A high-efficiency heat treatment process for improving the hardness of castings

Abstract

The application discloses a kind of efficient heat treatment processes for improving casting hardness, belongs to heat treatment technical field, including the following steps, multiple spiral grooves are arranged on the surface of casting;Casting is sent into heating device to heat, after heating, it is taken out, and the first stage of heat treatment is completed;Casting is placed in heating device again to heat, after heating, it is taken out, and the second stage of heat treatment is completed;Quenching treatment is carried out to casting;Casting is carried out first stage pickling, then it is taken out, and then washed with water and dried;Casting is carried out second stage pickling, then it is taken out, washed with water and dried, and heat treatment is completed.In the application, the stress field guided by spiral groove is consistent with the grain refinement direction of two-stage heat treatment, and then the hardness distribution uniformity is improved, the nano-porous surface formed in the first stage and the passivation film composite layer in the second stage are combined by chemical bonding, and then the adhesion is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat treatment, in particular to a high-efficiency heat treatment process for improving the hardness of castings. BACKGROUND

[0002] Heat treatment refers to a metal heat processing process that changes the microstructure or the chemical composition of a workpiece to improve its performance by heating, holding and cooling the workpiece in solid state. Compared with other processing techniques, heat treatment does not change the shape or the overall chemical composition of the workpiece, but changes the microstructure of the workpiece or the chemical composition of the workpiece surface to improve the performance of the workpiece.

[0003] Chinese patent application with publication number CN112481454A discloses a heat treatment process for improving the hardness of products. The process includes the following steps: first, placing the product in a heating furnace to heat it to a first critical point for annealing treatment; then, when the product is cooled to below 150 degrees, maintaining the temperature in the annealing furnace at 100-130 degrees, and standing for 10-15 minutes to cause internal solid heat melting reaction; then, quenching the product again, heating it to a second critical point (400-550 degrees) and standing for 5-10 minutes; then, performing secondary annealing, slowly cooling at a 50-degree interval; and finally, when the temperature is cooled to 150 degrees, rapidly cooling to complete the heat treatment.

[0004] However, the prior art has the following disadvantages:

[0005] The existing process does not consider the influence of the surface geometry of the casting on the heat flow distribution, resulting in a large difference in cooling rate between the surface layer and the core during cooling, which makes it difficult to form a uniform stress field distribution, and further affects the uniformity of the hardness distribution.

[0006] The heating time and holding parameters in the existing process are relatively fixed, which cannot effectively control the dislocation density and the solid solution state of carbides, making it difficult to accurately control the nano-scale microstructure, and resulting in limited strengthening effect.

[0007] Therefore, it is necessary to develop a new heat treatment process that can improve the hardness of castings and achieve uniform distribution through surface microstructure design and accurate multi-stage heat treatment parameter control. SUMMARY

[0008] To solve the above technical problems, the present application provides a high-efficiency heat treatment process for improving the hardness of castings.

[0009] A high-efficiency heat treatment process for improving the hardness of castings includes the following steps:

[0010] A plurality of spiral grooves are arranged on the surface of the casting;

[0011] The casting is sent into the heating device for heating, and after the heating is completed, the casting is taken out, and the first stage of heat treatment is completed;

[0012] The casting is sent into the heating device for heating, and after the heating is completed, the casting is taken out, and the first stage of heat treatment is completed;

[0013] The casting is quenched;

[0014] The casting is subjected to the first stage of pickling, and then taken out, washed with water and dried;

[0015] The casting is subjected to the second stage of pickling, and then taken out, washed with water and dried, and the heat treatment is completed.

[0016] As a preferred scheme of the present application, the cross section of the spiral groove gradually decreases from one side of the casting to the other side, and the lead angle of the spiral groove is 45±5°.

[0017] Through the arrangement of the spiral groove, a gradient heat flow channel is formed in the heat treatment, so that the grain refinement direction is consistent with the main stress direction.

[0018] As a preferred scheme of the present application, the first stage of heat treatment comprises the following steps,

[0019] The casting is sent into the heating device for heating, and after the heating is completed, the casting is taken out, and the first stage of heat treatment is completed;

[0020] The first heating for 0.8-1.2 h makes the surface layer of the casting rapidly austenitized, and the subsequent cooling for 1-2 h triggers the inhomogeneous nucleation of carbides, and when the second heating for 2.8-3.2 h, the carbides induce the grain boundary migration as heterogeneous cores.

[0021] As a preferred scheme of the present application, the second stage of heat treatment comprises the following steps,

[0022] The casting is sent into the heating device for heating, and after the heating is completed, the casting is taken out, and the first stage of heat treatment is completed;

[0023] The short-time pulse heating for 0.3-0.6 h triggers dynamic recrystallization, and the second heating for 0.7-1.3 h promotes the merging of subgrains, and high-angle grain boundaries are formed.

[0024] As a preferred scheme of the present application, after the first stage of heat treatment, the castings are cooled by air cooling or mist cooling.

[0025] As a preferred scheme of the present application, during the quenching process, the castings are placed in a quenching agent.

[0026] The quenching agent is any one or more of salt 18-sodium sulfate or quenching agent JW-30; the salt 18-sodium sulfate is a mixture of sodium sulfate, aluminum salt and sodium nitrite; the quenching agent JW-30 is a mixture of water, polyvinyl alcohol and phosphate ester.

[0027] As a preferred scheme of the present application, during the first stage of pickling, the pickling solution is a mixture of oxalic acid, hydrochloric acid and sulfuric acid; the volume ratio of hydrochloric acid to oxalic acid is 2-3:1, and the volume of sulfuric acid is 3-5% of the total volume of oxalic acid and hydrochloric acid.

[0028] The three combinations are used, oxalic acid preferentially attacks the oxide layer, hydrochloric acid accelerates the micro-etching of the substrate, and sulfuric acid inhibits the corrosion of the grain boundary, so that a nano-porous structure is formed on the surface, and the specific surface area is increased.

[0029] As a preferred scheme of the present application, during the second stage of pickling, the pickling solution is a mixture of formic acid, citric acid and nitric acid; the volume of nitric acid is 5-8% of the total volume of formic acid and citric acid, and the volume ratio of formic acid to citric acid is 3-5:1.

[0030] Formic acid induces the generation of amorphous Fe(HCOO)3, citric acid complex fills the pores, and nitric acid oxidizes to form y-Fe2O3 nanocrystals, and the film layer has both the corrosion resistance of amorphous and the hardness of nanocrystals.

[0031] As a preferred scheme of the present application, during the first stage of heat treatment, the heating temperature is 1065-1085℃, and the holding time is 3h.

[0032] As a preferred scheme of the present application, the quenching process comprises:

[0033] First stage quenching: cooling at 120-150℃ / s in the range of 400-550℃;

[0034] Second stage quenching: forming a thermal barrier layer by inverse solubility of the quenching agent below 300℃, and cooling at 15-20℃ / s;

[0035] Third stage quenching: cooling at 30-50℃ / s in the range of 180-220℃.

[0036] The present application has the following beneficial effects:

[0037] The design of the lead angle 45±5° forms a spiral heat flow channel, the gradient direction of the spiral groove depth is at an angle of 55-65° with the gradient direction of the quenching cooling rate, a three-dimensional composite stress field is formed, the micro zone cooling rate difference is generated by the gradient change of the groove depth, and the stress gradient is matched with the subsequent quenching. The stress field guided by the spiral groove is consistent with the grain refinement direction of the two-stage heat treatment, and then the hardness distribution uniformity is improved.

[0038] The 0.8-1.2h pulse heating of the first-stage heat treatment initiates dislocation avalanche effect, that is, the dislocation density reaches 1012 / m 2 , 3h holding makes the nanometer carbide completely solid-solution, and the austenite carbon content is homogenized; the 0.3-0.6h short-time heating of the second-stage heat treatment triggers dynamic recrystallization, forms ultra-fine bainite, and pins dislocation to improve strength; the holding of the quenching process, the use of salt 18-sodium sulfate, forms Al2(SO4)3-SiO2 composite film, and the cooling rate is improved, while the application of JW-30 generates amorphous B-O-Si network, and inhibits martensite cracking. Therefore, the austenite to bainite transformation rate is improved, and the residual austenite is stabilized at 8-10%.

[0039] Through the first-stage pickling, oxalic acid has strong chelation effect, preferentially dissolves the oxide layer, the ratio of oxalic acid and hydrochloric acid is used to balance the corrosion rate and dissolution efficiency, prevents surface passivation, the addition of sulfuric acid cooperates with oxalic acid to form a soluble complex, effectively reducing pickling residue. Through the second-stage pickling, the combination of formic acid and citric acid further forms a passivation protective layer on the basis of the nano-porous surface formed in the first stage, and the two-stage pickling realizes composite layer combination through chemical bonding, improving surface adhesion and corrosion resistance. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0041] Embodiment 1 provides an efficient heat treatment process for improving the hardness of castings, comprising the following steps,

[0042] A plurality of spiral grooves are arranged on the surface of the casting, the cross section of the spiral groove gradually decreases from one side of the casting to the other side, and the lead angle of the spiral groove is 40°.

[0043] The casting is sent into the heating device for heating, and after heating is completed, it is taken out, and the first-stage heat treatment is completed;

[0044] The first-stage heat treatment comprises the following steps,

[0045] The casting is sent into the heating device for heating, the heating temperature is 1050℃, the casting is heated for 0.8h and then taken out, and cooled for 1h;

[0046] The casting is sent into the heating device for heating again, the heating temperature is 1050℃, the heating is completed and the holding time is 2.8h, and the first stage of heat treatment is completed.

[0047] After the first stage of heat treatment, the casting is cooled by air cooling.

[0048] The casting is placed into the heating device for heating again, and the casting is taken out after the heating is completed, and the second stage of heat treatment is completed;

[0049] The second stage of heat treatment comprises the following steps,

[0050] The casting is sent into the heating device for heating, the heating temperature is 1035℃, the casting is heated for 0.3h and then taken out;

[0051] The casting is placed into the heating device again, the casting is heated for 0.7h, the heating temperature is 1035℃, and then the casting is taken out, and the second stage of heat treatment is completed.

[0052] The casting is quenched;

[0053] During the quenching, the casting is placed in a quenching agent; wherein the quenching agent is salt 18-sodium sulfate; the salt 18-sodium sulfate is a mixture of sodium sulfate, aluminum salt and sodium nitrite.

[0054] The casting is subjected to first stage pickling, and then taken out, and then subjected to water washing and drying;

[0055] During the first stage pickling, the pickling solution is a mixture of oxalic acid, hydrochloric acid and sulfuric acid; the volume ratio of hydrochloric acid to oxalic acid is 2:1, and the volume of sulfuric acid is 3% of the total volume of oxalic acid and hydrochloric acid.

[0056] The casting is subjected to second stage pickling, and then taken out, water washed and dried, and the heat treatment is completed;

[0057] During the second stage pickling, the pickling solution is a mixture of formic acid, citric acid and nitric acid; the volume of nitric acid is 5% of the total volume of formic acid and citric acid, and the volume ratio of formic acid to citric acid is 3:1.

[0058] Embodiment 2 provides a high-efficiency heat treatment process for improving the hardness of a casting, comprising the following steps,

[0059] A plurality of spiral grooves are arranged on the surface of the casting, the cross section of the spiral grooves gradually decreases from one side of the casting to the other side, and the lead angle of the spiral grooves is 45°.

[0060] The castings are sent into the heating device for heating, and after the heating is completed, the castings are taken out, and the first stage of heat treatment is completed;

[0061] The first stage of heat treatment includes the following steps,

[0062] The castings are sent into the heating device for heating, and after the heating is completed, the castings are taken out, and the first stage of heat treatment is completed;

[0063] The castings are sent into the heating device for heating, and after the heating is completed, the castings are taken out, and the first stage of heat treatment is completed;

[0064] After the first stage of heat treatment, the castings are cooled by fog cooling.

[0065] The castings are sent into the heating device for heating, and after the heating is completed, the castings are taken out, and the first stage of heat treatment is completed;

[0066] The first stage of heat treatment includes the following steps,

[0067] The castings are sent into the heating device for heating, and after the heating is completed, the castings are taken out, and the first stage of heat treatment is completed;

[0068] The castings are sent into the heating device for heating, and after the heating is completed, the castings are taken out, and the first stage of heat treatment is completed;

[0069] The castings are sent into the heating device for heating, and after the heating is completed, the castings are taken out, and the first stage of heat treatment is completed;

[0070] During the quenching treatment, the castings are placed in a quenching agent; wherein the quenching agent is quenching agent JW-30; the quenching agent JW-30 is a mixture of water, polyvinyl alcohol and phosphate ester.

[0071] The castings are subjected to first stage pickling, then taken out, and then subjected to water washing and drying;

[0072] During the first stage pickling, the pickling solution is a mixture of oxalic acid, hydrochloric acid and sulfuric acid; the volume ratio of hydrochloric acid to oxalic acid is 3:1, and the volume of sulfuric acid is 5% of the total volume of oxalic acid and hydrochloric acid.

[0073] The castings are subjected to first stage pickling, then taken out, and then subjected to water washing and drying;

[0074] During the second stage pickling, the pickling solution is a mixture of formic acid, citric acid and nitric acid; the volume of nitric acid is 8% of the total volume of formic acid and citric acid, and the volume ratio of formic acid to citric acid is 5:1.

[0075] Example 3 provides an efficient heat treatment process for improving the hardness of castings, including the following steps,

[0076] A plurality of spiral grooves are arranged on the surface of the casting, the cross section of the spiral grooves gradually decreases from one side to the other side of the casting, and the lead angle of the spiral grooves is 50°.

[0077] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0078] The first stage of heat treatment comprises the following steps,

[0079] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0080] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0081] The first stage of heat treatment comprises the following steps,

[0082] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0083] The first stage of heat treatment comprises the following steps,

[0084] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0085] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0086] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0087] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0088] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0089] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0090] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0091] The casting is sent into the heating device for heating, and is taken out after the heating is completed, and the first stage of heat treatment is completed;

[0092] Table 1: Effectiveness of Examples 1-3

[0093] Performance metrics Example 1 Example 2 Example 3 Surface hardness (HRC) 62±0.5 64±0.3 63±0.4 Core impact toughness (J) 50 46 52 Effective case depth (mm) 2.0±0.08 2.3±0.10 2.1±0.07 Salt spray test (rust-free time) 480h 360h 550h Surface roughness Ra (pm) 0.4 0.5 0.3

[0094] As can be seen from Table 1, Example 1 has balanced comprehensive performance, excellent salt spray corrosion resistance (480h) and surface roughness (0.4 pm), suitable for marine environment components, such as marine valves.

[0095] Example 2 has the highest surface hardness (64HRC), suitable for high load components, such as aircraft engine gears.

[0096] Example 3 has the best salt spray corrosion resistance, 550h, and the lowest surface roughness (0.3 pm), suitable for precision instruments and medical devices.

[0097] Comparative Example 1 differs from Example 1 in that the helical groove design is cancelled, a traditional flat surface is used, and the heat treatment, quenching, and pickling steps are exactly the same as Example 1.

[0098] Table 2: Comparison of Comparative Example 1 and Example 1

[0099] Performance metrics Example 1 Comparative Example 1 Mechanism analysis Surface hardness (HRC) 62±0.5 58±1.2 Lack of spiral groove stress field guiding, uneven grain refinement Crack initiation energy (kJ / m 2 ) 12.5 6.8 No three-dimensional compressive stress field to inhibit crack propagation Hardness uniformity (HRC difference) Surface-core difference 1.2 Surface-core difference 4.5 Lack of cooling rate gradient leading to uneven phase transformation Fatigue life 5.8 x 10 6 ]]> 1.2 x 10 6 ]]> Stress concentration causing early fatigue failure

[0100] As can be seen from Table 2, Comparative Example 1 lacks the lead angle and cross-sectional gradient of the helical groove, and cannot form a three-dimensional compressive stress field induced by thermal expansion difference, resulting in thermal stress concentration. The flat surface makes the quenching cooling rate uniform (80℃ / s at the surface → 80℃ / s at the core), and loses the micro-zone cooling rate difference, and the bainite transformation rate decreases from 85% to 60%.

[0101] Comparative Example 2 differs from Example 1 in that a traditional single-stage heat treatment is used, the first stage is continuous heating at 1050℃ for 3h, the second stage is cancelled, and direct quenching, and other steps are the same as Example 1.

[0102] Table 3: Comparison of Comparative Example 2 and Example 1

[0103] Performance metrics Example 1 Comparative Example 2 Mechanism analysis dislocation density ( / m 2 ) 1 x 10 12 ]] 3 x 10 10 ]] Insufficient dislocation multiplication Impact toughness (J) 50 28 Coarse carbides becoming crack sources Yield strength (MPa) 1450 980 Weak dislocation pinning effect

[0104] As can be seen from Table 3, Comparative Example 2 cancels 0.8h heating + 1h cooling, and the dislocation density is only 10 10 / m² (Example 1 is 10 12 / m²), which cannot trigger the dislocation avalanche effect.

[0105] Comparative Example 3 differs from Example 1 in that the first stage of pickling is 10% sulfuric acid solution (without oxalic acid, hydrochloric acid), the second stage of pickling is cancelled, and other steps are the same as Example 1.

[0106] Table 4 Comparison of Comparative Example 3 and Example 1

[0107] Performance metrics Example 1 Comparative Example 3 Mechanism analysis Surface roughness Ra (pm) 0.4 1.8 Sulfuric acid cannot selectively remove the Fe3O4layer corrosion current density (A / cm 2 )]> 50 28 Lack of composite passivation film protection Coating adhesion (ASTM) 1450 980 Surface without nano-porous structure anchoring Wastewater Fe 3 + concentration (ppm) 45 320 No citric acid chelation leading to metal ion residue

[0108] As can be seen from Table 4, Comparative Example 3 uses single sulfuric acid pickling, which cannot remove Fe304 (oxidation layer residual rate > 30%) by oxalate chelation, and the surface oxygen content reaches 1.5 at% (0.4 at% for the example). Without the second stage of formic acid-citric acid-nitric acid passivation, only a loose FeSO4 film is formed on the surface, and the corrosion resistance is reduced.

[0109] In summary: the design of the lead angle of 45±5° forms a spiral heat flow channel, the gradient direction of the spiral groove depth forms an angle of 55-65° with the gradient direction of the quenching cooling rate, forming a three-dimensional composite stress field, and the groove depth gradient change produces a micro zone cooling rate difference, which matches the stress gradient formed by subsequent quenching. The stress field guided by the spiral groove is consistent with the grain refinement direction of the two-stage heat treatment, thereby improving the uniformity of hardness distribution.

[0110] The 0.8-1.2h pulse heating of the first stage of heat treatment triggers the dislocation avalanche effect, i.e. the dislocation density reaches 1012 / m 2 , and the 3h holding time makes the nanocarbide completely solid-solute and the austenite carbon content uniform; the 0.3-0.6h short-time heating of the second stage of heat treatment triggers dynamic recrystallization, forming ultra-fine bainite and pinning dislocations to improve strength; the holding time of the quenching process, the use of salt 18-sodium sulfate, forms an Al2(SO4)3-SiO2 composite film, increases the cooling rate, and the application of JW-30 generates an amorphous B-O-Si network, inhibiting the cracking of martensite. Therefore, the austenite to bainite transformation rate is improved, and the residual austenite is stabilized at 8-10%.

[0111] Through the first stage of pickling, oxalic acid has strong chelation effect, preferentially dissolving the oxidation layer, and the ratio of oxalic acid and hydrochloric acid balances the corrosion rate and dissolution efficiency, preventing surface passivation, and the addition of sulfuric acid cooperates with oxalic acid to form a soluble complex, effectively reducing pickling residues. Through the second stage of pickling, the combination of formic acid and citric acid further forms a passivation protective layer on the basis of the nanoporous surface formed in the first stage, and the two-stage pickling realizes composite layer bonding through chemical bonding, improving surface adhesion and corrosion resistance.

[0112] Example 4 differs from Example 1 in that the heating temperature of the first stage of heat treatment is 1075℃, and the holding time is 3h.

[0113] The 1075℃ / 3h parameter combination is located at the inflection point of the carbide dissolution kinetics curve, which maximizes carbide dissolution and carbon homogenization while suppressing grain coarsening. This breakthrough in performance balance achieves a simultaneous increase in hardness by +1.6% and toughness by +8%, breaking the traditional trade-off relationship between hardness and toughness in heat treatment.

[0114] Example 4 further optimizes the overall performance of the material by precisely controlling the first-stage heat treatment parameters, while maintaining the core advantages of Example 1. It is particularly suitable for key components of aircraft engines that require extremely high fatigue life and corrosion resistance.

[0115] Example 5 differs from Example 1 in the quenching process, which specifically includes:

[0116] First-stage quenching: cooling at 120-150℃ / s in the 400-550℃ range, which is a rapid cooling stage that triggers the transformation of austenite to bainite;

[0117] Second-stage quenching: forming a thermal barrier layer through inverse solubility of the quenchant below 300℃, with a cooling rate of 15-20℃ / s, which is a slow cooling stage that stabilizes residual austenite;

[0118] Third-stage quenching: cooling at 30-50℃ / s in the 180-220℃ range, which is a medium-speed cooling stage that induces the formation of an Al-Fe-O-Si transition layer at the matrix interface.

[0119] The spiral groove depth gradient direction forms a 55-65° angle with the quenching cooling rate gradient direction, forming a three-dimensional composite stress field.

[0120] It is important to note that the spiral groove setting is combined with the quenching process, and the depth gradient change rate matches the quenching rate gradient, resulting in a hardness difference of ≤1.5HRC from the surface to the core. Additionally, the stress field direction matches the grain growth direction, enhancing crack propagation resistance.

[0121] Three-stage gradient phase transformation control ensures that the volume fraction of bainite is ≥90%, i.e., complete transformation is achieved through rapid cooling (120-150℃ / s); residual austenite is stabilized at 5-8%, and the thermal barrier layer slows down the inhibition of martensite explosive transformation; and a nano-transition layer is generated, with medium-speed cooling (30-50℃ / s) inducing interface reaction to improve corrosion resistance (salt spray test ≥720h without rust).

[0122] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, and all the modifications and equivalents should be included in the scope of the claims of the present application.

Claims

1. A high efficiency heat treatment process for increasing the hardness of a casting, characterized in that, It comprises the following steps: a plurality of spiral grooves are arranged on the surface of the casting; the casting is sent into a heating device for heating, and after the heating is completed, the casting is taken out, and the first stage of heat treatment is completed; the casting is re-placed in the heating device for heating, and after the heating is completed, the casting is taken out, and the second stage of heat treatment is completed; the casting is subjected to quenching treatment; the casting is subjected to first stage pickling, then taken out, and then subjected to water washing and drying; the casting is subjected to second stage pickling, then taken out, water washed and dried, and the heat treatment is completed; the cross section of the spiral groove gradually decreases from one side of the casting to the other side, and the lead angle of the spiral groove is 45±5°; the first stage of heat treatment comprises the following steps: the casting is sent into a heating device for heating, the heating temperature is 1050-1100℃, the casting is heated for 0.8-1.2h, and then taken out and cooled for 1-2h; the casting is again sent into a heating device for heating, the heating temperature is 1050-1100℃, the heating and holding are completed for 2.8-3.2h, and the first stage of heat treatment is completed; the second stage of heat treatment comprises the following steps: the casting is sent into a heating device for heating, the heating temperature is 1035-1055℃, the casting is heated for 0.3-0.6h, and then taken out; the casting is re-placed in the heating device, heated for 0.7-1.3h, the heating temperature is 1035-1055℃, and then taken out, and the second stage of heat treatment is completed; in the first stage pickling process, the pickling solution is a mixture of oxalic acid, hydrochloric acid and sulfuric acid; in the second stage pickling process, the pickling solution is a mixture of formic acid, citric acid and nitric acid; the quenching treatment comprises the following steps: first stage quenching: cooling at 120-150℃ / s in the range of 400-550℃; second stage quenching: forming a thermal barrier layer through inverse solubility of a quenching agent below 300℃, and cooling at 15-20℃ / s; third stage quenching: cooling at 30-50℃ / s in the range of 180-220℃; the gradient direction of the spiral groove depth forms an angle of 55-65° with the gradient direction of the quenching cooling rate, and a three-dimensional composite stress field is formed.

2. A high efficiency heat treatment process for enhancing the hardness of a casting according to claim 1, characterized in that, After the first stage of heat treatment is completed, the casting is cooled by air cooling or fog cooling.

3. A high efficiency heat treatment process for enhancing the hardness of a casting according to claim 2, wherein, In the quenching treatment, the casting is placed in a quenching agent; the quenching agent is any one or more of salt 18-sodium sulfate or quenching agent JW-30; the salt 18-sodium sulfate is a mixture of sodium sulfate, aluminum salt and sodium nitrite; the quenching agent JW-30 is a mixture of water, polyvinyl alcohol and phosphate ester.

4. A highly efficient heat treatment process for enhancing the hardness of a casting according to any one of claims 3, characterized in that, In the first stage of heat treatment, the heating temperature is 1065-1085℃, and the holding time is 3h.