Welding repair method for cracks of main frame of 20Mn5 cast steel cone crusher

Abstract

The invention discloses a welding repair method for cracks of a main frame of a 20Mn5 cast steel cone crusher, which comprises the following steps of: cleaning rust, dirt and oil dirt, punching a 65-80-degree double-groove and removing an oxide layer, using a high-strength and high-plasticity welding material and a direct-current welding machine, performing direct-current reverse connection, controlling the welding current to be 82.5-87.5 A and the electric arc length to be 1.2-1.8 mm, adopting a multi-layer welding mode, performing linear reciprocating operation on a first layer of welding bead, and performing welding on a second layer of welding bead and a third layer of welding bead, so as to repair the cracks of the main frame of the 20Mn5 cast steel cone crusher. And after the five layers of welding beads are welded, welding sine curves to strengthen the welding beads by taking a connecting line between the starting point and the ending point of the welding seam as a central line, preheating at 275-295 DEG C before welding, preserving heat at 210-230 DEG C for about 1.5 hours after welding, and carrying out shot peening hardening on ceramic shots of an ultrasonic flaw detector and the welding seam. According to the method, a high-strength and high-plasticity welding material and proper temperature control conditions are selected and used, welding cracks and welding deformation are effectively prevented, the tensile strength of a welding seam reaches 890 MPa and is higher than the tensile ultimate strength 785 MPa of 20Mn5, and welding repair of cracks of the main rack of the 20Mn5 cast steel cone crusher is met.

Description

Technical Field

[0001] The present invention relates to a method for welding and repairing cracks in the main frame of a cone crusher, and particularly to a welding and repairing process for cracks in the main frame of a cone crusher made of 20Mn5 cast steel. Background Art

[0002] The main frame of a cone crusher bears a large impact for a long time and is prone to cracks, resulting in damage. The main frame of a cone crusher made of 20Mn5 cast steel has high strength and good plasticity, but it is very difficult to weld and repair. Traditional welding and repair methods are difficult to effectively solve the crack problem, and even the degree of cracking becomes larger during welding. Therefore, it is necessary to find an effective welding and repair method for cracks in the main frame of a 20Mn5 cast steel cone crusher. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for welding and repairing cracks in the main frame of a 20Mn5 cast steel cone crusher, which can meet the welding and repair of cracks in the main frame of a 20Mn5 cast steel cone crusher; and can make the tensile strength of the welded and repaired part exceed the tensile strength of 20Mn5 cast steel, so as to improve the impact toughness and fracture toughness of the welded and repaired part and avoid the occurrence of new cracks.

[0004] The technical solution of the present invention is as follows: A method for welding and repairing cracks in the main frame of a 20Mn5 cast steel cone crusher, the steps are as follows: Step 1, cleaning: Sandblast and clean the rust, dirt and oil stain near the crack. The raw material for the first round of sandblasting is quartz sand with SiO 2 ≥99.5%, particle size 0.6 - 0.8mm, spraying pressure 1.15 - 1.25MPa, and the surface cleanliness of the crack reaches Sa2.5 level; the raw material for the second round of sandblasting is refined brown fused alumina with Al 2 O 3 ≥95%, spraying pressure 0.80 - 0.95MPa, and the surface cleanliness of the crack reaches Sa3.0 level; Step 2, rust removal: Use a plasma cutting machine to gas gouge double-sided bevels with an angle of 65 - 80 degrees on both sides of the crack, gas gouging current 75 - 85A, bevel gap 2.5 - 5mm; Use a rust and oxide layer removal agent to remove rust and oxide layer from the bevel for 3 - 3.5 minutes, and use a laser rust removal machine to clean the surface of the bevel, the power of the laser rust removal machine is 950 - 1050 watts; Step 3, preheating: Use an oxygen-acetylene flame to preheat the area 10 - 15 cm on both sides of the bevel to 275 - 295 °C; Step 4. Welding: Use high-strength and high-plasticity welding materials and an inverter DC welding machine to weld the groove; and adopt a multi-layer welding method; for each layer of welding, the DC reverse connection is used, the welding current is 82.5 - 87.5 A, and the arc length is 1.2 - 1.8 mm; Step 5. Heat preservation: After all the welds are completed, heat-insulate the area 10 - 15 cm on both sides of the weld to cool the weld; Step 6. Inspection: Use an ultrasonic flaw detector to detect the weld. After welding defects are found, use an electric grinding machine to grind off the defective position of the weld and re-weld; Step 7. Hardening: Use ceramic pellets to peen-harden the weld.

[0005] Preferably, the composition of the rust and oxide layer removing agent in Step 2 is: water: 66.0% - 68.0%, hydrochloric acid: 18.5% - 20%, phosphoric acid: 2.1% - 2.6%, oleic acid: 4.6% - 5.0%, ethanol: 5.6% - 6.2%, LAN-826: 0.09% - 0.11%, TX-10: 0.175% - 0.215%.

[0006] Preferably, in Step 4, the chemical composition and mass ratio of the high-strength and high-plasticity welding material are: C < 0.045%, Si < 0.55%, S < 0.03%, P < 0.03%, Mn: 0.90% - 1.05%, Ni: 67% - 73%, Cr: 17% - 20%, Mo: 2.25% - 3.15%, Cu: 1.8% - 2.1%, and the rest is iron and unavoidable impurities.

[0007] Preferably, Step 4 adopts a five-layer welding method: for the first layer of weld bead, the straight reciprocating movement of the electrode is used, and for the remaining four layers of weld beads, the figure-eight movement of the electrode is used; after welding one layer of weld bead, heat the weld bead with an oxyacetylene flame, control the temperature at 980 - 1030 °C, for a duration of 5 - 7 minutes, and when it cools naturally to 250 - 300 °C, hammer the weld for 30 - 40 s; clean the welding slag, and then continue to weld the next layer; after welding the five layers of weld beads, with the connection line between the starting point and the ending point of the weld as the center line, weld a sine curve reinforcing weld bead. The starting point and the ending point of the sine curve reinforcing weld bead are the farthest points from the center line, respectively more than 40 mm away from the starting point and the ending point of the weld, the amplitude is 70 - 90 mm, the period is 80 - 120 mm, the width of the sine curve reinforcing weld bead is 8 - 12 mm, the welding current is 95.5 - 102.5 A, and the arc length is 1.2 - 1.8 mm.

[0008] Preferably, in Step 5, the heat preservation temperature is 210 - 230 °C, the heat preservation duration is 1.45 - 1.55 hours, and the cooling duration is 25 - 30 minutes.

[0009] Preferably, in Step 7, ZrO in the ceramic pellets 2 and SiO 2The mass content of satisfies: 67.8% ≤ ZrO 2 ≤ 68.0%, 30.5 ≤ SiO 2 ≤ 31.2%.

[0010] Preferably, in step seven, the ceramic shot has a size of 0.7 - 0.9 mm; the shot peening pressure is 0.6 - 0.8 MPa.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The present invention selects high-strength and high-plasticity welding materials and appropriate temperature control conditions, effectively preventing the generation of welding cracks and welding deformation. The tensile strength of the weld reaches 890 MPa, which is higher than the tensile limit strength of 20Mn5, i.e., 785 MPa, meeting the welding repair requirements for cracks in the main frame of the 20Mn5 cast steel cone crusher. The specific analysis is as follows: The high-strength and high-plasticity welding materials selected by the present invention have a unique formulation, especially introducing 2.25% - 3.15% of Mo. Its technical advantages are as follows: further increasing the recrystallization temperature of the welding material, reducing the thermal expansion coefficient of the weld, improving the tensile strength, impact toughness, and fracture toughness of the weld, refining the grains of the weld metal, and significantly reducing welding crack defects.

[0012] The rust and oxide layer removing agent adopted by the present invention has a unique composition, especially introducing LAN826, ethanol, and TX - 10. At the same time, the contents of hydrochloric acid, phosphoric acid, and ethanol are all higher than those of the traditional formula. Adding LAN826 can inhibit the ability of the metal to absorb hydrogen and avoid "hydrogen embrittlement" of steel. Adding ethanol can remove oil stains, accelerate the drying speed, and adjust the viscosity and surface tension of the rust and oxide layer removing agent. TX - 10 has excellent wetting, dispersing, and washing properties, which can improve the cleaning effect of the rust and oxide layer removing agent, reduce the volatilization of hydrochloric acid, and inhibit the excessive corrosion of the hydrochloric acid in the rust and oxide layer removing agent on the metal matrix. A slightly higher hydrochloric acid content can improve the rust removal ability, a slightly higher phosphoric acid content can form a protective film to improve the corrosion inhibition effect, and a slightly higher ethanol content can improve the degreasing effect and accelerate the drying speed.

[0013] The ceramic shot adopted by the present invention has a unique composition. In particular, the content of ZrO 2 is relatively high. ZrO 2 has extremely high hardness, strength, toughness, and high-temperature resistance. With a relatively high ZrO 2 content, the ceramic shot for shot peening has higher hardness, strength, toughness, and high-temperature resistance. When sprayed on the surface of a weld with a tensile strength of over 800 MPa, it can still cause rapid plastic deformation on the surface, generating residual compressive stress and achieving a better shot peening hardening effect.

[0014] In the present invention, a plasma cutting machine is used to gouge double-sided bevels on both sides of the crack with a slope of 65-80 degrees (traditionally, it is generally 45-75 degrees). The slightly larger bevel slope is convenient for cleaning the failed metal and impurities such as oil stains, rust, and scale on the surfaces on both sides of the crack; it can enable the welding material to penetrate deeper into the root of the weld, reduce defects such as incomplete penetration and slag inclusion, improve the quality and strength of the weld; and provide a suitable space for the subsequent multi-layer welding.

[0015] Before welding in the present invention, an oxygen-acetylene flame is used to preheat the areas on both sides of the bevel to 275-295 °C (traditionally, it is generally 180-230 °C). It can effectively avoid the formation of hardened structures, improve the toughness and plasticity of the weld, reduce the generation of cold cracks; make the thermal expansion and contraction of the metal during the welding process more uniform, reduce crack defects caused by stress concentration, and enhance the bonding force between the welding material and the base metal.

[0016] The present invention adopts a multi-layer welding method with an arc length of 1.2-1.8 mm (traditionally, it is generally 2.0-3.0 mm). After welding one layer of the weld bead, the weld bead is immediately heated with an oxygen-acetylene flame, the temperature is controlled at 980-1030 °C (traditionally, it is generally 650-930 degrees) and the duration is 5-7 minutes. After natural air cooling to 250-300 degrees, the weld is quickly hammered for 30-40 s (traditionally, it is generally 60-300 s). Its technical advantages are as follows: a small arc length can reduce heat dissipation, reduce the heat-affected zone of the base metal, and the arc stability is good; the relatively high temperature of heating the weld bead after welding can promote the uniform distribution of alloying elements in the weld, improve the stability and performance of the structure, and can reduce the hydrogen content in the weld, reducing the tendency to form cracks. Due to the adoption of multi-layer welding, hammering for 30-40 s can effectively release stress, avoiding obvious pits, scratches and other damages on the surface of the weld caused by too long hammering time.

[0017] In addition, the present invention adopts a relatively high shot peening pressure. It can make the shot peening impact the surface of the weld metal at a higher speed, introduce higher residual compressive stress on the surface layer of the weld, improve the fatigue resistance of the weld, and can refine the grains on the surface of the weld, improving the hardness and strength of the weld surface. Specific embodiments

[0018] The present invention will be further described below in combination with embodiments and technical effects. Embodiment 1

[0019] The main frame of the cone crusher has a diameter of 1560 mm and is made of 20Mn5. A crack with a length of 97 cm and a depth of 29 mm appears in the upper middle part on the side of the main frame. For this crack, the following welding repair method is adopted in this embodiment.

[0020] Step 1: Sandblast to clean the rust, dirt and grease near the crack. The raw material for the first round of sandblasting is refined quartz sand, and SiO in the refined quartz sand2 The mass proportion is 99.67%, the particles are uniform, the particle size is 0.65 - 0.75 mm, the injection pressure is 1.18 - 1.23 MPa, and the cleanliness near the surface of the crack of the main frame of the 20Mn5 cast steel cone crusher reaches Sa2.5 level. The raw material for the second round of sandblasting is refined brown fused alumina, with a specification of 180# - 240#, Al 2 O 3 The mass proportion is 96.13%, the injection pressure is 0.86 - 0.91 MPa, and the cleanliness near the surface of the crack of the main frame of the 20Mn5 cast steel cone crusher reaches Sa3.0 level.

[0021] Step 2: Use a plasma cutting machine to gas gouge double-sided bevels with an angle of 69 - 73 degrees on both sides of the crack, the gas gouging current is 81 A, and the bevel gap is 3.3 - 4.3 mm; Use a rust and oxide layer removing agent to remove rust and oxide layer from the bevel for 200 seconds. Use a laser rust removal machine to clean the surface of the bevel three times, and the power of the laser rust removal machine is 982 watts.

[0022] The chemical composition and mass ratio of the rust and oxide layer removing agent are as follows: water: 67.3%, hydrochloric acid: 19.3%, phosphoric acid: 2.3%, oleic acid: 4.7%, ethanol: 6.1%, LAN - 826: 0.11%, TX - 10: 0.19%.

[0023] Step 3: Before welding, preheat the area 11 - 13 cm on both sides of the bevel to 282℃ using an oxygen - acetylene flame.

[0024] Step 4: Use high - strength and high - plasticity welding materials and a ZX7 - 500E inverter DC welding machine to weld the bevel. Adopt a multi - layer welding method, DC reverse connection, welding current 85.5 A, arc length 1.4 - 1.7 mm.

[0025] For the first layer of weld bead, use a straight reciprocating stringer bead. For the remaining four layers of weld beads, use an 8 - shaped stringer bead. Immediately after welding one layer of weld bead, heat the weld bead with an oxygen - acetylene flame, control the temperature at 992 - 1025℃ for 5.5 minutes, and when it cools naturally to 270 - 300℃, quickly hammer the weld seam for 35 s, clean the weld slag, and then continue to weld the next layer. After welding five layers of weld beads, take the line connecting the starting point and the ending point of the weld seam as the center line, and weld a sine - curve reinforcing weld bead. The starting point and the ending point of the sine - curve reinforcing weld bead are the farthest points from the center line, 45 mm and 44 mm away from the starting point and the ending point of the weld seam respectively, the amplitude is 76 - 87 mm, the period is 92 - 103 mm, the width of the sine - curve reinforcing weld bead is 8.5 - 11.5 mm, the welding current is 98.5 A, and the arc length is 1.2 - 1.8 mm.

[0026] The chemical composition and mass fraction of the high-strength and high-plasticity welding material are as follows: C = 0.031%, Si = 0.52%, S = 0.019%, P = 0.015%, Mn = 1.02%, Ni = 69.57%, Cr = 19.32%, Mo = 2.93%, Cu = 1.95%, and the rest is iron and unavoidable impurities.

[0027] Step Five: After all the welds are completed, the area 11 - 13 cm on both sides of the weld is insulated for 1.48 hours at an insulation temperature of 225°C, and then the weld is gradually cooled with a cooling time of 28.5 minutes.

[0028] Step Six: Use an ultrasonic flaw detector to detect the weld. After finding no welding defects such as pores, cracks, and delamination, use an electric grinding machine to grind off the defective part of the weld and re-weld. Step Seven: Shot peen the weld with ceramic pellets of 0.75 - 0.88 mm specification. The main chemical composition of the ceramic pellets is: ZrO 2 = 67.92%, SiO 2 = 30.89%, and the shot peening pressure is 0.70 - 0.75 MPa.

[0029] In Example One, a high-strength and high-plasticity welding material and appropriate temperature control conditions are selected, effectively preventing the generation of welding cracks and welding deformation. The tensile strength of the weld reaches 892 MPa, which is higher than the tensile limit strength of 20Mn5, 785 MPa, meeting the welding repair requirements for the cracks in the main frame of the 20Mn5 cast steel cone crusher. Example Two

[0030] The diameter of the main frame of the cone crusher is 1560 mm, and the material is 20Mn5. A crack with a length of 119 cm and a depth of 30 mm appears in the middle and lower part of the side of the main frame. For this crack, the following welding repair method is adopted in this example.

[0031] Step One: Sandblast and clean the rust, dirt, and grease near the crack. The raw material for the first round of sandblasting is refined quartz sand, with a mass fraction of SiO 2 of 99.61%, uniform particles, a particle size of 0.62 - 0.73 mm, a spraying pressure of 1.19 - 1.24 MPa, and the cleanliness near the surface of the crack on the main frame of the 20Mn5 cast steel cone crusher reaches Sa2.5 level. The raw material for the second round of sandblasting is refined brown corundum, with a specification of 180# - 240#, and the mass fraction of Al 2 O 3 of 96.48%, a spraying pressure of 0.84 - 0.89 MPa, and the cleanliness near the surface of the crack on the main frame of the 20Mn5 cast steel cone crusher reaches Sa3.0 level.

[0032] Step 2: Use a plasma cutting machine to gouge out a groove with an angle of 70 - 74 degrees on both sides of the crack. The gouging current is 81.5 A, and the groove gap is 3.1 - 4.2 mm. Use a rust and oxide layer removing agent to remove rust and oxide layer from the groove for 190 seconds. Use a laser rust remover to clean the surface of the groove three times, with a power of 995 watts.

[0033] The chemical composition and mass ratio of the rust and oxide layer removing agent are as follows: water: 67.1%, hydrochloric acid: 19.4%, phosphoric acid: 2.3%, oleic acid: 4.7%, ethanol: 6.2%, LAN - 826: 0.10%, TX - 10: 0.20%.

[0034] Step 3: Before welding, use an oxygen - acetylene flame to preheat the area of 11.5 - 13.5 cm on both sides of the groove to 286 °C.

[0035] Step 4: Use a high - strength and high - plasticity welding material and a ZX7 - 500E inverter DC welding machine to weld the groove. Adopt a multi - layer welding method, with DC reverse connection, welding current of 86 A, and arc length of 1.35 - 1.7 mm.

[0036] For the first layer of weld bead, use a straight reciprocating weaving method, and for the remaining four layers of weld beads, use an 8 - shaped weaving method. Immediately after welding one layer of weld bead, use an oxygen - acetylene flame to heat the weld bead, control the temperature at 986 - 1022 °C for 6 minutes, and when it cools naturally to 270 - 300 °C, quickly hammer the weld seam for 33 s, clean the welding slag, and then continue welding the next layer. After welding five layers of weld beads, take the line connecting the starting point and the ending point of the weld seam as the center line, and weld a sine - curve reinforcing weld bead. The starting point and the ending point of the sine - curve reinforcing weld bead are the farthest points from the center line, 44 mm and 45 mm away from the starting point and the ending point of the weld seam respectively, with an amplitude of 78 - 89 mm, a period of 94 - 105 mm, a width of the sine - curve reinforcing weld bead of 8.7 - 11.6 mm, welding current of 99.5 A, and arc length of 1.2 - 1.8 mm.

[0037] The chemical composition and mass fraction of the high - strength and high - plasticity welding material are as follows: C = 0.033%, Si = 0.51%, S = 0.017%, P = 0.016%, Mn = 1.04%, Ni = 69.38%, Cr = 19.15%, Mo = 2.98%, Cu = 1.91%, and the rest are iron and unavoidable impurities.

[0038] Step 5: After all welding of the weld seam is completed, keep the area of 11.5 - 13.5 cm on both sides of the weld seam insulated for 1.52 hours at an insulation temperature of 220 °C, and then gradually cool the weld seam, with a cooling time of 27.5 minutes.

[0039] Step 6: Use an ultrasonic flaw detector to detect the weld seam, and no welding defects such as pores, cracks, and delamination are found.

[0040] Step 7: Shot peen harden the weld seam with ceramic shots of 0.73 - 0.85 mm specification. The main chemical components of the ceramic shots are: ZrO 2 = 67.87%, SiO 2 = 30.92%. The shot peening pressure is 0.74 - 0.79 MPa.

[0041] In Example 2, high-strength and high-plasticity welding materials and appropriate temperature control conditions are selected to effectively prevent the generation of welding cracks and welding deformation. The tensile strength of the weld seam reaches 898 MPa, which is higher than the tensile ultimate strength of 20Mn5, 785 MPa, meeting the welding repair requirements for cracks in the main frame of the 20Mn5 cast steel cone crusher.

[0042] The LAN-826 described in the present invention is a commercially available general-purpose pickling inhibitor, purchased from Zhengzhou Guangjie Chemical Co., Ltd.; the TX-10 described in the present invention is a commercially available non-ionic surfactant, purchased from Taizhou Jiayin Chemical Co., Ltd. ​

Claims

1. A welding repair method for cracks in the main frame of a 20Mn5 cast steel cone crusher, characterized in that Here are the steps: Step 1. Cleaning: Sandblast to clean the rust, dirt and oil stains near the crack. The first round of sandblasting material is quartz sand with SiO2≥99.5%, particle size 0.6~0.8mm, spray pressure 1.15~1.25MPa, and the surface cleanliness of the crack reaches Sa2.5 level; the second round of sandblasting material is refined brown corundum with Al2O3≥95%, spray pressure 0.80~0.95MPa, and the surface cleanliness of the crack reaches Sa3.0 level; Step 2: Rust removal: Use a plasma cutting machine to gouge a 65-80 degree double-sided groove on both sides of the crack, with a gouging current of 75-85A and a groove gap of 2.5-5mm; use a rust and oxidation layer removal agent to remove rust and oxidation layer from the groove for 3-3.5 minutes, and use a laser rust removal machine to clean the groove surface. The power of the laser rust removal machine is 950-1050 watts; Step 3: Preheating: Use oxygen-acetylene flame to preheat the 10-15cm area on both sides of the groove to 275-295℃; Step 4: Welding: Use high-strength and high-plasticity welding materials and inverter DC welding machine to weld the groove; and adopt multi-layer welding method; each layer is welded with reverse DC, welding current 82.5~87.5A, arc length 1.2~1.8mm; Step 5: Insulation: After all the welds are welded, insulate the 10-15cm area on both sides of the weld and then cool the weld; Step 6. Inspection: Use an ultrasonic flaw detector to inspect the weld. If welding defects are found, use an electric grinder to grind away the weld defect and re-weld. Step 7. Hardening: Use ceramic shot peening to harden the weld.

2. The welding repair method for cracks in the main frame of a 20Mn5 cast steel cone crusher according to claim 1 is characterized in that: The ingredients of the rust and oxidation layer removing agent in step 2 are: water: 66.0%~68.0%, hydrochloric acid: 18.5%~20%, phosphoric acid: 2.1%~2.6%, oleic acid: 4.6%~5.0%, ethanol: 5.6%~6.2%, LAN-826: 0.09%~0.11%, and TX-10: 0.175%~0.215%.

3. The welding repair method for cracks in the main frame of a 20Mn5 cast steel cone crusher according to claim 1 is characterized in that: In step 4, the chemical composition and mass ratio of the high-strength and high-plasticity welding material are: C<0.045%, Si<0.55%, S<0.03%, P<0.03%, Mn: 0.90%~1.05%, Ni: 67%~73%, Cr: 17%~20%, Mo: 2.25%~3.15%, Cu: 1.8%~2.1%, and the rest are iron and unavoidable impurities.

4. The welding repair method for cracks in the main frame of a 20Mn5 cast steel cone crusher according to claim 1 is characterized in that: Step 4 adopts a five-layer welding method: the first layer of weld is moved back and forth in a straight line, and the remaining four layers of weld are moved in an 8-shaped pattern; after welding one layer of weld, the weld is heated with an oxygen-acetylene flame, and the temperature is controlled at 980-1030°C for 5-7 minutes. When it is naturally cooled to 250-300°C, the weld is hammered for 30-40 seconds; the welding slag is cleaned, and then the next layer is continued; after welding five layers of weld, the line between the starting point and the end point of the weld is used as the center line to weld the sinusoidal reinforced weld. The starting point and end point of the sinusoidal reinforced weld are both the farthest points from the center line, which are more than 40mm away from the starting point and end point of the weld, respectively, with an amplitude of 70-90mm, a period of 80-120mm, a width of 8-12mm, a welding current of 95.5-102.5A, and an arc length of 1.2-1.8mm.

5. The welding repair method for cracks in the main frame of a 20Mn5 cast steel cone crusher according to claim 1 is characterized in that: Step 5: Keep warm at 210~230℃, keep warm for 1.45~1.55 hours, and cool down for 25~30 minutes.

6. The welding repair method for cracks in the main frame of a 20Mn5 cast steel cone crusher according to claim 1 is characterized in that: Step 7: The mass contents of ZrO2 and SiO2 in the ceramic pellets satisfy the following conditions: 67.8%≤ ZrO2≤ 68.0%, 30.5≤ SiO2≤31.2%.

7. The welding repair method for cracks in the main frame of a 20Mn5 cast steel cone crusher according to claim 1 or 6, characterized in that: In step seven, the ceramic shot size is 0.7-0.9 mm, and the shot peening pressure is 0.6-0.8 MPa.