, the fineness of inclusions is less than 2 grade, in the embodiment, the thickness of a hot rolled coil plate with the mark of SK85 is 2.3mm, and the thickness of a finished product is 1.0 +/-0.03 mm; the thickness allowable deviation of the hot-rolled coil plate meets the specification of GB/T709, the convexity requirement is less than or equal to 60 mu m, bubbles, cracks, scabs, warping, pulling cracks and inclusions cannot be formed on the surface of the hot-rolled coil plate, the hot-rolled coil plate cannot be layered, and slight pockmarks, local deep pockmarks, small bubbles, slight scratches and roller indentations within half of the thickness tolerance range are allowed on the surface; the edges of the hot-rolled coil are neat and have no saw-tooth shape;

secondly, stress relief annealing, namely transferring the hot-rolled coil into a cover type annealing furnace through a hoisting device for stress relief annealing, wherein during the stress relief annealing, the annealing furnace is heated to 320 ℃ at full speed, and heat is preserved for 2 hours after the temperature is raised to 320 ℃; secondly, after the annealing furnace is subjected to heat preservation for 2 hours at the temperature of 320 ℃, heating the annealing furnace to 650 ℃ at full speed, and preserving heat for 10 to 12 hours after heating to 650 ℃; thirdly, after the annealing furnace is insulated for 10 to 12 hours at the temperature of 650 ℃, hood replacement air cooling is carried out on the annealing furnace, and the temperature of the annealing furnace is reduced to 320 ℃; fourthly, after the temperature of the annealing furnace is reduced to 320 ℃, the temperature of the annealing furnace is reduced from 320 ℃ to 100 ℃ by adopting a water cooling mode, wherein the temperature is shown in figure 1;

step three, acid pickling, namely transferring the coil plate obtained by stress relief annealing to an acid pickling production line through a hoisting device for acid pickling to obtain an acid-pickled coil plate;

step four, softening and annealing, namely loading the pickled coil plate into a hood-type annealing furnace for softening and annealing, heating the annealing furnace to 320 ℃ at full speed during the softening and annealing, preserving heat for 2h after heating to 320 ℃, preserving heat for 2h at 320 ℃, heating the annealing furnace to 730 ℃ at full speed, preserving heat for 14h after heating to 730 ℃, cooling to 650 ℃ along with the furnace after finishing the heat preservation, carrying out hood-changing air cooling on the annealing furnace after cooling to 650 ℃, reducing the temperature of the annealing furnace to 320 ℃, and then reducing the temperature of the annealing furnace to 320 ℃, and discharging the annealing furnace from 320 ℃ to 100 ℃ by adopting a water cooling mode, wherein the process is shown in figure 2;

fifthly, rolling, namely transferring the prepared softening annealing coiled plate to a rolling mill production line through a hoisting device for rolling, and preparing a rolled coiled plate, wherein the thickness of the rolled coiled plate is 1.0 +/-0.03 mm;

sixthly, spheroidizing annealing, namely transferring the rolled coil obtained after rolling into a cover type annealing furnace through a hoisting device for spheroidizing annealing, wherein during spheroidizing annealing, firstly, the annealing furnace is heated to 320 ℃ at full speed, and heat is preserved for 2 hours after the temperature is raised to 320 ℃; secondly, keeping the temperature of the annealing furnace at 320 ℃ for 2h, then raising the speed of the annealing furnace to 680 ℃ at full speed, and keeping the temperature for 2h after raising the temperature to 680 ℃; thirdly, keeping the temperature of the annealing furnace at 680 ℃ for 2h, heating the annealing furnace to 750 ℃ at full speed, and keeping the temperature for 4h after heating to 750 ℃; fourthly, after the annealing furnace is kept at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the annealing furnace is kept at the temperature of 720 ℃ for 2 hours; fifthly, after the annealing furnace is subjected to heat preservation at the temperature of 720 ℃ for 2 hours, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; sixthly, after the annealing furnace is subjected to heat preservation at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the heat preservation is carried out at the temperature of 720 ℃ for 2 hours; seventh; after the annealing furnace is subjected to heat preservation at the temperature of 720 ℃ for 2 hours, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; eighthly, after the annealing furnace is kept at the temperature of 750 ℃ for 4 hours, the annealing furnace is cooled to 720 ℃ along with the furnace, and the annealing furnace is kept at the temperature of 720 ℃ for 2 hours; ninth, after the annealing furnace is subjected to heat preservation for 2 hours at the temperature of 720 ℃, heating the annealing furnace to 750 ℃ at full speed, and preserving heat for 4 hours after heating to 750 ℃; tenthly, keeping the temperature of the annealing furnace at 750 ℃ for 4h, and cooling to 650 ℃ along with the furnace; eleventh, after the temperature of the annealing furnace is reduced to 650 ℃ in a furnace cooling mode, cover changing and air cooling are carried out on the annealing furnace, and the temperature of the annealing furnace is reduced to 320 ℃; twelfth, after the temperature of the furnace is reduced to 320 ℃, the temperature of the annealing furnace is reduced from 320 ℃ to 80 ℃ by adopting a water cooling mode, wherein the temperature is shown in fig. 3;

seventhly, slitting and splitting, namely transferring the prepared spheroidized annealed coil to a small slitting machine through a traveling crane device for slitting and splitting to prepare a split coil;

and step eight, packaging and warehousing, and packaging the split coiled plates obtained after slitting by using a packaging machine.

In the invention, specific operation flows of stress relief annealing, pickling, softening annealing, rolling, spheroidizing annealing and longitudinal shearing strip splitting are formulated according to the processing technology characteristics of the carbon tool steel plate, so that the stable product quality is effectively controlled and the product performance meeting the customer requirements is effectively controlled.

In the stress relief annealing, the softening annealing and the spheroidizing annealing, a detonating test is required before the temperature is raised, so that the purity of the hydrogen in the ammonia decomposition furnace is ensured; in the whole temperature rising and preserving process, the difference value of the actual temperature value and the process temperature value is less than 10 ℃, the actual temperature value is measured by a thermocouple, the detection frequency is 1 time/1 h, and in addition, a heat preserving platform can be properly added in the temperature rising process to meet the theoretical speed rising.

The strip steel needs to be subjected to secondary detection in the whole production process, wherein the feeding inspection is performed for one time, namely, the thickness and the width of the selected hot rolled material meet the requirements of a planned finished product, the chemical composition, the mechanical property and the tissue structure of the material must meet the standard requirements of an SK85 hot rolled material, bubbles, cracks, scabs, warping, pulling cracks and impurities cannot be formed on the surface of a hot rolled coil, the plate cannot be layered, slight pockmarks, local deep pockmarks, small bubbles, slight scratches and roller indentations within a half of the thickness tolerance range are allowed on the surface, and the edge of the coil is neat and has no sawtooth shape. Secondly, after spheroidizing annealing, before slitting, detecting the hardness of the spheroidizing annealed coil by a universal testing machine and a hardness tester, wherein the qualified range of the hardness of the spheroidizing annealed coil is HV 170-250; and performing metallographic detection on the spheroidized annealed coils with qualified hardness values, and putting the finish-rolled coils with qualified metallographic detection on a small slitting machine, wherein the metallographic detection is specified in the standard of JIS G3311-2004, and is shown in figure 4.

The surface of the rolled coil obtained in the rolling process has no warping, pits, pockmarks, yellow rust, water rust, scratches and straight plate shape; side part: no napping and broken edges. The surface of the split rolling plate obtained by shearing the split strips is free of warping, pockmarks, pits, water rust, scratches, yellow rust, coining, flat and straight in shape and free of broken edges at the edges; when slitting and slitting are carried out, the slitting and rolling plate needs to be coated with anti-rust oil by electrostatic spraying.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.