High-strength chain steel, high-corrosion-resistance ore chain and manufacturing method therefor

Abstract

Disclosed in the present invention are a high-strength chain steel, a high-corrosion-resistance ore chain and a manufacturing method therefor. The 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 being iron and inevitable impurities. The high-corrosion-resistance ore chain of the present invention has both high strength and good corrosion resistance, and can be widely applied in environments with more corrosive media such as engineering machinery, mines, ships and ocean engineering.

Description

High-strength chain steel, high-corrosion-resistant mining chain and manufacturing method thereof Technical Field

[0001] The present invention relates to the technical field of high-strength chain steel and chains, and in particular to a high-strength chain steel, a high-corrosion-resistant mining chain and a manufacturing method thereof. Background Art

[0002] Approximately one-sixth of the world's annual steel production is lost due to corrosion. In my country, direct economic losses from steel corrosion exceed 10 billion yuan annually. Furthermore, steel corrosion reduces the service life of steel structures, causes casualties and economic losses, and contributes to environmental pollution through emissions. Mining round-link chains are essential components for mechanized coal mining in underground coal mines, primarily serving as transmission chains for scraper conveyors, scraper transfer machines, shearers, and plows. They require high strength, toughness, fatigue resistance, and wear resistance. Currently, the mining round-link chain steel commonly used in the coal mining industry is typically the steel grades specified in "GB / T 10560-2017 Steel for Welded Round-Link Mining Chains." Among these, high-strength mining round-link chain steel grades such as 23MnNiMoCr54 (abbreviated as 54 steel) are the most widely used. Furthermore, to meet the demands of actual applications, major domestic steel mills have also developed a series of high-strength mining chain steels tailored to the diverse needs of downstream users.

[0003] A Chinese patent with publication number CN110714164A (publication date January 21, 2020, entitled "A high-quality Cr54 steel for coal mine chain links and its production method") discloses a high-quality 54 steel for coal mine chain links, 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] The Chinese patent with publication number CN104532143A (published on April 22, 2015, entitled "A large-size, high-strength mining chain steel and its manufacturing method") discloses an improved large-size mining chain steel with a diameter of Yield strength ≥980MPa, tensile strength ≥1180MPa, elongation ≥13%, cross-sectional shrinkage ≥50%, room temperature Charpy impact energy>100J.

[0005] In addition, there are some technologies that optimize steel based on the composition of 54 steel. For example, the Chinese patent with publication number CN111101078A (publication date May 5, 2020, named "A nickel-free high-strength mining round link chain steel and its production method") discloses a high-strength mining round link chain steel that does not contain Ni elements. It reduces the alloy content of the precious metal element Ni and increases the alloy content of C, Si, Cr, and Mo, thereby greatly reducing production costs while ensuring mechanical properties.

[0006] Referring to the above-mentioned prior art and combining it with many current improvement schemes, it is not difficult to find that researchers in this field mainly prepare higher-strength mining chain steel through component optimization design to improve the strength and wear resistance of the mining chain made of mining chain steel, so as to obtain a longer service life.

[0007] However, it should be noted that in actual use, underground coal mines are often humid working environments. High-strength mining chains are inevitably subject to environmental corrosion during use. Furthermore, high-strength mining chains are subject to high stress and are sensitive to stress corrosion. This can easily lead to corrosion fatigue fractures during use (frequent low-load brittle fractures can occur within a few days or several months), leading to premature failure of mining chains.

[0008] Based on this, the present invention aims to develop a new mining chain steel with excellent overall performance. This steel not only has high strength, but also achieves high strength and toughness at a low alloy cost. Furthermore, after being plated, the chain exhibits excellent corrosion resistance, effectively resolving the problem of existing mining chains suffering from a mismatch between strength and corrosion resistance, which limits their service life.

[0009] Summary of the Invention

[0010] To address the problem of existing mining chains in the prior art, which suffers from a mismatch between strength and corrosion resistance, thus shortening their service life, the present invention provides a high-strength chain steel, a highly corrosion-resistant mining chain, and a method for manufacturing the same. This high-strength chain steel reduces the amount of expensive alloys added, and, when combined with a specialized coating process, the resulting chain exhibits not only excellent overall strength and toughness, but also excellent corrosion resistance, making it suitable for widespread use in environments with a high concentration of corrosive media, such as construction machinery, mining, shipbuilding, and marine engineering.

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] A first aspect of the present invention provides a chain steel, which contains the following chemical components in percentage by mass: C: 0.20-0.30%, Si: 0.05-0.6%, preferably 0.15-0.6%, 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 is iron and unavoidable impurities.

[0013] Preferably, the chemical composition of the chain steel satisfies the following formula: 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6, more preferably 6≤30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≤24.43, where the symbols of each element are substituted into the numerical values ​​before the mass percentage of the corresponding element.

[0014] Preferably, among the unavoidable impurities, P≤0.015%, S≤0.01%, and O≤0.002%.

[0015] Preferably, the microstructure of the chain steel is acicular martensite.

[0016] Preferably, the chain steel has the following properties: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, section shrinkage Z≥50%, -20℃ Charpy impact energy A kv ≥60J.

[0017] A second aspect of the present invention provides a chain comprising: the above-mentioned chain steel and a galvanized layer coated on the chain steel.

[0018] Preferably, the thickness of the zinc plating layer in the chain is 10 to 150 μm, preferably 40 to 150 μm.

[0019] Preferably, the microstructure of the chain steel in the chain is tempered martensite and carbides dispersed between lamellae.

[0020] Preferably, the chain has the following properties: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, section shrinkage Z≥50%, -20℃ 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.

[0021] A third aspect of the present invention provides a method for manufacturing the above-mentioned chain, the manufacturing method comprising the following steps performed in sequence:

[0022] S1, smelting and casting molten steel to produce ingots;

[0023] S2, hot rolling the cast slab, wherein the compression ratio of the cast slab is ≥10;

[0024] S3, ring welding;

[0025] S4, quenching heat treatment, the heating temperature of the quenching heat treatment is 840-980°C, preferably 850-950°C, the holding time is 1-4h, preferably 1-3h, and then water cooling quenching is adopted;

[0026] S5, pickling pretreatment to produce chain steel;

[0027] S6, hot-dip galvanizing, the chain steel after the pickling pretreatment is preheated and then hot-dip galvanized to obtain a chain including chain steel and a galvanized layer formed on the chain steel, wherein the difference between the preheating temperature of the preheating treatment and the temperature of the galvanizing solution used for the hot-dip galvanizing is -30 to 30°C.

[0028] Preferably, in step S1, the smelting includes electric furnace or converter smelting, LF refining, VD or RH vacuum treatment; and the casting adopts a continuous casting process.

[0029] Preferably, the vacuum treatment time of the VD or RH vacuum treatment is 10 to 20 minutes; and the superheat of the molten steel in the tundish is controlled to be 15 to 40° C. during the casting process.

[0030] Preferably, in step S2, during the heating and rolling process, the heating temperature of the ingot is ≥1150°C, the heating time is 3-6 hours, the final rolling temperature is ≥850°C, and air cooling or slow cooling is adopted after rolling.

[0031] Preferably, in step S6, the preheating temperature is 400-550°C, and the preheating time is ≥0.5h; and the temperature of the galvanizing solution used in the hot-dip galvanizing is 400-530°C.

[0032] Preferably, the thickness of the zinc plating layer is 10 to 150 μm, preferably 40 to 150 μm.

[0033] Preferably, the microstructure of the chain steel in the chain obtained in step S6 is tempered martensite and carbides dispersed between lamellae.

[0034] Preferably, the chain has the following properties: yield strength Rp 0.2≥1050MPa, tensile strength Rm ≥1200MPa, elongation A ≥14%, section shrinkage Z ≥50%, -20℃ Charpy impact energy Akv ≥60J; after 120h of 5% NaCl neutral salt spray corrosion test, the corrosion rate is less than 0.2g / m 2 .h.

[0035] In the high strength chain steel of the present invention, the design principle of each chemical element is as follows: In this document, unless otherwise explicitly stated, the element content is expressed in mass percentage.

[0036] C: C is an element necessary to ensure the strength of steel. Increasing the C content in steel will increase the steel's ability to undergo non-equilibrium structural transformations, thereby significantly improving the steel's strength. In the present invention, the diffusion of C in steel can be suppressed by a quenching heat treatment process to form a shear-type martensitic phase transformation, thereby significantly improving the steel's strength. However, the C content in steel should not be too high. Excessive C content will have an adverse effect on the plasticity and toughness of the steel, and will significantly increase the carbon equivalent of the material, deteriorating the steel's welding performance. Based on this, in the high-strength chain steel of the present invention, the mass percentage of C is controlled to be between 0.20 and 0.30%.

[0037] Si: The Si element can be dissolved in steel and play a role in solid solution strengthening, which can significantly improve the yield strength, fatigue strength and hardness of the steel. However, the solubility of Si in cementite is very low, and the Si content in the steel should not be too high. When the Si content in the steel is too high, not only will a carbide-free bainite structure be formed, but the brittleness of the steel will also be increased. Based on this, in the high-strength chain steel of the present invention, the mass percentage of the Si element is controlled between 0.05 and 0.6%, preferably between 0.15 and 0.6%.

[0038] Mn: The Mn element can improve the stability of austenite in steel and at the same time improve the hardenability of steel. In addition, Mn can also improve the strength of martensite in steel through solid solution strengthening, thereby improving the strength of steel. However, it should be noted that the Mn content in steel should not be too high. When the Mn content in steel is too high, it will make the austenite grains grow easily during quenching heating and promote the segregation of harmful elements at the grain boundaries. Based on this, in the high-strength chain steel of the present invention, the mass percentage of the Mn element is controlled between 1.0 and 1.8%.

[0039] Cr: Adding an appropriate amount of Cr element can improve the hardenability of steel and has a secondary hardening effect. It can form a hardened martensitic structure, which is beneficial to improving the strength of steel. In addition, Cr carbides can slow down the grain growth in the heat-affected zone at the weld joint, which is very beneficial for the welding of steel; adding an appropriate amount of Cr and Ni elements to the steel is beneficial to improving the corrosion resistance of the steel. However, the Cr content in the steel should not be too high. When the Cr content in the steel is too high, a large amount of carbides will be generated and aggregated at the grain boundaries, reducing the toughness of the material and significantly increasing the carbon equivalent, deteriorating the welding performance of high-strength steel. Based on this, in the high-strength chain steel of the present invention, the mass percentage of Cr element is controlled between 0.4 and 0.8%.

[0040] Ni: As one of the main strengthening elements, Ni can exist in steel in the form of solid solution and can be infinitely solid-solved with iron. When Ni is used in combination with Cr, the hardenability of the steel will be significantly improved. In addition, adding an appropriate amount of Ni to the steel can also reduce the C content of the eutectic point, strengthen the ferrite and refine and increase the pearlite, which can improve the strength of the steel without significantly affecting the plasticity of the steel. Ni can improve the fatigue resistance of steel, reduce the sensitivity of steel to notches, lower the low-temperature brittle transition temperature of steel, and improve the impact toughness of steel. However, Ni is a precious alloy element, and adding excessive Ni will lead to an increase in alloy costs. Therefore, in the high-strength chain steel of the present invention, the mass percentage of Ni is controlled between 0.6 and 1.2%.

[0041] Mo: Mo exists primarily in steel in solid solution form, providing solid solution strengthening, improving the hardenability of the steel and allowing it to form martensite during quenching. However, the Mo content in steel should not be too high. Excessive Mo content significantly increases the carbon equivalent of the material, negatively impacting the weldability of the steel. Furthermore, Mo is a precious alloying element, and adding excessive amounts can increase alloy costs. Therefore, in the high-strength chain steel of the present invention, the mass percentage of Mo is controlled between 0.5% and 0.9%.

[0042] Ti: Ti has a strong affinity for nitrogen, oxygen, and carbon, and its precipitation temperature is relatively high. It is an effective element for fixing nitrogen and carbon, forming fine precipitates in steel, which can improve the steel's strength and toughness, particularly its impact toughness at low temperatures. However, excessive Ti content in steel can lead to the formation of coarse, angular TiN particles during the smelting process, reducing the steel's impact toughness. Therefore, in the high-strength chain steel of the present invention, the Ti content is controlled to 0.01-0.03%.

[0043] Al: Al's primary functions are deoxidation and nitrogen fixation. Al combined with nitrogen to form AlN effectively refines grains. However, it's important to note that excessive Al content in steel is not recommended. Excessive Al content can affect the steel's casting properties and compromise its toughness. Therefore, in the high-strength chain steel of the present invention, the mass percentage of Al is controlled between 0.02% and 0.05%.

[0044] B: The main function of B is to increase the hardenability of steel, improve the strength of steel after quenching and tempering, and slightly improve the plasticity, thereby saving other relatively rare and precious metals, such as nickel, chromium, molybdenum, etc. However, the B element is relatively active, and it has a strong affinity with elements such as oxygen and nitrogen. It is easy to form boron oxide, boron nitride, etc., which makes the B element ineffective, increases the fluctuation of the hardenability of steel, and affects the stability of steel performance. B is an active and easily segregated element. It is easy to segregate at the grain boundary and will produce temper brittleness, which is not good for the toughness of steel. Therefore, in the high-strength chain steel described in the present invention, the B element content is controlled to be: 0.001-0.005%

[0045] N: N is an austenite-forming element and also forms MX-type precipitates, contributing to grain refinement. However, in B-containing steels, N combines with B, depleting the B's alloying properties. To prevent N from consuming B, the N content in the steel must be strictly controlled. Therefore, in the high-strength chain steel of the present invention, the N content is controlled to between 0.002% and 0.006% by weight.

[0046] The present invention improves the hardenability and mechanical properties of steel by rationally designing the main alloying elements and adding the element B, reduces the amount of expensive alloy added, and fully utilizes the effects of various alloying elements and their interactions on microstructure and mechanical properties, so that the high-strength chain steel of the present invention has excellent comprehensive performance.

[0047] In a preferred embodiment, in the chemical composition of the chain steel, the B element satisfies the following formula with Cr, Ni, and Mo:

[0048] 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6, preferably 6≤30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≤24.43, where the symbols of each element are substituted into the corresponding numerical values ​​before the mass percentage of each element.

[0049] In the high-strength chain steel of the present invention, Cr, Ni, and Mo are important alloying elements. The contribution of each element to the toughness and hardenability of the chain steel varies, but excessive addition of expensive alloying elements will significantly increase the cost of the steel. Therefore, appropriate amounts of Cr, Ni, and Mo are added to the chain steel of the present invention, and these elements interact with the trace B element added to the steel. When the B element and the Cr, Ni, and Mo elements meet the ratio of 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6, the B element can be solid-dissolved in the matrix, segregated at the austenite grain boundaries, improve the stability of the austenite, increase the hardenability of the steel during the heat treatment process of the chain, and make the steel have better comprehensive properties such as high strength and high toughness. When the relationship between B element and Cr, Ni, and Mo elements is 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)<6, the content of B element added to the steel is low and cannot play a role in improving the hardenability of the steel. In this case, in order to ensure that the chain steel obtains good high strength and high toughness during quenching heat treatment and hot-dip galvanizing, expensive alloying elements must be added, which increases the production cost of the chain.

[0050] In the chain steel of the present invention, the unavoidable impurities are required to be P ≤ 0.015%, S ≤ 0.01%, and O ≤ 0.002%. P, S, and O are all impurity elements in steel. To achieve chain steel with improved performance and quality, the content of these impurities should be minimized, if technical conditions permit. In the chain steel of the present invention, P and S are both unavoidable, harmful impurities that degrade the steel's performance. Although P can improve the steel's weathering resistance, its overall side effects are greater. Therefore, in the present invention, P is controlled to meet P ≤ 0.015%, and S is controlled to meet S ≤ 0.01%. Accordingly, in the present invention, the impurity element O can form oxides and complex inclusions with deoxidizing elements such as Ti, B, and Al in the steel, which are detrimental to the steel's performance. Therefore, in the present invention, O is controlled to meet O ≤ 0.002%.

[0051] Of course, in some other embodiments, other harmful elements may be present in the steel, such as As, Pb, Sn, Sb, Bi and the like. Under the requirements of national laws, regulations and standards, the content of these harmful elements should be reduced as much as possible.

[0052] Compared with the existing production technology, the present invention has the following beneficial effects:

[0053] 1. The present invention adopts a reasonable chemical composition design and an optimized manufacturing method. By adding the element B, the hardenability and mechanical properties of the steel are improved, the amount of expensive alloys added is reduced, and the influence of various alloying elements and their interactions on the microstructure and mechanical properties is fully utilized, so that the chain steel of the present invention has excellent comprehensive performance. By preparing the chain by online quenching and hot-dip galvanizing the chain steel, on the one hand, fine carbides can be dispersed and precipitated in the supersaturated solid solution formed by the quenching heat treatment of the chain steel, thereby improving the performance of the chain; at the same time, a certain thickness of galvanized layer (or zinc layer) can be formed on the surface of the chain steel, so that the chain has excellent corrosion resistance.

[0054] 2. After the zinc coating is applied to the surface of the chain steel, the present invention can isolate the contact between the corrosive medium and the chain steel, thereby improving the corrosion resistance of the chain. When the zinc coating in some areas of the chain is worn, the zinc coating in other areas can also play an anodic protection role, preventing corrosion during the use of the chain, thereby increasing the service life of the chain.

[0055] 3. The chemical composition and process design of the high-strength chain steel of the present invention are reasonable, and the process window is wide, which can realize batch commercial production;

[0056] 4. The high-strength chain steel and chain of the present invention achieve excellent high strength and toughness as well as good corrosion resistance with a relatively low composition. They can be made into high-strength and corrosion-resistant structural parts and various high-performance industrial chains for mining, mooring, etc., and are widely used in engineering machinery, mining, marine engineering and other applications requiring high-strength, toughness and corrosion-resistant steel.

[0057] 5. The high corrosion-resistant mining chain made of the chain steel of the present invention not only has high strength and toughness and plasticity, but also has excellent corrosion resistance, and its application prospects are very broad. DETAILED DESCRIPTION

[0058] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below with reference to embodiments.

[0059] The present invention provides a high-strength chain steel, which comprises the following chemical components in percentage by mass: C: 0.20-0.30%, Si: 0.05-0.6%, preferably 0.15-0.6%, 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 is iron and unavoidable impurities.

[0060] The present invention improves the performance of the steel by adding the element B through reasonable design of the main alloying elements, reduces the amount of expensive alloy added, and fully utilizes the influence of various alloying elements and the interaction between them on the microstructure and mechanical properties. The microstructure of the steel of the present invention is precisely controlled to ensure that when the chain steel of the present invention is made into a chain through hot-dip galvanizing, a mixed microstructure of tempered martensite and carbides dispersed between the lamellar layers is formed in the chain steel. This microstructure enables the chain of the present invention to have both high strength and toughness-plasticity matching, and good wear resistance and fatigue resistance.

[0061] In a specific embodiment, the chemical composition of the chain steel meets the following requirements:

[0062] 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6, preferably 6≤30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≤24.43, where the symbols of each element are substituted into the corresponding values ​​before the mass percentage of each element;

[0063] In the present invention, Cr, Ni, and Mo are important alloying elements. Each element contributes differently to the toughness and hardenability of high-strength chain steel. However, excessive addition of expensive alloying elements can significantly increase the cost of the steel. Therefore, the present invention adds appropriate amounts of Cr, Ni, and Mo elements to the steel and allows them to interact with the trace amount of B element added to the steel. When the relationship between B element and Cr, Ni, and Mo elements satisfies "30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6", B element can be dissolved in the matrix and segregated at the austenite grain boundaries, thereby improving the stability of austenite and increasing the hardenability of the steel during the quenching heat treatment process of the chain steel, so that the steel has better comprehensive properties such as 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 and cannot play a role in improving the hardenability of the steel. In order to ensure that the chain steel obtains good high strength and high toughness during quenching and hot-dip galvanizing, expensive alloy elements must be added, which increases the production cost of the chain.

[0064] In the present invention, P, S and O are all impurity elements in steel. When technical conditions permit, in order to obtain high-strength steel with better performance and higher quality, the content of impurity elements in the material should be reduced as much as possible. Among them, P and S are both unavoidable harmful impurity elements in steel, and both will deteriorate the performance of steel. Although P can improve the weather resistance of steel, its side effects are generally greater. Therefore, among the unavoidable impurities, P≤0.015% and S≤0.01%. Correspondingly, the impurity element O can form oxides and complex inclusions with deoxidizing elements such as Ti, B, and Al in steel, which are not conducive to the performance of the steel. Therefore, O≤0.002%.

[0065] In a specific embodiment, the microstructure of the chain steel is acicular martensite. The microstructure of the chain steel in the chain formed after the high-strength chain steel is quenched and hot-dip galvanized is tempered martensite and carbides dispersed between the lamellar layers.

[0066] The properties of the high-strength mining chain steel meet the following requirements: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, section shrinkage Z≥50%, -20℃ Charpy impact energy A kv ≥60J.

[0067] The chain steel surface is hot-dip galvanized, and the corrosion rate of the chain is ≤0.2g / m after 120h of 5% NaCl neutral salt spray corrosion test. 2 .h.

[0068] The present invention provides a chain made of the above chain steel, the performance of which meets the following requirements: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, section shrinkage Z≥50%, -20℃ 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.

[0069] The present invention also provides a method for manufacturing the above-mentioned high-corrosion-resistant mining chain. The method is simple to produce, and the obtained chain has excellent high strength and toughness and good corrosion resistance.

[0070] The chain steel and chain manufacturing method of the present invention specifically include the following steps:

[0071] S1, smelting and casting molten steel to produce ingots;

[0072] Specifically, the smelting process includes electric furnace or converter smelting, LF refining, and VD or RH vacuum treatment. This involves smelting in an electric furnace or converter, followed by LF refining and VD or RH vacuum treatment. The vacuum treatment lasts 10 to 20 minutes, and the steel is tapped for casting after its chemical composition meets the requirements for chain steel. Accordingly, during the casting process, a continuous casting process is used to form ingots, with the tundish molten steel superheated at 15 to 40°C, ultimately producing ingots with chemical compositions that meet the requirements for chain steel.

[0073] S2, hot rolling the cast slab, wherein the compression ratio of the cast slab is ≥10;

[0074] Specifically, the ingot is heated in a heating furnace, removed from the furnace, dephosphorized with high-pressure water, and then rolled. The ingot is then rolled to produce finished round steel. The heating temperature is controlled to ≥1150°C for 3-6 hours, and the final rolling temperature is ≥850°C. After rolling, the ingot is air-cooled or slowly cooled to room temperature. During the rolling process, the compression ratio of the ingot is controlled to ≥10. The finished round steel has a size range of 30 to 150 mm.

[0075] S3, Ring Welding: Cut the round steel into fixed lengths and weave them into single rings on a braiding machine. Then use flash welding to weld them into a chain-like matrix of complete rings.

[0076] S4, quenching heat treatment, wherein the heating temperature of the quenching heat treatment is 850-950°C, the holding time is 1-3 hours, and water cooling quenching is adopted after heating;

[0077] Specifically, the chain-like matrix of the braided rings undergoes a quenching heat treatment at a temperature of 850-950°C for 1-3 hours, followed by a water-cooling quench. The high-temperature heating forms fine austenite grains with an austenite grain size of ≥7. After quenching, the microstructure of the chain-like matrix transforms from the high-temperature austenite structure to a fine, acicular martensite structure.

[0078] S5, Pickling Pretreatment: The chain-shaped substrate after quenching heat treatment is pickled to remove the oxide scale on the surface of the chain-shaped substrate after quenching, thereby obtaining chain steel. Preferably, a layer of flux is applied to the surface of the chain steel to maintain a certain degree of activity on the surface of the chain steel after pickling pretreatment, prevent oxidation of the chain steel during subsequent preheating, and enhance the bonding strength between the zinc coating and the chain steel. It should be noted that the flux in the present invention is a commonly used additive for zinc plating in the art and is commercially available.

[0079] S6, hot dip galvanizing, the chain steel after pickling pretreatment is preheated and then hot dip galvanized to obtain a chain including chain steel and a galvanized layer formed on the surface of the chain steel, wherein the difference between the preheating temperature of the preheating treatment and the temperature of the galvanizing solution used for hot dip galvanizing is controlled to be -30 to 30°C.

[0080] Specifically, in order to prevent problems such as zinc explosion during the hot-dip galvanizing process, the chain steel is preheated and then hot-dip galvanized to obtain a high-corrosion-resistant mining chain; wherein, the temperature difference between the preheating temperature of the chain and the galvanizing solution used in hot-dip galvanizing is controlled to be -30 to 30°C; wherein, the preheating temperature is 400 to 550°C, and the preheating time is ≥0.5h; the temperature of the galvanizing solution used in hot-dip galvanizing is 400 to 530°C, and the thickness of the galvanized layer on the surface of the chain steel is controlled to be 10 to 150 μm, preferably 40 to 150 μm.

[0081] During the hot-dip galvanizing process, the supersaturated acicular martensite structure formed after quenching the chain steel begins to precipitate fine carbides. Although this partially reduces the strength of the chain steel, its elongation and impact toughness begin to increase. The fine acicular martensite structure facilitates the precipitation of fine, dispersed carbides from the chain steel during hot-dip galvanizing, resulting in a chain with excellent strength and toughness.

[0082] The microstructure of the chain steel in the above-mentioned high corrosion-resistant mining chain is tempered martensite and carbides dispersed between the lamellar layers.

[0083] The performance of the above-mentioned high corrosion resistant mining chain meets the following requirements: yield strength Rp 0.2 ≥1050MPa, tensile strength Rm ≥1200MPa, elongation A ≥14%, section shrinkage Z ≥50%, -20℃ Charpy impact energy Akv ≥60J; after 120h of 5% NaCl neutral salt spray corrosion test, the corrosion rate is less than 0.2g / m 2 .h.

[0084] The present invention utilizes the influence of various alloying elements and the chain steel and chain production processes on the microstructure through the rational design of alloying elements and optimized preparation processes, thereby precisely controlling the chain steel's microstructure. The chain steel obtained after quenching heat treatment forms an acicular martensite structure. Hot-dip galvanizing of the chain steel not only allows the precipitation of fine, dispersed carbides during hot-dip galvanizing, improving the chain's strength and toughness, but also forms a thick galvanized layer on the chain steel surface, thereby enhancing the chain's corrosion resistance.

[0085] In the chain preparation process of the present invention, the quenching and tempering process of the traditional chain is combined with the hot-dip galvanizing process, which saves the tempering process of the chain and fully utilizes the chain steel during the hot-dip galvanizing process to achieve the precipitation of carbides in the steel, thereby achieving efficient production of high-strength and corrosion-resistant chains, so that the high-strength chain has both high strength and toughness-plasticity matching, and has good corrosion resistance.

[0086] The high-strength chain steel and high-corrosion-resistant mining chain and their manufacturing methods of the present invention are further described below with reference to specific examples. It should be understood that the following examples are only used to describe specific embodiments of the present disclosure and are not intended to limit the scope of protection of the present disclosure in any way.

[0087] Example

[0088] Examples 1 to 6

[0089] In combination with Table 1, Table 2-1 and Table 2-2, the high-strength chain steel and high-corrosion-resistant mining chain of Examples 1-6 were made using the following steps:

[0090] (1) Smelting and continuous casting are performed according to the chemical composition shown in Table 1 below to obtain ingots. The smelting can be performed in an electric furnace or a converter, and then undergoes LF refining and VD or RH vacuum treatment for 10 to 20 minutes. After the composition meets the requirements, the steel is tapped and then continuously cast into ingots. During the continuous casting process, the superheat of the molten steel in the tundish is controlled at 15 to 40°C.

[0091] (2) Hot rolling: The ingot is heated in a heating furnace and then dephosphorized with high-pressure water before being processed into finished round steel. The finished product size range is Φ30-150mm, and the ingot compression ratio is controlled to be ≥10. During the rolling process, the ingot is heated and then rolled into the finished product size. The heating temperature of the ingot is controlled to be ≥1150℃, the heating time is 3-6h, and the final rolling temperature is ≥850℃. After rolling, it is air-cooled or slowly cooled to room temperature.

[0092] (3) Ring welding: After the round steel is cut into fixed lengths and braided into single rings on a braiding machine, it is flash welded to form a chain-like base of a complete ring.

[0093] (4) Quenching heat treatment: The chain-shaped base after ring welding is subjected to quenching heat treatment, the heating temperature of the quenching heat treatment is controlled to be 840-980°C, the holding time is 1-4h, and then water-cooling quenching is performed.

[0094] (5) Pickling pretreatment: The chain-shaped substrate after quenching is pickled to remove the oxide scale on the surface of the chain-shaped substrate; then the chain-shaped substrate after pickling pretreatment is preheated. In order to prevent problems such as zinc explosion during the subsequent hot-dip galvanizing process, the preheating temperature of the chain-shaped substrate after pickling pretreatment is set to 400-550℃, and the preheating time is ≥0.5h. The difference between the preheating temperature of the chain-shaped substrate after pickling pretreatment and the temperature of the galvanizing solution used in the subsequent hot-dip galvanizing process is not more than ±30℃.

[0095] (6) Hot-dip galvanizing: The chain-shaped substrate after preheat treatment and pickling is hot-dip galvanized, the zinc liquid temperature is 400-530°C, and the thickness of the zinc coating on the surface of the chain steel is controlled to be 10-150 μm, thereby obtaining a highly corrosion-resistant mining chain, including the chain steel and the zinc coating on the surface of the chain steel.

[0096] The chemical composition design and related processes of the high-strength chain steel and high-corrosion-resistant mining chain of Examples 1 to 6 all meet the design specification requirements of the present invention.

[0097] Comparative Examples 1-2

[0098] The comparative steels of Comparative Examples 1-2 are finished steel products from different manufacturers. Their chemical compositions are shown in Table 1 below. Their processing techniques differ from those used in Examples 1-6. The heat treatment process employed for the comparative steels of Comparative Examples 1-2 follows the parameters recommended by the supplier. Specific values ​​are shown in Tables 2-1 and 2-2. The tempering temperatures and times in Table 2-2 refer to the tempering process used in Comparative Examples 1-2.

[0099] Table 1 shows the chemical compositions of the chain steels of Examples 1-6 and the comparative steels of Comparative Examples 1-2.

[0100] Table 1 (wt.%, the balance is Fe and other impurities except P and S)

[0101] Table 2-1 shows the specific process parameters during the preparation of the finished chains of Examples 1-6 and the comparative chains of Comparative Examples 1-2.

[0102] Table 2-1

[0103] Table 2-2 shows the specific process parameters during the preparation of the finished chains of Examples 1-6 and the comparative chains of Comparative Examples 1-2.

[0104] Table 2-2

[0105] The finished chains prepared in Examples 1-6 and the comparative chains prepared in Comparative Examples 1-2 were collected and their performance was further tested to obtain the performance of the finished chains of each Example and Comparative Example.

[0106] In the present invention, the finished chains of Examples 1-6 and the comparative chains of Comparative Examples 1-2 were subjected to a neutral salt spray corrosion test, a tensile test, and an impact performance test, respectively, and the test results are listed in Table 3.

[0107] The specific detection methods for relevant neutral salt spray corrosion test, tensile test and impact test are as follows:

[0108] (1) The neutral salt spray corrosion test was carried out by the following steps: 100 mm long round steel was taken from the finished chains of Examples 1-6 and the comparative chains of Comparative Examples 1-2 as salt spray corrosion specimens, both end faces were sealed with silicone rubber, and a 5 wt% NaCl salt spray corrosion test was carried out in accordance with GB / T 10125 (laboratory temperature 35°C, saturated barrel temperature 47°C, corrosive medium 5 wt.% NaCl aqueous solution, pH = 6.5, the test sample was longitudinally at an angle of 20°, the test time was 120 h, continuous spraying was adopted, and the salt spray deposition rate was 1.5 mL / (h·80 cm 2 After the 120-hour neutral salt spray test, the test sample was taken out, the silicone rubber at both ends was peeled off, and the surface corrosion products were removed. After the sample was dried, the mass was weighed and recorded as M'. The salt spray corrosion rate R of each embodiment and comparative example sample was then calculated as follows: R = (M-M') / (S·T)

[0109] Where M is the initial mass of the sample, with the dimension of g; M' is the mass of the sample after the corrosion products are removed and blown 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, the dimension is h; the salt spray corrosion rate R is g / m 2 .h.

[0110] Tensile test: The finished chains of Examples 1-6 and the comparative chains of Comparative Examples 1-2 were sampled and made into tensile specimens according to the national standard GB / T 2975. The tensile performance test was carried out according to the national standard GB / T 228.1 to measure the yield strength Rp of the finished chains of Examples 1-6 and the chains of Comparative Examples 1-2. 0.2 , tensile strength R m , elongation A and cross-sectional shrinkage Z.

[0111] Impact test: The finished chains of Examples 1-6 and the comparative chains of Comparative Examples 1-2 were sampled and made into impact specimens according to the national standard GB / T 2975. The impact performance test was carried out according to the national standard GB / T 229 to measure the low-temperature impact energy A of the finished chains of Examples 1-6 and the chains of Comparative Examples 1-2. kv .

[0112] Table 3 shows the performance parameters of the finished chains of Examples 1-6 and the comparative chains of Comparative Examples 1-2.

[0113] Table 3

[0114] As shown in Table 3, the comprehensive performance of the high corrosion resistant mining chains in Examples 1-6 of the present invention is excellent, and the yield strength Rp 0.2 Between 1076 and 1185 MPa, the tensile strength R m Between 1212 and 1315 MPa, elongation A≥14%, section shrinkage Z≥50%, -20℃ Charpy impact energy A kv ≥60J. The neutral salt spray corrosion rate of the high corrosion resistant mining chain in Examples 1-6 is ≤0.19g / m 2 h, which is much lower than the neutral salt spray corrosion rate of the comparative chain in Comparative Examples 1-2. This shows that the corrosion resistance of the high-strength chain steel of the present invention after quenching heat treatment and hot-dip galvanizing is significantly better than that of the existing comparative steel selected in Comparative Examples 1-2.

[0115] In summary, the present invention combines the heat treatment of traditional chains and the subsequent galvanizing process through reasonable chemical composition design to form an optimized quenching heat treatment and hot-dip galvanizing process, and finally obtains a high-performance, high-corrosion-resistant mining chain. The chain steel of the present invention has excellent comprehensive performance. It not only has high strength, but also has excellent toughness-plasticity matching. After being made into mining chains, it has excellent corrosion resistance and can well solve the problem of the existing mining chains that affect the service life due to the mismatch of strength, toughness, plasticity and corrosion resistance. The chain steel can be made into various high-performance industrial chains such as mining and mooring, and is widely used in engineering machinery, mining and marine engineering, etc., which require high-strength, high-toughness and high-corrosion-resistant chains.

[0116] It should be noted that all technical features described in this application can be freely combined or combined in any way unless there is a contradiction between them. Various modifications and variations can be made to the present invention without departing from the scope of the present invention, which will be apparent to those skilled in the art. For example, a feature shown or described as part of one embodiment can be used together with another embodiment to produce another embodiment. Therefore, the present invention is intended to encompass these modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A chain steel, characterized in that: The chain steel contains the following chemical components in mass percentage: C: 0.20-0.30%, Si: 0.05-0.6%, preferably 0.15-6%, 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 is iron and unavoidable impurities.

2. The chain steel according to claim 1, characterized in that: The chemical composition of the chain steel satisfies the following formula: 30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≥6, preferably 6≤30000*B / (300*B+0.7*Ni+2*Cr+5*Mo)≤24.43, where the symbols of each element are substituted into the numerical values ​​before the mass percentage of the corresponding element.

3. The chain steel according to claim 1, characterized in that: Among the unavoidable impurities, P≤0.015%, S≤0.01%, and O≤0.002%.

4. The chain steel according to claim 1, characterized in that: The chain steel microstructure is acicular martensite.

5. The chain steel according to claim 1, characterized in that: The properties of the chain steel meet the following requirements: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, section shrinkage Z≥50%, -20℃ Charpy impact energy A kv ≥60J.

6. A chain comprising: The chain steel according to any one of claims 1 to 5 and a galvanized layer coated on the chain steel.

7. The chain according to claim 6, characterized in that The thickness of the galvanized layer is 10-150 μm, preferably 40-150 μm; or / and the microstructure of the chain steel is tempered martensite and carbides dispersedly distributed between lamellar layers.

8. The chain according to any one of claims 6, characterized in that The performance of the chain meets the following requirements: yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, section shrinkage Z≥50%, -20℃ 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.

9. A method for manufacturing a chain as claimed in any one of claims 6 to 8, characterized in that: The manufacturing method comprises the following steps performed in sequence: S1, smelting and casting molten steel to obtain ingots; S2, heating and rolling the ingot, wherein the compression ratio of the ingot is ≥10; S3, ring welding; S4, quenching heat treatment, the heating temperature of the quenching heat treatment is 840-980°C, preferably 850-950°C, the holding time is 1-4 hours, preferably 1-3 hours, and then water cooling quenching is adopted; S5, pickling pretreatment to obtain chain steel; S6, hot dip galvanizing, the chain steel after pickling pretreatment is subjected to preheating treatment and then hot dip galvanizing to obtain a chain including chain steel and a galvanized layer formed on the surface of the chain steel, and the temperature difference between the preheating temperature of the preheating treatment and the galvanizing liquid used for the hot dip galvanizing is controlled to be -30 to 30°C.

10. The manufacturing method according to claim 9, characterized in that: In the step S1, the smelting includes electric furnace or converter smelting, LF refining, VD or RH vacuum treatment; the casting adopts a continuous casting process; preferably, the vacuum treatment time of the VD or RH vacuum treatment is 10 to 20 minutes; the superheat of the molten steel in the tundish is controlled to be 15 to 40° C. during the casting process; and / or In the step S2, during the heating and rolling process, the heating temperature of the ingot is ≥1150°C, the heating time is 3-6h, the final rolling temperature is ≥850°C, and air cooling or slow cooling is adopted after rolling; and / or In the step S6, the preheating temperature is 400-550°C, and the preheating time is ≥0.5h; the temperature of the galvanizing solution used in the hot-dip galvanizing is 400-530°C.

11. The manufacturing method according to claim 9, characterized in that: The thickness of the zinc plating layer is 10 to 150 μm, preferably 40 to 150 μm.

12. The manufacturing method according to claim 9, characterized in that: The microstructure of the chain steel in the chain obtained in step S6 is tempered martensite and carbides dispersedly distributed between lamellae.

13. The manufacturing method according to claim 9, characterized in that: The performance of the chain meets the following requirements: Yield strength Rp 0.2 ≥1050MPa, tensile strength R m ≥1200MPa, elongation A≥14%, section shrinkage Z≥50%, -20℃ Charpy impact energy A kv ≥60J; After 120h of 5% NaCl neutral salt spray corrosion test, the corrosion rate is less than 0.2g / m 2 .h.

Images