Steel H12 module for die and manufacturing method of steel H12 module

Abstract

The invention relates to a steel H12 module for a die and a manufacturing method of the steel H12 module, the steel H12 module is obtained on the basis of an H12 material in the mode that low Cr, low Si and high Mo are adopted and Ni and Co alloys are added, the material comprises the following chemical components in percentage by mass: 0.30-0.34% of C, less than or equal to 0.20% of Si, less than or equal to 0.20% of Mn, less than or equal to 0.012% of P, less than or equal to 0.003% of S, less than or equal to 0.30% of Cr, 3.05-3.15% of Mo, 1.10-1.30% of W, 2.00-2.30% of Ni, 0.70-0.90% of Co, 0.010-0.025% of Al and the balance of Fe, and the method mainly comprises the following steps that H12 molten the molten steel is poured into an ingot in a die casting mode, demolding is carried out, heating, forging forming and annealing are carried out after cleaning and hot delivery are carried out, finally, quality inspection is carried out on an annealed forge piece, a process route of upsetting, drawing-forging to a finished product through an oil press is adopted in forging, the center porosity can reach 1.5 levels or below, and the general porosity is smaller than or equal to 2.0 levels; ingot segregation and dot segregation are avoided; and the sum of non-metallic inclusions can be less than or equal to 3.0 grade.

Description

Technical Field

[0001] The present invention relates to the technical field of die steel manufacturing, and in particular to a design method of using low Cr, low Si, high Mo and adding Ni and Co alloys on the basis of H12 material to obtain a die steel H12 module that meets the requirements and a manufacturing method thereof. Background Art

[0002] H12 die steel is widely used in industrial manufacturing fields such as automobile, aerospace, forging, etc. due to its good thermal stability, wear resistance, thermal fatigue and excellent comprehensive mechanical properties. With the advancement of current industrial technology, various industrial manufacturing fields have put forward high requirements for H12 extrusion dies, die-casting dies, and forging dies, such as high quality, long service life, and performance that can meet harsh service environments. The quality of the die depends on the quality of the die material.

[0003] Therefore, in order to meet the increasing demand for molds in various industrial manufacturing fields, it is urgent to make corresponding adjustments to the chemical composition of mold materials to ensure that they can adapt to a variety of harsh service environments and meet the requirements of long service life. For example, CN118773514A discloses a high-temperature resistant mold steel material and a preparation method thereof, which improves the formula of Cr5MoSiV, adopts a design method of low Si, low Cr, high Mo, high W, and introduces Cu and Ti to obtain a new high-temperature resistant mold material; CN118064800A discloses an H13 mold steel improved by adding boron and a preparation method thereof, which adds a small amount of boron element to the composition of H13 steel to make it have higher strength and hardness than traditional H13 mold steel, while the toughness is not reduced, and can be used for new extrusion molds and die-casting molds.

[0004] Traditional high-quality mold steel manufacturing methods all use electroslag remelting. In order to meet the market demand for low-cost mold steel, it is urgent to optimize the manufacturing process to ensure that the various indicators of mold steel produced by low-cost manufacturing methods can also meet the requirements. At present, there are few high-quality mold steel materials in China, and in order to meet market demand, it is necessary to adjust the composition of existing steel grades to develop mold steel materials with better performance and optimize the manufacturing process. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an H12 mold steel module from smelting to forging and a manufacturing method thereof. The H12 module manufactured by this method can achieve [P]≤0.010%, [S]≤0.002%, central porosity≤1.5, general porosity≤2.0, no ingot-type segregation and point segregation, the total amount of non-metallic inclusions≤3.0, and a grain size of 10-7.5.

[0006] The present invention is achieved through the following technical solutions:

[0007] A mold steel H12 module comprises the following chemical components in mass percentage: C: 0.30-0.34%, Si≤0.20%, Mn≤0.20%, P≤0.012%, S≤0.003%, Cr≤0.30%, Mo: 3.05-3.15%, W: 1.10-1.30%, Ni: 2.00-2.30%, Co: 0.70-0.90%, Al: 0.010-0.025%, and the balance is Fe; scrap steel, pig iron, tungsten iron, nickel plate, molybdenum iron, cobalt alloy, and aluminum block are used as raw materials, and an H12 steel ingot is obtained through electric furnace, LF refining, VD refining, and die casting; the steel ingot is formed after forging, and then annealed, and finally the annealed forging is inspected to obtain a finished product with quality meeting the requirements.

[0008] A manufacturing method of the H12 module of mold steel is realized by short-process smelting and hydraulic press forging. The specific technical route is as follows: electric furnace smelting (EAF / IF) + refining (LF) + vacuum refining (VD) → die casting (IC) → demoulding cleaning, hot delivery → heating + forging → annealing after forging → inspection. The steps of implementing the technical route are as follows:

[0009] Step 1), electric furnace smelting: the raw materials are scrap steel, tungsten iron, nickel plate, molybdenum iron, cobalt alloy, aluminum block, and 20-30% pig iron is added according to the mass percentage; in the electric furnace smelting process, the harmful elements [As], [Sn], [Pb], [Sb], [Bi] are all controlled to be ≤0.015%, the electric furnace is smelted according to the end point [C] ≥0.05%, [P] ≤0.006%, the steel tapping temperature is ≥1640°C, and the steel retention operation is adopted, and the steel retention amount is ≥5t;

[0010] Step 2), LF refining: After the refining bag is in place, connect argon gas, add calcium carbide 1-2.0kg / t, carbon powder deoxidizer 2.0-4.0kg / t to deliver electrochemical slag, and use carbon powder, aluminum powder, ferrosilicon powder 1.0-2.0kg / t for deoxidation in small quantities to maintain a reducing atmosphere during refining. The white slag time is ≥20min, and the chemical composition is controlled according to the following mass percentages: C: 0.30-0.34%, Si≤0.20%, Mn≤0.20%, P≤0.012%, S≤0.003%, Cr≤0.30%, Mo: 3.05-3.15%, W: 1.10-1.30%, Ni: 2.00-2.30%, Co: 0.70-0.90%, Al: 0.010-0.025%, and the balance is Fe;

[0011] Step 3), vacuum refining: at a bag temperature of 1635-1655°C, the bag enters the vacuum tank from the LF furnace for degassing, and is maintained at ≤0.7mbar for ≥20min. After breaking the air, H and O are determined online, and the glass tube is sampled and analyzed for [N] content, and [H] is controlled to be ≤1.3ppm, [O] ≤5.0ppm, and [N] ≤70ppm. The residual aluminum is controlled to be 0.010-0.025%, and the silicon-calcium wire is fed at 0.2-0.4m / t according to the silicon content, and the weak stirring time is ≥15min;

[0012] Step 4), mold casting, demoulding and cleaning: bake the steel ingot mold in advance during mold casting to ensure that the use temperature is ≥30℃, ensure that the pouring system is clean and dry, use argon filling and argon protection pouring in the mold throughout the whole process, the pouring temperature is 1525-1535℃, the calming time is ≥8min, the pouring time of the ingot body riser is in the upper and lower limits, strengthen the control of riser shrinkage, and control the pouring excess to be not less than 1.0t. After the steel ingot is demoulded, clean the burrs and flash at both ends, and then hot delivery, demoulding and hoisting and loading must close the surrounding doors and windows;

[0013] Step 5), hot delivery and heating forging: Check the surface quality of the steel ingot during forging, load the steel ingot into the heating furnace for heating, heat the hot delivery ingot to 1200-1300℃ and keep it warm for 25-35h, the initial forging temperature of the module is 1220-1000℃, and the final forging temperature is ≥800℃.

[0014] Step 6), forging with a 3150t hydraulic press: first use an upsetting plate for upsetting, the upsetting ratio is controlled between 2.0 and 2.3, then use an upper upsetting plate and a lower platform for two passes of drawing, and finally use upper and lower flat anvils for drawing and forging to a finished product;

[0015] Step 7) After forging, annealing is performed. The formed forging is placed in an annealing furnace for annealing. The annealing temperature is 600-700°C.

[0016] After step 7), an inspection is also carried out: including inspection of the surface quality, size, curvature, low magnification, non-metallic inclusions, annealing structure, carbide band segregation and grain size of the forging.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The H12 module produced by the present invention can reach a central porosity of less than 1.5 in low-power detection, a general porosity of ≤2.0, no ingot-type segregation and point segregation; the sum of non-metallic inclusions can reach ≤3.0; the austenite grain size is 7.5-10, and the annealing structure and carbide band segregation can meet the qualified level of the North American Die Casting Association NADCA#207-2006 standard. The present invention has been verified and trial-produced many times and can be mass-produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the technical route of the present invention. Specific implementation methods

[0021] The technical route of the present invention is further described below in conjunction with the accompanying drawings.

[0022] Embodiment: The present invention provides an H12 module with a specification of 135-295×630mm and a length of up to 2700-5000mm and a manufacturing method thereof. An electric furnace, LF refining, and VD refining are used to obtain molten steel that meets the quality requirements. The molten steel is lifted by an overhead crane to a steel casting car for casting. The steel ingots are cleaned after demolding, and then hot-sent to a forging workshop for forging. The forging workshop first uses a heating furnace to heat the hot-sent steel ingots, and then forges them through a hydraulic press. Finally, the forgings are annealed after forging. Finally, the annealed finished products are tested. The present invention focuses on the control of steelmaking raw and auxiliary materials, refining bottom blowing argon flow, VD refining vacuum, vacuum time, molten steel temperature and composition, pouring speed, riser shrinkage compensation, forging tooling preheating, initial forging temperature, deformation, and final forging temperature during the production process, so that the quality of the finished product meets the technical requirements. The specific technical scheme is as follows:

[0023] Step 1), Electric furnace steelmaking process:

[0024] In view of the finished product chemical composition requirements of H12 module, taking into account factors such as finished product performance and cost, the internal control composition of H12 steel is set, and the mass percentage is as follows: C: 0.30-0.34%, Si≤0.20%, Mn≤0.20%, P≤0.012%, S≤0.003%, Cr≤0.30%, Mo: 3.05-3.15%, W: 1.10-1.30%, Ni: 2.00-2.30%, Co: 0.70-0.90%, Al: 0.010-0.025%, and the balance is Fe.

[0025] When this type of steel is smelted in an electric furnace, the raw materials should be clean and dry, and [As], [Sn], [Pb], [Sb], and [Bi] should be controlled to be ≤0.015%, non-toxic and harmless (such as mercury, radiation), the electric furnace endpoint [C] ≥0.05%, [P] ≤0.006%, to prevent overoxidation of molten steel, the tapping temperature ≥1640℃, the steel retention operation is adopted, and the steel retention amount is ≥5t to prevent slag during tapping. During the tapping process, 2.0-4.0kg / t of aluminum blocks and 4-6kg / t of lime are added for early deoxidation and slag making.

[0026] Step 2), LF refining process: after steel is tapped, LF refining is started. After the refining bag is in place, argon is connected, 1-2.0 kg / t of calcium carbide and 2.0-4.0 kg / t of carbon powder deoxidizer are added to deliver electrochemical slag, and desulfurization and alloying are carried out according to the internal control composition. During refining, 1.0-2.0 kg / t of carbon powder, aluminum powder and ferrosilicon powder are used for deoxidation in small amounts for many times to maintain a reducing atmosphere, and the white slag time is ≥20 min;

[0027] Step 3), vacuum refining process: at a temperature of 1635-1655°C, the bag is hung from the LF furnace and enters the vacuum tank for degassing, and is kept at ≤0.7mbar for ≥20min. After breaking the air, H and O are determined online, and the glass tube is sampled and analyzed for [N] content, and [H] is controlled to be ≤1.3ppm, [O] ≤5.0ppm, and [N] ≤70ppm. The residual aluminum is controlled to be 0.010-0.025%, and the silicon-calcium wire is fed at 0.2-0.4m / t according to the silicon content. The weak stirring time is ≥15min, and the bag temperature is 1535-1545°C;

[0028] Step 4), mold casting, demoulding and cleaning: After the gas and temperature are suitable, the steel is poured. Carefully select the steel ingot mold with good inner wall quality, and grind and clean it. The steel ingot mold is baked in advance during mold casting to ensure that the use temperature is ≥30℃, and the pouring system is clean and dry. The whole process adopts argon filling and argon protection pouring in the mold. The pouring temperature is 1525-1535℃, the calming time is ≥8min, and the pouring time of the ingot body riser is in the middle and upper limits. Strengthen the control of riser shrinkage, and control the pouring surplus to be not less than 1.0t. After the pouring is completed, add the heating agent, and the addition amount is controlled at 1.0-3.0kg / t. After adding the heating agent, add carbonized rice husk in time. After the steel ingot is demoulded, clean the burrs and flash at both ends, and then hot delivery, demoulding and hoisting and loading must close the surrounding doors and windows;

[0029] Step 5), hot delivery and heating forging: check the surface quality of the steel ingot during forging, load the steel ingot into the heating furnace for heating, load the hot delivery ingot into the heating furnace for heating, keep it warm for 28 hours after the temperature reaches 1250℃, ensure that the temperature of the steel ingot is uniform, there is no positive and negative surface, the initial forging temperature is 1220~1000℃, and the final forging temperature is ≥800℃; the specifications of 135~215×630mm are forged by a 3150t hydraulic press in one fire, first upsetting to H=750(~Φ1100)mm, using the upper upsetting plate and the lower platform for drawing in 2 passes, the first pass is pressed to 700mm, and then pressed to 900mm after turning, and then drawn and forged to the finished product on the upper and lower flat anvils, and the total forging ratio is 8.1~9.1;

[0030] Step 6), the module with specifications of 235~295×630mm is forged by a 3150t hydraulic press in two fires, and the module is upset to H=750 (~Φ1100) mm in one fire, and then drawn by the upper upsetting plate and the lower platform for two passes, and then drawn to 700mm on the upper and lower flat anvils, slightly inverted, and pressed down 50-100mm on one side. After secondary heating (keeping warm for 3 hours), it is upset to H=750mm and drawn to the finished product, and the total forging ratio is 7.8~6.6; after forging, the forging is loaded into the annealing furnace for annealing, and the annealing temperature is 650℃.

[0031] Step 7) Inspection:

[0032] The macrostructure inspection of the H12 module produced by the present invention is carried out according to the provisions of GB / T226, and is evaluated according to the third level diagram of GB / T1299. The general porosity is evaluated according to GB / T1979, the central porosity can reach below level 1.5, the general porosity is ≤ level 2.0, and there is no ingot type segregation and point segregation; the non-metallic inclusions are evaluated according to the ISO rating diagram of GB / T10561-2005 standard, and the total can reach ≤ level 3.0; the austenite grain size is inspected according to ASTM E112, and can reach level 7.5-10; the annealed structure and carbide band segregation can meet the qualified level of the North American Die Casting Association NADCA#207-2006 standard.

[0033] Appendix: Chemical composition of H12 steel is shown in Table 1

[0034] Table 1 Chemical composition (%)

[0035]

[0036]

[0037] Appendix: H12 steel gas is shown in Table 2 Table 2 Gas (ppm)

[0038] element Target This embodiment [H] ≤1.3 0.8 [O] ≤5 3.5 [N] ≤70 40

[0039] Appendix: H12 steel inclusions are shown in Table 3 Table 3 Inclusions (grade)

[0040]

[0041]

[0042] Appendix: Low magnification and grain size of H12 steel are shown in Table 4 Table 4 Low magnification and grain size (grade)

[0043]

Claims

1. A mold steel H12 module, characterized in that: The mold steel H12 module includes the following chemical components in mass percentage: C: 0.30-0.34%, Si≤0.20%, Mn≤0.20%, P≤0.012%, S≤0.003%, Cr≤0.30%, Mo: 3.05-3.15%, W: 1.10-1.30%, Ni: 2.00-2.30%, Co: 0.70-0.90%, Al: 0.010-0.025%, and the balance is Fe; scrap steel, pig iron, tungsten iron, nickel plate, molybdenum iron, cobalt alloy, and aluminum block are used as raw materials to obtain H12 steel ingots through electric furnace, LF refining, VD refining, and die casting; the steel ingots are formed after forging, and then annealed, and finally the annealed forgings are inspected to obtain finished products that meet quality requirements.

2. A method for manufacturing a mold steel H12 module as claimed in claim 1, characterized in that: It is realized by short-process smelting and hydraulic press forging. The specific technical route is as follows: electric furnace smelting (EAF / IF) + refining (LF) + vacuum refining (VD) → die casting (IC) → demoulding cleaning, hot delivery → heating + forging → annealing after forging → inspection. The steps of the technical route are as follows: Step 1), electric furnace smelting: the raw materials are scrap steel, tungsten iron, nickel plate, molybdenum iron, cobalt alloy, aluminum block, and 20-30% pig iron is added according to the mass percentage; in the electric furnace smelting process, the harmful elements [As], [Sn], [Pb], [Sb], [Bi] are all controlled to be ≤0.015%, the electric furnace is smelted according to the end point [C] ≥ 0.05%, [P] ≤ 0.006%, the steel tapping temperature is ≥ 1640℃, and the steel retention operation is adopted, and the steel retention amount is ≥ 5t; Step 2), LF refining: After the refining bag is in place, connect argon gas, add 1-2.0kg / t of calcium carbide and 2.0-4.0kg / t of carbon powder deoxidizer to deliver electrochemical slag, and use 1.0-2.0kg / t of carbon powder, aluminum powder, and ferrosilicon powder for deoxidation several times during refining to maintain a reducing atmosphere. The white slag time is ≥20min, and the chemical composition is controlled according to the mass percentage as follows: C: 0.30-0.34%, Si≤0.20%, Mn≤0.20%, P≤0.012%, S≤0.003%, Cr≤0.30%, Mo: 3.05-3.15%, W: 1.10-1.30%, Ni: 2.00-2.30%, Co: 0.70-0.90%, Al: 0.010-0.025%, and the balance is Fe; Step 3), vacuum refining: at a bag temperature of 1635-1655℃, the bag is placed in a vacuum tank from the LF furnace for degassing, and maintained at ≤0.7mbar for ≥20min. After breaking the air, H and O are determined online, and the glass tube is sampled and analyzed for [N] content, and [H] is controlled to be ≤1.3ppm, [O] ≤5.0ppm, and [N] ≤70ppm. The residual aluminum is controlled to be 0.010-0.025%, and the silicon-calcium wire is fed at 0.2-0.4m / t according to the silicon content, and the weak stirring time is ≥15min; Step 4), mold casting, demoulding and cleaning: bake the steel ingot mold in advance during mold casting to ensure that the use temperature is ≥30℃, ensure that the pouring system is clean and dry, use argon filling and argon protection pouring in the mold throughout the process, the pouring temperature is 1525-1535℃, the calming time is ≥8min, the pouring time of the ingot body riser is in the middle and upper limits, strengthen the control of riser shrinkage, and control the pouring excess to be not less than 1.0t. After the steel ingot is demoulded, clean the burrs and flash at both ends, and then hot delivery, demoulding and hoisting and loading must close the surrounding doors and windows; Step 5), hot delivery and heating forging: Check the surface quality of the steel ingot during forging, load the steel ingot into the heating furnace for heating, heat the hot delivery ingot to 1200-1300℃ and keep it warm for 25-35h, the initial forging temperature of the module is 1000℃-1220℃, and the final forging temperature is ≥800℃; Step 6), forging with a 3150t hydraulic press: first use an upsetting plate for upsetting, the upsetting ratio is controlled between 2.0 and 2.3, then use an upper upsetting plate and a lower platform for two passes of drawing, and finally use upper and lower flat anvils for drawing and forging to the finished product; Step 7), after forging, annealing treatment is performed, and the formed forging is placed in an annealing furnace for annealing, and the annealing temperature is 600-700°C.

3. The method for manufacturing a mold steel H12 module according to claim 1, characterized in that: After step 7), inspection is also carried out: including inspection of the surface quality, size, curvature, low magnification, non-metallic inclusions, annealing structure, carbide band segregation and grain size of the forging.

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