A high-strength chain steel and a high-corrosion-resistant mining chain and a manufacturing method thereof

Abstract

The application discloses a high-strength chain steel and a high-corrosion-resistance mine chain and a manufacturing method thereof. The high-strength chain steel comprises the following chemical components in percentage by mass: C: 0.20-0.30%, Si: 0.05-0.6%, Mn: 1.0-1.8%, Cr: 0.4-0.8%, Ni: 0.6-1.2%, Mo: 0.5-0.9%, Ti: 0.01-0.03%, Al: 0.02-0.05%, B: 0.001-0.005%, N: 0.002-0.006%, and the balance of iron and inevitable impurities. The high-corrosion-resistance mine chain has high strength and good corrosion resistance, and can be widely applied to environments with more corrosion mediums, such as engineering machinery, mines, ships and ocean engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-strength chain steel and chain, and particularly relates to a high-strength chain steel and a high-corrosion-resistance mining chain and a manufacturing method thereof. BACKGROUND

[0002] About 1 / 6 of the annual steel production in the world is lost due to corrosion, and the direct economic loss caused by the corrosion of steel in China is more than 10 billion yuan per year. The corrosion of steel reduces the service life of steel structures, causes personnel casualties and economic losses, and emits environmental pollution. The mining round-link chain is an important component of mechanized coal mining in underground coal mines, and is mainly used as a transmission chain on a scraper conveyor, a scraper transfer machine, a coal mining machine and a coal plough. The mining round-link chain is required to have high strength and toughness, fatigue resistance, wear resistance and other properties. At present, the mining round-link chain steel commonly used in the coal mining industry is generally a mining chain steel grade in "GB / T 10560-2017 Steel for Mining Welded Round-Link Chain", wherein the high-strength mining round-link chain steel is mainly the 23MnNiMoCr54 steel (referred to as 54 steel) and other grades, and a series of high-strength mining chain steels are developed by domestic steel plants according to different needs of downstream users.

[0003] A Chinese patent with the publication number CN110714164A, the publication date of January 21, 2020 and the name of "A high-quality Cr54 steel for coal mine chain ring and a production method thereof" discloses a high-quality 54 steel for coal mine chain ring, which introduces carbon equivalent, cold crack sensitivity coefficient and hot crack sensitivity coefficient to ensure the welding performance of the chain steel and improve the cold and hot brittleness resistance of the chain steel.

[0004] A Chinese patent with the publication number CN104532143A, the publication date of April 22, 2015 and the name of "A large-specification and high-strength mining chain steel and a manufacturing method thereof" discloses an improved large-specification mining chain steel, which has a diameter of a yield strength of ≥980 MPa, a tensile strength of ≥1180 MPa, an elongation of ≥13%, a reduction of area of ≥50% and a room temperature Charpy impact energy of >100 J.

[0005] In addition, some technologies optimize the steel based on the composition of the 54 steel, such as a Chinese patent with the publication number CN111101078A, the publication date of May 5, 2020 and the name of "A nickel-free high-strength mining round-link chain steel and a production method thereof", which discloses a high-strength mining round-link chain steel without Ni element. By reducing the content of the noble metal element Ni alloy and increasing the content of C, Si, Cr and Mo alloy elements, the production cost is greatly reduced under the premise of ensuring the mechanical properties.

[0006] In view of the prior art and in combination with the current improvement schemes, it can be found that the researchers in the field mainly prepare high-strength mine chain steel through component optimization design to improve the strength and wear resistance of the mine chain prepared from the mine chain steel, so that the mine chain has a higher service life.

[0007] However, it should be noted that in actual application, the working environment in the coal mine is usually humid, the high-strength mine chain is inevitably affected by environmental corrosion during use, the high-strength mine chain is sensitive to stress corrosion due to the high stress, and corrosion fatigue fracture is easily caused during use (frequent brittle fracture occurs in several months or even several days under low load), which causes early failure of the mine chain.

[0008] Therefore, the present application aims to obtain a new mine chain steel with excellent comprehensive performance, which not only has high strength and good high-strength and high-toughness performance at a low alloy cost, but also has excellent corrosion resistance after coating treatment, thereby solving the problem of mismatch between strength and corrosion resistance of the existing mine chain. SUMMARY

[0009] In view of the problem of mismatch between strength and corrosion resistance of the existing mine chain, the present application aims to provide a high-strength chain steel and a high-corrosion-resistance mine chain and a manufacturing method thereof.

[0010] To achieve the above-mentioned object, the present application adopts the following technical scheme:

[0011] The first aspect of the present application provides a high-strength chain steel, which comprises the following chemical components in terms of mass percentage: C: 0.20-0.30%, Si: 0.05-0.6%, Mn: 1.0-1.8%, Cr: 0.4-0.8%, Ni: 0.6-1.2%, Mo: 0.5-0.9%, Ti: 0.01-0.03%, Al: 0.02-0.05%, B: 0.001-0.005%, N: 0.002-0.006%, and the balance being iron and inevitable impurities.

[0012] Preferably, the components satisfy the following requirements: 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6.

[0013] Preferably, in the inevitable impurities, P≤0.015%, S≤0.01%, O≤0.002%.

[0014] Preferably, the austenite grain size of the high-strength chain steel is≥7 grade; after quenching heat treatment and thermal coating treatment, the microstructure of the high-strength chain steel is tempered martensite and interlamellar dispersed carbide.

[0015] Preferably, after heat treatment and thermal coating treatment, the high-strength chain steel has the following properties: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, reduction of area Z≥50%, Charpy impact energy A kv ≥60J.

[0016] Preferably, after the surface of the high-strength chain steel is treated by thermal coating, the corrosion rate is≤0.2g / m 2 .h.

[0017] The second aspect of the present application provides a high-corrosion-resistance mine chain prepared from the high-strength chain steel of the first aspect of the present application, which has the following properties: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, reduction of area Z≥50%, Charpy impact energy A kv ≥60J; after 120h of 5% NaCl neutral salt spray corrosion test, the corrosion rate is≤0.2g / m 2 .h.

[0018] The third aspect of the present application provides a manufacturing method of the high-corrosion-resistance mine chain according to the second aspect of the present application, comprising the following steps:

[0019] S1, smelting and casting;

[0020] S2, heating rolling, controlling the compression ratio of the material to be≥10;

[0021] S3, ring welding;

[0022] S4, quenching heat treatment, the heating temperature of the quenching heat treatment is 850-950℃, the holding time is 1-3h, and then water quenching is adopted;

[0023] S5, pickling pretreatment;

[0024] S6, hot-dip galvanizing, the chain after the pickling pretreatment is preheated and then hot-dip galvanized to obtain the high corrosion resistance mine chain, the preheating temperature of the preheating is controlled to be -30-30℃ different from the temperature of the hot-dip galvanizing liquid used in the hot-dip galvanizing.

[0025] Preferably, in the step S1, the smelting includes electric furnace or converter smelting, LF refining, VD or RH vacuum treatment; the casting adopts continuous casting process.

[0026] Preferably, the vacuum treatment time of the VD or RH vacuum treatment is 10-20min; the superheat degree of the molten steel in the tundish is controlled to be 15-40℃ during the casting.

[0027] Preferably, in the step S2, during the heating rolling, the heating temperature of the casting blank is controlled to be ≥1150℃, the heating time is 3-6h, the finish rolling temperature is ≥850℃, and air cooling or slow cooling is adopted after rolling.

[0028] Preferably, in the step S6, the preheating temperature is 400-550℃, and the preheating time is ≥0.5h; the temperature of the hot-dip galvanizing liquid used in the hot-dip galvanizing is 400-530℃.

[0029] Preferably, the thickness of the zinc layer on the surface of the high corrosion resistance mine chain is 10-150μm.

[0030] Preferably, the microstructure of the high corrosion resistance mine chain is tempered martensite and carbonide dispersedly distributed between the layers.

[0031] Preferably, the performance of the high corrosion resistance mine chain satisfies: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A ≥14%, reduction of area Z ≥50%, Charpy impact energy A kv ≥60J at -20℃; after 5% NaCl neutral salt spray corrosion test for 120h, the corrosion rate is lower than 0.2g / m 2 .h.

[0032] In the high strength chain steel of the present application, the design principles of each chemical element are as follows:

[0033] C: In the high-strength chain steel of the present application, C is an essential element for ensuring the strength of the steel, and increasing the C content in the steel will increase the non-equilibrium structure transformation ability of the steel, thereby significantly improving the strength of the steel; in the present application, the diffusion of the C element in the steel can be inhibited by the quenching and tempering heat treatment process to form a shear type of martensite phase change, thereby significantly improving the strength of the steel. However, the C content in the steel should not be too high, and too high C content will adversely affect the plasticity and toughness of the steel, and will significantly increase the carbon equivalent of the material, thereby deteriorating the welding performance of the steel. Therefore, in the high-strength chain steel of the present application, the mass percentage of the C element is controlled to be between 0.20-0.30%.

[0034] Si: In the high-strength chain steel of the present application, the Si element can be dissolved in the steel and play a role of solid solution strengthening, which can significantly improve the yield strength, fatigue strength and hardness of the steel. The solubility of Si in cementite is very low, and the Si content in the steel should not be too high, because when the Si content in the steel is too high, not only will the bainite structure without carbide be formed, but also the brittleness of the steel will be increased. Therefore, in the high-strength chain steel of the present application, the mass percentage of the Si element is controlled to be between 0.05-0.6%.

[0035] Mn: In the high-strength chain steel of the present application, the Mn element can improve the stability of austenite in the steel, and also can improve the hardenability of the steel. In addition, Mn can also improve the strength of martensite in the steel through solid solution strengthening, thereby improving the strength of the steel. However, it should be noted that the Mn content in the steel should not be too high, because when the Mn content in the steel is too high, the austenite grains will easily grow during quenching heating, and the harmful elements will also be segregated at the grain boundaries. Therefore, in the high-strength chain steel of the present application, the mass percentage of the Mn element is controlled to be between 1.0-1.8%.

[0036] Cr: In the high-strength chain steel of the present application, adding an appropriate amount of Cr element can improve the hardenability of the steel, and has the effect of secondary hardening, which can form hardened martensite structure, thereby improving the strength of the steel. In addition, the carbide of Cr can slow down the grain growth in the heat affected zone of the welding joint, which is very beneficial to the welding of the steel; adding appropriate amount of Cr and Ni elements in the steel is beneficial to improving the corrosion resistance of the steel. However, the Cr content in the steel should not be too high, because when the Cr content in the steel is too high, a large amount of carbide will be generated and will be gathered at the grain boundaries, thereby reducing the toughness of the material and significantly increasing the carbon equivalent, thereby deteriorating the welding performance of the high-strength steel. Therefore, in the high-strength chain steel of the present application, the mass percentage of the Cr element is controlled to be between 0.4-0.8%.

[0037] Ni: In the high-strength chain steel of the present application, Ni exists in the form of solid solution in the steel as one of the main strengthening elements, and can be infinitely solid-solved with iron. When the Ni element is used in combination with the Cr element, the hardenability of the steel material is significantly improved. In addition, the addition of an appropriate amount of Ni element in the steel can also reduce the C content of the eutectoid point, strengthen the ferrite and refine and increase the pearlite, so as to improve the strength of the steel without significantly affecting the plasticity of the steel. The Ni element can improve the fatigue resistance of the steel, reduce the sensitivity of the steel to notches, reduce the low-temperature embrittlement transition temperature of the steel, and improve the impact toughness of the steel. Ni is a precious alloy element, and the addition of excessive Ni will cause the increase of the alloy cost. In the high-strength chain steel of the present application, the mass percentage of the Ni element is controlled to be between 0.6% and 1.2%.

[0038] Mo: In the high-strength chain steel of the present application, the Mo element mainly exists in the form of solid solution in the steel, which can have a solid solution strengthening effect and is beneficial to improve the hardenability of the steel material, so that the steel forms martensite during quenching. However, the Mo element content in the steel should not be too high. When the Mo element in the steel is too high, the carbon equivalent of the material will be significantly increased, which is not conducive to the welding performance of the steel material; in addition, Mo is also a precious alloy element, and the addition of excessive Mo will also cause the increase of the alloy cost. Based on this, in the high-strength chain steel of the present application, the mass percentage of the Mo element is controlled to be between 0.5% and 0.9%.

[0039] Ti: In the high-strength chain steel of the present application, Ti has a strong affinity with nitrogen, oxygen and carbon, and has a high precipitation temperature, which is a good effective element for fixing nitrogen and carbon, forms fine precipitates in the steel, and can improve the strength and toughness of the steel, especially the impact toughness at low temperature. However, when the Ti element content in the steel is too high, coarse TiN particles with edges and corners will be formed during smelting, which will reduce the impact toughness of the steel. Therefore, in the high-strength chain steel of the present application, the Ti element content is controlled to be: Ti≤0.01%.

[0040] Al: In the high-strength chain steel of the present application, the main role of Al is deoxidization and nitrogen fixation, and A1N formed by the combination of A1 and N can effectively refine the grains. However, it should be noted that the Al element content in the steel should not be too high. When the Al element content in the steel is too high, the pouring performance of the steel material will be affected, and the toughness of the steel will be damaged. Based on this, in the high-strength chain steel of the present application, the mass percentage of the Al element is controlled to be between 0.02% and 0.05%.

[0041] B: In the high-strength chain steel of the present application, the main role of B is to increase the hardenability of the steel, to increase the strength of the steel after quenching and tempering, and to slightly increase the plasticity, thereby saving other more expensive metals such as nickel, chromium, molybdenum, etc. However, the B element is relatively active, and it has a strong affinity with oxygen, nitrogen and other elements, easily forming boron oxide, boron nitride, etc., which makes the B element ineffective, increases the fluctuation of the hardenability of the steel, and affects the stability of the steel properties. B is an active and easily segregated element, which is prone to segregate at the grain boundaries and will produce temper brittleness, which is not conducive to the toughness of the steel, therefore, in the high-strength chain steel described in the present application, the content of B element is controlled to be 0.001-0.005%

[0042] N: In the high-strength chain steel of the present application, N is an austenite-forming element and also an MX precipitate-forming element, which plays a role in refining the grains; in B-containing steel, the N element in the steel will combine with the B element, thereby making the B in the steel lose its alloying effect. In order to avoid the consumption of B element by N element, the content of N element in the steel must be strictly controlled, and in the high-strength chain steel of the present application, the mass percentage content of N element is controlled to be between 0.002 and 0.006%.

[0043] For the present application, by reasonably designing the main alloying elements, the hardenability and mechanical properties of the steel are improved by adding B element, the addition amount of expensive alloy is reduced, and the influence of various alloying elements and their interactions on the microstructure and mechanical properties is fully utilized, so that the high-strength chain steel of the present application has excellent comprehensive performance.

[0044] In the preferred embodiment, in the chemical composition of the high-strength chain steel, the substitution coefficient between B element and Cr, Ni, Mo alloy satisfies:

[0045] 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6;

[0046] In the high-strength chain steel of the present application, Cr, Ni and Mo elements are important alloying elements, each element has different contribution to the strength and toughness and hardenability of the chain steel, and excessive addition of expensive alloying elements will greatly increase the cost of the steel. Therefore, in the high-strength chain steel, appropriate amounts of Cr, Ni and Mo elements are added and interact with the addition of trace B element in the steel, when the substitution coefficient between B element and Cr, Ni and Mo alloy satisfies 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6, the B element can be solid-solved in the matrix, segregated at the austenite grain boundary, improve the stability of austenite, increase the hardenability of the steel during the heat treatment of the chain, and make the steel have better comprehensive properties of high strength and high toughness. When 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)<6, the content of B element added in the steel is low, which cannot improve the hardenability of the steel, in order to ensure that the chain steel obtains good high-strength and high-toughness properties during heat treatment, expensive alloying elements must be added, which increases the production cost of the chain.

[0047] In the high-strength chain steel of the present application, for unavoidable impurities, P≤0.015%, S≤0.01%, O≤0.002%. Among them, P element, S element and O element are all impurity elements in the steel, in the case of technical conditions, in order to obtain high-strength chain steel with better performance and quality, the content of impurity elements in the material should be as low as possible. In the high-strength chain steel of the present application, P element and S element are both harmful impurity elements in the steel, and will deteriorate the performance of the steel, although P element can improve the weather resistance of the steel, but overall its side effects are greater, therefore in the present application, P element is controlled to satisfy: P≤0.015%, and S element is controlled to satisfy: S≤0.01%. Correspondingly, in the present application, impurity element O can form oxide and compound inclusions with deoxidizing elements such as Ti, B and Al in the steel, which is not conducive to the performance of the steel, therefore in the present application, O element is controlled to satisfy: O≤0.002%.

[0048] Of course, in some other embodiments, other harmful elements such as As, Pb, Sn, Sb, Bi and the like may also exist in the steel, under the requirements of national laws, regulations and standards, the content of these harmful elements should be as low as possible.

[0049] Compared with the existing production technology, the present application has the following beneficial effects:

[0050] 1、The high strength chain steel provided by the present application has excellent comprehensive performance, and the chain has excellent corrosion resistance after on-line quenching and hot-dip galvanizing treatment, because the addition of B element improves the hardenability and mechanical properties of the steel, reduces the amount of expensive alloy, and makes full use of the influence of various alloy elements and their interaction on microstructure and mechanical properties.

[0051] 2、The zinc layer on the surface of the chain can prevent the chain from contacting corrosive medium and improve the corrosion resistance of the chain.

[0052] 3、The chemical composition and process design of the high strength chain steel are reasonable, and the process window is wide, so that batch commercial production can be realized.

[0053] 4、The high strength chain steel and the chain have excellent high strength and toughness and good corrosion resistance, and can be made into high strength corrosion-resistant structural parts and various mining, mooring and other high-performance industrial chains, and are widely used in engineering machinery, mining and ocean engineering and other places requiring high strength and toughness and high corrosion resistance.

[0054] 5、The high strength chain steel has high strength, toughness and plasticity, and excellent corrosion resistance, and has a very broad application prospect. DETAILED DESCRIPTION

[0055] In order to better understand the above technical solutions of the present application, the technical solutions of the present application will be further described below in combination with examples.

[0056] The high strength chain steel provided by the present application has excellent comprehensive performance, and the chain has excellent corrosion resistance after on-line quenching and hot-dip galvanizing treatment, because the addition of B element improves the hardenability and mechanical properties of the steel, reduces the amount of expensive alloy, and makes full use of the influence of various alloy elements and their interaction on microstructure and mechanical properties.

[0057] The application improves the performance of the steel by adding B element and reducing the addition amount of expensive alloy, fully utilizes the influence of various alloy elements and their interaction on microstructure and mechanical properties, and precisely controls the microstructure of the steel to ensure that the high-strength chain steel of the application forms a mixed structure of tempered martensite and interlamellar dispersed carbides, which can make the high-strength steel of the application have higher strength and toughness and plasticity matching, and good wear resistance and fatigue resistance.

[0058] In specific embodiments, the composition of the high-strength chain steel satisfies the following requirements:

[0059] 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6;

[0060] In the application, Cr, Ni and Mo are important alloying elements, each element has different contribution to the strength and toughness and hardenability of the high-strength chain steel, and excessive addition of expensive alloying elements will greatly increase the cost of the steel. Therefore, appropriate amounts of Cr, Ni and Mo are added to the steel and interact with the trace amount of B element added in the steel, when the substitution coefficient between B element and Cr, Ni and Mo alloy satisfies 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6, the B element can be solid-solved in the matrix, segregated at the austenite grain boundary, improve the stability of austenite, increase the hardenability of the steel during heat treatment of the chain, and make the steel have better comprehensive performance of high strength and high toughness. When 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)<6, the content of B element added in the steel is low, which cannot improve the hardenability of the steel, in order to ensure that the chain steel has good high strength and high toughness performance during heat treatment, expensive alloy elements must be added, which increases the production cost of the chain.

[0061] In the application, P element, S element and O element are impurity elements in the steel, in the case of technical conditions, in order to obtain high-strength steel with better performance and quality, the content of impurity elements in the material should be reduced as much as possible; among them, P element and S element are inevitable harmful impurity elements in the steel, and both will deteriorate the performance of the steel, although P element can improve the weather resistance of the steel, but overall, its side effects are greater, therefore, among the inevitable impurities, P≤0.015%, S≤0.01%; correspondingly, impurity element O can form oxide and complex inclusions with Ti, B, Al and other deoxidizing elements in the steel, which is not conducive to the performance of the steel, therefore, O≤0.002%.

[0062] In specific embodiments, the high-strength chain steel has an austenite grain size of ≥ 7, and after quenching and thermal coating treatment, the microstructure of the high-strength chain steel is tempered martensite and interlaminar dispersed carbides.

[0063] After quenching and thermal coating treatment, the high-strength mining chain steel has the following properties: yield strength Rp 0.2 ≥ 1050 MPa, tensile strength R m ≥ 1200 MPa, elongation A ≥ 14%, reduction of area Z ≥ 50%, Charpy impact energy A kv ≥ 60 J.

[0064] After the surface of the high-strength mining chain steel is treated by thermal coating, the corrosion rate is ≤ 0.2 g / m 2 .h.

[0065] The application provides a high-corrosion-resistance mining chain made of the high-strength chain steel, which has the following properties: yield strength Rp 0.2 ≥ 1050 MPa, tensile strength R m ≥ 1200 MPa, elongation A ≥ 14%, reduction of area Z ≥ 50%, Charpy impact energy A kv ≥ 60 J; and after 120 h of neutral salt spray corrosion test in 5% NaCl, the corrosion rate is ≤ 0.2 g / m 2 .h.

[0066] The application also provides a manufacturing method of the high-corrosion-resistance mining chain, which is simple and easy to produce, and the obtained high-strength steel chain has excellent high-strength toughness and good corrosion resistance;

[0067] The high-strength chain steel and the manufacturing method of the high-corrosion-resistance mining chain specifically include the following steps:

[0068] S1, smelting and casting;

[0069] Specifically, the smelting operation includes electric furnace or converter smelting, LF refining, VD or RH vacuum treatment; that is, smelting is performed by using an electric furnace or a converter, and LF refining, VD or RH vacuum treatment is performed, wherein the vacuum treatment time is 10-20 min, and after the chemical composition meets the requirements of the high-strength chain steel, the molten steel is tapped for casting; correspondingly, in the casting process, the continuous casting process is used to cast an ingot blank, the overheat degree of the tundish molten steel is controlled to be 15-40 ℃, and finally a cast blank with a chemical composition meeting the high-strength chain steel is obtained.

[0070] S2, heating and rolling, and controlling the compression ratio of the material to be ≥ 10;

[0071] Specifically, the cast blank is heated in a heating furnace, and then discharged to start rolling after high-pressure water dephosphorization, and the cast blank is rolled to obtain round steel of finished size, i.e. high-strength chain steel, the heating temperature of the cast blank is controlled to be greater than or equal to 1150 ℃, the heating time is 3-6 h, and the finish rolling temperature is greater than or equal to 850 ℃; the round steel is air-cooled or slowly cooled to room temperature after rolling; wherein, the compression ratio of the material in the rolling process is greater than or equal to 10; the finished size specification of the high-strength chain steel is Φ30-150 mm.

[0072] S3, ring welding: the high-strength chain steel is cut into a fixed length, and then welded into a complete circular chain on a braiding machine by using flash welding.

[0073] S4, quenching heat treatment, the heating temperature of the quenching heat treatment is 850-950 ℃, the holding time is 1-3 h, and the chain is water-cooled after heating;

[0074] Specifically, the ring-welded chain is subjected to quenching heat treatment, the heating temperature of the quenching heat treatment is 850-950 ℃, the holding time is 1-3 h, and then water-cooling is performed; when the chain is heated at a high temperature, fine austenite grains are formed in the steel, and the austenite grain size is greater than or equal to 7 levels; after quenching, the structure of the chain is transformed from austenite structure at high temperature to fine needle-shaped martensite structure.

[0075] S5, pickling pretreatment: the chain after quenching heat treatment is subjected to pickling pretreatment to remove the oxide skin on the surface of the chain after quenching, and a layer of plating aid liquid is coated on the surface of the chain, so that the surface of the chain after pickling can maintain a certain activity, avoid oxidation of the chain in the subsequent preheating process, and enhance the bonding force between the zinc plating layer and the substrate.

[0076] S6, hot-dip galvanizing, the chain after pickling pretreatment is subjected to preheating treatment, and then subjected to hot-dip galvanizing to obtain a high-corrosion-resistance mining chain, and the temperature difference between the preheating temperature of the preheating treatment and the temperature of the hot-dip galvanizing liquid used in the hot-dip galvanizing is controlled to be-30-30 ℃.

[0077] Specifically, in order to prevent problems such as zinc explosion during hot-dip galvanizing, the chain after pickling pretreatment is subjected to preheating treatment, and then subjected to hot-dip galvanizing to obtain a high-corrosion-resistance mining chain; the temperature difference between the preheating temperature of the chain and the temperature of the hot-dip galvanizing liquid used in the hot-dip galvanizing is controlled to be-30-30 ℃; wherein, the preheating temperature is 400-550 ℃, and the preheating time is greater than or equal to 0.5 h; the temperature of the hot-dip galvanizing liquid used in the hot-dip galvanizing is 400-530 ℃, and the thickness of the zinc layer on the surface of the high-corrosion-resistance mining chain is controlled to be 10-150 μm.

[0078] In the hot-dip galvanizing process, the supersaturated martensite structure formed after quenching of the chain begins to precipitate fine carbides, the strength of the chain decreases, but the elongation and impact toughness begin to increase. The fine martensite needle is conducive to the precipitation of fine and dispersed carbides from the steel during hot-dip galvanizing, and a high-strength chain with excellent strength and toughness is obtained.

[0079] The microstructure of the high-corrosion-resistance mine chain described above is tempered martensite and interlamellar dispersed carbides.

[0080] The performance of the high-corrosion-resistance mine chain described above meets: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A ≥14%, reduction of area Z ≥50%, Charpy impact energy A kv ≥60J at -20℃; after 120h of neutral salt spray corrosion test in 5% NaCl, the corrosion rate is less than 0.2g / m 2 .h.

[0081] The present application fully utilizes various alloying elements and the influence of the preparation process of the high-corrosion-resistance mine chain on the microstructure by reasonable design of alloying elements and optimization of the preparation process, and accurately controls the microstructure of the high-strength chain steel. After quenching heat treatment, the high-strength chain steel forms a needle-shaped martensite structure. Through hot-dip galvanizing treatment of the chain after quenching, on the one hand, fine and dispersed carbides can be precipitated from the chain steel during hot-dip galvanizing, and the strength and toughness of the chain can be improved; on the other hand, a certain thickness of zinc layer can be formed on the surface of the chain, thereby improving the corrosion resistance of the chain.

[0082] In the chain preparation process of the present application, the quenching and tempering process of the traditional chain is combined with the hot-dip galvanizing process, the tempering process of the chain is saved, the precipitation of carbides in the steel during hot-dip galvanizing of the chain is fully utilized, and efficient production of high-strength corrosion-resistant chains is realized, so that the high-strength chain steel has high strength and toughness and plasticity matching, and good corrosion resistance.

[0083] The high-strength chain steel and the high-corrosion-resistance mine chain and the manufacturing method thereof of the present application will be further described below with specific examples.

[0084] Examples

[0085] As shown in Table 1, Table 2-1 and Table 2-2, the high-strength chain steel and the high-corrosion-resistance mine chain of Examples 1-6 are prepared by the following steps:

[0086] (1) The cast billets are obtained by smelting and continuous casting according to the chemical composition shown in Table 1 below. The smelting can be carried out by electric furnace or converter smelting, and after LF refining and VD or RH vacuum treatment, the vacuum treatment time is 10-20 min, and after the composition meets the requirements, the molten steel is discharged, and then continuous casting can be used to cast the cast billets. The molten steel overheat degree in the tundish is controlled to be 15-40℃ during continuous casting.

[0087] (2) Heating and rolling: After heating the cast billets in the heating furnace, the high-strength chain steel of finished size is obtained by high-pressure water phosphorus removal, that is, the high-strength chain steel is rolled to finished size after heating, and the rolling finished size specification range is Φ30-150mm, and the material compression ratio is controlled to be ≥10. In the rolling process, the cast ingot is heated and rolled to finished size, the cast billet heating temperature is controlled to be ≥1150℃, the heating time is 3-6h, and the finish rolling temperature is ≥850℃; after rolling, air cooling or slow cooling to room temperature.

[0088] (3) Ring weaving and welding: the high-strength chain steel is cut into a certain length of round steel, and then is woven into a single ring on a weaving machine, and then is welded into a complete circular ring chain by flash welding.

[0089] (4) Quenching heat treatment: the chain after ring weaving and welding is subjected to quenching heat treatment, the heating temperature of quenching heat treatment is controlled to be 850-950℃, the holding time is 1-3h, and then water quenching is carried out.

[0090] (5) Pickling pretreatment: the chain after quenching is pickled to remove the scale on the surface of the chain; then the pickled chain is preheated to prevent problems such as zinc explosion in the subsequent hot-dip galvanizing process, the chain preheating temperature is 400-550℃, the preheating time is ≥0.5h, and the temperature difference between the chain preheating temperature and the temperature of the zinc liquid used in the subsequent hot-dip galvanizing is not higher than ±30℃.

[0091] (6) Hot-dip galvanizing: the preheated chain is subjected to hot-dip galvanizing, the zinc liquid temperature is 400-530℃, and the thickness of the zinc layer on the surface of the chain is controlled to be 10-150μm.

[0092] The chemical composition design and related process of the high-strength chain steels of examples 1-6 and the high-corrosion-resistance mining chains meet the design specification requirements of the present application. The comparative steels of comparative examples 1-2 belong to finished steels from different manufacturers, the chemical composition design thereof can be seen from Table 1 below, and the processing technology thereof is different from the preparation process of examples 1-6. The heat treatment process adopted by the comparative steels of comparative examples 1-2 refers to the parameters recommended by the supplier, and the specific values are shown in Table 2-1 and Table 2-2.

[0093] Table 1 Chemical composition of chain steel (wt.%, the balance is Fe and other impurities except P and S)

[0094]

[0095] Table 2-1 Process parameters during preparation of examples and comparative examples

[0096]

[0097] Table 2-2 Process parameters during preparation of examples and comparative examples

[0098]

[0099] The plated finished chains of examples 1-6 and the comparative chains of comparative examples 1-2 were collected and further tested for performance to obtain the performance of the finished chains of examples and comparative examples.

[0100] In the present application, the high-strength steel materials of examples 1-6 and the comparative steel materials of comparative examples 1-2 were respectively subjected to neutral salt spray corrosion test, tensile test and impact performance test, and the test results are listed in Table 3.

[0101] The specific detection means of the relevant neutral salt spray corrosion test, tensile test and impact test are as follows:

[0102] (1) The neutral salt spray corrosion test was carried out by the following steps: 100 mm long round steel was taken from the plated finished chains of examples 1-6 and the chains of comparative examples 1-2 as salt spray corrosion samples, the two end faces were closed with silicone rubber, and 5wt% NaCl salt spray corrosion test was carried out according to GB / T10125 standard (laboratory temperature 35℃, saturated barrel temperature 47℃, corrosion medium 5wt.% NaCl aqueous solution, pH=6.5, test sample longitudinal angle 20°, test time 120h, continuous spraying mode, salt spray deposition 1.5mL / (h·80cm 2 )) was used. After 120h neutral salt spray test, the test sample was taken out, the two end silicone rubbers were peeled off, the surface corrosion products were removed, the sample was blown dry and weighed as M', then the salt spray corrosion rate R of each example and comparative example sample was calculated:

[0103] R=(M-M') / (S·T)

[0104] Wherein, M is the initial mass of the sample, with the dimension of g; M' is the mass of the sample after removing the corrosion products and blowing dry, with the dimension of g; S is the corrosion test area of the sample, with the dimension of m 2 ; T is the corrosion time, with the dimension of h; the salt spray corrosion rate R has the dimension of g / m 2 .h.

[0105] Tensile test: the plated finished chain of examples 1-6 and the chain of comparative examples 1-2 were sampled according to national standard GB / T 2975 to make tensile test samples, and the tensile property test was carried out according to GB / T 228.1 national standard to measure the yield strength Rp 0.2 , tensile strength R m , elongation A and reduction of area Z of the finished chain of examples 1-6 and the chain of comparative examples 1-2.

[0106] Impact test: the plated finished chain of examples 1-6 and the chain of comparative examples 1-2 were sampled according to national standard GB / T 2975 to make impact test samples, and the impact property test was carried out according to GB / T 229 national standard to measure the low temperature impact energy A kv of the plated finished chain of examples 1-6 and the chain of comparative examples 1-2.

[0107] Table 3: properties of the chain of examples and comparative examples

[0108]

[0109]

[0110] In combination with Table 3, the high corrosion resistant mine chain of examples 1-6 has excellent comprehensive properties, the yield strength Rp 0.2 is between 1076-1185 MPa, the tensile strength R m is between 1212-1315 MPa, the elongation A is ≥14%, the reduction of area Z is ≥50%, and the Charpy impact energy A kv at -20℃ is ≥60 J. The neutral salt spray corrosion rate of the high corrosion resistant mine chain of examples 1-6 is ≤0.19 g / m 2 .h, which is much lower than the neutral salt spray corrosion rate of the comparative chain of comparative examples 1-2. Therefore, it can be seen that the corrosion resistance of the high strength chain steel of the present application after heat treatment and hot dip galvanizing is obviously superior to the existing comparative steel material selected in comparative examples 1-2.

[0111] It can be seen from the above that the high corrosion resistance mine chain with excellent performance can be obtained by the reasonable chemical component design, the combination of the chain heat treatment and the subsequent galvanizing process, the formation of the optimized quenching heat treatment and the hot dip galvanizing process. The high strength chain steel has excellent comprehensive performance, has higher strength, has excellent toughness plasticity matching, has excellent corrosion resistance after being made into the mine chain, and can well solve the problem that the service life is affected by the mismatching of the strength, the toughness plasticity and the corrosion resistance of the existing mine chain. The high strength chain steel can be made into various high performance industrial chains such as mine chains and mooring chains, and is widely applied to occasions needing high strength toughness and high corrosion resistance chains such as engineering machinery, mines and ocean engineering.

[0112] It should be noted that those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not used as the limitation of the present application, and the changes and modifications of the above described embodiments within the scope of the spirit of the present application will fall within the scope of the claims of the present application.

Claims

1. A high strength chain steel characterized by, comprises the following chemical components in mass percentage: C: 0.20-0.30%, Si: 0.05-0.6%, Mn: 1.0-1.8%, Cr: 0.4-0.8%, Ni: 0.6-1.2%, Mo: 0.5-0.9%, Ti: 0.01-0.03%, Al: 0.02-0.05%, B: 0.001-0.005%, N: 0.002-0.006%, the balance being iron and inevitable impurities, The austenite grain size of the high-strength chain steel is greater than or equal to 7 levels; and after quenching heat treatment and hot plating treatment, the microstructure of the high-strength chain steel is tempered martensite and interlaminar dispersed carbide. After quenching and heat treatment, its properties meet the following requirements: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, reduction of area Z≥50%, Charpy impact energy A at -20℃ kv ≥60J; The high-strength chain steel surface is treated by hot coating plating, and after 120h of 5% NaCl neutral salt spray corrosion test, the corrosion rate is ≤0.2g / m 2 ·h.

2. The high strength chain steel of claim 1, wherein, The components satisfy the following requirements: 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6.

3. The high strength chain steel of claim 1, wherein, In the inevitable impurities, P≤0.015%, S≤0.01%, O≤0.002%.

4. A high corrosion resistant mining chain made of the high strength chain steel according to any one of claims 1 to 3, characterized in that, Its properties satisfy: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, reduction of area Z≥50%, Charpy impact energy A at -20℃ kv ≥60J; after 120h of neutral salt spray corrosion test in 5% NaCl, its corrosion rate is ≤0.2g / m³. 2 ·h.

5. A method of manufacturing a high corrosion resistant mine chain as claimed in claim 4, characterized by, The method comprises the following steps: S1, smelting and casting; S2, heating rolling, the compression ratio of the material is controlled to be greater than or equal to 10; S3, ring welding; S4, quenching heat treatment, the heating temperature of the quenching heat treatment is 850-950℃, the holding time is 1-3h, and then water quenching is adopted; S5, pickling pretreatment; S6, hot-dip galvanizing, the chain after the pickling pretreatment is preheated and then hot-dip galvanized to obtain the high-corrosion-resistance mine chain, and the temperature difference between the preheating temperature of the preheating treatment and the temperature of the hot-dip galvanizing solution used in the hot-dip galvanizing is controlled to be-30-30℃.

6. The manufacturing method of the high-corrosion-resistance mine chain according to claim 5, characterized in that, In the step S1, the smelting comprises electric furnace or converter smelting, LF refining, VD or RH vacuum treatment, and the casting adopts continuous casting process, wherein the vacuum treatment time of the VD or RH vacuum treatment is 10-20min, and the superheat degree of the molten steel in the tundish is controlled to be 15-40℃ during the casting; In the step S2, during the heating rolling, the heating temperature of the cast blank is controlled to be greater than or equal to 1150℃, the heating time is 3-6h, and the final rolling temperature is greater than or equal to 850℃, and then air cooling is adopted after rolling; In the step S6, the preheating temperature is 400-550℃, and the preheating time is greater than or equal to 0.5h; and the temperature of the hot-dip galvanizing solution used in the hot-dip galvanizing is 400-530℃.

7. The method of manufacturing a high corrosion-resistant mine chain according to claim 5, characterized by, The thickness of the zinc layer on the surface of the high-corrosion-resistance mine chain is 10-150μm.

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