1. The hot work die steel with high heat strength and high toughness is characterized by being prepared from the following raw materials in percentage by mass: 0.20-0.40% of carbon, 0.05-0.20% of silicon, 0.30-0.60% of manganese, 1.00-4.00% of chromium, 0.50-1.50% of molybdenum, 0.20-0.60% of vanadium, 0.60-1.00% of cobalt, 0.06-0.16% of titanium, 0.03-0.08% of yttrium, 0.03-0.08% of niobium, 0.005-0.012% of phosphorus, 0.003-0.008% of sulfur and the balance of iron.

2. The hot work die steel with high heat strength and high toughness as claimed in claim 1, wherein: the alloy comprises 0.30-0.40% of carbon, 0.05-0.10% of silicon, 0.20-0.30% of manganese, 2.00-3.00% of chromium, 0.80-1.20% of molybdenum, 0.30-0.50% of vanadium, 0.70-0.90% of cobalt, 0.08-0.12% of titanium, 0.04-0.06% of yttrium and 0.04-0.06% of niobium.

3. A high-heat-strength, high-toughness hot work die steel according to claim 2, characterized in that: the carbon content is 0.35%, the silicon content is 0.08%, the manganese content is 0.25%, the chromium content is 2.50%, the molybdenum content is 1.00%, the vanadium content is 0.40%, and the cobalt content is 0.80%.

4. The hot work die steel with high heat strength and high toughness as claimed in claim 3, wherein: the ratio of the titanium content to the vanadium content is 1: 4.

5. The hot work die steel with high heat strength and high toughness as claimed in claim 3, wherein: the ratio of the yttrium content to the niobium content is 1: 1.

6. A process for manufacturing a hot work die steel with high heat strength and high toughness according to any one of claims 1 to 5, comprising the steps of:

smelting materials: putting the raw materials into a furnace body for smelting and refining, then carrying out vacuum degassing, and then pouring into steel ingots;

and (3) diffusion annealing: preserving the heat of the steel ingot at the high temperature of 1100-1200 ℃ for 9-15 h;

forging: carrying out multidirectional forging processing on the steel ingot subjected to diffusion annealing to obtain a forged blank;

heat treatment after forging: carrying out fog cooling on the forging stock, then carrying out air cooling, then carrying out heat preservation on the forging stock subjected to air cooling at 950-1150 ℃ for 8-10h, and then carrying out air cooling to obtain a heat treatment forging stock;

and (3) dehydrogenation annealing: preserving the heat of the heat-treated forging stock for 25-30 h at 600-700 ℃, and cooling to obtain a dehydrogenation annealing forging stock;

tempering heat treatment: and (3) preserving the heat of the dehydrogenation annealing forging stock for 15-20 h at the temperature of 550-600 ℃, cooling the forging stock to the temperature of 200 ℃, and then performing air cooling to obtain the hot work die steel.

7. The process for manufacturing a hot work die steel with high heat strength and high toughness as claimed in claim 6, wherein: the heating rate in the steps of the heat treatment after forging, the dehydrogenation annealing and the tempering heat treatment is 8-13 ℃/min.

8. The process for manufacturing a hot work die steel with high heat strength and high toughness as claimed in claim 6, wherein: the cooling rate in the steps of the heat treatment after forging, the dehydrogenation annealing and the tempering heat treatment is 15-20 ℃/min.

Background

The hot-working die steel is alloy tool steel for dies suitable for hot deformation processing of metals, and generally, the hot-working dies need to bear large impact force and pressure during working, the dies can also be in direct contact with high-temperature objects, repeated heating and cooling are also needed, and the using conditions are extremely severe, so that the hot-working die steel is required to have better comprehensive performance.

The common hot work die steel in the related art is mainly 4Cr5MoSiV1(H13) steel, and is widely applied in the market due to good processability and toughness.

With respect to the related art among the above, the inventors consider that the following drawbacks exist: when the service temperature of the 4Cr5MoSiV1(H13) steel exceeds 550 ℃, carbide in steel aggregates greatly, so that a steel matrix is softened, the thermal stability of the material is reduced, the high-temperature strength and hardness of the material are reduced, and cracking failure is easy to occur.

Disclosure of Invention

In order to solve the problems that when the service temperature of steel exceeds 550 ℃, the high-temperature strength and hardness of the material are reduced, and cracking failure is easy to occur, the application provides the hot work die steel with high heat strength and high toughness and the manufacturing process thereof.

The application provides a high-heat-strength high-toughness hot-work die steel and a manufacturing process thereof, which adopt the following technical scheme: in a first aspect, the present application provides a hot work die steel with high heat strength and high toughness, which adopts the following technical scheme:

the hot work die steel with high heat strength and high toughness comprises the following raw materials in percentage by mass: 0.20-0.40% of carbon, 0.05-0.20% of silicon, 0.30-0.60% of manganese, 1.00-4.00% of chromium, 0.50-1.50% of molybdenum, 0.20-0.60% of vanadium, 0.60-1.00% of cobalt, 0.06-0.16% of titanium, 0.03-0.08% of yttrium, 0.03-0.08% of niobium, 0.005-0.012% of phosphorus, 0.003-0.008% of sulfur and the balance of iron.

By adopting the technical scheme, the cobalt is dissolved in the matrix material, so that the structural stability of the steel in high-temperature operation can be improved, and the mechanical property of the material at high temperature can be maintained; the titanium, the yttrium and the niobium can further improve the thermal stability of the material in a high-temperature environment; the MC-type carbides can be formed in the preparation process of the material by cobalt, titanium, yttrium, niobium and the like, and the carbides formed by the carbides and manganese, chromium, molybdenum and vanadium are mutually soluble to form a multi-element complex precipitated phase which has a coherent interface relation with a matrix, so that the high-temperature performance stability can be improved, the multi-element complex precipitated phase can play a role in strengthening the material in the tempering process, the secondary hardening phenomenon in the tempering process can be greatly improved, and the comprehensive performance of steel can be obviously improved; simultaneously, this application has still carried out more reasonable regulation to the content of each composition in the steel, makes the carbide that forms in the steel more reasonable distribute in the steel, promotes comprehensive properties such as hot strength nature and toughness of material.

Preferably, the carbon content is 0.30-0.40%, the silicon content is 0.05-0.10%, the manganese content is 0.20-0.30%, the chromium content is 2.00-3.00%, the molybdenum content is 0.80-1.20%, the vanadium content is 0.30-0.50%, the cobalt content is 0.70-0.90%, the titanium content is 0.08-0.12%, the yttrium content is 0.04-0.06%, and the niobium content is 0.04-0.06%.

By adopting the technical scheme, the content of each component in the steel is further optimized, and the comprehensive properties of the steel, such as heat strength, toughness and the like, can be further improved.

Preferably, the carbon content is 0.35%, the silicon content is 0.08%, the manganese content is 0.25%, the chromium content is 2.50%, the molybdenum content is 1.00%, the vanadium content is 0.40%, and the cobalt content is 0.80%.

By adopting the technical scheme, the content of each component in the steel is further optimized, and the comprehensive properties of the steel, such as heat resistance, toughness and the like, are further enhanced.

Preferably, the ratio of the titanium content to the vanadium content is 1: 4.

By adopting the technical scheme, when the titanium content and the vanadium content in the steel are 1:4, the titanium and the vanadium have similar atomic radii and are easy to dissolve mutually to form a multi-element complex precipitated phase, and the thermal stability of the material can be further improved in the tempering process of the material.

Preferably, the ratio of the yttrium content to the niobium content is 1: 1.

By adopting the technical scheme, when the ratio of the content of yttrium to the content of niobium in the steel is 1:1, carbides formed by yttrium and niobium can be better dissolved mutually, and further the thermal stability of the material in the tempering process can be further improved.

In a second aspect, the present application provides a manufacturing process of a hot work die steel with high heat strength and high toughness, which adopts the following technical scheme:

a manufacturing process of hot work die steel with high heat strength and high toughness comprises the following steps:

smelting materials: putting the raw materials into a furnace body for smelting and refining, then carrying out vacuum degassing, and then pouring into steel ingots;

and (3) diffusion annealing: preserving the heat of the steel ingot at the high temperature of 1100-1200 ℃ for 9-15 h;

forging: carrying out multidirectional forging processing on the steel ingot subjected to diffusion annealing to obtain a forged blank;

heat treatment after forging: carrying out fog cooling on the forging stock, then carrying out air cooling, then carrying out heat preservation on the forging stock subjected to air cooling at 950-1150 ℃ for 8-10h, and then carrying out air cooling to obtain a heat treatment forging stock;

and (3) dehydrogenation annealing: preserving the heat of the heat-treated forging stock for 25-30 h at 600-700 ℃, and cooling to obtain a dehydrogenation annealing forging stock;

tempering heat treatment: and (3) preserving the heat of the dehydrogenation annealing forging stock for 15-20 h at the temperature of 550-600 ℃, cooling the forging stock to the temperature of 200 ℃, and then performing air cooling to obtain the hot work die steel.

By adopting the technical scheme, the raw materials can be well dissolved into the matrix through high-temperature solid solution, carbides can be precipitated during tempering treatment, and the precipitated carbides can improve the thermal stability of steel; meanwhile, the structure of the steel can be improved and the comprehensive properties of the steel, such as heat strength, toughness and the like, can be improved by adjusting the temperature and the heat preservation time in the steps of heat treatment after forging, dehydrogenation annealing and tempering heat treatment.

Preferably, the heating rate in the steps of the heat treatment after forging, the dehydrogenation annealing and the tempering heat treatment is 8-13 ℃/min.

By adopting the technical scheme, the heating rate in the steps of heat treatment after forging, dehydrogenation annealing and tempering heat treatment is adjusted, so that atoms such as cobalt, titanium, yttrium, niobium and the like in the steel can be better fused into a steel billet, the steel can be further strengthened, and the comprehensive properties such as heat strength, toughness and the like of the steel are improved.

Preferably, the cooling rate in the steps of the heat treatment after forging, the dehydrogenation annealing and the tempering heat treatment is 15-20 ℃/min.

Through adopting above-mentioned technical scheme, can stabilize the organizational structure of steel, can also make the carbide stably precipitate simultaneously to further promote the heat-intensity and the toughness of steel.

In summary, the present application has the following beneficial effects:

1. the cobalt is melted in the base material, so that the structural stability of the steel in high-temperature operation can be improved, and the mechanical property of the material at high temperature can be maintained; the titanium, the yttrium and the niobium can further improve the thermal stability of the material in a high-temperature environment; the MC-type carbides can be formed in the preparation process of the material by cobalt, titanium, yttrium, niobium and the like, and the carbides formed by the carbides and manganese, chromium, molybdenum and vanadium are mutually soluble to form a multi-element complex precipitated phase which has a coherent interface relation with a matrix, so that the high-temperature performance stability can be improved, the multi-element complex precipitated phase can play a role in strengthening the material in the tempering process, the secondary hardening phenomenon in the tempering process can be greatly improved, and the comprehensive performance of steel can be obviously improved; meanwhile, the content of each component in the steel is more reasonably adjusted, so that carbide formed in the steel is more reasonably distributed in the steel, and the comprehensive properties of the material, such as heat resistance, toughness and the like, are improved;

2. when the titanium content and the vanadium content in the steel are 1:4, the titanium and the vanadium have similar atomic radii and are easy to dissolve to form a multi-element complex precipitated phase, and the thermal stability of the material can be further improved in the tempering process of the material;

3. according to the method, the raw materials can be well dissolved into the matrix through high-temperature solid solution, carbides can be precipitated during tempering treatment, and the precipitated carbides can improve the thermal stability of steel; meanwhile, the structure of the steel can be improved and the comprehensive properties of the steel, such as heat strength, toughness and the like, can be improved by adjusting the temperature and the heat preservation time in the steps of heat treatment after forging, dehydrogenation annealing and tempering heat treatment.

Detailed Description

With the rapid development of the industry, the usage amount of the die steel is more and more, and the hot die steel as one of the steel materials is often applied to the working environment of high temperature and high pressure, so that the hot die steel is required to have high heat strength and high toughness so as to achieve the use of normal industry, and the service life of the die is prolonged, wherein the most commonly used hot die steel is 4Cr5MoSiV1(H13) steel, but the performance of the 4Cr5MoSiV1(H13) steel is poor in many severe high temperature and high pressure production environments; the inventor finds that the heat strength and the toughness of the steel can be well improved by adding cobalt, titanium, yttrium and niobium and adjusting the content of each component in the steel.

Examples

Examples 1 to 6

The following description will be given by taking example 1 as an example, and the manufacturing process of the hot work die steel with high heat strength and high toughness comprises the following steps:

smelting materials: putting the raw materials into a furnace body for smelting and refining at 1600 ℃, then carrying out vacuum degassing, and then pouring into steel ingots;

and (3) diffusion annealing: keeping the temperature of the steel ingot at the high temperature of 1100 ℃ for 9 hours;

forging: carrying out multidirectional forging processing on the steel ingot subjected to diffusion annealing to obtain a forged blank;

heat treatment after forging: carrying out fog cooling on the forging stock, then carrying out air cooling until the temperature is reduced to be below 200 ℃, then carrying out heat preservation on the forging stock subjected to air cooling at 950 ℃ for 8 hours, and then carrying out air cooling until the temperature is reduced to be below 200 ℃ to obtain a heat-treated forging stock;

and (3) dehydrogenation annealing: and (3) preserving the heat treatment forging stock for 25h at the temperature of 600 ℃, and cooling to the temperature of below 250 ℃ to obtain the dehydrogenation annealing forging stock.

Tempering heat treatment: and (3) preserving the heat of the dehydrogenation annealing forging stock for 15h at 550 ℃, cooling the forging stock to 200 ℃, and then performing air cooling to obtain the hot work die steel.

The heating rate in the steps of heat treatment after forging, dehydrogenation annealing and tempering heat treatment is 8 ℃/min, and the cooling rate is 15 ℃/min.

As shown in Table 1, the hot-work die steels of examples 1 to 6 having high heat resistance and high toughness are mainly different in the content by mass of each component in the steel materials.

TABLE 1

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6
							Carbon (C)	0.20	0.30	0.40	0.30	0.40	0.035
Silicon	0.05	0.12	0.20	0.05	0.10	0.08
							Manganese oxide	0.30	0.04	0.60	0.20	0.30	0.25
Chromium (III)	1.00	2.00	4.00	2.00	3.00	2.50
							Molybdenum (Mo)	0.50	1.00	1.50	0.80	1.20	1.00
Vanadium oxide	0.20	0.40	0.60	0.30	0.50	0.40
							Cobalt	0.60	0.80	1.00	0.70	0.90	0.80
Titanium (IV)	0.06	0.12	0.16	0.08	0.12	0.12
							Yttrium salt	0.03	0.05	0.08	0.04	0.06	0.06
Niobium (Nb)	0.03	0.06	0.08	0.04	0.06	0.06
							Phosphorus (P)	0.005	0.01	0.012	0.005	0.005	0.005
Sulfur	0.003	0.004	0.008	0.003	0.003	0.003
							Iron	97.022	95.096	91.36	95.482	93.352	94.687
Total up to	100	100	100	100	100	100

Examples 7 to 10

As shown in Table 2, examples 7 to 9 are different from example 6 mainly in the weight ratio of titanium to vanadium in the steel material, and example 10 is different from example 6 mainly in the weight ratio of yttrium to niobium in the steel material. The manufacturing process of the hot work die steel of high heat resistance and high toughness of examples 7 to 10 was the same as that of example 1.

TABLE 2

	Example 7	Example 8	Example 9	Example 10
					Carbon (C)	0.035	0.035	0.035	0.035
Silicon	0.08	0.08	0.08	0.08
					Manganese oxide	0.25	0.25	0.25	0.25
Chromium (III)	2.50	2.50	2.50	2.50
					Molybdenum (Mo)	1.00	1.00	1.00	1.00
Vanadium oxide	0.40	0.30	0.50	0.40
					Cobalt	0.80	0.80	0.80	0.80
Titanium (IV)	0.10	0.10	0.10	0.10
					Yttrium salt	0.06	0.06	0.06	0.03
Niobium (Nb)	0.06	0.06	0.06	0.06
					Phosphorus (P)	0.005	0.005	0.005	0.005
Sulfur	0.003	0.003	0.003	0.003
					Iron	94.707	94.807	94.607	94.737
Total up to	100	100	100	100

Example 11

Example 11 differs from example 7 in that the temperature in the diffusion annealing step was 1200 ℃ and the soak time was 15 h. The heat treatment after forging is as follows: the forging stock is cooled in fog, then cooled in air until the temperature is reduced to below 200 ℃, then the forging stock after air cooling is insulated for 10 hours at 1150 ℃, and then cooled in air until the temperature is below 200 ℃ to obtain the heat treatment forging stock. The dehydrogenation annealing comprises the following steps: and (3) preserving the heat treatment forging stock for 30h at 700 ℃, and cooling to below 250 ℃ to obtain the dehydrogenation annealing forging stock. The tempering heat treatment comprises the following steps: and (3) preserving the heat of the dehydrogenation annealing forging stock for 20h at the temperature of 600 ℃, cooling the forging stock to the temperature of 200 ℃, and then performing air cooling to obtain the hot work die steel.

Example 12

Example 12 differs from example 7 in that the temperature in the diffusion annealing step was 1150 ℃ and the soak time was 12 hours. The heat treatment after forging is as follows: the forging stock is cooled in fog, then cooled in air until the temperature is reduced to below 200 ℃, then the forging stock after air cooling is insulated for 9 hours at 1050 ℃, and then cooled in air until the temperature is below 200 ℃ to obtain the heat treatment forging stock. The dehydrogenation annealing comprises the following steps: and (3) preserving the heat treatment forging stock for 28h at 650 ℃, and cooling to below 250 ℃ to obtain the dehydrogenation annealing forging stock. The tempering heat treatment comprises the following steps: and (3) preserving the heat of the dehydrogenation annealing forging stock for 18h at 580 ℃, cooling the forging stock to 200 ℃, and then performing air cooling to obtain the hot work die steel.

Example 13

Example 13 is different from example 12 in that the temperature increase rate in the post-forging heat treatment, dehydrogenation annealing and tempering heat treatment steps is 13 ℃/min and the temperature decrease rate is 15 ℃/min.

Example 14

Example 14 is different from example 12 in that the temperature increase rate in the post-forging heat treatment, the dehydrogenation annealing and the tempering heat treatment steps is 10 ℃/min and the temperature decrease rate is 15 ℃/min.

Example 15

Example 15 is different from example 14 in that the temperature increase rate in the post-forging heat treatment, the dehydrogenation annealing and the tempering heat treatment steps is 10 ℃/min and the temperature decrease rate is 20 ℃/min.

Example 16

Example 16 is different from example 14 in that the temperature increase rate in the post-forging heat treatment, dehydrogenation annealing and tempering heat treatment steps was 10 ℃/min and the temperature decrease rate was 17 ℃/min.

Comparative example

Comparative example 1

The hot work die steel of comparative example 1 was a commercially available 4Cr5MoSiV1(H13) steel.

Performance test

Detection method/test method

And (3) testing tensile strength: tensile strength tests were performed according to GB/T2975-1, and the side 5 data were averaged.

And (3) testing impact strength: the impact strength test was performed according to the NADCA #207-90 standard, and the side 5 data were averaged.

The results of the above tests are shown in Table 3.

TABLE 3

As can be seen by combining examples 1-6 and Table 3, the tensile strength, yield strength and impact strength of examples 4-6 at 500 ℃ are all higher overall than those of examples 1-3, with example 6 having the best overall performance, which indicates that the overall performance of the steel can be improved by adjusting the contents of the components of the hot-work die steel.

It can be seen from the combination of examples 7-9 and table 3 that the tensile strength, yield strength and impact strength at 500 ℃ in example 7 are all higher than those in examples 8 and 9, and good thermal strength and toughness are shown, which indicates that the thermal strength and toughness of steel can be improved by adjusting the weight ratio of titanium to vanadium, so that the steel has better comprehensive performance, because the atomic radii of titanium and vanadium are close, the structure is similar, and the titanium and vanadium are more easily dissolved into each other to form multiple complex precipitated phases, the thermal stability of the material can be further improved in the tempering process of the material, so that the strength of the material in a high-temperature environment is increased, and the toughness of the material in the high-temperature environment can also be increased. As can be seen by combining example 7 with example 10, the overall performance of example 7 is higher than that of example 10, which shows that the overall performance of the steel can be improved by adjusting the weight ratio of yttrium to niobium in the steel.

By combining the example 7 with the examples 11 to 12 and combining the table 3, it can be seen that the temperature and the heat preservation time of the diffusion annealing have certain influence on the overall performance of the steel in the manufacturing process of the hot die steel, but the overall performance is not greatly different; the temperature and the heat preservation in the steps of heat treatment after forging, dehydrogenation annealing and tempering heat treatment also have certain influence on the overall performance of the material, but the overall performance of the material is not greatly different. In combination with examples 12-16, it can be seen that the rate of temperature increase and decrease in the post-forging heat treatment, the dehydrogen annealing and the tempering heat treatment steps have some effect on the overall properties of the steel, but have good heat resistance and high toughness.

As can be seen by combining all the examples and the comparative example 1 and combining the table 3, the tensile strength, the yield strength and the impact strength of all the examples at 500 ℃ are higher than those of the comparative example 1, which shows that the hot-work die steel prepared by the method has higher heat resistance and toughness and better comprehensive performance.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.