A ZK40E rod for hollow drill and production method

Abstract

The invention relates to a ZK40E rod for hollow drill and a production method thereof, wherein the chemical composition comprises, by mass percentage, C: 0.38% to 0.42%, Si: 1.32% to 1.48%, Mn: 0.90% to 1.00%, P≤0.012%, S≤0.010%, Cr: 0.72% to 0.82%, Ni: 0.43% to 0.53%, Mo: 0.21% to 0.28%, and the rest is Fe and inevitable impurities. The advantages are: the production adopts EBT electric furnace smelting + LF + VD and rolling process, the grain is refined, the wear resistance and fatigue resistance are met, the high-end use requirements are met, the electric furnace continuous casting process is realized, and the batch production is realized, which not only ensures the indicators such as the low-magnification structure, non-metallic inclusions, mechanical properties and the like of the finished steel of the ZK40E rod for hollow drill, but also ensures the surface quality level of the ZK40E rod for hollow drill.

Description

Technical Field

[0001] The invention belongs to the field of rods of metallurgical materials, and in particular relates to a ZK40E rod for hollow drill tools and a production method. Background Art

[0002] With the rapid development of my country's industry, the demand for mining resources and electric energy in various industries in China is growing, and the quality requirements for drill steel and drill tools are getting higher and higher. Compared with international advanced drill tool steel, my country's drill steel has relatively few steel grades, and the service life and quality of the drill tool products made are also quite different, which cannot fully meet the production needs. The production material of drill tools is usually rods, which are required to have excellent mechanical properties, high wear resistance and high steel purity to meet the requirements of high-end products. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a ZK40E rod for hollow drill tools and a production method, which ensures the indicators such as macrostructure, non-metallic inclusions, mechanical properties, etc. of the finished steel ZK40E rod for hollow drill tools, and also ensures the surface quality level of the ZK40E rod for hollow drill tools.

[0004] To achieve the above object, the present invention is implemented through the following technical solutions:

[0005] A ZK40E rod for a hollow drill, wherein the chemical composition of the ZK40E rod comprises, by mass percentage:

[0006] C: 0.38% ~ 0.42%, Si: 1.32% ~ 1.48%, Mn: 0.90% ~ 1.00%, P ≤ 0.012%, S ≤ 0.010%, Cr: 0.72% ~ 0.82%, Ni: 0.43% ~ 0.53%, Mo: 0.21% ~ 0.28%, the rest is Fe and unavoidable impurities.

[0007] A production method of ZK40E rods for hollow drill tools, the production process route is: EBT electric furnace smelting → LF refining → VD vacuum degassing → continuous casting → heating furnace heating → initial rolling → continuous rolling → heat treatment, wherein the continuous rolling adopts three rolling passes, including the following steps:

[0008] 1) In the first pass, the height of the rolled piece is reduced by 30-35 mm, the width of the rolled piece is increased by 13-18 mm, and the area of ​​the rolled piece is reduced by 1300-1500 mm 2 , the roll gap is controlled at 8.1-8.4 mm, the rolling speed is 1.2-1.8 m / s, and the roll speed is controlled at 40-43 rpm / min;

[0009] 2) In the second pass, the height of the rolled piece increases by 12-15 mm, the width of the rolled piece decreases by 40-45 mm, and the area of ​​the rolled piece decreases by 980-1000 mm 2 , the roll gap is controlled at 7.9-8.1mm, the rolling speed is 1.9-2.0m / s, and the roll speed is controlled at 53-55rpm / min;

[0010] 3) In the third pass, the height of the rolled piece is reduced by 15-17 mm, the width of the rolled piece is increased by 4-5 mm, and the area of ​​the rolled piece is reduced by 700-800 mm 2 The roll gap is controlled at 5.8-6.1 mm, the rolling speed is 2.35-2.4 m / s, and the roll speed is controlled at 92-93 rpm / min.

[0011] The initial rolling adopts 1150mm BD initial rolling mill to produce the blank.

[0012] The heating process of the heating furnace is as follows: the preheating section of the heating furnace is ≤750°C, the second heating section is 840°C to 880°C, the first heating section is 1190°C to 1220°C, the soaking section is 1180°C to 1210°C, the furnace outlet temperature is 1170°C to 1190°C, and the total heating time is ≥210min.

[0013] The heat treatment comprises the following steps:

[0014] 1) Quenching: 870-890℃, keep warm for 60-70min, oil cooling;

[0015] 2) Tempering: 540-560℃, keep warm for 90-100min, water cooling.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The ZK40E rods for hollow drill tools are produced by EBT electric furnace smelting + LF + VD and rolling process, which has refined grains, wear resistance, fatigue resistance, and meets high-end usage requirements. The electric furnace continuous casting process has achieved mass production, which not only ensures the indicators of the finished steel macrostructure, non-metallic inclusions, mechanical properties, etc. of the ZK40E rods for hollow drill tools, but also ensures the surface quality level of the ZK40E rods for hollow drill tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the heating process curve of the heating furnace. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0020] Example 1

[0021] The chemical composition of ZK40E rods for hollow drills includes:

[0022] C: 0.40%, Si: 1.37%, Mn: 0.98%, P≤0.010%, S≤0.008%, Cr: 0.76%, Ni: 0.45%, Mo: 0.23%, and the rest are Fe and unavoidable impurities.

[0023] The production process of ZK40E bars for hollow drills: 50t EBT electric furnace smelting → refining outside the furnace (LF+VD) → 235mm×265mm continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. It includes the following steps:

[0024] (1) 50t electric furnace smelting: 65wt% molten iron and 35wt% scrap steel are used for smelting; the tapping temperature is 1678℃, C is 0.05% and P is 0.008% when tapping, slag, coke powder recarburizer 60kg / t and ferroalloy are added when 1 / 4 to 1 / 3 of the steel is tapped. The amount of alloy added per ton of steel: 2.7kg / t of aluminum iron, 2.3kg / t of alumina powder, 11kg / t of silicon manganese and 10kg / t of high carbon ferrochrome.

[0025] (2) LF furnace: 22000A high current is used to heat and melt slag, and the refining time is 65min. When the temperature of the molten steel reaches 1652℃, diffusion deoxidizer is added for diffusion deoxidation. When the temperature of the molten steel reaches 1668℃, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, diffusion deoxidizer is added to continue slag adjustment. Added alloy: high carbon ferromanganese 3.8kg / t, high carbon ferrochrome 1.35kg / t, ferrosilicon 18kg / t, ferrosilicon powder 2.2kg / t, alumina powder 0.8kg / t, aluminum wire 1.8m / t, ferromolybdenum 3.7kg / t, nickel plate 4.1kg / t. Auxiliary materials: active lime 12kg / t, fluorite briquette 1.7kg / t, coke powder recarburizer 1.35kg / t. At the same time, the white slag is smelted for 25min. The composition of the slag sample after LF is shown in Table 1. Binary alkalinity guarantees R1≥10, ternary alkalinity R2≥12, and quaternary alkalinity R3≥1.5.

[0026] Table 1 Composition of slag samples after LF (%)

[0027]

[0028] (3) VD refining: The temperature before entering VD is 1670℃. Before the vacuum pump is started, the argon pressure is controlled at 0.15MPa. The slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the holding time is 18min. The vacuum breaking temperature is 1600℃. Depending on the composition of the molten steel, alloy is added. At the same time, the argon pressure is adjusted to 0.4MPa. The static argon blowing time is 30min. After the static argon blowing is completed, add Calcium silicon cored wire is 2.3m / t, carbonized rice husk is added at 1.8kg / t, and the bag temperature is 1560℃.

[0029] (4) Continuous casting: the temperature at the stage is 1560℃, the amount of molten steel in the ladle is 49t, the pouring amount is 49t, the medium billet of 235mm×265mm is cast, the pouring time is 38min, the length of a single billet is 8100mm, the temperature of the tundish is maintained at 1508℃, and the casting speed is 0.83m / min when pouring. The water pressure of the crystallizer equipment is 0.49MPa, the air pressure is 0.58MPa, and the water volume of the secondary cooling is 0.56L / kg. The ladle is well sealed, and the large ladle covering agent, the tundish covering agent, and the high-basicity tundish slag are used. The argon gas in the tundish is used for casting.

[0030] (5) Heating process

[0031] Heating process: According to the characteristics of ZK40E steel, the preheating section of the heating furnace is ≤750℃, the second heating section is 860℃, the first heating section is 1195℃, the soaking section is 1190℃, the furnace discharge temperature is 1180℃, and the total heating time is ≥210min. See the heating process curve for details. Figure 1 .

[0032] (6) Product specifications Rolling process:

[0033] BD billeting process: 1150mm BD primary rolling mill is used for billeting, and three passes are performed. The small bar rolling process is as follows:

[0034] 1) In the first pass, the height of the rolled piece is reduced by 32 mm, the width of the rolled piece is increased by 15 mm, and the area of ​​the rolled piece is reduced by 1380 mm 2 , the roll gap is controlled at 8.2mm, the rolling speed is 1.4m / s, and the roll speed is controlled at 41rpm / min;

[0035] 2) In the second pass, the height of the rolled piece increases by 13 mm, the width of the rolled piece decreases by 43 mm, and the area of ​​the rolled piece decreases by 985 mm 2 , the roll gap is controlled at 7.9mm, the rolling speed is 1.9m / s, and the roll speed is controlled at 54rpm / min;

[0036] 3) In the third pass, the height of the rolled piece is reduced by 15 mm, the width of the rolled piece is increased by 4 mm, and the area of ​​the rolled piece is reduced by 750 mm 2, the roll gap is controlled at 5.9mm, the rolling speed is 2.38m / s, and the roll speed is controlled at 92rpm / min.

[0037] (7) Insulation process

[0038] Insulation process: Steel is piled and cooled, and steel is prohibited from being placed at the air outlet; the pile cooling process requires the stack temperature to be 350℃, and the bundles are hoisted and transferred to the next process in time. During the pile cooling process, the single pile cooling capacity is required to be 45 tons, and the pile is stacked for 10 hours before being dismantled.

[0039] The advantages of the present invention are:

[0040] Finished product inspection results are shown in Table 3, Table 4, and Table 5:

[0041] Table 3 Φ55mm specification macrostructure

[0042] Serial number Generally loose Loose center Ingot segregation General spot segregation Edge spot segregation standard ≤2.0 ≤2.0 ≤2.0 ≤1.0 ≤1.0 1 1.0 0.5 0.5 0 0 2 1.0 0.5 0.5 0 0 3 1.5 0.5 0.5 0 0 4 1.0 0.5 0.5 0 0

[0043] Table 4 Non-metallic inclusions

[0044]

[0045] Table 5 ZK40E rods for hollow drill Mechanical properties

[0046]

[0047] Example 2

[0048] The chemical composition of ZK40E rods for hollow drills includes:

[0049] C: 0.39%, Si: 1.38%, Mn: 0.96%, P: 0.008%, S: 0.005%, Cr: 0.75%, Ni: 0.46%, Mo: 0.24%, and the rest are Fe and inevitable impurities.

[0050] The production process of ZK40E bars for hollow drills: 50t EBT electric furnace smelting → refining outside the furnace (LF+VD) → 235mm×265mm continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. It includes the following steps:

[0051] (1) 50t electric furnace smelting: 67wt% molten iron and 33wt% scrap steel are used for smelting; the tapping temperature is 1675℃, C is 0.06% and P is 0.006% when tapping, slag, coke powder recarburizer 62kg / t and ferroalloy are added when 1 / 4 to 1 / 3 of the steel is tapped. The amount of alloy added per ton of steel: 2.6kg / t of aluminum iron, 2.2kg / t of alumina powder, 11kg / t of silicon manganese and 10.2kg / t of high carbon ferrochrome.

[0052] (2) LF furnace: 22000A high current is used to heat up and melt slag, and the refining time is 63min. When the temperature of the molten steel reaches 1653℃, diffusion deoxidizer is added for diffusion deoxidation. When the temperature of the molten steel reaches 1666℃, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, diffusion deoxidizer is added to continue slag adjustment. Addition of alloy: high carbon ferromanganese 3.7kg / t, high carbon ferrochrome 1.32kg / t, ferrosilicon 18.5kg / t, ferrosilicon powder 2.2kg / t, alumina powder 0.82kg / t, aluminum wire 1.7m / t, ferromolybdenum 3.8kg / t, nickel plate 4.15kg / t. Auxiliary materials: active lime 12.5kg / t, fluorite briquette 1.73kg / t, coke powder recarburizer 1.33kg / t. At the same time, continue to maintain white slag smelting for 28min. The composition of the slag sample after LF is shown in Table 1. Binary basicity guarantees R1 (CaO / SiO 2 )≥10, ternary basicity R2(CaO+MgO) / SiO 2 ≥12, quaternary basicity R3(CaO+MgO) / (SiO 2 +Al 2 O 3 )≥1.5.

[0053] (3) VD refining: The temperature before entering VD is 1668℃. Before the vacuum pump is started, the argon pressure is controlled at 0.17MPa. The slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the holding time is 18min. The vacuum breaking temperature is 1600℃. Depending on the composition of the molten steel, alloy is added. At the same time, the argon pressure is adjusted to 0.4MPa. The static argon blowing time is 30min. After the static argon blowing is completed, add Calcium silicon cored wire is 2.3m / t, carbonized rice husk is added at 1.8kg / t, and the bag temperature is 1560℃.

[0054] (4) Continuous casting: the temperature at the stage is 1560℃, the amount of molten steel in the ladle is 49t, the pouring amount is 49t, the medium billet of 235mm×265mm is cast, the pouring time is 38min, the length of a single billet is 8100mm, the temperature of the tundish is maintained at 1509℃, and the casting speed is 0.84m / min when pouring. The water pressure of the crystallizer equipment is 0.48MPa, the air pressure is 0.57MPa, and the water volume of the secondary cooling is 0.57L / kg. The ladle is well sealed, and the large ladle covering agent, the tundish covering agent, and the high-basicity tundish slag are used. The argon gas in the tundish is used for casting.

[0055] (5) Heating process

[0056] Heating process: According to the characteristics of ZK40E steel, the preheating section of the heating furnace is 650℃, the second heating section is 865℃, the first heating section is 1197℃, the soaking section is 1192℃, the furnace discharge temperature is 1183℃, and the total heating time is 240min. See the heating process curve for details. Figure 1 .

[0057] (6) Product specifications Rolling process:

[0058] BD billeting process: 1150mm BD primary rolling mill is used for billeting, and three passes are performed. The small bar rolling process is as follows:

[0059] 1) In the first pass, the height of the rolled piece is reduced by 32 mm, the width of the rolled piece is increased by 14 mm, and the area of ​​the rolled piece is reduced by 1380 mm 2 , the roll gap is controlled at 8.3mm, the rolling speed is 1.4m / s, and the roll speed is controlled at 41rpm / min;

[0060] 2) In the second pass, the height of the rolled piece increases by 13 mm, the width of the rolled piece decreases by 42 mm, and the area of ​​the rolled piece decreases by 960 mm 2 , the roll gap is controlled at 8mm, the rolling speed is 2.0m / s, and the roll speed is controlled at 54rpm / min;

[0061] 3) In the third pass, the height of the rolled piece is reduced by 16 mm, the width of the rolled piece is increased by 5 mm, and the area of ​​the rolled piece is reduced by 780 mm 2 , the roll gap is controlled at 5.9mm, the rolling speed is 2.38m / s, and the roll speed is controlled at 93rpm / min.

[0062] (7) Insulation process

[0063] Insulation process: Steel is piled and cooled, and steel is prohibited from being placed at the air outlet; the pile cooling process requires the stack temperature to be 350℃, and the bundles are hoisted and transferred to the next process in time. During the pile cooling process, the single pile cooling capacity is required to be 45 tons, and the pile is stacked for 10 hours before being dismantled.

[0064] The advantages of the present invention are:

[0065] Finished product inspection results are shown in Table 3, Table 4, and Table 5:

[0066] Table 3 Φ55mm specification macrostructure

[0067] Serial number Generally loose Loose center Ingot segregation General spot segregation Edge spot segregation standard ≤2.0 ≤2.0 ≤2.0 ≤1.0 ≤1.0 1 1.5 0.5 0.5 0 0 2 1.0 0.5 0.5 0 0 3 1.0 0.5 0.5 0 0 4 1.5 0.5 0.5 0 0

[0068] Table 4 Non-metallic inclusions

[0069]

[0070] Table 5 ZK40E rods for hollow drill Mechanical properties

[0071]

[0072]

[0073] Example 3

[0074] The chemical composition of ZK40E rods for hollow drills includes:

[0075] C: 0.41%, Si: 1.39%, Mn: 0.95%, P: 0.007%, S: 0.004%, Cr: 0.77%, Ni: 0.47%, Mo: 0.24%, and the rest are Fe and inevitable impurities.

[0076] The production process of ZK40E bars for hollow drills: 50t EBT electric furnace smelting → refining outside the furnace (LF+VD) → 235mm×265mm continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. It includes the following steps:

[0077] (1) 50t electric furnace smelting: 68wt% molten iron and 32wt% scrap steel are used for smelting; the tapping temperature is 1673℃, C is 0.06% and P is 0.006% when tapping, slag, coke powder recarburizer 62kg / t and ferroalloy are added when 1 / 4 to 1 / 3 of the steel is tapped. The amount of alloy added per ton of steel: 2.8kg / t of aluminum iron, 2.3kg / t of alumina powder, 11kg / t of silicon manganese and 10.3kg / t of high carbon ferrochrome.

[0078] (2) LF furnace: 22000A high current is used to heat up and melt slag, and the refining time is 63min. When the temperature of the molten steel reaches 1654℃, diffusion deoxidizer is added for diffusion deoxidation. When the temperature of the molten steel reaches 1667℃, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, diffusion deoxidizer is added to continue slag adjustment. Addition of alloy: high carbon ferromanganese 3.6kg / t, high carbon ferrochrome 1.35kg / t, ferrosilicon 18.7kg / t, ferrosilicon powder 2.25kg / t, alumina powder 0.84kg / t, aluminum wire 1.8m / t, ferromolybdenum 3.8kg / t, nickel plate 4.17kg / t. Auxiliary materials: active lime 12.6kg / t, fluorite briquette 1.76kg / t, coke powder recarburizer 1.34kg / t. At the same time, continue to maintain white slag smelting for 27min. The composition of the slag sample after LF is shown in Table 1. Binary basicity guarantees R1 (CaO / SiO 2 ): 11, ternary basicity R2(CaO+MgO) / SiO 2 :12.5, quaternary basicity R3(CaO+MgO) / (SiO 2 +Al2 O 3 ):1.7.

[0079] (3) VD refining: The temperature before entering VD is 1669℃. Before the vacuum pump is started, the argon pressure is controlled at 0.18MPa. The slag surface is slightly moved and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the holding time is 19min. The vacuum breaking temperature is 1605℃. Depending on the composition of the molten steel, alloy is added. At the same time, the argon pressure is adjusted to 0.45MPa. The static argon blowing time is 32min. After the static argon blowing is completed, add Calcium silicon cored wire is 2.4m / t, carbonized rice husk is added at 1.75kg / t, and the bag temperature is 1558℃.

[0080] (4) Continuous casting: the temperature at the stage is 1562℃, the amount of molten steel in the ladle is 49.5t, the pouring amount is 49.5t, the medium billet of 235mm×265mm is cast, the pouring time is 39min, the length of a single billet is 8100mm, the temperature of the tundish is maintained at 1508℃, and the casting speed is 0.83m / min when pouring. The water pressure of the crystallizer equipment is 0.49MPa, the air pressure is 0.59MPa, and the water volume of the secondary cooling is 0.58L / kg. The ladle is well sealed, and the large ladle covering agent, the tundish covering agent, and the high-basicity tundish slag are used. The argon gas in the tundish is used for casting.

[0081] (5) Heating process

[0082] Heating process: According to the characteristics of ZK40E steel, the preheating section of the heating furnace is 640℃, the second heating section is 867℃, the first heating section is 1198℃, the soaking section is 1194℃, the furnace discharge temperature is 1185℃, and the total heating time is 260min. See the heating process curve for details. Figure 1 .

[0083] (6) Product specifications Rolling process:

[0084] BD billeting process: 1150mm BD primary rolling mill is used for billeting, and three passes are performed. The small bar rolling process is as follows:

[0085] 1) In the first pass, the height of the rolled piece is reduced by 35 mm, the width of the rolled piece is increased by 16 mm, and the area of ​​the rolled piece is reduced by 1360 mm 2 , the roll gap is controlled at 8.3mm, the rolling speed is 1.5m / s, and the roll speed is controlled at 42rpm / min;

[0086] 2) In the second pass, the height of the rolled piece increases by 14 mm, the width of the rolled piece decreases by 44 mm, and the area of ​​the rolled piece decreases by 985 mm 2 , the roll gap is controlled at 8.0mm, the rolling speed is 2.0m / s, and the roll speed is controlled at 55rpm / min;

[0087] 3) In the third pass, the height of the rolled piece is reduced by 16 mm, the width of the rolled piece is increased by 4.5 mm, and the area of ​​the rolled piece is reduced by 750 mm 2 , the roll gap is controlled at 6.0mm, the rolling speed is 2.4m / s, and the roll speed is controlled at 92rpm / min.

[0088] (7) Insulation process

[0089] Insulation process: Steel is piled and cooled, and steel is prohibited from being placed at the air outlet; the pile cooling process requires the stack temperature to be 350℃, and the bundles are hoisted and transferred to the next process in time. During the pile cooling process, the single pile cooling capacity is required to be 45 tons, and the pile is stacked for 10 hours before being dismantled.

[0090] The advantages of the present invention are:

[0091] Finished product inspection results are shown in Table 3, Table 4, and Table 5:

[0092] Table 3 Φ55mm specification macrostructure

[0093] Serial number Generally loose Loose center Ingot segregation General spot segregation Edge spot segregation standard ≤2.0 ≤2.0 ≤2.0 ≤1.0 ≤1.0 1 1.5 0.5 0.5 0 0 2 1.0 0.5 0.5 0 0 3 1.0 0.5 0.5 0 0 4 1.0 0.5 0.5 0 0

[0094] Table 4 Non-metallic inclusions

[0095]

[0096] Table 5 ZK40E rods for hollow drill Mechanical properties

[0097]

[0098] Example 4

[0099] The chemical composition of ZK40E rods for hollow drills includes:

[0100] C: 0.40%, Si: 1.38%, Mn: 0.94%, P: 0.006%, S: 0.003%, Cr: 0.76%, Ni: 0.46%, Mo: 0.25%, and the rest are Fe and inevitable impurities.

[0101] The production process of ZK40E bars for hollow drills: 50t EBT electric furnace smelting → refining outside the furnace (LF+VD) → 235mm×265mm continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. It includes the following steps:

[0102] (1) 50t electric furnace smelting: 67wt% molten iron and 33wt% scrap steel are used for smelting; the tapping temperature is 1672℃, C is 0.07% and P is 0.007% when tapping, slag, coke powder recarburizer 61kg / t and ferroalloy are added when 1 / 4 to 1 / 3 of the steel is tapped. The amount of alloy added per ton of steel: 2.85kg / t of aluminum iron, 2.35kg / t of alumina powder, 11kg / t of silicon manganese, and 10.2kg / t of high carbon ferrochrome.

[0103] (2) LF furnace: 22000A high current is used to heat and melt slag, and the refining time is 64 minutes. When the temperature of the molten steel reaches 1653℃, diffusion deoxidizer is added for diffusion deoxidation. When the temperature of the molten steel reaches 1666℃, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, diffusion deoxidizer is added to continue slag adjustment. Addition of alloy: high carbon ferromanganese 3.65kg / t, high carbon ferrochrome 1.34kg / t, ferrosilicon 18.6kg / t, ferrosilicon powder 2.28kg / t, alumina powder 0.85kg / t, aluminum wire 1.8m / t, ferromolybdenum 3.7kg / t, nickel plate 4.18kg / t. Auxiliary materials: active lime 12.7kg / t, fluorite briquette 1.78kg / t, coke powder recarburizer 1.35kg / t. At the same time, continue to maintain white slag smelting for 29 minutes. The composition of the slag sample after LF is shown in Table 1. Binary basicity guarantees R1 (CaO / SiO 2 ): 11.5, ternary basicity R2(CaO+MgO) / SiO 2 :12.4, quaternary basicity R3(CaO+MgO) / (SiO 2 +Al 2 O 3 ):1.8.

[0104] (3) VD refining: The temperature before entering VD is 1670℃, the argon pressure is controlled at 0.17MPa before the vacuum pump is started, the slag surface is slightly moved and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the holding time is 19min. The vacuum breaking temperature is 1603℃. Depending on the composition of the molten steel, alloy is added. At the same time, the argon pressure is adjusted to 0.44MPa. The static argon blowing time is 33min. After the static argon blowing is completed, add Calcium silicon cored wire is 2.3m / t, carbonized rice husk is added at 1.78kg / t, and the bag temperature is 1557℃.

[0105] (4) Continuous casting: the temperature at the stage is 1561℃, the amount of molten steel in the ladle is 49.4t, the pouring amount is 49.4t, the medium billet of 235mm×265mm is cast, the pouring time is 38min, the length of a single billet is 8100mm, the temperature of the tundish is maintained at 1506℃, and the casting speed is 0.82m / min when pouring. The water pressure of the crystallizer equipment is 0.48MPa, the air pressure is 0.58MPa, and the water volume of the secondary cooling is 0.57L / kg. The ladle is well sealed, and the large ladle covering agent, the tundish covering agent, and the high-basicity tundish slag are used. The argon gas in the tundish is used for casting.

[0106] (5) Heating process

[0107] Heating process: According to the characteristics of ZK40E steel, the preheating section of the heating furnace is 660℃, the second heating section is 869℃, the first heating section is 1197℃, the soaking section is 1195℃, the furnace temperature is 1184℃, and the total heating time is 270min. See the heating process curve for details. Figure 1 .

[0108] (6) Product specifications Rolling process:

[0109] BD billeting process: 1150mm BD primary rolling mill is used for billeting, and three passes are performed. The small bar rolling process is as follows:

[0110] 1) In the first pass, the height of the rolled piece is reduced by 36 mm, the width of the rolled piece is increased by 17 mm, and the area of ​​the rolled piece is reduced by 1365 mm 2 , the roll gap is controlled at 8.35mm, the rolling speed is 1.55m / s, and the roll speed is controlled at 42rpm / min;

[0111] 2) In the second pass, the height of the rolled piece increases by 13 mm, the width of the rolled piece decreases by 45 mm, and the area of ​​the rolled piece decreases by 987 mm 2 , the roll gap is controlled at 8.1mm, the rolling speed is 2.1m / s, and the roll speed is controlled at 56rpm / min;

[0112] 3) In the third pass, the height of the rolled piece is reduced by 17 mm, the width of the rolled piece is increased by 4.4 mm, and the area of ​​the rolled piece is reduced by 760 mm 2 , the roll gap is controlled at 6.1mm, the rolling speed is 2.45m / s, and the roll speed is controlled at 93rpm / min.

[0113] (7) Insulation process

[0114] Insulation process: Steel is piled and cooled, and steel is prohibited from being placed at the air outlet; the pile cooling process requires the stack temperature to be 350℃, and the bundles are hoisted and transferred to the next process in time. During the pile cooling process, the single pile cooling capacity is required to be 45 tons, and the pile is stacked for 10 hours before being dismantled.

[0115] The advantages of the present invention are:

[0116] Finished product inspection results are shown in Table 3, Table 4, and Table 5:

[0117] Table 3 Φ55mm specification macrostructure

[0118] Serial number Generally loose Loose center Ingot segregation General spot segregation Edge spot segregation standard ≤2.0 ≤2.0 ≤2.0 ≤1.0 ≤1.0 1 1.5 0.5 0.5 0 0 2 1.0 0.5 0.5 0 0 3 1.5 0.5 0.5 0 0 4 1.5 0.5 0.5 0 0

[0119] Table 4 Non-metallic inclusions

[0120]

[0121]

[0122] Table 5 ZK40E rods for hollow drill Mechanical properties

[0123]

Claims

1. A method for producing ZK40E rods for hollow drill tools, characterized in that: The chemical composition of the ZK40E bar material includes, by mass percentage: C: 0.38% ~ 0.42%, Si: 1.32% ~ 1.48%, Mn: 0.90% ~ 1.00%, P ≤ 0.012%, S ≤ 0.010%, Cr: 0.72% ~ 0.82%, Ni: 0.43% ~ 0.53%, Mo: 0.21% ~ 0.28%, the rest is Fe and unavoidable impurities; The production method of ZK40E rod for hollow drill tool has the following production process route: EBT electric furnace smelting → LF refining → VD vacuum degassing → continuous casting → heating in a heating furnace → initial rolling → continuous rolling → heat treatment, wherein the continuous rolling adopts three rolling passes, and comprises the following steps: 1) In the first pass, the height of the rolled piece is reduced by 30-35 mm, the width of the rolled piece is increased by 13-18 mm, and the area of ​​the rolled piece is reduced by 1300-1500 mm 2 , the roll gap is controlled at 8.1-8.4 mm, the rolling speed is 1.2-1.8 m / s, and the roll speed is controlled at 40-43 rpm / min; 2) In the second pass, the height of the rolled piece increases by 12-15 mm, the width of the rolled piece decreases by 40-45 mm, and the area of ​​the rolled piece decreases by 980-1000 mm 2 , the roll gap is controlled at 7.9-8.1mm, the rolling speed is 1.9-2.0m / s, and the roll speed is controlled at 53-55rpm / min; 3) In the third pass, the height of the rolled piece is reduced by 15-17 mm, the width of the rolled piece is increased by 4-5 mm, and the area of ​​the rolled piece is reduced by 700-800 mm 2 The roll gap is controlled at 5.8-6.1 mm, the rolling speed is 2.35-2.4 m / s, and the roll speed is controlled at 92-93 rpm / min.

2. The method for producing a ZK40E rod for hollow drill according to claim 1, characterized in that: The initial rolling is carried out by using a 1150mmBD initial rolling mill.

3. The method for producing a ZK40E rod for hollow drill according to claim 1, characterized in that: The heating process of the heating furnace is as follows: the preheating section of the heating furnace is ≤750°C, the second heating section is 840°C to 880°C, the first heating section is 1190°C to 1220°C, the soaking section is 1180°C to 1210°C, the furnace outlet temperature is 1170°C to 1190°C, and the total heating time is ≥210min.

4. The method for producing a ZK40E rod for hollow drill according to claim 1, characterized in that: The heat treatment comprises the following steps: 1) Quenching: 870-890℃, keep warm for 60-70min, oil cooling; 2) Tempering: 540-560℃, keep warm for 90-100min, water cooling.

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