High-purity die steel and smelting process thereof

Abstract

The invention discloses high-purity die steel and a smelting process thereof, and belongs to the technical field of smelting processes. The smelting steps of intermediate frequency furnace coarse smelting, LF furnace refining and VD vacuum furnace treatment are firstly carried out, and then advanced deoxidation, slagging and degassing treatment technologies are adopted, so that impurities and gas in steel can be effectively removed, the purity of the die steel is improved, and the service life of the die is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of smelting technology, and in particular relates to a high-purity die steel and a smelting technology thereof. Background Art

[0002] At present, with the development of manufacturing industry, especially precision machining and mold manufacturing technology, mold steel is widely used in automobile parts, electronic components, plastic products, metal products and other industries due to its excellent thermal stability, strength and toughness, as well as good wear resistance and corrosion resistance. Although traditional mold steel can meet the use requirements of general molds, in some specific application scenarios, its purity is not enough to cope with more stringent processing conditions. It is often accompanied by high temperature wear during use, which may cause surface defects or shortened service life of the product. Therefore, the research and application of high-purity mold steel is particularly important. Since it is difficult to achieve the ideal purity with traditional smelting processes, improving the purity of mold steel has become the key to improving its performance. Summary of the invention

[0003] In order to solve the problem of low purity in the prior art, the present invention provides a high-purity die steel and a smelting process thereof.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A smelting process for high-purity die steel comprises the following steps:

[0006] Step 1: Rough refining in medium frequency furnace

[0007] The steel material is melted in a medium frequency furnace, smelted until it is completely melted, and then alloys are added to adjust the chemical composition to the internal control standard to obtain molten steel. Aluminum particles are added to the molten steel for deoxidation, and then furnace slag agent is added to slag to obtain slag. Finally, electric heating is applied at a heating temperature of 1520-1560°C to obtain molten steel after rough refining in a medium frequency furnace;

[0008] Step 2: LF furnace refining

[0009] The molten steel after rough refining in the medium frequency furnace is sent to the LF furnace for smelting, and is heated to 1480-1600℃ by electricity. After sampling and analysis, the chemical composition is adjusted to the internal control standard, 0.8-1.2kg / t aluminum wire is fed, and the calming time is 1-2min. Then 0.4-0.6kg / t SiCa wire is fed, and the aluminum content in the molten steel is adjusted to 0.03-0.05%. Steel is tapped to obtain the molten steel after refining in the LF furnace;

[0010] Step 3: VD vacuum furnace treatment

[0011] The molten steel refined in the LF furnace is sent to the VD furnace for smelting and vacuumed. After the vacuum degree reaches 60-67Pa, the argon flow rate is maintained at 50-60NL / min. Degassing treatment is then carried out for 15-30 minutes. The vacuuming is stopped and the argon flow rate is reduced to 10-20NL / min. Sampling is performed to adjust the chemical composition to the internal control standard to obtain high-purity mold steel.

[0012] Furthermore, the composition of the steel material is as follows by weight percentage: C: 0.83-0.88%, Si: 0.2-0.4%, Mn: 0.2-0.4%, P≤0.03%, S≤0.015%, Cr≥3.9%, Mo≥4.55%, W≥5.5%, Ni≤0.3%, Cu≤0.3%, V≥1.8%.

[0013] Furthermore, in step 1, the weight ratio of the slag forming agent to the steel material is (5-10):1000.

[0014] Furthermore, in step 1, the slag is 2-3% of the weight of the molten steel.

[0015] Furthermore, the furnace slag agent in step 1 includes the following raw materials in parts by weight: 8-15 parts of lime powder and 2-4 parts of fluorite powder;

[0016] Furthermore, the method for refining the furnace slag agent comprises the following steps:

[0017] Step 1, according to the weight parts, add lime powder and fluorite powder into a mixer and stir, add 80-100 parts of deionized water, stir at a speed of 300-380r / min for 30-60min, and the stirring temperature is 15-25°C to obtain a slurry;

[0018] Step 2: Add the slurry into a mold and dry it at a temperature of 80-95° C. to obtain a furnace slag agent.

[0019] Furthermore, in step 1, the pH of the slag is maintained at 2.6-3.4.

[0020] Furthermore, in step 2, the tapping temperature is between 1540°C and 1660°C. Beneficial effects of the present invention:

[0021] 1. The present invention provides a high-purity mold steel and a smelting process thereof. Through the smelting steps of medium frequency furnace roughing, LF furnace refining and VD vacuum furnace treatment, impurities and gases in the steel can be effectively removed, the purity of the mold steel can be improved, and the service life of the mold can be extended.

[0022] 2. By adding aluminum particles and aluminum wire for deoxidation and calming, and feeding SiCa wire to adjust the aluminum content, the content of alloy elements in the steel can be accurately controlled to meet specific usage requirements.

[0023] 3. The smelting process adopts advanced deoxidation, slagging and degassing treatment technologies during the smelting process, which can effectively reduce the emission of waste gas, waste slag and other pollutants. At the same time, by accurately controlling the smelting temperature and time, it can save energy consumption and reduce production costs, which is in line with the development trend of environmental protection and energy conservation. DETAILED DESCRIPTION

[0024] Step 1: Rough refining in medium frequency furnace

[0025] The steel material is melted in a medium frequency furnace, smelted until it is completely melted, and then the alloy is added to adjust the chemical composition to the internal control standard to obtain molten steel. 1.2-1.3kg / t of aluminum particles are added to the molten steel for deoxidation, and then furnace slag agent is added to slag to obtain slag. Finally, electric heating is supplied at a heating temperature of 1520-1560℃ to obtain molten steel after rough refining in a medium frequency furnace;

[0026] Step 2: LF furnace refining

[0027] The molten steel after rough refining in the medium frequency furnace is sent to the LF furnace for smelting, and is heated to 1480-1600℃ by electricity. After sampling and analysis, the chemical composition is adjusted to the internal control standard, 0.8-1.2kg / t aluminum wire is fed, and the calming time is 1-2min. Then 0.4-0.6kg / t SiCa wire is fed, and the aluminum content in the molten steel is adjusted to 0.03-0.05%. Steel is tapped to obtain the molten steel after refining in the LF furnace;

[0028] Step 3: VD vacuum furnace treatment

[0029] The molten steel refined in the LF furnace is sent to the VD furnace for smelting, vacuumed, and the argon flow rate is maintained. Degassing is then carried out, and the vacuuming is stopped, the argon flow rate is reduced, and sampling is performed to adjust the chemical composition to the internal control standard to obtain high-purity mold steel.

[0030] Furthermore, the composition of the steel material is as follows by weight percentage:

[0031] C: 0.83-0.88%, Si: 0.2-0.4%, Mn: 0.2-0.4%, P≤0.03%, S≤0.015%, Cr≥3.9%, Mo≥4.55%, W≥5.5%, Ni≤0.3%, Cu≤0.3%, V≥1.8%.

[0032] Furthermore, in step 1, the weight ratio of the slag-forming agent to the steel material is (5-10):1000, more preferably the weight ratio of the slag-forming agent to the steel material is (6-8):1000, and more preferably 7.6:1000.

[0033] Furthermore, in step 1, the slag is 2-3% of the weight of the molten steel, more preferably the slag is 2.2-2.8% of the weight of the molten steel, and more preferably the slag is 2.6% of the weight of the molten steel.

[0034] Furthermore, in step 1, the pH of the slag is maintained at 2.6-3.4, more preferably the pH of the slag is maintained at 2.8-3.2, and more preferably the pH of the slag is maintained at 3.

[0035] Furthermore, in step 2, the steel tapping temperature is 1540-1660°C, further preferably 1544-1658°C, and more preferably 1580°C.

[0036] Furthermore, in step 3, the vacuum degree is 60-67Pa, more preferably 61-65Pa, and more preferably 64Pa.

[0037] Furthermore, the degassing treatment time in step 3 is 15-30 min, more preferably 16-28 min, and more preferably 26 min.

[0038] Furthermore, in the step 3, after vacuuming, the argon flow rate is maintained at 50-60NL / min, and then degassing is performed, and then the vacuuming is stopped and the argon flow rate is reduced to 10-20NL / min. It is further preferred that after vacuuming, the argon flow rate is maintained at 52-58NL / min, and then degassing is performed, and then the vacuuming is stopped and the argon flow rate is reduced to 12-18NL / min. It is more preferred that after vacuuming, the argon flow rate is maintained at 56NL / min, and then degassing is performed, and then the vacuuming is stopped and the argon flow rate is reduced to 14NL / min.

[0039] Furthermore, the furnace slag agent in step 1 includes the following raw materials in parts by weight: 8-15 parts of lime powder and 2-4 parts of fluorite powder;

[0040] Furthermore, the method for refining the furnace slag agent comprises the following steps:

[0041] Step 1: Add lime powder and fluorite powder into a mixer according to weight proportions, add 80-100 parts of deionized water, stir at a speed of 300-380 r / min for 30-60 min, and stir at a temperature of 15-25° C. to obtain a slurry; Step 2: Add the slurry into a mold and dry it at a drying temperature of 80-95° C. to obtain a furnace slag agent.

[0042] Furthermore, in step 1 of the refining method of the furnace slag agent, the weight portions of the furnace slag agent are 8-15 parts of lime powder, 2-4 parts of fluorite powder and 80-100 parts of deionized water, further preferably 10-14 parts of lime powder, 2-4 parts of fluorite powder and 85-95 parts of deionized water, more preferably 12 parts of lime powder, 3 parts of fluorite powder and 90 parts of deionized water.

[0043] Furthermore, in step 1 of the refining method of the furnace slag agent, stirring is performed at a rotation speed of 300-380 r / min for 30-60 min, and a stirring temperature of 15-25°C. It is further preferred that stirring is performed at a rotation speed of 320-360 r / min for 32-58 min, and a stirring temperature of 16-24°C. It is more preferred that stirring is performed at a rotation speed of 360 r / min for 40 min, and a stirring temperature of 20°C.

[0044] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] A factory uses a 20t medium frequency furnace - 20t LF furnace - VD vacuum treatment production line to smelt mold steel. The internal control standard of chemical composition (in weight percentage) is C: 0.83-0.88%, Si: 0.2-0.4%, Mn: 0.2-0.4%, P≤0.03%, S≤0.015%, Cr≥3.9%, Mo≥4.55%, W≥5.5%, Ni≤0.3%, Cu≤0.3%, V≥1.8%.

[0047] The chemical composition of the high-purity mold steels prepared in Example 1 and Comparative Example 1 was detected by a detection instrument, and compared with the chemical composition of the mold steels prepared by the conventional process, as shown in Table 1.

[0048] Table 1: Example 1, chemical composition comparison of mold steel made by common process

[0049]

[0050]

[0051] It can be seen from Table 1 that the P element content of Example 1 is 0.0026, and the S element content is 0.0022, which are significantly lower than those of the ordinary process, indicating that the obtained mold steel has high purity.

[0052] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A smelting process for high purity die steel, characterized in that: The following steps are involved: Step 1: Rough refining in medium frequency furnace The steel material is melted in a medium frequency furnace, smelted until it is completely melted, and then alloys are added to adjust the chemical composition to the internal control standard to obtain molten steel. Aluminum particles are added to the molten steel for deoxidation, and then furnace slag agent is added to slag to obtain slag. Finally, electric heating is applied at a heating temperature of 1520-1560°C to obtain molten steel after rough refining in a medium frequency furnace; Step 2: LF furnace refining The molten steel after rough refining in the medium frequency furnace is sent to the LF furnace for smelting, and is heated to 1480-1600℃ by electricity. After sampling and analysis, the chemical composition is adjusted to the internal control standard, 0.8-1.2kg / t aluminum wire is fed, and the calming time is 1-2min. Then 0.4-0.6kg / t SiCa wire is fed, and the aluminum content in the molten steel is adjusted to 0.03-0.05%. Steel is tapped to obtain the molten steel after refining in the LF furnace; Step 3: VD vacuum furnace treatment The molten steel refined in the LF furnace is sent to the VD furnace for smelting and vacuumed. After the vacuum degree reaches 60-67Pa, the argon flow rate is maintained at 50-60NL / min. Degassing treatment is then carried out for 15-30 minutes. The vacuuming is stopped and the argon flow rate is reduced to 10-20NL / min. Sampling is performed to adjust the chemical composition to the internal control standard to obtain high-purity mold steel.

2. The smelting process of a high purity die steel according to claim 1, characterized in that: The composition of the steel material is as follows by weight percentage: C: 0.83-0.88%, Si: 0.2-0.4%, Mn: 0.2-0.4%, P≤0.03%, S≤0.015%, Cr≥3.9%, Mo≥4.55%, W≥5.5%, Ni≤0.3%, Cu≤0.3%, V≥1.8%.

3. The smelting process of a high purity die steel according to claim 1, characterized in that: In step 1, the weight ratio of the slag-forming agent to the steel material is (5-10):1000.

4. The smelting process of a high purity die steel according to claim 1, characterized in that: In step 1, the slag is 2-3% of the weight of the molten steel.

5. The smelting process of a high purity die steel according to claim 1, characterized in that: The furnace slag agent in step 1 includes the following raw materials in parts by weight: 8-15 parts of lime powder and 2-4 parts of fluorite powder; The refining method of the furnace slag agent comprises the following steps: Step 1, according to the weight parts, add lime powder and fluorite powder into a mixer and stir, add 80-100 parts of deionized water, stir at a speed of 300-380r / min for 30-60min, and the stirring temperature is 15-25°C to obtain a slurry; Step 2: Add the slurry into a mold and dry it at a temperature of 80-95° C. to obtain a furnace slag agent.

6. The smelting process of a high purity die steel according to claim 1, characterized in that: In step 1, the pH of the slag is maintained at 2.6-3.

4.

7. The smelting process of high purity die steel according to claim 1, characterized in that: In step 2, the tapping temperature is between 1540 and 1660°C.

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