Method for smelting H13 die steel by using all-return scraps

Abstract

The invention belongs to the technical field of iron and steel smelting in the metallurgical industry, and discloses a method for smelting H13 die steel by using all return scraps. The method comprises the following steps: (1) loading the H13 die steel return scrap into an electric arc furnace, and carrying out electric smelting to obtain mother liquor; (2) carrying out AOD (argon oxygen decarburization) refining on the mother liquor, carrying out decarburization by argon-oxygen mixed blowing in the refining process to produce molten steel with qualified components, and tapping the molten steel into a steel ladle; and (3) carrying out LF refining and VD vacuum treatment on the molten steel in the steel ladle, and pouring to obtain a steel ingot. The H13 die steel is smelted through the all-return scraps, and the furnace burden cost is reduced by 10% or above compared with a traditional smelting process; the molten steel is subjected to decarburization and chromium protection in the AOD, so that the problem of high carbon content of the return scrap is solved, and meanwhile, the problems of burning loss of alloy elements and low yield are solved. The full-return scrap H13 die steel smelting process provided by the invention is relatively low in process difficulty, high in alloy yield, stable in product quality, suitable for industrial large-scale production and relatively high in economic value.

Description

Technical Field

[0001] The invention discloses a method for smelting H13 die steel by utilizing full return materials, and relates to the technical field of steel smelting in the metallurgical industry. Background Art

[0002] Since its development, H13 steel has been widely studied and applied due to its excellent mechanical properties (high strength, red hardness, high toughness and good plasticity), high hardenability, medium temperature stability, etc. It is often used as hot extrusion dies, high-speed precision forging dies, aluminum alloy die-casting dies, etc.

[0003] The chemical composition of H13 die steel is shown in Table 1, which contains a large amount of alloy elements such as Mo, V, Cr, Si, etc. If the return material can be used in steelmaking and most of the alloy elements can be recovered, there will be huge economic and social benefits.

[0004] Table 1 Chemical composition of H13 mold steel

[0005]

[0006] The H13 return materials recycled on the market are often mixed with a large amount of impurities such as lubricating oil and cutting fluid that remain during processing and use, resulting in a carbon content higher than the C content requirements in Table 1. Using the return materials as raw materials requires oxygen blowing and decarburization during the smelting process, such as China Patent CN113737083A, a method for smelting die steel H13 with return materials, which uses oxygen blowing and decarburization for treatment. Therefore, if return materials are used to melt H13 die steel in the current field, oxygen blowing and decarburization are usually required after smelting. Oxygen blowing will cause decarburization and oxidation and burning of easily oxidized elements such as Si, V, and Cr in the molten steel, resulting in a low alloy yield. After decarburization, a large amount of alloy elements need to be added, resulting in an increase in the cost of the furnace charge. Although China Patent CN113737083A, a method for smelting die steel H13 with return materials, has improved the yield of Cr through certain improvements in smelting methods, reducing costs to a certain extent, other alloy elements still have large burns, and the yield of Cr elements still has room for improvement. Therefore, the present invention provides a method for smelting H13 die steel using all returned materials, which effectively improves the yield of each alloy element, reduces production costs, and fills the technical gap in the efficient utilization of returned materials in the field. Summary of the invention

[0007] The purpose of the present invention is to solve the problems of low alloy yield and high cost in the existing traditional H13 return material smelting process mentioned in the background technology, and to provide a full return material H13 mold steel smelting process with low process difficulty, high alloy yield and stable product quality.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A method for smelting H13 die steel using full return material, the method comprising the following steps:

[0010] (1) Loading H13 die steel return material into an electric arc furnace and sending it for electric smelting to obtain mother liquor;

[0011] (2) the mother liquor is subjected to AOD refining, during which argon-oxygen mixed blowing is used for decarburization, and molten steel with qualified composition is produced and tapped into a ladle;

[0012] (3) The molten steel in the ladle is refined by LF and vacuum treated by VD before being cast into steel ingots.

[0013] Preferably, in step (1), H13 return material is loaded into the arc furnace through a basket, and the return material addition ratio is 100%. The method of the present invention can be applied to all return materials and achieve excellent alloy yield, effectively reducing economic costs.

[0014] Preferably, in step (1), oxygen is not blown during the entire smelting process to avoid burning of precious alloy elements. This is different from the conventional return material process in the field. The current return material process in the field requires oxygen blowing during the smelting process to assist melting and decarburization, while in the present invention, oxygen blowing needs to be avoided during the smelting process to minimize oxidation burning of precious alloy elements.

[0015] Preferably, in step (1), the H13 return material is melted and the temperature reaches 1570-1620° C. before being tapped into the transfer package.

[0016] Preferably, in the step (2), the mother liquor smelted in the electric arc furnace is directly mixed with AOD through the transfer bag. 2 : Ar volume ratio of 1:4 to 5 for argon-oxygen mixed blowing decarburization, promote decarburization and avoid oxidation of alloy elements such as Cr, Si, V, Mo, etc., stop blowing when the carbon content reaches the target value, and effectively achieve the retention of elements such as Si. Si is very easy to oxidize. In the conventional AOD blowing process, Si will be oxidized before carbon in the early rapid decarburization stage with a low argon ratio. Therefore, if the traditional AOD smelting process is adopted and H13 full return material is used for blowing, although decarburization and chromium preservation can be achieved, the Si in the H13 return material cannot be effectively utilized, and a high element loss is still caused. When H13 full return material is produced, the initial carbon content is not too high, usually about 0.5-0.6%, and the final carbon content is about 0.3-0.4%, and the decarburization task is not heavy. Therefore, the present invention skips the early rapid decarburization stage with a low argon ratio and directly enters the stage with a high argon ratio, which can effectively achieve decarburization while avoiding the burning of alloys such as silicon, chromium, vanadium, and molybdenum.

[0017] Preferably, after the decarburization in the AOD in step (2) is completed, ferrosilicon and / or lime are added to the AOD for reduction deoxidation and argon blowing and stirring to reduce most of the alloy elements such as vanadium, chromium, and molybdenum oxidized during the decarburization process. More preferably, the amount of ferrosilicon added is 10-30 kg / t of molten steel, and the amount of lime added is 45-55 kg / t of molten steel.

[0018] Preferably, after the reduction in step (2), the slag is removed, and lime and / or fluorite are added to make high-basicity slag for refining, and argon is blown and stirred for more than 5 minutes during the refining process to ensure denitrification and dehydrogenation of the molten steel. More preferably, the amount of lime added is 10-20 kg / t molten steel, and the amount of fluorite added is 1-5 kg / t molten steel; more preferably, the basicity is 2.5-3.5.

[0019] Preferably, in the step (3), the molten steel produced by AOD is heated in a LF refining furnace and its composition is finely adjusted. After all the components are qualified and the temperature reaches 1660-1680° C., the molten steel is hoisted into a VD furnace.

[0020] Preferably, in step (3), the molten steel is vacuum refined in a VD furnace, and the high vacuum (≤67 Pa) is maintained for more than 15 minutes.

[0021] Preferably, after the VD vacuum refining in step (3) is completed, soft blowing is performed for no less than 10 minutes to cast the steel ingot.

[0022] Preferably, the Si yield of the method is not less than 80%, and the alloy yield of Cr, Mo and V is not less than 90%.

[0023] The present invention utilizes the characteristics of AOD and utilizes H13 full return material to melt molten steel, thereby reducing the oxidation loss of alloy elements during carbon blowing and improving the yield of alloy. AOD utilizes argon and oxygen gas to blow molten steel, which is generally blown into the molten pool from the bottom or side of the furnace in the form of mixed gas, but can also be blown into the molten pool separately at the same time. During the blowing process, 1 mol of oxygen reacts with carbon in the steel to generate 2 mol of CO, but 1 mol of argon does not change after passing through the molten pool and still escapes as 1 mol of gas, thereby reducing the partial pressure of CO in the upper part of the molten pool. Since the CO partial pressure is reduced by dilution of argon, the equilibrium relationship between carbon and chromium in the molten steel is changed. Under the same temperature condition, due to the reduction of CO partial pressure, the chromium content balanced with carbon is greatly increased, that is, when the chromium content in the steel is the same, the carbon can be oxidized to the required level at a relatively low temperature. For example, when oxygen is blown into the molten pool by ordinary back blowing method at 1820°C, when carbon is oxidized to 0.02%, only 3% of chromium can be preserved in the steel. If CO is diluted with argon and oxygen is blown at a CO partial pressure of 10kPa, more than 20% of the chromium in the steel can be preserved, which is beneficial to the decarburization and chromium preservation of stainless steel. In addition, the basic principle of AOD argon oxygen blowing is similar to that of oxygen blowing decarburization under vacuum. Vacuum oxygen blowing decarburization uses vacuum conditions to reduce the partial pressure of CO, the decarburization product, while argon oxygen blowing uses gas dilution to reduce the partial pressure of CO. Therefore, there is no need to assemble expensive vacuum equipment, which can further reduce costs.

[0024] However, in traditional AOD blowing, Si is usually blown off first before carbon blowing begins, mainly because Si is very easy to oxidize. In the conventional AOD blowing process, Si will be oxidized before carbon in the early rapid decarburization stage when the argon ratio is low. Therefore, if the traditional AOD smelting process is adopted and H13 full return material is used for blowing, although decarburization and chromium preservation can be achieved, the Si in the H13 return material cannot be utilized. When H13 full return material is produced, the initial carbon content is not too high, usually around 0.5-0.6%, and the final carbon content is around 0.3-0.4%, so the decarburization task is not heavy. Therefore, the present invention skips the early rapid decarburization stage with a low argon ratio and directly enters the stage with a high argon ratio, which can effectively achieve decarburization and silicon preservation.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Using all return materials to smelt H13 mold steel can reduce the cost of furnace materials by more than 10% compared with the traditional smelting process.

[0027] (2) The molten steel is decarburized and chromium is preserved in the AOD, which not only solves the problem of high carbon in the returned material, but also solves the problems of alloy element burnout and low yield. And by adopting the method of argon-oxygen mixed blowing decarburization, the silicon yield is effectively improved;

[0028] (3) The molten steel is refined by blowing argon in the AOD to achieve denitrification and dehydrogenation and remove non-metallic inclusions, thereby improving the purity of the molten steel.

[0029] (4) The all-return material H13 mold steel smelting process provided by the present invention has low process difficulty, high alloy yield, stable product quality, effective cost reduction, is suitable for industrial large-scale production, has high economic value and environmental significance, and achieves the green development goal of resource recycling. DETAILED DESCRIPTION

[0030] In order to better clarify and understand the purpose, process scheme and advantages of the present invention, the technical scheme and implementation method of the present invention are further described clearly, completely and in detail through specific examples. It should be noted that the embodiments described in the present invention are implemented on the premise of the technical scheme of the present invention, and detailed implementation methods and specific operation processes are given, but they are only part of the embodiments of the present invention, not all of the embodiments. The specific implementation methods described are limited to explaining and interpreting the present invention, and do not limit the present invention. Based on the embodiments in the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] The experimental methods and conditions used in the following examples are conventional methods and conventional conditions unless otherwise specified, and the materials, reagents or instruments used in the examples, unless otherwise specified, can be obtained from commercial sources. The reaction conditions embodied in the content of the invention of the present invention can achieve the reaction and obtain the product of the expected effect. Due to space limitations, only some embodiments are listed below to further illustrate the advantages of the technical solution of the present invention.

[0032] Example 1

[0033] The present embodiment produces a 17-inch (1.85 ton) H13 die steel ingot.

[0034] Step 1: In a 40-ton electric arc furnace, all H13 return materials are loaded through a basket, and after the materials are added, the electrified materials are sent without using an oxygen lance to blow oxygen to assist melting. When all the materials are melted, samples are taken to confirm the carbon content and the temperature is adjusted to the target steel-out temperature.

[0035] The carbon content is 0.55% and the tapping temperature is 1578°C;

[0036] Step 2: Add the mother liquor from the transfer bag to the AOD and start blowing oxygen-argon mixed gas for decarburization. The ratio of oxygen to argon during the decarburization period is 6Nm 3 :24Nm 3Blow for 15 minutes. After the oxygen blowing is completed, take a sample to confirm the carbon content. After confirming that the carbon content reaches 0.38% and is qualified, enter the reduction period. During the reduction period, add 15kg / ton of ferrosilicon and blow argon to stir. The reduction time is 6 minutes. After the reduction is completed, manually scrape the slag. After scraping off 80% of the slag, add 15kg / ton of lime and 3kg / ton of fluorite and blow argon for refining. The refining time is 6 minutes. After the molten steel is refining, it is discharged into the ladle.

[0037] Step 3: The molten steel in the ladle is transferred to the LF refining furnace to heat up and fine-tune the composition. After the temperature reaches 1675℃ and all the components reach the target value, it enters the VD furnace for vacuuming. The ultimate vacuum degree in the VD furnace is 25Pa, and the high vacuum is maintained for 18 minutes. After the vacuuming is completed, soft blowing is performed for 12 minutes, and the molten steel is hoisted to the pouring position and cast into a 17-inch steel ingot (1.85 tons). The final molten steel composition and alloy yield are shown in Tables 2 and 3.

[0038] Example 2

[0039] The present embodiment produces a 20-inch (2.2-ton) H13 die steel ingot.

[0040] Step 1: In a 40-ton electric arc furnace, all H13 return materials are loaded through a basket, and after the materials are added, the electrified materials are sent without using an oxygen lance to blow oxygen to assist melting. When all the materials are melted, samples are taken to confirm the carbon content and the temperature is adjusted to the target steel-out temperature.

[0041] The carbon content is 0.82% and the tapping temperature is 1576°C;

[0042] Step 2: Add the mother liquor from the transfer bag to the AOD and start blowing oxygen-argon mixed gas for decarburization. The ratio of oxygen to argon during the decarburization period is 6Nm 3 :24Nm 3 Blowing lasted for 18 minutes. After the oxygen blowing was completed, a sample was taken to confirm the carbon content. After the carbon content reached 0.36%, it entered the reduction period. During the reduction period, 28kg / ton of steel ferrosilicon and 50kg / ton of steel lime were added and stirred with argon blowing. The reduction time was 6 minutes. After the reduction was completed, the slag was manually removed. After 80% of the slag was removed, 15kg / ton of steel lime and 3kg / ton of steel fluorite were added and argon blowing was performed for refining. The refining time was 6 minutes. After the molten steel was refining, the steel was discharged into the ladle.

[0043] Step 3: The molten steel in the ladle is transferred to the LF refining furnace to increase the temperature and adjust the composition. After the temperature reaches 1678℃ and the composition reaches the target value, it enters the VD furnace for vacuuming. The ultimate vacuum degree in the VD furnace is 22Pa, and the high vacuum is maintained for 16 minutes. After the vacuuming is completed, soft blowing is performed for 15 minutes, and the molten steel is hoisted to the pouring position and cast into a 20-inch steel ingot (2.2 tons). The final molten steel composition and alloy yield are shown in Tables 2 and 3.

[0044] Example 3

[0045] The present embodiment produces a 17-inch (1.85 ton) H13 die steel ingot.

[0046] Step 1: In a 40-ton electric arc furnace, all H13 return materials are loaded through a basket, and after the materials are added, the electrified materials are sent without using an oxygen lance to blow oxygen to assist melting. When all the materials are melted, samples are taken to confirm the carbon content and the temperature is adjusted to the target steel-out temperature.

[0047] The carbon content is 0.66% and the tapping temperature is 1577°C;

[0048] Step 2: Add the mother liquor from the transfer bag to the AOD and start blowing oxygen-argon mixed gas for decarburization. The ratio of oxygen to argon during the decarburization period is 6Nm 3 :24Nm 3 Blow for 15 minutes. After the oxygen blowing is completed, take a sample to confirm the carbon content. After confirming that the carbon content reaches 0.36% and is qualified, it enters the reduction period. During the reduction period, 18kg / ton of ferrosilicon is added and argon is blown and stirred. The reduction time is 6 minutes. After the reduction is completed, the slag is manually removed. After 80% of the slag is removed, 15kg / ton of lime and 3kg / ton of fluorite are added and argon is blown for refining. The refining time is 6 minutes. After the molten steel is refining, the steel is tapped into the ladle.

[0049] Step 3: The molten steel in the ladle is transferred to the LF refining furnace to heat up and adjust the composition. After the temperature reaches 1669℃ and the composition reaches the target value, it enters the VD furnace for vacuuming. The ultimate vacuum degree in the VD furnace is 24Pa, and the high vacuum is maintained for 15 minutes. After the vacuuming is completed, soft blowing is performed for 15 minutes, and the molten steel is hoisted to the pouring position and cast into a 20-inch steel ingot (2.2 tons). The final molten steel composition meets the chemical composition requirements of H13 mold steel, and the Si element alloy recovery rate is not less than 80%, and the Cr, Mo and V element alloy recovery rates are not less than 90%.

[0050] Example 4

[0051] The present embodiment produces a 20-inch (2.2-ton) H13 die steel ingot.

[0052] Step 1: In a 40-ton electric arc furnace, all H13 return materials are loaded through a basket, and after the materials are added, the electrified materials are sent without using an oxygen lance to blow oxygen to assist melting. When all the materials are melted, samples are taken to confirm the carbon content and the temperature is adjusted to the target steel-out temperature.

[0053] The carbon content is 0.74% and the tapping temperature is 1582°C;

[0054] Step 2: Add the mother liquor from the transfer bag to the AOD and start blowing oxygen-argon mixed gas for decarburization. The ratio of oxygen to argon during the decarburization period is 6Nm 3 :24Nm 3Blow for 20 minutes. After the oxygen blowing is completed, take a sample to confirm the carbon content. After confirming that the carbon content reaches 0.34% and is qualified, enter the reduction period. During the reduction period, add 25kg / ton of steel ferrosilicon and 52kg / ton of steel lime and blow argon to stir. The reduction time is 6 minutes. After the reduction is completed, the slag is manually removed. After removing 80% of the slag, add 18kg / ton of steel lime and 3kg / ton of steel fluorite and blow argon for refining. The refining time is 6 minutes. After the molten steel is refining, the steel is tapped into the ladle.

[0055] Step 3: The molten steel in the ladle is transferred to the LF refining furnace to heat up and adjust the composition. After the temperature reaches 1675℃ and the composition reaches the target value, it enters the VD furnace for vacuuming. The ultimate vacuum degree in the VD furnace is 25Pa, and the high vacuum is maintained for 20 minutes. After the vacuuming is completed, soft blowing is performed for 15 minutes, and the molten steel is hoisted to the pouring position and cast into a 20-inch steel ingot (2.2 tons). The final molten steel composition meets the chemical composition requirements of H13 mold steel, and the Si element alloy recovery rate is not less than 80%, and the Cr, Mo and V element alloy recovery rates are not less than 90%.

[0056] Example 5

[0057] The present embodiment produces a 20-inch (2.2-ton) H13 die steel ingot.

[0058] Step 1: In a 40-ton electric arc furnace, all H13 return materials are loaded through a basket, and after the materials are added, the electrified materials are sent without using an oxygen lance to blow oxygen to assist melting. When all the materials are melted, samples are taken to confirm the carbon content and the temperature is adjusted to the target steel-out temperature.

[0059] The carbon content is 0.78% and the tapping temperature is 1575°C;

[0060] Step 2: Add the mother liquor from the transfer bag to the AOD and start blowing oxygen-argon mixed gas for decarburization. The ratio of oxygen to argon during the decarburization period is 6Nm 3 :30Nm 3 Blowing lasted for 18 minutes. After the oxygen blowing was completed, a sample was taken to confirm the carbon content. After the carbon content reached 0.35%, it entered the reduction period. During the reduction period, 28kg / ton of steel ferrosilicon and 50kg / ton of steel lime were added and stirred with argon blowing. The reduction time was 6 minutes. After the reduction was completed, the slag was manually removed. After 80% of the slag was removed, 15kg / ton of steel lime and 3kg / ton of steel fluorite were added and argon blowing was performed for refining. The refining time was 6 minutes. After the molten steel was refining, the steel was discharged into the ladle.

[0061] Step 3: The molten steel in the ladle is transferred to the LF refining furnace to heat up and adjust the composition. After the temperature reaches 1670℃ and the composition reaches the target value, it enters the VD furnace for vacuuming. The ultimate vacuum degree in the VD furnace is 30Pa, and the high vacuum is maintained for 20 minutes. After the vacuuming is completed, soft blowing is performed for 15 minutes, and the molten steel is hoisted to the pouring position and cast into a 20-inch steel ingot (2.2 tons). The final molten steel composition meets the chemical composition requirements of H13 mold steel, and the Si element alloy recovery rate is not less than 80%, and the Cr, Mo and V element alloy recovery rates are not less than 90%.

[0062] Comparative Example

[0063] The present embodiment produces a 20-inch (2.2-ton) H13 die steel ingot.

[0064] Step 1: Load the 40-ton electric arc furnace with H13 return material through the basket, and then send the electrified material and blow oxygen for decarburization. After all the materials are melted, take samples to confirm the chemical composition, confirm that the carbon content is ≤0.4%, and tap the steel after the temperature reaches 1550-1600℃.

[0065] Step 2: According to the above sampling confirmation results, add ferrosilicon, ferromolybdenum, ferrovanadium, low carbon ferrochrome and other alloys into the ladle during the steel tapping process;

[0066] Step 3: The molten steel in the ladle is transferred to the LF refining furnace to increase the temperature and adjust the composition. After the temperature reaches 1688℃ and the composition reaches the target value, it enters the VD furnace for vacuuming. The ultimate vacuum degree in the VD furnace is 26Pa, and the high vacuum is maintained for 15 minutes. After the vacuuming is completed, soft blowing is performed for 15 minutes, and the molten steel is hoisted to the pouring position and cast into a 20-inch steel ingot (2.2 tons). The final molten steel composition and alloy yield are shown in Tables 2 and 3.

[0067] Table 2 Final composition of molten steel

[0068]

[0069] Table 3 Alloy element recovery rate

[0070]

[0071] From the above comparison, it can be seen that compared with the current H13 return material alloy recovery method comparison example, the technical scheme of the present invention can significantly improve the recovery rate of alloys such as Si, Cr, Mo and V, among which the recovery rate of Si is not less than 80%, and the recovery rate of Cr, Mo and V alloys is not less than 90%, which are significantly better than the comparison example, breaking through the existing technical barriers, and effectively realizing the recovery of alloys in return materials, thereby further reducing costs and improving economic benefits.

[0072] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A method for melting H13 die steel using full return material, characterized in that: The method comprises the following steps: (1) Loading H13 die steel return material into an electric arc furnace and sending it for electric smelting to obtain mother liquor; (2) the mother liquor is subjected to AOD refining, during which argon-oxygen mixed blowing is used for decarburization, and the refined molten steel is tapped into a ladle; (3) The molten steel in the ladle is refined by LF and vacuum treated by VD before being cast into steel ingots.

2. A method for smelting H13 die steel using full return material according to claim 1, characterized in that: In the step (1), the proportion of H13 die steel return material added is 100%.

3. The method for smelting H13 die steel using full return material according to claim 1, characterized in that: In the step (1), oxygen is not blown during the entire smelting process.

4. The method for smelting H13 die steel using full return material according to claim 1, characterized in that: In the step (1), the H13 return material is melted and the temperature reaches 1580-1620° C. before steel is tapped.

5. The method for smelting H13 die steel using full return material according to claim 1, characterized in that: In the step (2), argon-oxygen mixed blowing decarburization is performed with a volume ratio of O2:Ar of 1:4-5, and blowing is stopped when the carbon content reaches the target value.

6. The method for smelting H13 die steel using full return material according to claim 1, characterized in that: After the decarburization in the AOD in step (2) is completed, ferrosilicon and / or lime are continuously added to the AOD for reduction deoxidation and argon blowing and stirring.

7. A method for smelting H13 die steel using full return material according to claim 6, characterized in that: After the reduction in step (2) is completed, the slag is removed and lime and / or fluorite is added to make high-basicity slag for refining. During the refining process, argon is blown and stirred for more than 5 minutes to ensure denitrification and dehydrogenation of the molten steel.

8. The method for smelting H13 die steel using full return material according to claim 1, characterized in that: In the step (3), the molten steel produced by AOD is heated in the LF refining furnace and its composition is finely adjusted. After all the components are qualified and the temperature reaches 1660-1680°C, the molten steel is hoisted into the VD furnace.

9. A method for smelting H13 die steel using full return material according to claim 8, characterized in that: In the step (3), the molten steel is vacuum refined in a VD furnace, and the high vacuum is ≤67Pa and maintained for more than 15 minutes.

10. A method for smelting H13 die steel using full return material according to claim 9, characterized in that: After the VD vacuum refining in step (3) is completed, soft blowing is performed for no less than 10 minutes to cast the steel into an ingot.

Images