Pouring method to improve internal solidification quality of H13 die steel ingot

Abstract

The present invention relates to a casting method for improving the solidification quality of H13 mold steel ingots weighing less than 10 tons and avoiding the occurrence of solidification defects. The method comprises a bottom-casting type H13 mold steel ingot casting process, which covers a method for calculating the thermophysical properties of molten steel, preparing refractory materials for casting and complying with national standards, pre-casting preparations, and determining casting process parameters. The casting process can reduce the central porosity level of the ingot and alleviate the degree of macrosegregation, thereby improving the internal solidification quality of the H13 mold steel ingot. The final product performance of the cast H13 steel ingot can meet the requirements of the GB / T 1299-2014 standard.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking process, and relates to a casting method for improving the solidification quality of H13 type mold steel ingots below 10 tons and avoiding the occurrence of solidification defects, thereby improving the internal solidification quality of H13 type mold steel ingots. Background Art

[0002] With the rapid development of industries like automotive, aerospace, and electronics in recent years, the upstream mold industry has also grown significantly. H13 mold steel, a common material for aluminum extrusion molds, enjoys significant industry demand. Its alloy content is ≥8%, making it a medium-to-high alloy chromium-molybdenum steel. Its solidification process is more complex than that of medium-to-low alloy steels. Ingot products solidify slowly and sequentially, allowing ample time for alloying elements to separate and crystallize. Furthermore, the molten steel experiences significant shrinkage during solidification, making the internal solidification quality of the ingot difficult to control. Solidification defects in ingot products are generally unavoidable, and as the die casting process is the final step in the solidification and forming process, control of the pouring process is particularly crucial.

[0003] In order to control the internal solidification quality of H13 type mold steel ingots, the present invention proposes a casting method for improving the internal solidification quality of H13 type mold steel ingots with a weight of less than 10t. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a casting method for improving the internal solidification quality of H13 type mold steel ingots below 10t by regulating various indicators and measures of the casting process. The steel ingots cast by this method can, to a certain extent, compensate for the loose shrinkage cavity defects caused by insufficient riser shrinkage feeding and reduce the macro-segregation defects inside the steel ingot. The final product performance can meet the performance requirements set forth in the GB / T1299-2014 standard.

[0005] The object of the present invention is achieved by providing a casting method for improving the internal solidification quality of H13 type mold steel ingots, wherein the casting method is applicable to bottom-cast mold-cast steel ingots of less than 10 tons, wherein the cast steel ingots are of H13 type steel grade and the composition complies with the national standard GB / T 1299-2014. The method comprises the following steps:

[0006] Step 1) Calculation of molten steel pouring temperature: According to the target composition value of the steelmaking process design, the liquidus temperature of the molten steel under the target composition is calculated using the empirical formula (1) to accurately control the pouring temperature of the steel ingot;

[0007] T=1534-80×C%-14×Si%-4×Mn%-35×P%-1.4×Cr%-2.6×Ni%-1.2×Mo%-18×Ti-3.9×Al% (1)

[0008] Where T is the liquidus temperature in °C;

[0009] Step 2) Preparation before pouring:

[0010] Step 2.1) Select a steel ingot mold with good inner wall quality, and the steel ingot mold needs to be dried and baked;

[0011] Step 2.2) The riser uses an embedded split insulation board and needs to be dried at high temperature before use. The high temperature drying temperature is 70-90℃ and the high temperature drying time is ≥72 hours;

[0012] Step 2.3), the flow steel bricks used in the soup channel and the middle injection pipe are made of mullite;

[0013] Step 2.4) After the ingot mold is seated, use dry air to blow away the sand and dust inside the ingot mold, soup channel, and center pouring pipe to ensure the purity of the molten steel;

[0014] Step 2.5) Before pouring, fill the ingot mold and the hot pot channel with argon gas from the bell mouth in advance;

[0015] Step 3) Powder hanging:

[0016] Step 3.1) Use medium-low carbon protective slag as protective slag. The drying system of medium-low carbon protective slag is as follows: drying temperature 70-90℃, drying time ≥72 hours;

[0017] Step 3.2) Before pouring, hang the fully baked mold slag into the ingot mold in advance. The mold slag hanging method is to hang it in multiple gradients at different heights.

[0018] Step 4), pouring process control:

[0019] After step 4.1) VD vacuuming is completed, the composition of the molten steel meets the requirements of GB / T 1299-2014 standard, and the weak stirring time of the molten steel is ≥12 minutes to ensure that the inclusions are fully floated;

[0020] Step 4.2) When the steel ingot is poured, the superheat of the molten steel is controlled at a target value of 40°C, which is the pouring temperature; the pouring process is carried out on a 120-ton die-cast steel pouring car;

[0021] Step 4.3) The ingot pouring process adopts slow pouring. The pouring speed of the ingot body of the ingot ≤10t is controlled at 12-17Kg / s, and the pouring speed of the riser is controlled at ≤2Kg / s. Argon protection is used throughout the pouring process;

[0022] Step 4.4) allows multiple trays to be poured from one package. The number of trays required for pouring is ≤3 trays, and the number of ingots poured per tray is ≥2. By limiting the number of pouring trays, splashing when a single ingot is poured can be avoided, and the stability of the molten steel pouring process can be improved.

[0023] Step 4.5), after the riser is poured to two-thirds, add 2.0-3.0 kg / t of exothermic agent to the top of the riser, and add 0.5-1.5 kg / t of carbonized rice husk to the top of the riser; add them evenly to the top of the riser, and add the exothermic agent first and then the carbonized rice husk;

[0024] Step 5) Demolding and hot delivery: After solidification is completed, demould immediately and hot delivery is sent to the forging process into the furnace for heating and forging. The surface temperature of the ingot is controlled to be ≥600℃ during demoulding and hot delivery.

[0025] In step 2.1), the drying and baking temperature of the ingot mold is 300-500°C, and the baking time is ≥2 hours. Before the ingot mold is seated, the inside of the ingot mold is polished until there is no residual steel or slag. After polishing, it is blown clean with dry air to ensure the surface quality of the ingot after demolding.

[0026] In step 2.2), the embedded split insulation panels used in the riser comply with the YB / T 58 standard. The tolerance of the embedded split insulation panels after assembly is ≤ 2 mm. The gaps are tightly plugged with wooden wedges to prevent the formation of a thin steel shell between the riser insulation panels during the solidification process, thereby ensuring the riser's thermal insulation effect.

[0027] In step 2.3), the mullite flow steel bricks used meet the YB / T 4637-2018 standard, and the mullite flow steel bricks used need to be dried at high temperature, with the high temperature drying temperature being 70-90°C and the high temperature drying time being ≥72 hours.

[0028] In step 2.4), the steel ingot mold needs to be selected, and the steel ingot mold with good internal quality is selected. Before the mold is placed, the inner wall of the steel ingot mold is polished one by one using an electric polishing device until no residual steel residue remains. After polishing, it is blown clean with compressed dry air to ensure the surface quality of the steel ingot.

[0029] In step 3.2), the protective slag is hung at multiple gradients at different heights. The operation method is to hang the protective slag near the bottom, and the hanging weight of the protective slag is controlled at 0.5-1.0 kg / t. The specific hanging quantity follows the principle of hanging fewer small ingots and more large ingots. The remaining protective slag is hung at a vertical distance of 300-400 mm from the bottom of the mold, and the total hanging weight of the protective slag is controlled at 1.5-2.5 kg / t.

[0030] The beneficial effects of the present invention are as follows: By integrating factors influencing the solidification process and regulating pouring parameters, the present invention achieves a pouring method that combines low superheat, slow pouring, and mold slag hanging. Furthermore, the number of ingot pouring trays and the number of pouring branches per tray are controlled, thereby reducing the central porosity of the ingot and the degree of macrosegregation, thereby achieving the purpose of improving the internal solidification quality of H13 mold steel ingots. The implementation process of the present invention mainly involves the coordinated control of each pouring link and the lean quantification of each link indicator, thereby improving the internal solidification quality of H13 mold steel ingots with little or no increase in production and labor costs. DETAILED DESCRIPTION

[0031] Example 1: A casting method for improving the internal solidification quality of an H13 mold steel ingot. The casting method is applicable to bottom-cast mold-cast steel ingots weighing less than 10 tons. Specifically, the ingot weight is 7 tons, and the number of cast trays is three. The cast steel grade belongs to the H13 category, and the composition complies with the national standard GB / T 1299-2014. The method comprises the following steps:

[0032] Step 1) Calculation of liquidus temperature of molten steel: According to the target composition value of the steelmaking process design, the liquidus temperature of molten steel under the target composition is calculated using the empirical formula (1) to accurately control the pouring temperature of the steel ingot;

[0033] T=1534-80×C%-14×Si%-4×Mn%-35×P%-1.4×Cr%-2.6×Ni%-1.2×Mo%-18×Ti-3.9×Al% (1)

[0034] T is the liquidus temperature, °C; the target value of pouring superheat is 40 °C, and the pouring temperature is determined according to the calculated liquidus temperature;

[0035] Step 2) Preparation before pouring:

[0036] Step 2.1) Select an ingot mold with good inner wall quality. The cold ingot mold needs to be dried and baked at a temperature of 300-500°C for ≥2 hours. Before the ingot mold is placed, use an electric grinding device to grind the inside of the ingot mold until there is no residual steel or slag. After grinding, use dry air to blow it clean to ensure the surface quality of the ingot after demoulding.

[0037] Step 2.2) The riser uses embedded split insulation boards, which need to be dried at high temperature before use. The high-temperature drying temperature is 70-90°C and the high-temperature drying time is ≥72 hours. The insulation boards used in the riser comply with the YB / T 58 standard. The riser uses split insulation boards, which need to be dried at high temperature before use. The high-temperature drying temperature is 70-90°C and the high-temperature drying time is ≥72 hours. The embedded riser is used, and the tolerance of the split insulation boards used after assembly is ≤2mm. The gaps are tightly plugged with wooden wedges to prevent the formation of a thin steel shell between the riser insulation boards during the solidification process, thereby ensuring the heat preservation effect of the riser.

[0038] Step 2.3), the flow steel bricks used in the soup channel and the middle injection pipe are made of mullite; the indicators of the mullite flow steel bricks used are in line with the YB / T 4637-2018 standard. The mullite flow steel bricks used need to be dried at high temperature, the high temperature drying temperature is 70-90℃, the high temperature drying time is ≥72 hours, and they are selected before use;

[0039] Step 2.4) After the ingot mold is seated, use compressed dry air to blow away the gravel and dust inside the ingot mold, soup channel, and center pouring pipe to reduce the source of exogenous inclusions and ensure the purity of the molten steel;

[0040] Step 2.5) Before pouring, fill the ingot mold and the hot pot channel with argon gas from the bell mouth in advance;

[0041] Step 3) Powder hanging:

[0042] Step 3.1) Use medium-low carbon protective slag as protective slag. The drying system of medium-low carbon protective slag is as follows: drying temperature 70-90℃, drying time ≥72 hours;

[0043] Step 3.2) Before pouring, hang the fully baked protective slag into the ingot mold in advance. The protective slag hanging method is to hang it in multiple gradients at different heights. The protective slag hanging operation method is to hang part of the protective slag near the bottom of the center line. The protective slag hanging weight is controlled at 0.5-1.0 kg / t. The specific hanging quantity follows the principle of hanging less small ingots and more large ingots. The total weight of the protective slag hanging is controlled at 1.5-2.5 kg / t. The remaining protective slag is hung at a vertical distance of 300-400 mm from the bottom of the mold.

[0044] Step 4), pouring process control:

[0045] After step 4.1) VD vacuuming is completed, the composition of the molten steel meets the requirements of GB / T 1299-2014 standard, and the weak stirring time of the molten steel is ≥12 minutes to ensure that the inclusions are fully floated;

[0046] Step 4.2) When the steel ingot is poured, the superheat of the molten steel is controlled at a target value of 40°C, which is the pouring temperature; the pouring process is carried out on a 120-ton die-cast steel pouring car; the pouring process is automatically controlled;

[0047] Step 4.3) The ingot pouring process adopts slow pouring. The pouring speed of the ingot body of the ingot ≤10t is controlled at 12-17Kg / s, and the pouring speed of the riser is controlled at ≤2Kg / s. Argon protection is used throughout the pouring process;

[0048] Step 4.4) allows multiple trays to be poured from one package. The number of trays required for pouring is ≤3 trays, and the number of ingots poured per tray is ≥2. By limiting the number of pouring trays, splashing when a single ingot is poured can be avoided, and the stability of the molten steel pouring process can be improved.

[0049] Step 4.5) Use a combination of protective slag + exothermic agent + carbonized rice husk for insulation to ensure the riser shrinkage feeding effect. The exothermic agent and carbonized rice husk are added after the riser is poured to two-thirds, and are added to the top of the riser in a uniform and scattered manner. The order of addition is to add the exothermic agent first and then the carbonized rice husk. The amount of exothermic agent added is controlled at 2.0-3.0 kg / t, and the amount of carbonized rice husk added is controlled at 0.5-1.5 kg / t;

[0050] Step 5) Demolding and hot delivery: After solidification is completed, demould immediately and hot delivery is sent to the forging process into the furnace for heating and forging. The surface temperature of the ingot is controlled to be ≥600℃ during demoulding and hot delivery.

[0051] It is understood that the complete steelmaking process is EAF (60t) - LF (60t) - VD (60t) - IC. The above detailed description of the present invention is only for the purpose of illustrating the present invention and is not intended to limit the technical solutions described in the embodiments of the present invention. Those skilled in the art will understand that the present invention can still be modified or replaced with equivalents to achieve the same technical effects; as long as the application requirements are met, they are all within the scope of protection of the present invention.

Claims

1. A casting method for improving the internal solidification quality of H13 mold steel ingots, characterized by: The pouring method is applicable to bottom-cast steel ingots with a weight of less than 10 tons. The steel grade of the cast steel ingot belongs to H13 and the composition complies with the national standard GB / T1299-2014. The method comprises the following steps: Step 1) Calculation of molten steel pouring temperature: According to the target composition value of the steelmaking process design, the liquidus temperature of the molten steel under the target composition is calculated using the empirical formula (1) to accurately control the pouring temperature of the steel ingot; T=1534-80×C%-14×Si%-4×Mn%-35×P%-1.4×Cr%-2.6×Ni%-1.2×Mo%-18×Ti-3.9×Al% (1) Where T is the liquidus temperature in °C; Step 2) Preparation before pouring: Step 2.1) Select a steel ingot mold with good inner wall quality, and the steel ingot mold needs to be dried and baked; Step 2.2) The riser uses an embedded split insulation board and needs to be dried at high temperature before use. The high temperature drying temperature is 70-90℃ and the high temperature drying time is ≥72 hours; Step 2.3), the flow steel bricks used in the soup channel and the middle injection pipe are made of mullite; Step 2.4) After the ingot mold is seated, use dry air to blow away the sand and dust inside the ingot mold, soup channel, and center pouring pipe to ensure the purity of the molten steel; Step 2.5) Before pouring, fill the ingot mold and the hot pot channel with argon gas from the bell mouth in advance; Step 3) Powder hanging: Step 3.1) Use medium-low carbon protective slag as protective slag. The drying system of medium-low carbon protective slag is as follows: drying temperature 70-90℃, drying time ≥72 hours; Step 3.2) Before pouring, hang the fully baked mold slag into the ingot mold in advance. The mold slag hanging method is to hang it in multiple gradients at different heights. Step 4), pouring process control: After step 4.1) VD vacuuming is completed, the composition of the molten steel meets the requirements of GB / T 1299-2014 standard, and the weak stirring time of the molten steel is ≥12 minutes to ensure that the inclusions are fully floated; Step 4.2) When the steel ingot is poured, the superheat of the molten steel is controlled at a target value of 40°C, which is the pouring temperature; the pouring process is carried out on a 120-ton die-cast steel pouring car; Step 4.3) The ingot pouring process adopts slow pouring. The pouring speed of the ingot body of the ingot ≤10t is controlled at 12-17Kg / s, and the pouring speed of the riser is controlled at ≤2Kg / s. Argon protection is used throughout the pouring process; Step 4.4) allows multiple trays to be poured from one package. The number of trays required for pouring is ≤3 trays, and the number of ingots poured per tray is ≥2. By limiting the number of pouring trays, splashing when a single ingot is poured can be avoided, and the stability of the molten steel pouring process can be improved. Step 4.5), after the riser is poured to two-thirds, add 2.0-3.0 kg / t of exothermic agent to the top of the riser, and add 0.5-1.5 kg / t of carbonized rice husk to the top of the riser; add them evenly to the top of the riser, and add the exothermic agent first and then the carbonized rice husk; Step 5) Demolding and hot delivery: After solidification is completed, demould immediately and hot delivery is sent to the forging process into the furnace for heating and forging. The surface temperature of the ingot is controlled to be ≥600℃ during demoulding and hot delivery.

2. A casting method for improving the internal solidification quality of H13 mold steel ingot according to claim 1, characterized in that: In step 2.1), the drying and baking temperature of the ingot mold is 300-500°C, and the baking time is ≥2 hours. Before the ingot mold is seated, the inside of the ingot mold is polished until there is no residual steel or slag. After polishing, it is blown clean with dry air to ensure the surface quality of the ingot after demolding.

3. The pouring method for improving the internal solidification quality of H13 mold steel ingot according to claim 1, characterized in that: In step 2.2), the embedded split insulation panels used in the riser comply with the YB / T 58 standard. The tolerance of the embedded split insulation panels after assembly is ≤ 2 mm. The gaps are tightly plugged with wooden wedges to prevent the formation of a thin steel shell between the riser insulation panels during the solidification process, thereby ensuring the riser's thermal insulation effect.

4. The pouring method for improving the internal solidification quality of H13 mold steel ingot according to claim 1, characterized in that: In step 2.3), the mullite flow steel bricks used meet the YB / T 4637-2018 standard, and the mullite flow steel bricks used need to be dried at high temperature, with the high temperature drying temperature being 70-90°C and the high temperature drying time being ≥72 hours.

5. The pouring method for improving the internal solidification quality of H13 mold steel ingot according to claim 1, characterized in that: In step 2.4), the steel ingot mold needs to be selected, and the steel ingot mold with good internal quality is selected. Before the mold is placed, the inner wall of the steel ingot mold is polished one by one using an electric polishing device until no residual steel residue remains. After polishing, it is blown clean with compressed dry air to ensure the surface quality of the steel ingot.

6. The pouring method for improving the internal solidification quality of H13 mold steel ingot according to claim 1, characterized in that: In step 3.2), the protective slag is hung at multiple gradients at different heights. The operation method is to hang the protective slag near the bottom, and the hanging weight of the protective slag is controlled at 0.5-1.0 kg / t. The specific hanging quantity follows the principle of hanging fewer small ingots and more large ingots. The remaining protective slag is hung at a vertical distance of 300-400 mm from the bottom of the mold, and the total hanging weight of the protective slag is controlled at 1.5-2.5 kg / t.