CN118406976A - Hot rolled steel strip for die cutting knife and preparation method thereof - Google Patents

Abstract

The present invention provides a hot-rolled steel strip for a die-cutting knife and a preparation method thereof, and relates to the technical field of steel production. In terms of weight percentage, the components of the hot-rolled steel strip include: C: 0.38-0.45%, Si: 0.17-0.37%, Mn: 0.80-1.00%; P: 0-0.030%, S: 0-0.015%, Cr: 0.35-0.55%, Ti: 0.025-0.050%, Ca: 0.0010-0.0040%, Al: 0.010-0.050%, and the remainder is Fe and unavoidable impurities. The hot-rolled steel strip provided by the present invention has better strength, better toughness, better hardenability, better welding performance and better fatigue resistance. The die-cutting knife made of the hot-rolled steel strip provided by the invention has a suitable hardness and a high service life of more than 100,000 times.

Description

Hot-rolled steel strip for die-cutting knife and preparation method thereof

Technical Field

The invention relates to the technical field of steel production, and in particular to a hot-rolled steel strip for a die-cutting knife and a preparation method thereof.

Background technique

Die cutters, also called beer cutters or creasing cutters, are sheet materials made of steel with a blade on the top for arranging die-cutting plates. Die cutters are widely used in industries such as shoes and clothing, toys, luggage, stationery and sports goods, and automotive interiors. The materials used for ordinary die cutters are mainly high-quality carbon structural steels such as 40Mn, 42Mn, and 45Mn. However, it is found during use that the service life of ordinary die cutters is generally within 50,000 times. Frequent replacement of die cutters leads to increased production costs and reduced production efficiency. Therefore, die cutters with longer service life have become the direction of industry development. High-service die cutters first require steel to have better strength and better toughness, and the service life of die cutters is also related to the hardenability, welding performance, and fatigue resistance of steel; steel has better hardenability, which is conducive to improving the hardness and wear resistance of die cutters, so that die cutters have a longer service life; steel has better welding performance, which is conducive to reducing the risk of cracking at the welding position of die cutters. Therefore, how to obtain steel with better strength, better toughness, better hardenability, better welding performance and better fatigue resistance has become a technical problem that needs to be solved urgently.

Summary of the invention

The problem solved by the invention is: how to obtain steel having better strength, better toughness, better hardenability, better welding performance and better fatigue resistance.

In order to solve the above problems, the present invention provides a hot-rolled steel strip for a die-cutting knife, wherein the components thereof include, by weight percentage: C: 0.38-0.45%, Si: 0.17-0.37%, Mn: 0.80-1.00%; P: 0-0.030%, S: 0-0.015%, Cr: 0.35-0.55%, Ti: 0.025-0.050%, Ca: 0.0010-0.0040%, Al: 0.010-0.050%, and the remainder is Fe and unavoidable impurities; the metallographic structure of the hot-rolled steel strip for the die-cutting knife is pearlite and ferrite.

Compared with the prior art, the hot-rolled steel strip provided by the present invention adopts a medium carbon content and Cr-Mn-Ti alloying method. By controlling the Cr content in the range of 0.38-0.45%, the decomposition rate of austenite can be slowed down, which is beneficial to improving the hardenability of the hot-rolled steel strip, thereby improving the hardness and wear resistance of the die cutter; by controlling the Mn content in the range of 0.80-1.00%, the martensitic transformation temperature of the steel and the speed of phase transformation in the steel can be greatly reduced, further improving the hardenability of the hot-rolled steel strip, and the Ar1 temperature of the steel can be greatly reduced, which plays a role in refining pearlite, thereby improving the strength and toughness of the hot-rolled steel strip; and it can avoid the situation where the overheating sensitivity and temper brittleness of the steel due to excessive Mn content are increased; by controlling the Ti content in the range of 0.80-1.00%, the martensitic transformation temperature of the steel and the speed of phase transformation in the steel can be greatly reduced, thereby further improving the hardenability of the hot-rolled steel strip, and the Ar1 temperature of the steel can be greatly reduced, thereby playing a role in refining pearlite, thereby improving the strength and toughness of the hot-rolled steel strip; and it can avoid the situation where the overheating sensitivity and temper brittleness of the steel due to excessive Mn content are increased; by controlling the Ti content in the range of 0.80-1.00%, the martensitic transformation temperature and the speed of phase transformation in the steel can be greatly reduced, thereby improving the hardenability of the hot-rolled steel strip, and Controlled within the range of 0.025-0.050%, the Ti element forms highly dispersed small carbonitride particles with C and N. The small carbonitride particles will not dissolve under high temperature conditions of heating or welding, which can hinder the growth of austenite grains and reduce the overheating sensitivity of steel, thereby improving the welding performance of the die cutter, thereby reducing the risk of cracking at the welding position of the die cutter, effectively improving the service life of the die cutter, and significantly improving the grain coarsening resistance of the steel, achieving the refinement of pearlite grains in the hot-rolled steel strip, thereby further improving the strength and toughness of the hot-rolled steel strip; by controlling the Ca content within the range of 0.0010-0.0040%, the inclusions in the molten steel can be accelerated to float and removed, and the modification of non-metallic inclusions can be achieved, which is beneficial to improving the fatigue resistance of the hot-rolled steel strip. In summary, the hot-rolled steel strip provided by the present invention has better strength, better toughness, better hardenability, better welding performance and better fatigue resistance. The die cutting knife made of the hot-rolled steel strip provided by the invention has appropriate hardness and a long service life of more than 100,000 times.

The present invention also provides a method for preparing the hot-rolled steel strip for the die-cutting knife as described above, comprising:

Step S1, smelting the pretreated molten iron and scrap steel in a converter to obtain primary molten steel;

Step S2, tapping the primary molten steel, and adding ferrosilicon and ferroaluminum into the ladle during the tapping process for preliminary alloying to obtain primary alloyed molten steel;

Step S3, adding ferrochrome and ferrotitanium to the primary alloyed molten steel for re-alloying, and adding ferromanganese and ferrosilicon for fine-tuning the composition so that the contents of C, Si, Cr, Mn and Ti in the molten steel meet the target composition requirements, and then adding lime and pre-melted slag for slagging and desulfurization to obtain refined molten steel;

Step S4, feeding calcium silicon wire into the refined molten steel, blowing argon gas, to obtain calcium treated refined molten steel;

Step S5, transferring the calcium-treated refined molten steel into a tundish for continuous casting to obtain a continuous casting billet; performing electromagnetic stirring during the continuous casting process;

Step S6, heating the continuous casting billet, hot rolling and coiling the billet to obtain a hot rolled steel strip.

Optionally, in step S1, the S content in the pretreated molten iron is less than or equal to 0.005%.

Optionally, in step S2, the tapping temperature is 1625-1665°C, and the tapping time is greater than or equal to 5 minutes; the amount of ferrosilicon and manganese added is 10-11 kg/ton of primary molten steel, and the amount of ferroaluminum added is 0.7-1.8 kg/ton of primary molten steel.

Optionally, in step S3, the amount of ferrochrome added is 7.0-8.0 kg/ton of primary molten steel, the amount of ferrotitanium added is 0.9-1.4 kg/ton of primary molten steel, the amount of lime added is 4.9-5.2 kg/ton of primary molten steel, and the amount of pre-melted slag added is 3.2-3.4 kg/ton of primary molten steel.

Optionally, in step S5, during the continuous casting process, the superheat is 13-25° C., the frequency of the electromagnetic stirring is 7 Hz, and the current is 280-320A.

Optionally, during the continuous casting process, the tundish temperature is 1505-1530° C. and the billet drawing speed is 0.8-1.2 m/min.

Optionally, in step S6, the hot rolling includes rough rolling and finish rolling, the inlet temperature of the finish rolling is 1000-1070°C, and the final rolling temperature of the finish rolling is 860-910°C.

Optionally, in step S6, the coiling temperature is 610-660°C.

Optionally, during the coiling process, the temperature of the end section 20m of the steel strip is 20°C higher than the temperature of the middle section.

Compared with the prior art, the preparation method of the hot-rolled steel strip provided by the present invention uses pre-treated molten iron and scrap steel as raw materials, obtains primary molten steel through converter smelting, and transfers to LF refining furnace for refining after steel tapping. During the refining process, the elements in the molten steel are adjusted according to the target component requirements, and then slag desulfurization is performed to obtain refined molten steel; the refined molten steel is fed to silicon-calcium wire and then continuously cast to obtain a continuous casting billet, and segregation is changed by electromagnetic stirring during the continuous casting process, which can avoid the generation of defects in the continuous casting billet; the continuous casting billet is heated and hot-rolled and coiled to obtain a hot-rolled steel strip. The preparation method of the hot-rolled steel strip provided by the present invention has a simple process and reasonable preparation cost; it is found through experiments that the hot-rolled steel strip prepared by the method of the present invention has uniform material, small component segregation, and low banded structure level, small fluctuations in metallographic structure and mechanical properties of the hot-rolled steel strip, good processing performance, and good consistency in quenching and tempering performance; the purity of the hot-rolled steel strip is high, the content of harmful elements P and S is low, and there are few non-metallic inclusions. The hot-rolled steel strip prepared by the method of the present invention has uniform material, better strength, better toughness, better hardenability, better welding performance and better fatigue resistance, good processing and heat treatment performance, and can meet the quality requirements of long-life die cutting knives.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic flow diagram of a method for preparing a hot-rolled steel strip for a die-cutting knife in an embodiment of the present invention;

FIG2 is a metallographic structure picture of the hot-rolled steel strip obtained in Example 1;

FIG3 is a metallographic structure picture of the blade of the die-cutting knife prepared in Application Example 1;

FIG. 4 is a metallographic structure picture of the blade of the die-cutting knife prepared in Application Example 1.

Detailed ways

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by those skilled in the art to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific implementation methods and are not intended to limit this application;

The term "including" and its variations used in this article are open inclusions, that is, "including but not limited to"; the term "based on" is "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first" and "second" mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship. In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, the meaning of "multiple" is two or more.

In addition, it should be noted that Kg/ton of primary molten steel in the present invention refers to the amount of a substance added per ton of primary molten steel. The contents of C, Si, Cr, Mn and Ti in the molten steel in the present invention meet the target composition requirements, which means that the contents of C, Si, Cr, Mn and Ti in the molten steel are respectively: C: 0.38-0.45%, Si: 0.17-0.37%, Cr: 0.35-0.55%, Mn: 0.80-1.00%, Ti: 0.025-0.050%.

A hot-rolled steel strip for a die-cutting knife provided in an embodiment of the present invention comprises, by weight percentage, the following components: C: 0.38-0.45%, Si: 0.17-0.37%, Mn: 0.80-1.00%; P: 0-0.030%, S: 0-0.015%, Cr: 0.35-0.55%, Ti: 0.025-0.050%, Ca: 0.0010-0.0040%, Al: 0.010-0.050%, and the remainder is Fe and unavoidable impurities; the metallographic structure of the hot-rolled steel strip for the die-cutting knife is pearlite and ferrite.

The hot-rolled steel strip provided in the embodiment of the present invention adopts a medium carbon content and Cr-Mn-Ti alloying method. By controlling the Cr content in the range of 0.38-0.45%, the decomposition rate of austenite can be slowed down, which is beneficial to improving the hardenability of the hot-rolled steel strip, thereby improving the hardness and wear resistance of the die cutter; by controlling the Mn content in the range of 0.80-1.00%, the martensitic transformation temperature of the steel and the speed of phase transformation in the steel can be greatly reduced, further improving the hardenability of the hot-rolled steel strip, and the Ar1 temperature of the steel can be greatly reduced, which plays a role in refining pearlite, thereby improving the strength of the hot-rolled steel strip; and it can avoid the situation where the overheating sensitivity and temper brittleness of the steel due to excessive Mn content are increased; by controlling the Ti content in the range of 0 In the range of 0.025-0.050%, the Ti element forms highly dispersed small carbonitride particles with C and N. The small carbonitride particles will not dissolve under high temperature conditions of heating or welding, which can hinder the growth of austenite grains and reduce the overheating sensitivity of steel, thereby improving the welding performance of the die cutter, thereby reducing the risk of cracking at the welding position of the die cutter, effectively improving the service life of the die cutter, and significantly improving the grain coarsening resistance of steel, achieving the refinement of pearlite grains in the hot-rolled steel strip, thereby further improving the strength and toughness of the hot-rolled steel strip; by controlling the Ca content to 0.0010-0.0040%, the inclusions in the molten steel can be accelerated to float and removed, and the modification of non-metallic inclusions can be achieved, which is beneficial to improving the fatigue resistance of the hot-rolled steel strip. In summary, the hot-rolled steel strip provided by the embodiment of the present invention has better strength, better toughness, better hardenability, better welding performance and better fatigue resistance. The die-cutting knife made of the hot-rolled steel strip provided by the embodiment of the invention has an appropriate hardness and a high service life of more than 100,000 times.

As shown in FIG1 , an embodiment of the present invention further provides a method for preparing the hot-rolled steel strip for the die-cutting knife as described above, comprising:

Step S1, smelting the pretreated molten iron and scrap steel in a converter to obtain primary molten steel;

Step S2, tapping the primary molten steel, and adding ferrosilicon and ferroaluminum into the ladle during the tapping process for preliminary alloying to obtain primary alloyed molten steel;

Step S3, adding ferrochrome and ferrotitanium to the primary alloyed molten steel for re-alloying, and adding ferromanganese and ferrosilicon for fine-tuning the composition so that the contents of C, Si, Cr, Mn and Ti in the molten steel meet the target composition requirements, and then adding lime and pre-melted slag for slagging and desulfurization to obtain refined molten steel;

Step S4, feeding calcium silicon wire into the refined molten steel, blowing argon gas, to obtain calcium treated refined molten steel;

Step S5, transferring the calcium-treated refined molten steel into a tundish for continuous casting to obtain a continuous casting billet; performing electromagnetic stirring during the continuous casting process;

Step S6, heating the continuous casting billet, hot rolling and coiling the billet to obtain a hot rolled steel strip.

The preparation method of the hot-rolled steel strip provided by the embodiment of the present invention uses pre-treated molten iron and scrap steel as raw materials, obtains primary molten steel through converter smelting, and transfers to LF refining furnace for refining after steel is tapped. During the refining process, the elements in the molten steel are adjusted according to the target component requirements, and then slag desulfurization is performed to obtain refined molten steel; the refined molten steel is fed to silicon-calcium wire and then continuously cast to obtain a continuous casting billet, and the segregation is changed by electromagnetic stirring during the continuous casting process, which can avoid the generation of defects in the continuous casting billet; the continuous casting billet is heated and hot-rolled and coiled to obtain a hot-rolled steel strip. The preparation method of the hot-rolled steel strip provided by the embodiment of the present invention has a simple process and reasonable preparation cost; it is found through experiments that the hot-rolled steel strip prepared by the method of the embodiment of the present invention has uniform material, small component segregation, and low banded structure level, small fluctuations in the metallographic structure and mechanical properties of the hot-rolled steel strip, good processing performance, and good consistency in quenching and tempering performance; the purity of the hot-rolled steel strip is high, the content of harmful elements P and S is low, and there are few non-metallic inclusions. The hot-rolled steel strip produced by the method of the embodiment of the present invention has uniform material, better strength, better toughness, better hardenability, better welding performance and better fatigue resistance, good processing and heat treatment performance, and can meet the quality requirements of long-life die cutting knives.

In some embodiments of the present invention, in step S1, the S content in the pretreated molten iron is less than or equal to 0.005%.

In some embodiments of the present invention, in step S2, the tapping temperature is 1625-1665°C, the tapping time is greater than or equal to 5 minutes, the amount of ferrosilicon and manganese added is 10-11 kg/ton of primary molten steel, and the amount of ferroaluminum added is 0.7-1.8 kg/ton of primary molten steel, thereby ensuring the effects of preliminary alloying and deoxidation.

In some embodiments of the present invention, in step S3, the amount of ferrochrome added is 7.0-8.0 kg/ton of primary molten steel, the amount of ferrotitanium added is 0.9-1.4 kg/ton of primary molten steel, the amount of lime added is 4.9-5.2 kg/ton of primary molten steel, and the amount of pre-melted slag added is 3.2-3.4 kg/ton of primary molten steel.

In some embodiments of the present invention, in step S5, during the continuous casting process, the superheat is 13-25° C., the frequency of the electromagnetic stirring is 7 Hz, and the current is 280-320 A. By controlling the frequency and current of the electromagnetic stirring, the possibility of defects in the continuous casting billet is further reduced.

In some embodiments of the present invention, during the continuous casting process, the tundish temperature is 1505-1530°C and the billet drawing speed is 0.8-1.2 m/min. By controlling the billet drawing speed to 0.8-1.2 m/min, low segregation continuous casting is achieved and corner cracks and edge cracks of the continuous casting billet are avoided.

In some embodiments of the present invention, in step S6, the hot rolling includes rough rolling and finish rolling, the inlet temperature of the finish rolling is 1000-1070°C, and the final rolling temperature of the finish rolling is 860-910°C.

In some embodiments of the present invention, in step S6, the coiling temperature is 610-660°C.

In some embodiments of the present invention, during the coiling process, the temperature of the end section 20m of the steel strip is 20°C higher than that of the middle section. Since the tail of the finished steel strip cools faster than the middle section after rolling, the coiling process easily leads to differences in the structure and performance of the tail and the middle section. In order to reduce this difference, a tail temperature rise control mode is adopted, that is, during the coiling process, the temperature of the end section 20m of the steel strip is 20°C higher than that of the middle section. Through this treatment method, the uniformity of the hot-rolled steel strip can be effectively improved, ensuring that the difference in tensile strength of the hot-rolled steel strip in the length direction is within 60MPa.

The present invention is further described below in conjunction with specific embodiments. It should be noted that in embodiments 1-3 of the present invention, the ferrosilicon manganese used is FeMn68Si18, which contains 68% manganese, 18% silicon, less than 5% impurities, and the remainder is iron; the ferroaluminum used is FeAl40, which contains 40% aluminum, less than 5% other impurities, and the remainder is iron; the ferrochromium used is FeCr55C0.50, which contains 55% chromium, less than 5% other impurities, and the remainder is iron; the ferrotitanium used is FeTi30, and the ferromanganese used is FeMn68C7.0; the ferrosilicon used is FeSi75, which contains 75% silicon, less than 5% other impurities, and the remainder is iron; the calcium silicon wire used is Si50Ca28, which contains 50% silicon, 28% calcium, less than 5% other impurities, and the remainder is iron.

Example 1

A1. Performing desulfurization pretreatment on blast furnace molten iron to obtain pretreated molten iron; wherein the S content of the pretreated molten iron is 0.0043%.

A2. 200.610t of pretreated molten iron and 15.620t of scrap steel are added into the converter for converter smelting to obtain primary molten steel; the end point of the converter smelting is a C content of 0.0779% and a P content of 0.0093%.

A3. The primary molten steel is tapped, and during the tapping process, ferrosilicon manganese and ferroaluminum are added to the ladle for preliminary alloying to obtain primary alloyed molten steel; wherein a double slag blocking method is adopted during tapping, the tapping temperature is 1632° C., and the tapping time is 6 min; the amount of ferrosilicon manganese added is 2230 kg, and the amount of ferroaluminum added is 260 kg.

A4. Add ferrochrome and ferrotitanium to the primary alloyed molten steel for re-alloying, and add ferromanganese and ferrosilicon to fine-tune the composition so that the contents of C, Si, Cr, Mn and Ti in the molten steel meet the target composition requirements, and then add lime and pre-melted slag for slagging and desulfurization to obtain refined molten steel; wherein the amount of ferrochrome added is 1518kg, the amount of ferrotitanium added is 260kg, the amount of lime added is 1076kg, and the amount of pre-melted slag added is 709kg.

A5. Feed calcium silicon wire into the refined molten steel and blow argon gas to obtain calcium treated refined molten steel; wherein the feeding amount of calcium silicon wire is 650m3, the argon gas is blown in a soft blowing manner, and the blowing time is 6 minutes.

A6. The calcium-treated refined molten steel is transferred into a tundish for continuous casting to obtain a continuously cast billet; during the continuous casting process, electromagnetic stirring is performed and the superheat is controlled to be 20°C, the frequency of the electromagnetic stirring is 7Hz, and the current is 300A; during the continuous casting process, the temperature of the tundish is 1509-1514°C, and the billet drawing speed is 0.9m/min; the thickness of the continuously cast billet is 230mm and the width is 1250mm.

A7. The continuous casting billet is subjected to heat treatment to obtain a heat-treated continuous casting billet; wherein, the furnace entry temperature of the continuous casting billet is 600° C., the total heating time is 250 min, the soaking time is 27 min, the furnace exit temperature of the continuous casting billet is 1210° C., and a weak reducing atmosphere is always maintained during the heating process.

A8. The heat-treated continuous casting billet is subjected to rough rolling and finish rolling to obtain a finished steel strip; wherein the inlet temperature of the finish rolling is 1050° C., the final rolling temperature of the finish rolling is 890° C., and the thickness of the finished steel strip is 3.5 mm.

A9. Cool the finished steel strip to 628-649℃ and coil it to obtain a hot-rolled steel strip. During the coiling process, the temperature of the end section 20m of the steel strip is 20℃ higher than that of the middle section. The hot-rolled steel strip is sampled and analyzed, and the analysis method adopts GB/T223 "Chemical Analysis Methods for Steel and Alloys". After testing, the components of the hot-rolled steel strip include, by weight percentage: C: 0.3903%, Si: 0.236%, Mn: 0.892%; P: 0.0103%, S: 0.0028%, Cr: 0.3971%, Ti: 0.00372%, Ca: 0.0013%, Al: 0.0331%, and the balance is Fe and unavoidable impurities.

Example 2

A1. Performing desulfurization pretreatment on blast furnace molten iron to obtain pretreated molten iron; wherein the S content of the pretreated molten iron is 0.0045%.

A2. 200.40t of pretreated molten iron and 15.590t of scrap steel are added into the converter for converter smelting to obtain primary molten steel; the end point of the converter smelting is a C content of 0.0776% and a P content of 0.0092%.

A3. The primary molten steel is tapped, and during the tapping process, ferrosilicon manganese and ferroaluminum are added to the ladle for preliminary alloying to obtain primary alloyed molten steel; wherein a double slag blocking method is adopted during tapping, the tapping temperature is 1625° C., and the tapping time is 6 minutes; the amount of ferrosilicon manganese added is 2235 kg, and the amount of ferroaluminum added is 255 kg.

A4. Add ferrochrome and ferrotitanium to the primary alloyed molten steel for re-alloying, and add ferromanganese and ferrosilicon to fine-tune the composition so that the contents of C, Si, Cr, Mn and Ti in the molten steel meet the target composition requirements, and then add lime and pre-melted slag for slagging and desulfurization to obtain refined molten steel; wherein the amount of ferrochrome added is 1520kg, the amount of ferrotitanium added is 259kg, the amount of lime added is 1075kg, and the amount of pre-melted slag added is 710kg.

A5. Feed calcium silicon wire into the refined molten steel and blow argon gas to obtain calcium treated refined molten steel; wherein the feeding amount of calcium silicon wire is 650m3, the argon gas is blown in a soft blowing manner, and the blowing time is 6 minutes.

A6. The calcium-treated refined molten steel is transferred into a tundish for continuous casting to obtain a continuously cast billet; during the continuous casting process, electromagnetic stirring is performed and the superheat is controlled at 13°C, the frequency of the electromagnetic stirring is 7Hz, and the current is 320A; during the continuous casting process, the temperature of the tundish is 1530°C, and the billet drawing speed is 1.2m/min; the thickness of the continuously cast billet is 230mm, and the width is 1250mm.

A7. The continuous casting billet is subjected to heat treatment to obtain a heat-treated continuous casting billet; wherein, the furnace entry temperature of the continuous casting billet is 600° C., the total heating time is 250 min, the soaking time is 27 min, the furnace exit temperature of the continuous casting billet is 1210° C., and a weak reducing atmosphere is always maintained during the heating process.

A8. The heat-treated continuous casting billet is subjected to rough rolling and finish rolling to obtain a finished steel strip; wherein the inlet temperature of the finish rolling is 1070° C., the final rolling temperature of the finish rolling is 900° C., and the thickness of the finished steel strip is 3.5 mm.

A9. Cool the finished steel strip to 627-650℃ and coil it to obtain a hot-rolled steel strip. During the coiling process, the temperature of the end section 20m of the steel strip is 20℃ higher than that of the middle section. The hot-rolled steel strip is sampled and analyzed, and the analysis method adopts GB/T223 "Chemical Analysis Methods for Steel and Alloys". After testing, the components of the hot-rolled steel strip include, by weight percentage: C: 0.4009%, Si: 0.273%, Mn: 0.891%; P: 0.0135%, S: 0.0023%, Cr: 0.3897%, Ti: 0.00378%, Ca: 0.0015%, Al: 0.0338%, and the balance is Fe and unavoidable impurities.

Example 3

A1. Performing desulfurization pretreatment on blast furnace molten iron to obtain pretreated molten iron; wherein the S content of the pretreated molten iron is 0.0042%.

A2. Add 200.30t of pretreated molten iron and 15.560t of scrap steel into the converter for converter smelting to obtain primary molten steel; the end point of the converter smelting is a C content of 0.0775% and a P content of 0.0090%.

A3. The primary molten steel is tapped, and during the tapping process, ferrosilicon manganese and ferroaluminum are added to the ladle for preliminary alloying to obtain primary alloyed molten steel; wherein a double slag blocking method is adopted during tapping, the tapping temperature is 1665° C., and the tapping time is 7 minutes; the amount of ferrosilicon manganese added is 2230 kg, and the amount of ferroaluminum added is 250 kg.

A4. Add ferrochrome and ferrotitanium to the primary alloyed molten steel for re-alloying, and add ferromanganese and ferrosilicon to fine-tune the composition so that the contents of C, Si, Cr, Mn and Ti in the molten steel meet the target composition requirements, and then add lime and pre-melted slag for slagging and desulfurization to obtain refined molten steel; wherein the added amount of the ferrochrome is 1523kg, the added amount of the ferrotitanium is 258kg, the added amount of the lime is 1072kg, and the added amount of the pre-melted slag is 712kg.

A5. Feed calcium silicon wire into the refined molten steel and blow argon gas to obtain calcium treated refined molten steel; wherein the feeding amount of calcium silicon wire is 650m3, the argon gas is blown in a soft blowing manner, and the blowing time is 6 minutes.

A6. The calcium-treated refined molten steel is transferred into a tundish for continuous casting to obtain a continuously cast billet; during the continuous casting process, electromagnetic stirring is performed and the superheat is controlled to be 24°C, the frequency of the electromagnetic stirring is 7Hz, and the current is 290A; during the continuous casting process, the temperature of the tundish is 1520°C, and the billet drawing speed is 0.8m/min; the thickness of the continuously cast billet is 230mm, and the width is 1250mm.

A7. The continuous casting billet is subjected to heat treatment to obtain a heat-treated continuous casting billet; wherein, the furnace entry temperature of the continuous casting billet is 600° C., the total heating time is 249 min, the soaking time is 26 min, the furnace exit temperature of the continuous casting billet is 1210° C., and a weak reducing atmosphere is always maintained during the heating process.

A8. The heat-treated continuous casting billet is subjected to rough rolling and finish rolling to obtain a finished steel strip; wherein the inlet temperature of the finish rolling is 1000° C., the final rolling temperature of the finish rolling is 860° C., and the thickness of the finished steel strip is 3.5 mm.

A9. Cool the finished steel strip to 626-651℃ and coil it to obtain a hot-rolled steel strip. During the coiling process, the temperature of the end section 20m of the steel strip is 20℃ higher than that of the middle section. The hot-rolled steel strip is sampled and analyzed, and the analysis method adopts GB/T223 "Chemical Analysis Methods for Steel and Alloys". After testing, the components of the hot-rolled steel strip include, by weight percentage: C: 0.3962%, Si: 0.260%, Mn: 0.890%; P: 0.0123%, S: 0.0030%, Cr: 0.3824%, Ti: 0.00396%, Ca: 0.0015%, Al: 0.0359%, and the balance is Fe and unavoidable impurities.

Comparative Example

The composition of the hot-rolled steel strip prepared in the comparative example meets the composition requirements of 42Mn steel.

Application Example 1

The hot-rolled steel strip in Example 1 is pickled, stripped, rolled, heat treated, sharpened, polished and the blade is quenched and tempered to obtain a die-cutting knife.

Application Example 2

The hot-rolled steel strip in Example 2 is pickled, stripped, rolled, heat treated, sharpened, polished and the blade is quenched and tempered to obtain a die-cutting knife.

Application Example 3

The hot-rolled steel strip in Example 3 is pickled, stripped, rolled, heat treated, sharpened, polished and the blade is quenched and tempered to obtain a die-cutting knife.

Comparative Application Examples

The hot-rolled steel strip in the comparative example is pickled, stripped, rolled, heat treated, sharpened, polished and the blade is quenched and tempered to obtain a die-cutting knife.

Experimental example

The metallographic structures of the hot-rolled steel strips prepared in Examples 1-3 and the comparative examples were tested. The metallographic structures of the hot-rolled steel strips prepared in Examples 1-3 and the comparative examples were all pearlite + ferrite. The non-metallic inclusion level, banded structure level and decarburization layer depth of the hot-rolled steel strips prepared in Examples 1-3 and the comparative examples were tested, and the results are shown in Table 1. It can be seen from Table 1 that compared with the comparative example, the hot-rolled steel strips prepared in Examples 1-3 have fewer non-metallic inclusions, a lower banded structure level, and no decarburization layer. Figure 2 is a metallographic structure picture of the hot-rolled steel strip prepared in Example 1. It can be seen from Figure 2 that the hot-rolled steel strip prepared in Example 1 has good structural uniformity.

The specified plastic extension strength, tensile strength and elongation after fracture of the hot-rolled steel strips prepared in Examples 1-3 and the comparative example were tested, and the results are shown in Table 2. It can be seen from Table 2 that compared with the comparative example, the specified plastic extension strength, tensile strength and elongation after fracture of the hot-rolled steel strips prepared in Examples 1-3 are higher, indicating that the hot-rolled steel strips prepared in Examples 1-3 have better strength and better toughness.

Table 1

Table 2

The blade hardness, blade hardness and service life of the die cutters prepared in the corresponding application examples 1-3 and the comparative application examples were tested, and the results are shown in Table 3. It can be seen from Table 3 that compared with the comparative application examples, the blade hardness and blade hardness of the die cutters prepared in application examples 1-3 are both higher, and the service life of the die cutters prepared in application examples 1-3 is longer. The metallographic structures of the blade and blade of the die cutter prepared in the corresponding application example 1 were observed respectively, and the results are shown in Figures 3 and 4. It can be seen from Figure 3 that the metallographic structure of the blade of the die cutter prepared in application example 1 is tempered troostite, so the blade of the die cutter prepared in application example 1 has higher hardness and better bending toughness; it can be seen from Figure 4 that the metallographic structure of the blade of the die cutter prepared in application example 1 is martensite, so the blade of the die cutter prepared in application example 1 has good sharpness.

table 3

It should be noted that the mechanical properties in the present invention are tested by a universal mechanical testing machine, and the testing standard is GB/T13239 "Low-temperature tensile test method for metallic materials"; the metallographic structure is tested by an optical metallographic microscope, and the testing standards are GB/T13299 "Method for evaluating the microstructure of steel", GB/T34474.1 "Evaluation of banded structure in steel Part 1: Standard rating chart method", GB/T10561 "Standard rating chart microscopic examination method for determination of non-metallic inclusion content in steel" and GB/T224 "Determination method for the depth of decarburization layer in steel".

The pre-melted slag used in Examples 1-3 of the present invention is a product called pre-melted aluminum composite deoxidizer produced by Shanghai Yinkun Industrial Development Co., Ltd. The chemical composition of the product is shown in Table 4.

Table 4

Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims (10)

1. A hot-rolled steel strip for a die-cutting knife, characterized in that, in terms of weight percentage, its components include: C: 0.38-0.45%, Si: 0.17-0.37%, Mn: 0.80-1.00%; P: 0-0.030%, S: 0-0.015%, Cr: 0.35-0.55%, Ti: 0.025-0.050%, Ca: 0.0010-0.0040%, Al: 0.010-0.050%, and the balance is Fe and unavoidable impurities; the metallographic structure of the hot-rolled steel strip for the die-cutting knife is pearlite and ferrite. 2. A method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 1, characterized in that it comprises: Step S1, smelting the pretreated molten iron and scrap steel in a converter to obtain primary molten steel; Step S2, tapping the primary molten steel, and adding ferrosilicon and ferroaluminum into the ladle during the tapping process for preliminary alloying to obtain primary alloyed molten steel; Step S3, adding ferrochrome and ferrotitanium to the primary alloyed molten steel for re-alloying, and adding ferromanganese and ferrosilicon for fine-tuning the composition so that the contents of C, Si, Cr, Mn and Ti in the molten steel meet the target composition requirements, and then adding lime and pre-melted slag for slagging and desulfurization to obtain refined molten steel; Step S4, feeding calcium silicon wire into the refined molten steel, blowing argon gas, to obtain calcium treated refined molten steel; Step S5, transferring the calcium-treated refined molten steel into a tundish for continuous casting to obtain a continuous casting billet; performing electromagnetic stirring during the continuous casting process; Step S6, heating the continuous casting billet, hot rolling and coiling the billet to obtain a hot rolled steel strip. 3. The method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 2, characterized in that, in the step S1, the S content in the pretreated molten iron is less than or equal to 0.005%. 4. The method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 2 is characterized in that, in the step S2, the tapping temperature is 1625-1665°C, and the tapping time is greater than or equal to 5 minutes; the amount of ferrosilicon manganese added is 10-11 kg/ton of primary molten steel, and the amount of ferroaluminum added is 0.7-1.8 kg/ton of primary molten steel. 5. The method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 2 is characterized in that, in the step S3, the amount of ferrochrome added is 7.0-8.0 kg/ton of primary molten steel, the amount of ferrotitanium added is 0.9-1.4 kg/ton of primary molten steel, the amount of lime added is 4.9-5.2 kg/ton of primary molten steel, and the amount of pre-melted slag added is 3.2-3.4 kg/ton of primary molten steel. 6. The method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 2, characterized in that in the step S5, during the continuous casting process, the superheat is 13-25°C, the frequency of the electromagnetic stirring is 7Hz, and the current is 280-320A. 7. The method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 6 is characterized in that during the continuous casting process, the tundish temperature is 1505-1530°C and the billet drawing speed is 0.8-1.2 m/min. 8. The method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 2, characterized in that in the step S6, the hot rolling includes rough rolling and finish rolling, the inlet temperature of the finish rolling is 1000-1070°C, and the final rolling temperature of the finish rolling is 860-910°C. 9. The method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 2, characterized in that in the step S6, the coiling temperature is 610-660°C. 10. The method for preparing a hot-rolled steel strip for a die-cutting knife according to claim 9, characterized in that during the coiling process, the temperature of the end section 20m of the steel strip is 20°C higher than the temperature of the middle section.