Preparation method of cold work die steel

Abstract

The invention provides a preparation method of cold work die steel, and relates to the technical field of steelmaking. The preparation method of the cold work die steel comprises the following steps: S1, preparing raw materials; s2, smelting; s3, ingot casting; s4, electroslag treatment; s5, a forging process; s6, finishing process; and S7, inspecting. By optimizing the component proportion, the material quality is improved, the use requirement of a cold-working die is met, higher strength and toughness are achieved, better wear resistance is achieved, the cold and hot machining process performance is excellent, heat treatment deformation is small, universality is high, and the material is suitable for manufacturing a cold extrusion die, a cold micro die and a cold punching die which bear high loads; according to the method, waste of raw materials is reduced, production efficiency is improved, energy consumption is reduced, the production cost can be reduced, in addition, the use of expensive alloy elements can be reduced by accurately controlling the addition amount of the alloy elements, and the cost is further reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking, in particular to a method for preparing cold-working die steel. Background Art

[0002] Cold working die steel refers to a die that is used to deform metal at room temperature, such as blanking dies, bending dies and shearing dies. It is also called cold deformation die steel or cold die steel. It has high hardness and wear resistance, high strength and fatigue strength, and sufficient toughness. It also has good process properties, such as forging, cutting processability, hardenability and hardenability. Small deformation during heat treatment is its characteristic.

[0003] Traditional Cr12 series steel has good wear resistance, red hardness and other characteristics, and is suitable for making cold punching dies and punches, cold shear knives, drill bushings, gauges, wire drawing dies, etc. that are subject to less impact load and require higher wear resistance. However, Cr12 type has poor high temperature performance, and its high carbon content is easy to form ledeburite eutectic carbides, which will cause defects such as deformation and cracking during use. Therefore, technicians in this field provide a preparation method for cold working die steel to solve the problems raised in the above background technology. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the deficiencies in the prior art, the present invention provides a method for preparing cold working die steel, which solves the problems that traditional Cr12 series steels have poor high temperature performance, high carbon content, easy formation of ledeburite eutectic carbides, and defects such as deformation and cracking during use.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for preparing cold working die steel comprises the following steps:

[0008] S1. Prepare raw materials, select carbon, silicon, manganese, phosphorus, sulfur, chromium, molybdenum, vanadium and niobium, determine the precise ratio of each element according to the performance requirements of the mold steel, pre-treat the selected alloy elements, including crushing, screening and washing to ensure the purity and uniformity of the raw materials, and mix the alloy elements uniformly according to the predetermined ratio to form a mixture;

[0009] S2. Smelting: Place the mixed material in the medium frequency furnace and perform smelting operations according to the job regulations;

[0010] S2.1. For molten steel refining furnace, perform refining operation according to the job regulations, the white slag retention time is required to be ≥30 minutes, and strive to ensure that the main chemical composition of the steel out of the molten steel refining furnace is within the internal control range;

[0011] S2.2. Vacuum degassing: perform vacuum operation according to the job regulations, vacuum degree ≤ 67 bar, holding time ≥ 10 minutes, tank outlet temperature T = 1560-1580℃;

[0012] S3. Ingot casting, casting temperature T = 1540-1560 ° C, mold temperature control 20-80 ° C, use electrode rod demoulding after sand cooling, hood cooling or red annealing;

[0013] S4. Electroslag: Operate according to the job regulations, use CaF2:Al2O3=70:30 binary slag system, and cool the electroslag ingot after demoulding. Annealing or hot forging is arranged within 2 days after cooling. It is not allowed to leave the hood before annealing.

[0014] S5. Forging process, firstly, heat treatment is performed by preheating the above-mentioned ingot into a furnace, the temperature is ≤500°C, the forging heating temperature is 1170-1190°C, the start forging temperature is 1120-1150°C, and the final forging temperature is ≥900°C;

[0015] S5.1. Forging shall be carried out in accordance with the current operating procedures, with a forging ratio of ≥4.5. The hammer shall be light at the beginning of forging, and then gradually increased to prevent cracks;

[0016] S5.2. Cooling: After forging, the billet is air-cooled to 500-550℃ and then put into the pit for sand cooling or red annealing;

[0017] S5.3. Annealing: There are microstructure and hardness requirements. Isothermal annealing process is performed. The annealing process is as follows:

[0018] The steel ingots and steel products are annealed according to the above process. The heating temperature and holding time are adjusted within the prescribed allowable range according to the steel product size and furnace load.

[0019] S6. Finishing process: according to enterprise standards and machining operation procedures, the steel is finished to meet the corresponding appearance, shape and size requirements;

[0020] S7. Inspection: According to the enterprise's requirements, steel is sampled, inspected and judged, and can be put into storage after meeting the standard quality requirements.

[0021] (III) Beneficial effects

[0022] The present invention provides a method for preparing cold working die steel, which has the following beneficial effects:

[0023] 1. In the present invention, by optimizing the ingredient ratio, the material quality is improved to meet the use requirements of cold working dies, and the material has higher strength and toughness, better wear resistance, excellent process performance of hot and cold processing, small heat treatment deformation, strong versatility, and is suitable for making cold extrusion dies, cold micro-dies, and cold punching dies that withstand high loads.

[0024] 2. In the present invention, by optimizing the preparation process, reducing the waste of raw materials, improving production efficiency and reducing energy consumption, the production cost can be reduced. In addition, by accurately controlling the addition amount of alloy elements, the use of expensive alloy elements can be reduced, further reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the size of the forged flat steel and its allowable deviation in the present invention;

[0026] Figure 2 It is a schematic diagram of the size of forged round steel and its allowable deviation in the present invention;

[0027] Figure 3 This is a schematic diagram of the chemical composition table of the finished steel material in the present invention;

[0028] Figure 4 is a schematic diagram of non-metallic inclusions in steel in the present invention;

[0029] Figure 5 A schematic diagram of the ultrasonic flaw detection qualification level in the present invention;

[0030] Figure 6 It is a schematic diagram of the inspection items, sampling quantity, sampling location and test method of the steel material in the present invention;

[0031] Figure 7 It is a schematic diagram of the steel grade and chemical composition internal control requirements in the present invention;

[0032] Figure 8 This is a process diagram for annealing the motor rod and electroslag ingot in the present invention;

[0033] Fig. 9 It is a schematic diagram of the trend of the heating and heat preservation process in the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Embodiment 1:

[0036] like Figure 1-9 As shown, an embodiment of the present invention provides a method for preparing cold working die steel, comprising the following steps:

[0037] S1. Prepare raw materials, select carbon, silicon, manganese, phosphorus, sulfur, chromium, molybdenum, vanadium and niobium, determine the precise ratio of each element according to the performance requirements of the mold steel, pre-treat the selected alloy elements, including crushing, screening and washing to ensure the purity and uniformity of the raw materials, and mix the alloy elements uniformly according to the predetermined ratio to form a mixture;

[0038] S2. Smelting: Place the mixed material in the medium frequency furnace and perform smelting operations according to the job regulations;

[0039] S2.1. For molten steel refining furnace, perform refining operation according to the job regulations, the white slag retention time is required to be ≥30 minutes, and strive to ensure that the main chemical composition of the steel out of the molten steel refining furnace is within the internal control range;

[0040] S2.2. Vacuum degassing: perform vacuum operation according to the job regulations, vacuum degree ≤ 67 bar, holding time ≥ 10 minutes, tank outlet temperature T = 1560-1580℃;

[0041] S3. Ingot casting, casting temperature T = 1540-1560 ° C, mold temperature control 20-80 ° C, use electrode rod demoulding after sand cooling, hood cooling or red annealing;

[0042] S4. Electroslag: Operate according to the job regulations, use CaF2:Al2O3=70:30 binary slag system, and cool the electroslag ingot after demoulding. Annealing or hot forging is arranged within 2 days after cooling. It is not allowed to leave the hood before annealing.

[0043] S5. Forging process, firstly, heat treatment is performed by preheating the above-mentioned ingot into a furnace, the temperature is ≤500°C, the forging heating temperature is 1170-1190°C, the start forging temperature is 1120-1150°C, and the final forging temperature is ≥900°C;

[0044] S5.1. Forging shall be carried out in accordance with the current operating procedures, with a forging ratio of ≥4.5. The hammer shall be light at the beginning of forging, and then gradually increased to prevent cracks;

[0045] S5.2. Cooling: After forging, the billet is air-cooled to 500-550℃ and then put into the pit for sand cooling or red annealing;

[0046] S5.3. Annealing: There are microstructure and hardness requirements. Isothermal annealing process is performed. The annealing process is as follows:

[0047] The steel ingots and steel products are annealed according to the above process. The heating temperature and holding time are adjusted within the prescribed allowable range according to the steel product size and furnace loading. The annealing Brinell hardness is ≤229HBW;

[0048] S6. Finishing process: According to enterprise standards and machining operation procedures, the steel is finished to meet the corresponding appearance, shape and size requirements. The allowable deviation of forged flat steel is Figure 1 Implementation, forged round steel allowable deviation according to Figure 2 Implementation: Steel delivery length ≥ 2m, curvature should be ≤ 4mm / m, full length curvature ≤ 0.5% L, end face bevel ≤ 5mm, weight: Steel is delivered according to actual weight;

[0049] S7. Inspection: According to the requirements of the enterprise, steel shall be sampled, inspected and judged, and shall be put into storage after meeting the standard quality requirements. The steel grade, chemical composition, smelting analysis, shall meet the requirements of Figure 3 The allowable deviation of chemical composition of finished steel shall comply with the provisions of GB / T222; Macrostructure: There shall be no visible shrinkage, bubbles, cracks, inclusions, peeling and white spots on the acid-etched macrostructure test piece of the cross section of the steel. It shall be evaluated according to the third level diagram of GB / T1299. The qualified level requirements are center porosity ≤3.0 and ingot segregation ≤3.0; Non-metallic inclusions: Non-metallic inclusions shall be tested according to method A of GB / T10561 standard, and the qualified level shall not exceed Figure 3 Grade regulations; Microstructure: Pearlite structure of steel shall be evaluated according to GB / T1299 Grade 2 diagram, and the results shall be reported as actual measurement, which shall not be used as the basis for judgment; Ultrasonic flaw detection: Steel shall be ultrasonically tested one by one according to SEP1921, and metallurgical defects such as cracks, white spots, shrinkage holes, etc. are not allowed to exist inside. The qualified level shall meet Figure 4 Regulations; Surface quality: The steel surface shall not have visible cracks, scars, slag inclusions and other defects that affect the use. Surface defects can be ground, the depth does not exceed half of the dimensional tolerance, the width is greater than 5 times the grinding depth, and the transition is uniform; Test method: The test method of the inspection item, the sampling location should meet Figure 6 The re-inspection and determination rules of steel shall be in accordance with the relevant provisions of GB / T17505. If the supplier can ensure that the finished steel is qualified, for the steel or billet of the same furnace number, low-multiple structure and non-metallic inclusions can be replaced by billet, and large can be replaced by small.

[0050] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing cold working die steel, characterized in that: The following steps are involved: S1. Prepare raw materials, select carbon, silicon, manganese, phosphorus, sulfur, chromium, molybdenum, vanadium and niobium, determine the precise ratio of each element according to the performance requirements of the mold steel, pre-treat the selected alloy elements, including crushing, screening and washing to ensure the purity and uniformity of the raw materials, and mix the alloy elements uniformly according to the predetermined ratio to form a mixture; S2. Smelting: Place the mixed material in the medium frequency furnace and perform smelting operations according to the job regulations; S2.

1. For molten steel refining furnace, perform refining operation according to the job regulations, and keep the white slag for ≥30 minutes, and strive to keep the main chemical composition of the steel produced by the molten steel refining furnace within the internal control range; S2.

2. Vacuum degassing: perform vacuum operation according to the job regulations, vacuum degree ≤ 67 bar, holding time ≥ 10 minutes, tank outlet temperature T = 1560-1580℃; S3. Ingot casting, casting temperature T = 1540-1560 ° C, mold temperature control 20-80 ° C, use electrode rod demoulding after sand cooling, hood cooling or red annealing; S4. Electroslag: Operate according to the job regulations, use CaF2:Al2O3=70:30 binary slag system, and cool the electroslag ingot after demoulding. Annealing or hot forging is arranged within 2 days after cooling. It is not allowed to leave the hood before annealing. S5. Forging process, firstly, heat treatment is performed by preheating the above-mentioned ingot into a furnace, the temperature is ≤500°C, the forging heating temperature is 1170-1190°C, the start forging temperature is 1120-1150°C, and the final forging temperature is ≥900°C; S5.

1. Forging shall be carried out in accordance with the current operating procedures, with a forging ratio of ≥4.

5. The hammer shall be light at the beginning of forging, and then gradually increased to prevent cracks; S5.

2. Cooling: After forging, the billet is air-cooled to 500-550℃ and then put into the pit for sand cooling or red annealing; S5.

3. Annealing: There are microstructure and hardness requirements. Isothermal annealing process is performed. The annealing process is as follows: The steel ingots and steel products are annealed according to the above process. The heating temperature and holding time are adjusted within the prescribed allowable range according to the steel product size and furnace load. S6. Finishing process: according to enterprise standards and machining operation procedures, the steel is finished to meet the corresponding appearance, shape and size requirements; S7. Inspection: According to the enterprise's requirements, steel is sampled, inspected and judged, and can be put into storage after meeting the standard quality requirements.

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