Pouring method for improving internal solidification quality of H13 type die steel ingot

Abstract

The invention relates to a pouring method for improving the internal solidification quality of an H13 type die steel ingot, which can improve the solidification quality of the H13 type die steel ingot below 10t and avoid solidification defects. The H13 type die steel bottom pouring type steel ingot pouring process covers a molten steel thermophysical property calculation method, preparation of a refractory material for pouring and national standard standards, preparation work before pouring and determination of parameters in the pouring process, and by means of the pouring process, the steel ingot center porosity grade and the macrosegregation degree can be reduced; and therefore, the internal solidification quality of the H13 type die steel ingot is improved, and the performance of a final product of the poured H13 type steel ingot can meet the GB / T 1299-2014 standard requirement.

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 die steel ingots below 10 tons and avoiding the occurrence of solidification defects, thereby improving the internal solidification quality of H13 type die steel ingots. Background Art

[0002] In recent years, with the rapid development of industries such as automobiles, aerospace, and electronics, the upstream mold industry has also become increasingly large. H13 mold steel is a commonly used material for aluminum extrusion molds, and the industry has a huge demand. Its alloy content is ≥8%, and it belongs to medium-high alloy chromium-molybdenum steel. Its solidification process is more complicated than that of medium-low alloy steel. For steel ingot products, the solidification law is slow sequential solidification, and the alloy elements have sufficient time for selection and crystallization. The solidification shrinkage of the molten steel is large, and the solidification quality inside the steel ingot is difficult to control. Solidification defects of steel ingot products are usually unavoidable, and the die casting process is the last step in the solidification and molding of the steel ingot, so the control of the casting process is particularly important.

[0003] In order to control the internal solidification quality of H13 type die steel ingot, the present invention provides a casting method for improving the internal solidification quality of H13 type die steel ingot below 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 compensation and reduce the macro-segregation defects inside the steel ingot. The final product performance can meet the performance requirements proposed by GB / T1299-2014 standard.

[0005] The object of the present invention is achieved by: a casting method for improving the internal solidification quality of H13 type die steel ingot, the casting method is implemented in the pouring type mold casting steel ingot of less than 10t, the steel grade of the cast steel ingot belongs to H13 type, and the composition conforms to the national standard GB / T 1299-2014, and 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), and the pouring temperature of the steel ingot is accurately controlled;

[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 adopts an embedded split insulation board, which needs 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;

[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 injection pipe to ensure the purity of the molten steel;

[0014] Step 2.5) Before pouring, fill the ingot mold and the hot water 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, and the drying system of medium-low carbon protective slag is: drying temperature 70-90°C, drying time ≥72 hours;

[0017] Step 3.2), before pouring, hang the fully baked protective slag into the ingot mold in advance, and the protective slag hanging method is multi-gradient hanging at different heights;

[0018] Step 4), pouring process control:

[0019] Step 4.1) After 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 float fully;

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

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

[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 to the top of the riser in a uniform scattered manner, and the order of adding is to 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 for heating and forging in the furnace. 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 steel ingot mold is 300-500°C, and the baking time is ≥2 hours; before the steel ingot mold is seated, the inside of the steel ingot mold is polished until there is no residual steel and slag left. After polishing, it is blown clean with dry air to ensure the surface quality of the steel ingot after demolding.

[0026] In step 2.2), the embedded split insulation board used in the riser complies with the YB / T 58 standard, and the tolerance of the embedded split insulation board after assembly is ≤2mm. The gaps are 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 insulation effect of the riser.

[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, the high temperature drying temperature is 70-90°C, and the high temperature drying time is ≥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 seated, an electric grinding device is used to grind the inner wall of the steel ingot mold one by one until there is no residual steel residue. After grinding, 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 different heights and multiple gradients. The operation method is to hang the protective slag close to the bottom. 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 less 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. 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: The present invention realizes a casting method of low superheat + slow casting + protective slag hanging by integrating the factors affecting the solidification process and adjusting the casting parameters, and controls the number of ingot casting plates and the number of casting branches per plate, thereby reducing the looseness of the center of the ingot and reducing the degree of macro-segregation, thereby achieving the purpose of improving the internal solidification quality of H13 type mold steel ingots. The implementation process of the present invention is mainly to coordinate the control of each link of casting, lean quantify the indicators of each link, and improve the internal solidification quality of H13 type mold steel ingots with a small increase or even no increase in production and labor costs. DETAILED DESCRIPTION

[0031] Embodiment 1: A casting method for improving the internal solidification quality of H13 type mold steel ingot, the casting method is implemented for bottom-casting steel ingots of less than 10 tons, the specific weight of the cast steel ingot is 7 tons, the specific number of cast plates is three, the cast steel grade belongs to H13 type, and the composition conforms to 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 estimated 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 pouring superheat target value is 40 °C, and the pouring temperature is determined based on 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 seated, 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 adopts an embedded split insulation board, which needs to be dried at high temperature before use, with a high temperature drying temperature of 70-90°C and a high temperature drying time of ≥72 hours; the insulation board used for the riser conforms to the YB / T 58 standard, the riser adopts a split insulation board, which needs to be dried at high temperature before use, with a high temperature drying temperature of 70-90°C and a high temperature drying time of ≥72 hours, and an embedded riser is used. The tolerance of the split insulation board used after assembly is ≤2mm, and the gap is plugged with wooden wedges to prevent the formation of a thin steel shell between the riser insulation boards during the solidification process to ensure the insulation 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 meet the YB / T 4637-2018 standard, and the mullite flow steel bricks used need to be dried at high temperature, the high temperature drying temperature is 70-90°C, 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 sand and dust inside the ingot mold, soup channel, and center injection 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 water 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, and the drying system of medium-low carbon protective slag is: drying temperature 70-90°C, drying time ≥72 hours;

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

[0044] Step 4), pouring process control:

[0045] Step 4.1) After 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 float fully;

[0046] Step 4.2), when the steel ingot is poured, the superheat of the molten steel is controlled according to the target value of 40°C, which is the pouring temperature; the pouring process is carried out on a 120-ton die-casting 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 ≤10t is controlled at 12-17Kg / s, and the pouring speed of the riser is controlled at ≤2Kg / s; the whole pouring process adopts argon protection pouring;

[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), using protective slag + exothermic agent + carbonized rice husk combination insulation to ensure the shrinkage compensation effect of the riser, 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 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 for heating and forging in the furnace. The surface temperature of the ingot is controlled to be ≥600℃ during demoulding and hot delivery.

[0051] It is understandable that the complete steelmaking process route is EAF (60t) - LF (60t) - VD (60t) - IC. The above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solution described in the embodiment of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effect; as long as the use requirements are met, they are within the protection scope of the present invention.

Claims

1. A casting method for improving the internal solidification quality of H13 type die steel ingot, characterized in that: The pouring method is implemented for bottom-casting steel ingots of less than 10 tons. The steel grade of the poured steel ingot belongs to H13 and the composition conforms to 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), and the pouring temperature of the steel ingot is accurately controlled; 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 adopts an embedded split insulation board, which needs 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; 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 injection pipe to ensure the purity of the molten steel; Step 2.5) Before pouring, fill the ingot mold and the hot water 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, and the drying system of medium-low carbon protective slag is: drying temperature 70-90°C, drying time ≥72 hours; Step 3.2), before pouring, hang the fully baked protective slag into the ingot mold in advance, and the protective slag hanging method is multi-gradient hanging at different heights; Step 4), pouring process control: Step 4.1) After 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 float fully; Step 4.2), when the steel ingot is poured, the superheat of the molten steel is controlled according to the target value of 40°C, which is the pouring temperature; the pouring process is carried out on a 120-ton die-casting steel pouring car; Step 4.3), the ingot pouring process adopts slow pouring, the pouring speed of the ingot body of ≤10t is controlled at 12-17Kg / s, and the pouring speed of the riser is controlled at ≤2Kg / s; the whole pouring process adopts argon protection pouring; 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 to the top of the riser in a uniform scattered manner, and the order of adding is to 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 for heating and forging in the furnace. 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 type die steel ingot according to claim 1, characterized in that: In step 2.1), the drying and baking temperature of the steel ingot mold is 300-500°C, and the baking time is ≥2 hours; before the steel ingot mold is seated, the inside of the steel ingot mold is polished until there is no residual steel and slag left. After polishing, it is blown clean with dry air to ensure the surface quality of the steel ingot after demolding.

3. A casting method for improving the internal solidification quality of H13 type die steel ingot according to claim 1, characterized in that: In step 2.2), the embedded split insulation board used in the riser complies with the YB / T 58 standard, and the tolerance of the embedded split insulation board after assembly is ≤2mm. The gaps are 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 insulation effect of the riser.

4. A casting method for improving the internal solidification quality of H13 type die 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, the high temperature drying temperature is 70-90°C, and the high temperature drying time is ≥72 hours.

5. A casting method for improving the internal solidification quality of H13 type die 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 seated, an electric grinding device is used to grind the inner wall of the steel ingot mold one by one until there is no residual steel residue. After grinding, it is blown clean with compressed dry air to ensure the surface quality of the steel ingot.

6. A casting method for improving the internal solidification quality of H13 type die steel ingot according to claim 1, characterized in that: In step 3.2), the protective slag is hung at different heights and multiple gradients. The operation method is to hang the protective slag close to the bottom. 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 less 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. The total hanging weight of the protective slag is controlled at 1.5-2.5 kg / t.