Corrosion-resistant mining grinding steel ball and production method thereof

Abstract

The invention relates to a corrosion-resistant mining grinding steel ball and a production method thereof, and the steel comprises the following elemental components in percentage by mass: 0.90 to 1.10 percent of C, 0.15 to 0.35 percent of Si, 0.90 to 1.10 percent of Mn, 0.35 to 0.65 percent of Cr, 0.20 to 0.40 percent of Cu, 0.010 to 0.030 percent of Ti, 0.15 to 0.30 percent of Ni and the balance of Fe and inevitable impurity elements. The production diameter phi of the steel ball is 25-30 mm, the final metallographic structure is martensite and retained austenite, the martensite accounts for 95% or above, the surface hardness and the volume hardness are 63-66 HRC and are close to the hardness requirement of a high-chromium cast iron ball, and the steel ball has high wear resistance. The corrosion rate is not greater than 7mg / cm < 2 > h in a 24-hour standard corrosion resistance test, and the corrosion resistance is realized.

Description

Technical Field

[0001] The invention belongs to a steel ball production method in the technical field of metallurgy. Background Art

[0002] Mining ball mill grinding balls are suitable for grinding various ores and other materials. They are the main consumables of ball mills and are widely used in various mines, cement plants, power plants, building materials and chemical industries. For the mining of magnetite resources, the hardness of the raw ore is very high, higher than the hardness of ordinary hematite. For example, the magnetite ore mined by CITIC Pacific Mining has a hardness coefficient F value of up to 38. The iron ore of domestic steel mills is generally only 10 to 18, and the ore density is 3.5. The density of ordinary ore is only 3.0 to 3.2. For this heavy and hard ore, the ball mill needs to use very high hardness grinding balls after mining to meet the grinding needs.

[0003] Patent publication number CN113953426A discloses a method for making a high-strength and tough wear-resistant steel ball for mining, which includes the following steps: making round steel, heating the round steel in a natural gas stepping furnace, feeding the heated round steel to the roller of a hot shear using a feeding device, evenly distributing the round steel according to the set length using an infrared laser intelligent distance measuring device, starting the hot shear to segment the round steel according to the distribution information of the infrared laser intelligent distance measuring device, and obtaining a steel billet; using a manipulator to clamp the steel billet to a CNC full hydraulic die forging hammer, and a temperature measuring device to measure the temperature of the steel billet, and transmitting the measured temperature of the steel billet to the CNC full hydraulic die forging hammer, and the CNC full hydraulic die forging hammer calculates the striking energy and number of striking of the steel billet according to the temperature of the steel billet and strikes the steel billet, so as to obtain the high-strength and tough wear-resistant steel ball for mining. The invention is to accurately control the process parameters by a CNC full hydraulic die forging hammer to ensure the roundness of the prepared steel ball, thereby improving the production efficiency of the steel ball. The chemical elements and mass percentages contained in the round steel are as follows: C: 0.5-0.7wt.%, Si: 1.6-2.0wt.%, Mn: 0.65-0.95wt.%, Cr: 0.7-0.95wt.%, and the remainder is Fe and unavoidable impurities. This method belongs to the heating forging process, which is suitable for the production of large-size forged steel balls. The production must use heating equipment, forging equipment and many auxiliary tools. Compared with rolled steel balls, its production cost is relatively high, and the carbon content C: 0.5-0.7wt.% belongs to the medium carbon content. Theoretically, the wear resistance is relatively poor compared to the high carbon steel with C: 0.9-1.1wt.%, and the steel balls designed with this composition do not have ideal corrosion resistance to the corrosive solution in the ball mill.

[0004] With the large-scale mining mills, the demand for wear-resistant steel balls is gradually increasing. The main forming processes are induction heating, air hammer forging or press extrusion. The medium-frequency induction heating has a short time, which causes uneven temperature inside and outside the round steel and large temperature difference during the rapid heating process, resulting in uneven round steel structure, poor product quality uniformity and unstable quality; the air hammer forging process has high process environment temperature, high labor intensity, low production efficiency, and it is difficult to ensure the stability of product quality; and the press extrusion does not meet the steel ball forming compression ratio, resulting in poor density of the steel ball and failure to refine the grain size, thus affecting the quality of the steel ball product.

[0005] Therefore, it is of great significance to develop a low-cost production method for corrosion-resistant and highly wear-resistant mining grinding ball steel. Summary of the invention

[0006] The invention relates to a grinding steel ball for mining and a manufacturing method thereof. The grinding steel ball of the invention is formed by high-carbon, high-manganese and low-alloying smelting, rolling process, online quenching and self-tempering process, and has the production advantages of low cost and easy production compared with the steel ball production process in the prior art. The obtained steel ball has the characteristics of high hardness, uniform structure, good wear resistance and good corrosion resistance, and is conducive to the use of grinding in a ball mill for magnetite and other ores with high hardness.

[0007] The present invention adopts high-carbon low-alloy manufacturing process, mainly because of fierce market competition and processing cost restrictions, and uses expensive high-chromium wear-resistant cast balls with a chromium content of up to 20%. The current market lacks corresponding low-cost and high-wear-resistant alloy steel balls.

[0008] With respect to the production method of steel balls, the present invention effectively controls non-metallic inclusions, because non-metallic inclusions in steel destroy the continuity and uniformity of metal. In the process of grinding ore with steel balls, inclusions easily cause stress concentration, become fatigue crack sources, and reduce the fatigue life of steel balls, especially for hard and brittle inclusions, such as large non-deformed particle-shaped or spherical inclusions (Ds type), because they have no plasticity, they are difficult to deform during the processing and use of steel balls, shortening the fatigue crack initiation period and affecting the improvement of fatigue performance. In order to improve the service life of the final product, the purity of the steel is very important, and the non-metallic inclusions in the steel must be reduced as much as possible.

[0009] Since the steel ball has a high requirement for surface quality during use, in addition to not allowing inclusions on the surface or under the skin to damage the continuity of the matrix and thus reduce the service life, if the steel surface itself has surface defects such as folds, scratches, pressed iron oxide scale, etc., it will also directly lead to early failure of the product. Therefore, it is necessary to ensure that the product has good surface quality.

[0010] In order to solve the above problems, the present invention provides a low-cost wear-resistant steel ball steel based on low alloy element content and a manufacturing method thereof by rationally designing the chemical composition of the steel and targetedly controlling the production process. The specification group interval is φ25-30mm, and the total processing compression ratio from the blank to the finished steel ball should be ≥16. The produced steel ball has the characteristics of good surface quality, high hardness, uniform organization and low cost. The specific technical scheme of the present invention is as follows: A steel for grinding steel balls is designed, the mass percentage of its elemental components are as follows: C: 0.90-1.10%, Si: 0.15-0.35%, Mn: 0.90-1.10%, Cr: 0.35-0.65%, Cu: 0.20-0.40%, Ti: 0.010-0.030%, Ni: 0.15-0.30%, and the remainder is Fe and unavoidable impurity elements.

[0011] In the above scheme, after the chemical composition is determined, the theoretical critical hardenability diameter Di is calculated using the Caterpillar hardenability coefficient and Di value calculation formula, and the hardenability Di value is controlled at 230 to 350 mm.

[0012] The functions and dosages of the components contained in the steel ball of the present invention are selected based on the following: Carbon: C is the most economical and basic strengthening element in steel. It can significantly improve the hardness and wear resistance of steel through solid solution strengthening and precipitation strengthening. However, too high a C content will have an adverse effect on the toughness and ductility of the steel, and is also not conducive to atmospheric corrosion resistance. The C content of the present invention is determined to be in the range of 0.90-1.10%, and the steel material to which the present invention relates belongs to the category of high carbon steel; Silicon: Adding Si to steel can strengthen ferrite, improve strength, elastic limit and hardenability. When a certain amount of silicon is heated at high temperature, it can form a silicon dioxide film on the steel surface to prevent oxidation of the steel, thereby improving corrosion resistance. However, Si increases the overheating sensitivity, cracks and decarburization tendency in the steel. The range of Si content in the present invention is determined to be 0.15-0.35%.

[0013] Manganese: Mn, as a deoxidizing element in the steelmaking process, can improve the hardenability of steel, help steel form a stable corrosion layer in a weakly corrosive environment, reduce the corrosion rate, and improve the corrosion resistance of steel. However, excessive Mn will lead to the growth of corrosion product particles and increase the tendency of temper brittleness. The range of the Mn content of the present invention is determined to be 0.90-1.10%.

[0014] Chromium: Cr is a carbide-forming element, which can improve the hardenability of steel, and improve the corrosion resistance, oxidation resistance and passivation ability of steel. The range of Cr content in the present invention is determined to be 0.35-0.65%.

[0015] Copper: Compared with conventional steel, adding Cu can form an anti-rust protective layer on the steel matrix, especially when added together with chromium, it can significantly improve the atmospheric corrosion resistance. Combining with the nickel element in the steel to form a CuNi compound can prevent the occurrence of copper brittle cracks. The present invention controls the Cu content to 0.20-0.40%.

[0016] Titanium: Ti is added as a grain refining element and can form dispersed and fine nano-scale titanium nitride dispersed particles with N in the steel and distributed on the grain boundaries to prevent the growth of grains and thus refine the grains. The Al content of the present invention is determined to be in the range of 0.010-0.030%.

[0017] Nickel: Ni can improve the strength of steel while maintaining good plasticity and toughness. It also helps to improve the corrosion resistance of alloys in corrosive environments. At the same time, adding nickel can improve the copper brittle crack quality defects of copper-containing steel, and can produce CuNi compounds between crystals with a high melting point to prevent the occurrence of copper brittle cracks. However, since Ni is a scarce and precious resource, and in order to reduce costs, the Ni content of this project steel is determined to be within the range of 0.15-0.30%.

[0018] Oxygen: A large number of tests have shown that excessively high oxygen content will increase the content of oxide inclusions in steel, causing impure steel matrix structure and reducing the fatigue life of steel. The range of the O content in the present invention is determined to be ≤0.0015%.

[0019] Hydrogen: Too high hydrogen content in steel will increase the generation of white spot defects in the steel, increase internal stress and cause internal cracks, causing early rupture and failure of the steel ball. The range of H content in the present invention is determined to be ≤0.00010%.

[0020] The production method of the steel ball comprises the steps of: designing the chemical composition to carry out steelmaking to obtain a continuous casting billet, heating and rolling the round steel to obtain the round steel, segmenting the round steel and then heating and rolling it into a steel ball, and performing quenching and self-tempering heat treatment to obtain a finished steel ball.

[0021] Molten steel smelting: The H content in the molten steel must be ≤0.0001%. The molten steel is cast into a cross-sectional area of ​​≥5.76×10 4 mm 2 The continuous casting billet meets the following requirements: center segregation: equal to or better than level 1.0, center porosity: equal to or better than level 1.0, no center crack, corner crack and triangular crack; inclusions: A, B, D type coarse and fine series ≤ 1.5, C type coarse and fine series ≤ 0.5, Ds ≤ 1.0; Round steel rolling: heat the continuous casting billet to 1050-1150℃, keep it warm for more than 3 hours after reaching the temperature, and then carry out high-pressure water descaling treatment after the insulation is completed, and then roll it. The starting rolling temperature is 1000-1100℃, and the final rolling temperature is 900-930℃. Roll it into round steel. During the rolling process, the reduction of the first two passes of rough rolling should be ≥50%, and the reduction of the next two passes should be ≥30%. The total compression ratio of the rolled billet to the material should be ≥25; after rolling, control cooling is carried out, online slow cooling to below 400℃, air cooling, cutting, packaging and collection, and round bars with specifications of φ25-30mm are obtained; Steel ball rolling: The round steel is divided into sections, heated to 800-960℃, the average temperature is kept at 1000-1060℃, the total heating time is 40-60 minutes, and the steel ball is rolled using wedge cross rolling method, the rolling mill inclination angle is 3°-3.3°, the starting rolling temperature is 850-950℃, and the steel balls are rolled into finished product specifications.

[0022] Furthermore, the steel balls are subjected to residual heat temperature control after rolling, and the temperature is controlled at 760-880°C. They are quenched in water online, and the surface temperature of the steel balls out of water is controlled at 60-100°C. They are then sent to an insulation room for self-tempering heat treatment, and the self-tempering insulation temperature of the steel balls is 160-230°C.

[0023] The present invention aims at the performance requirements of mining steel balls, uses microalloying designed chemical composition, controls the purity of molten steel, and uses continuous casting billets directly as billets. It adopts a large reduction controlled rolling + controlled cooling method to manufacture round bars, which are formed into steel balls by wedge cross rolling. It adopts a process of online quenching + self-tempering heat treatment after hot rolling, which reduces the reheating heat treatment process after rolling, reduces production costs, and shortens production cycles. The steel ball specification is φ25-30mm, and the final metallographic structure is martensite accounting for more than 95%, and a small part is residual austenite. The surface hardness and volume hardness are above 63-66HRC, which is close to the hardness requirements of high chromium cast iron balls and has high wear resistance.

[0024] Compared with the prior art, the main advantages of the present invention are: The steel balls manufactured according to the method of the present invention have the advantages of fast production pace and high production efficiency when hot-rolled compared to forged steel balls, and the cost is lower than that of forged steel balls; compared to the heat treatment process of reheating the steel balls for quenching and tempering after rolling, the online quenching and self-tempering process adopted by the present invention reduces the two reheating processes, and has the advantages of low cost and easy production. At the same time, the steel balls after heat treatment have the characteristics of high hardness, uniform structure and good wear resistance. At the same time, due to the unique chemical composition design, the corrosion resistance is also high, which is conducive to the use of grinding in ball mills for ores with high hardness such as magnetite, and has a good application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1It is a schematic diagram of processing the steel ball hardness sample of the present invention (front view).

[0026] Figure 2 Schematic diagram of processing of steel ball hardness specimen of the present invention (top view).

[0027] Figure 3 This is the surface organization diagram of the steel ball of comparative example 1 (400×).

[0028] Figure 4 This is the microstructure diagram of the steel ball center of comparative example 1 (400×).

[0029] Figure 5 This is the surface organization diagram of the steel ball of comparative example 2 (400×).

[0030] Figure 6 This is the microstructure diagram of the steel ball center of comparative example 2 (400×).

[0031] Figure 7 This is the surface organization diagram of the steel ball in Example 1 (400×).

[0032] Figure 8 This is the microstructure diagram of the steel ball core of Example 1 (400×). DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with examples. The examples are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0034] The element compositions (wt %) of the grinding steel balls of Examples 1-3, the forged steel balls of Comparative Example 1, and the rolled steel balls of Comparative Example 2 are shown in Table 1, where P and S are unavoidable residual elements.

[0035] Table 1 C Si Mn P S Cr Cu Ni Ti Example 1 1.00 0.21 0.92 0.016 0.002 0.41 0.023 0.20 0.015 Example 2 0.99 0.23 0.95 0.015 0.002 0.42 0.021 0.19 0.016 Example 3 1.00 0.24 0.94 0.014 0.001 0.43 0.020 0.18 0.015 Comparative Example 1 0.61 1.70 0.75 0.017 0.008 0.71 0.03 0.01 0.005 Comparative Example 2 0.90 0.28 1.022 0.015 0.001 0.54 0.02 0.02 0.008 The production process and specific process of steel for steel balls in each embodiment of the present invention are as follows: prepare molten iron + scrap steel → primary smelting in BOF furnace → refining in LF furnace → vacuum degassing in RH furnace → continuous casting of CCM square billets → slow cooling → peeling of continuous casting billets → shot blasting cleaning of continuous casting billets → heating and rolling → controlled cooling → shearing / sawing → packaging and stacking cooling → finished product inspection → packaging.

[0036] Further, the above steelmaking and continuous casting process is: first smelting in a converter, then LF refining, deoxidation should be strengthened during LF refining, and the slag with good deoxidation time should be kept for more than 15 minutes and with good fluidity. After refining, the ladle is transferred to the VD furnace for high vacuum degassing treatment, and the time is kept at a high vacuum pressure of 1.33mbar for more than 15 minutes. After the VD is broken, aluminum wire, titanium wire, silicon calcium wire, etc. are fed first for adjustment, and the titanium and other components are adjusted to enter the control range. After all the alloys are added, the ladle is softly blown with argon for more than 10 minutes to ensure the degassing effect and the inclusions can fully float. The target superheat of molten steel during continuous casting is controlled at 20-35℃, and the residence time of the ingot in the high temperature zone is shortened as much as possible. Anti-oxidation protection is used throughout the continuous casting process to reduce the number of inclusions in the steel, and the appropriate pulling speed and cooling intensity of the second cooling section are equipped. At the same time, the continuous casting adopts the dual measures of crystallizer M-EMS and terminal F-EMS electromagnetic stirring to effectively improve and reduce the component segregation of the continuous casting ingot. The obtained rectangular continuous casting billet has a cross-sectional size of 300mm×340mm. The continuous casting billet meets the following requirements: center segregation, ingot segregation: 0.5 level, center porosity: 0.5 level, no center crack, corner crack and triangular crack, inclusions: A, B type coarse system ≤1.0, C, D type coarse system ≤0.5 level; A, B type fine system ≤1.5 level, C, D type fine system, Ds type ≤1.0.

[0037] Furthermore, after the surface of the ingot is inspected and cleaned, the round steel production stage is carried out. The specific process of the ingot heating and rolling stage is: the continuous casting ingot is slowly heated to 1050℃-1150℃ in a heating furnace with a neutral atmosphere and kept warm for 3 hours. The holding time in the high temperature section should be no less than 30 minutes to fully dissolve the alloy elements in the steel. After being removed from the furnace, it is directly sent to the multi-stand continuous rolling unit for rolling after being descaled by high-pressure water. The starting rolling temperature is 1000℃-1100℃ and the final rolling temperature is 900-930℃. The rolling deformation process is reasonably designed. The rough rolling adopts a diamond-shaped hole series, and the horizontal and vertical rolling mills are arranged alternately in the middle and fine rolling to roll the finished round steel. During the rolling process, the rough rolling adopts a large reduction. The single-pass reduction of the first two rough rolling should be 50-60%, and the single-pass reduction of the next two rough rolling should be 30-40%. The total rolling reduction ratio is above 25. After rolling, the product is slowly cooled under the cooling bed insulation cover. When the temperature of the rolled product is ≤400℃, it is air-cooled out of the cover, and then cut, packaged and collected to obtain round bars with a specification of φ25-30mm.

[0038] Furthermore, the round steel is segmented and enters a natural gas stepping furnace with a heating temperature of 800-960°C, an average temperature of 1000-1060°C, and a total heating time of 40-60 minutes.

[0039] Furthermore, after the heated steel rod is pushed out of the heating furnace, it is rolled using a wedge cross rolling process, with a rolling mill inclination of 3-3.3°, a rolling start temperature of 850-950°C, and a finished steel ball specification of φ25-30mm.

[0040] Furthermore, after rolling, the steel ball is temperature-controlled at 760-880℃ residual heat, and quenched in water online. The water flow and water temperature are controlled according to the process. The surface temperature of the steel ball out of water is controlled at 60-100℃. Then it is sent to the insulation room for self-tempering heat treatment. The tempering insulation temperature is 160-230℃. The high temperature at the center of the steel ball is transmitted to the surface to reach the temperature required by the tempering process. There is no need for re-tempering heating, and finally a high-hardness finished wear-resistant steel ball that is not prone to stress cracking is obtained.

[0041] The element composition of the grinding steel ball of the present invention increases the corrosion resistance in acidic and other corrosive solutions compared with the similar low-alloy steel ball with a chromium content of less than 1% previously published. The corrosion resistance test of the steel ball in each embodiment is carried out according to the JB / T7901-1999 standard. The circular sample is processed along the axis of the steel ball, with a size of: φ25 (±2) mm×thickness 5 (±0.1) mm. The original metal surface layer on the surface is ground off with sandpaper, and the surface is ground with water sandpaper with a grit of 120 as specified in GB / T 2481 (the finish is better than Ra: 3.2um). Each steel grade is subjected to a 24-hour sulfuric acid corrosion resistance test: The test solution is a 50wt% sulfuric acid solution. The samples are weighed separately, and the mass of the steel samples before the test is recorded in turn. The sizes of the samples are accurately measured, and their surface areas are calculated. Sulfuric acid solution is added to beakers according to the surface areas of the samples. The amount of test solution is required to be not less than 20mL per sample surface area. The beakers containing sulfuric acid solution are placed in a 70℃ constant temperature water bath in sequence for heating, and the temperature of the solution is measured with a thermometer. When the temperature of the sulfuric acid solution reaches 70℃, the samples are placed in beakers according to their numbers and soaked. The timing starts at this time. After the specified time is reached, the samples are taken out and washed in running water, then washed with alcohol, and dried with cold air. The mass of each steel sample after the test is weighed separately, and the corrosion rate of each steel sample is calculated according to the following formula.

[0042] c =( W 0 - W 1 ) / ( S * h ) In the formula, c : Corrosion rate, W 0 : The mass of the sample before the test, mg, W 1 : The mass of the sample after the test, mg, S : Total area of ​​the sample cm 2 , h : Test time h.

[0043] The 24-hour corrosion rates of Examples 1-3 and Comparative Examples 1 and 2 are shown in Table 2.

[0044] Table 2 <![CDATA[24-hour corrosion rate c, (mg / cm 2 h)]]> The difference in corrosion rate from comparative example 1, % The difference in corrosion rate from comparative example 2, % Example 1 6.74 -16.6% -11.6% Example 2 6.69 -17.5% -12.4% Example 3 6.85 -14.7% -9.8% Comparative Example 1 7.86 / / Comparative Example 2 7.52 / / In Table 2, the corrosion rate difference = (corrosion rate of this example - corrosion rate of the comparative example) / corrosion rate of this example × 100%.

[0045] It can be seen from Table 2 that the steel ball of the embodiment has better performance than the common forged balls and rolled balls used in the market, and the corrosion rate is basically reduced by more than 10%, and the 24-hour corrosion rate does not exceed 7 mg / cm 2 h.

[0046] For the test of hardness, an important indicator of steel ball wear resistance, the hardness (HRC) test is carried out according to the requirements of ISO 6508-1 standard. When preparing the sample, wire cutting or electric spark cutting is used to cut the sample along the equator and poles of the rolled steel ball. Figure 1 and Figure 2 Cut the slices and smooth the surface with sandpaper or grinder, mark 3 / 4, 1 / 2, 1 / 4, and center along surface A. Check the surface hardness 2-4 mm from the surface along surface B. The comparison of the corrosion results of the embodiment with comparative examples 1 and 2 is shown in Table 3.

[0047] Table 3 Surface hardness (HRC) 3 / 4 radius hardness (HRC) 1 / 2 radius hardness (HRC) 1 / 4 radius hardness (HRC) Core hardness (HRC) Average volume hardness* (HRC) Example 1 64.2 63.6 64 64.5 64 64.0 Example 2 63.7 64.5 64.5 63.7 64.2 64.3 Example 3 64.2 64.5 63.5 64 64.5 64.2 Comparative Example 1 57 61 60.8 60 58 59.8 Comparative Example 2 60.5 62 61 61.6 62 61.4 In Table 3, the average volume hardness is calculated using the formula given in the industry standard YB / T 091-2019 "Forged (Rolled) Steel Balls".

[0048] It can be seen from Table 3 that the steel balls manufactured in the embodiment are superior to ordinary forged balls and rolled balls used in the market in terms of both surface hardness and core hardness. The average volume hardness is above 64HRC, which is 2-3HRC higher than the comparative example. The high hardness means that the steel balls are more wear-resistant. The ball mill production can reduce the cycle of replacing steel balls and improve the grinding production efficiency.

[0049] Comparing the metallographic structures of Example 1 with those of Comparative Examples 1 and 2, the martensite structure of the present embodiment is relatively uniform, whether on the surface or in the core of the steel ball, and some residual austenite is distributed therein, accounting for no more than 5%. In Comparative Example 1, in addition to martensite, there are also some pearlite structures, and the structure is uneven, resulting in uneven hardness.

[0050] In addition to the above embodiments, the present invention also includes other implementation modes. Any technical solutions formed by equivalent transformation or equivalent replacement should fall within the protection scope of the claims of the present invention.

Claims

1. A corrosion-resistant grinding steel ball for mining, characterized by: The mass percentage of elemental components of steel are: C: 0.90~1.10%, Si: 0.15~0.35%, Mn: 0.90~1.10%, Cr: 0.35~0.65%, Cu: 0.20~0.40%, Ti: 0.010~0.030%, Ni: 0.15~0.30%, and the remainder is Fe and unavoidable impurity elements.

2. The corrosion-resistant mining grinding steel ball according to claim 1, characterized in that: In the steel, O≤0.0015% and H≤0.00010%.

3. The corrosion-resistant mining grinding steel ball according to claim 1, characterized in that: The diameter of the steel ball is φ25-30 mm, the final metallographic structure is martensite and residual austenite, the martensite accounts for more than 95%, the surface hardness and volume hardness are 63-66 HRC, and the corrosion rate of the 24-hour standard corrosion resistance test is no more than 7 mg / cm 2 h.

4. A method for producing the steel ball according to claim 1, characterized in that: include, Molten steel smelting: The H content in the molten steel must be ≤0.0001%. The molten steel is cast into a cross-sectional area of ​​≥5.76×10 4 mm 2 The continuous casting billet meets the following requirements: center segregation: equal to or better than level 1.0, center porosity: equal to or better than level 1.0, no center crack, corner crack and triangular crack; inclusions: A, B, D type coarse and fine series ≤ 1.5, C type coarse and fine series ≤ 0.5, Ds ≤ 1.0; Round steel rolling: heat the continuous casting billet to 1050-1150℃, keep it warm for more than 3 hours after reaching the temperature, and then carry out high-pressure water descaling treatment after the insulation is completed, and then roll it. The starting rolling temperature is 1000-1100℃, and the final rolling temperature is 900-930℃. Roll it into round steel. During the rolling process, the reduction of the first two passes of rough rolling should be ≥50%, and the reduction of the next two passes should be ≥30%. The total compression ratio of the rolled billet to the material should be ≥25; after rolling, control cooling is carried out, online slow cooling to below 400℃, air cooling, cutting, packaging and collection, and round bars with specifications of φ25-30mm are obtained; Steel ball rolling: The round steel is divided into sections, heated to 800-960℃, the average temperature is kept at 1000-1060℃, the total heating time is 40-60 minutes, and the steel ball is rolled using wedge cross rolling method, the rolling mill inclination angle is 3°-3.3°, the starting rolling temperature is 850-950℃, and the steel balls are rolled into finished product specifications.

5. The method according to claim 4, characterized in that: After rolling, the steel balls are subjected to residual heat temperature control at 760-880°C, and then put into water for quenching online. The surface temperature of the steel balls out of water is controlled at 60-100°C, and then they are put into the insulation room for self-tempering heat treatment. The self-tempering insulation temperature of the steel balls is 160-230°C.

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