WO2023160613A1 - Mooring chain steel and production method therefor, and mooring chain and production method therefor - Google Patents

Abstract

The present invention relates to a mooring chain steel and a production method therefor. The mooring chain steel comprises the following components, in percentages by mass: C: 0.18-0.32, Mn: 1.95-2.60, Si: 0.15-0.50, Cr: 0.45-1.20, Mo: 0.008-0.250, Ni: 0.02-1.20, Cu≤0.40, S≤0.005, Al: 0.005-0.250, (V+Ti+Nb)≤0.35, (Sn+As+Sb)≤0.06, N: 0.004-0.024, O≤0.002, H≤0.00015 and the balance of Fe and inevitable impurities. On the basis of improving the cost performance of R3, R4 and R4S grade mooring steel, by utilizing a river-bay effect of a continuous cooling curve of structural steel influenced by Mn, namely similar to the influence rule of Mo, as the content of alloy Mn is increased to a certain amount, the continuous cooling curve of the steel begins to appear in a river bend shape, a component system for increasing cheap elements Mn and Al and reducing precious elements Mo and Ni is designed, and by means of trial production of the steel and a chain, the effects of reducing the cost of a chain product and improving the strength and toughness thereof are achieved. The present invention also relates to a mooring chain and a production process therefor.

Description

A kind of mooring chain steel and its production method, as well as the mooring chain and its production method

This application claims the priority of the Chinese patent application submitted to the China Patent Office on February 23, 2022, with the application number CN202210167428.X, and the title of the invention "a mooring chain steel and its production process, and the mooring chain and its production process" , the entire contents of which are incorporated in this application by reference.

technical field

The invention relates to the technical field of low alloy steel and the field of marine engineering accessories, in particular to a mooring chain steel and its production method, as well as the mooring chain and its production method.

Background technique

Mooring chain steel finger diameter in Between the mooring chains with round steel. Because the mooring chain is immersed in seawater for a long time and the service environment is harsh, the mooring chain steel must have high strength, good toughness, seawater corrosion resistance, hydrogen evolution embrittlement resistance, fatigue resistance, wear resistance and other characteristics. In addition, in practical applications, it is usually bent into a ring, and the mooring chain steel needs to have good hot bending and welding properties.

The target composition of R4 grade mooring chain steel with million-ton production is 0.22Mn1.5Cr0.8Ni0.8Mo0.45Nb0.03, provided by Shanghai No. 5 Iron and Steel Works (Liu Yongxin, Xu Yun, Chen Yifeng, Zhao Ronghua, The optimization of the heat treatment process parameters of the four-grade anchor chain steel, "Thermal Processing Technology" 1990No533~35), has been used in China for decades. Due to the large diameter of the offshore mooring chain link, the quenching and cooling conditions are limited. In order to ensure the hardenability of the chain link and obtain stable strength and toughness, the MnCrNiMo composition of the R4 chain steel products of various steel companies has not changed significantly over the years. . Although there were 5 patents on R4 grade chain steel published from 1998 to 2015, among which the Chinese patent application No. 98110160.7 stipulated that the upper limit of Mn was 1.90wt%, in fact, none of these patents had practical records.

Paper Tom Lassen, Agder, Jose L. Arana, Luis Canada, Jan Henriksen, Nina Kholthe, CRACK GROWTH IN HIGH STRENGTH CHAIN STEEL SUBJECTED TO FATIGUE LOADINGIN A CORROSIVE ENVIRONMENT, Proceedings of OMAE200524th International Conference on Offshore Mechanics and Arctic Engineering (OMAE 2005) June 12-17, 2005, Halkidiki, Greece, OMAE2005-67242, published the composition of R4S grade mooring chain: 0.23Mn1.3Cr1.0Ni1.0Mo0.5V0.09, except for the addition of microalloying element V, the composition is the same as the above Shanghai The R4 grade chain steel of the Fifth Iron and Steel Works is similar. As far as R3, R4, and R4S grade chains are concerned, there is no new type of high-strength and tough steel that can meet their cost-effective requirements. For large diameter R3, R4, R4S grade chains, the above steel No. is not satisfied.

In addition, cracks in mooring chain steel ingots and continuous casting slabs have always been a problem that affects production efficiency and cost (such as Zeng Haixia, Yang Jia, Analysis of cracks in R4 mooring chain steel, Special Steel Technology, 25 (2019) No2)), There has been no comprehensive solution for many years.

Contents of the invention

The object of the present invention is to provide a kind of mooring chain steel, on the basis of improving the cost performance of R3, R4, R4S grade mooring steel, utilize Mn to affect the bay effect of the continuous cooling curve of structural steel, that is, the law of influence is similar to Mo, When the alloy Mn content increases to a certain amount, the continuous cooling curve of the steel begins to appear a river bend. The composition system of increasing the cheap elements Mn and Al and reducing the precious elements Mo and Ni is designed. After the trial production of steel and chain, The effect of reducing the cost of chain products and improving their strength and toughness is obtained.

In order to achieve the purpose of the above invention, the present invention provides a mooring chain steel, the composition content of which is C 0.18～0.32, Mn 1.95～2.60, Si 0.15～0.50, Cr 0.45～1.20, Mo 0.008～ 0.250, Ni 0.02～1.20, Cu≤0.40, S≤0.005, Al 0.005～0.250, (V+Ti+Nb)≤0.35, (Sn+As+Sb)≤0.06, N 0.004～0.024, O≤0.002, H ≤0.00015, the balance is Fe and unavoidable impurities.

The following are the effects and explanations of the main alloying elements of the present invention:

The composition of the present invention: the amount of Mn is higher than that of the prior art. The amount of Al is higher than that of the prior art, the amount of Mo is lower than that of the prior art, and the amount of Cr and Ni is lower than or equal to the prior art.

C 0.18～0.32%

Carbon can increase the strength and hardenability of steel and chains. If the carbon content is lower than 0.18%, it is difficult to meet the strength requirements. Not only does it need to increase the amount of alloy, but also it is easy to cause cracks due to the peritectic reaction during the liquid-solid phase transition process; if it is higher than 0.32%, it will not only increase the brittle transition of steel and chains Temperature will reduce the plasticity and toughness of steel, and will accelerate the corrosion rate of steel and chain. In addition, carbon is the element that most strongly reduces the martensitic transformation temperature, which significantly increases crack sensitivity, and does not allow the high-temperature heating process of steel ingots and continuous casting slabs for the purpose of uniform composition and structure, so as to avoid overburning. Therefore, the C content must be strictly controlled. In order to obtain stable structure and performance, it is necessary to maintain the balance of carbon and alloying element content in the composition design.

Mn 1.95～2.60％

In chain steels, manganese was once the main alloying element added to improve hardenability, strength and toughness. However, its content has never exceeded 1.90%. In the case of large-diameter chain ring quenching, the technology of reducing manganese, increasing chromium and adding molybdenum to improve the hardenability of bainite once appeared. The present invention then discovers and utilizes manganese to also be able to improve bainite The characteristics of hardenability and the technology to improve the performance of flash butt welding process, increasing manganese and reducing nickel, molybdenum and chromium. Improved cost performance of steel and chains. If manganese is lower than 1.95%, the above effects cannot be achieved; if it is higher than 2.60%, the segregation of components will not be easily reduced or eliminated, thus affecting the structure and mechanical properties, the uniformity of process performance and other additional properties, such as hydrogen embrittlement susceptibility. In particular, it should be pointed out that steel and chains contain more than 1.95% manganese, and the content of martensite in the structure does not increase but decreases. Due to the reasonable combination of soft and hard phases, the yield ratio of quenched-high temperature tempered steel is controllable; the steel with composite bainite (BU+BL+M) structure, the edge and center of the cross-section of the chain, the base metal and The strength difference of the weld seam is greatly reduced. It is also possible to evaluate the mechanical properties of the weld. In a word, compared with the existing technology of reducing manganese, increasing chromium and adding molybdenum, the steel of the present invention in which the increased amount of manganese is combined with other elements can also increase and stabilize the phase transformation temperature of austenite during cooling from the austenitizing temperature, Increase the volume fraction of bainite in the matrix of the bainite/martensite quenching structure, expand the cooling rate range for the stable formation of bainite phase, and overcome the high crack sensitivity and heat treatment sensitivity of ultra-high-strength steel, especially for large diameter The difficult problem of poor productivity of chain continuous heat treatment has created conditions for satisfying the controllable low yield ratio of the invented steel after tempering. In particular, the reduction of the carbide-forming element chromium and the reduction of the M3C type carbide FeCr3C are beneficial to reduce the micro-battery effect and improve the corrosion performance.

Si 0.15～0.50%

Silicon can improve the strength and hardenability of steel, and has the same deoxidation effect as manganese, and can improve the corrosion performance of steel and chains in seawater. The present invention controls its residual content to be 0.15% or above. However, if the silicon content is too high, the toughness will be affected. Therefore, its upper limit is set at 0.50%.

Cr 0.45～1.20%

Chromium is also the main element to improve the strength and hardenability of chain steel, increase tempering stability and corrosion resistance in seawater. The chromium content should not be lower than 0.45%. Since a large amount of manganese has been added to the steel of the present invention, considering the cost and effect, the upper limit is 1.20%.

Ni 0.02～1.20%

According to ship regulations, the nickel content of chain steel above grade 4 shall not be less than 0.20%. Nickel is not easy to burn out during flash welding, which is beneficial to improve the uniformity of the weld. But the content is too high to increase the cost. Moreover, due to the increase of the corrosion potential of the chain, it is easy to be affected by cathodic overprotection and affect the sensitivity of stress corrosion (SCC). The steel of the present invention stipulates that the addition amount shall not exceed 1.20%. The carbon equivalent (Ceq) coefficient of nickel is low, and it can be used to balance Ceq if necessary, so as not to make Ceq too high. Nickel improves the hardenability, and ensures good strain-slip ability of the link, including the weld joint, and reduces the brittle transition temperature, which is beneficial to improve the low-temperature toughness of the link weld. Its solid solution strengthening effect is weak.

Mo 0.008～0.250％

Molybdenum delays the ferrite-pearlite transformation of steel, prevents temper brittleness, and significantly improves the impact toughness of steel. Molybdenum also improves the corrosion resistance of steel, and is an element that is not easily burned during flash welding. Molybdenum, molybdenum and chromium, especially the combination with manganese can stabilize the bainite content, control the bainite/martensite ratio, increase the phase transition temperature, reduce the crack sensitivity, and benefit the stability and buckling of the cross-section of the link. Stronger control. Since molybdenum is classified as a precious element, it increases the cost of steel. Compared with the technology that the traditional chain steel contains molybdenum ≥ 0.45%, and the diameter ≥ 160mm, the performance can only be stable if the molybdenum content is more than 0.5%, the present invention substitutes manganese for molybdenum, reducing the amount of molybdenum by more than half.
(V+Ti+Nb)≤0.35%

Microalloying elements vanadium V, titanium Ti, and niobium Nb have the effects of strengthening, refining, and hydrogen trapping, and they are also commonly used elements in marine chain steel in the past 10 years. Due to factors such as raw materials and furnace lining, titanium is unavoidable. In the present invention, vanadium is used as a strengthening element to form extremely fine VCN of 1 to 4 nm. These VCNs are not only high-energy strong hydrogen traps, which can limit the diffusion of hydrogen embrittlement steel, but also increase the micro-zone yield strength, reduce the local hydrogen accumulation caused by micro-zone strain (micro-yield), and reduce the HE sensitivity on the other hand. sex. As far as the present invention is concerned, the highest tensile strength of the steel and the chain has not reached 1250MPa of the R6 grade, so the addition of vanadium is not so much necessary as it is sufficient and supplementary. That is, the addition of vanadium plays the role of expanding the process window. It is recommended to decide whether to add or not by comprehensively considering cost, equipment, operation, etc. As a refinement element, niobium can supplement the deficiency of aluminum (AlN) and titanium (TiN) refinement. Considering the cost factor, it is stipulated that the sum of the three shall not exceed 0.35%.
Cu≤0.40%,

When the content of copper is low, its effect is similar to that of nickel, which can improve the strength and toughness of steel, and in steel with low tin content and nickel addition, a small amount of copper will not induce hot brittle cracks on the surface, but it can improve the atmospheric weather resistance of steel. Conducive to chain factory storage and planning arrangements. Copper or also contributes to the corrosion resistance of the link in the splash zone. However, there is not much data for this use case and needs to be accumulated. Copper has a low Ceq coefficient and is cheaper than nickel, so it can be properly utilized. However, if the content is too high, the compactness of the oxide film on the surface of the link may be reduced.

Al 0.005～0.250%;

Aluminum is the main deoxidizing element, and it can form AlN, refine grains, and a small amount of aluminum can improve the comprehensive mechanical properties of the chain base material and weld. When aluminum exceeds 0.2%, it can also improve the corrosion resistance of steel. When niobium is used to refine the grains of alloy structural steel, the role of aluminum can only be deoxidation, and the residual aluminum is allowed to be not less than 0.005% when the steel is lifted. The implementation of the present invention shows the corrosion resistance tendency of aluminum in seawater, and limits it to ≤0.250%, and controls restrain its influence on the phase transition. The premise of applying higher aluminum is that the flash butt welding process is in place, and the size and quantity of oxide inclusions in the weld joint are limited to not exceed the normal level.

N 0.004～0.024%;

Nitrogen in steel is unavoidable, and fixed into AlN, TiN, VN, NbN can prevent strain aging, refine grains and/or increase strength. Smelting engineers to reduce the oxygen, hydrogen and nitrogen targets of structural steel. However, the inventors feel that the potential of oxygen in the compound existing as a solid phase transition core and nitrogen as a light element has yet to be brought into play through practical applications. In the process of nitrogen utilization, it is necessary to prevent excessive free nitrogen or solid solution nitrogen from forming pores during the solidification of molten steel, and to prevent the precipitation of microalloy nitrides from increasing crack sensitivity. The invention allows the actual nitrogen content of product steel and chain to be 0.004-0.024wt%. It should be noted that the combination of available nitrogen and microalloying elements in compounds forming the required scale range follows the stoichiometric law. The “technology of controlling nitrogen and microalloying elements” that deviates from this law cannot achieve the desired effect.
H≤0.00015%

In order to prevent internal hydrogen from causing steel defects, it is stipulated that the hydrogen content of molten steel waiting to be tapped after refining outside the furnace-vacuum degassing is ≤0.00015%.
O≤0.0020%

In order to reduce the level and total amount of oxide inclusions, an upper limit of oxygen is specified.
(Sn+As+Sb)≤0.06%,

Similar to sulfur and phosphorus, Tramp elements such as antimony, arsenic, and tin also embrittle the grain boundaries of prior austenite, reduce toughness, and may cause hot working cracks when the content is large. Although it is hoped that the lower the better, considering the cost of industrial products, the total amount is allowed to be no more than 0.06%.

The second object of the present invention is to provide a kind of production method of above-mentioned mooring chain steel, comprising the following steps,

S1, the mass percentage of the tapping composition is: C 0.18～0.32, Mn 1.95～2.60, Si 0.15～0.50, Cr0.45～1.20, Mo 0.008～0.250, Ni 0.02～1.20, Cu≤0.40, S≤0.005, Al 0.005～0.250, (V+Ti+Nb)≤0.35, (Sn+As+Sb)≤0.06, N 0.004～0.024, O≤0.002, H≤0.00015, the balance is Fe and unavoidable impurities;

S2. According to the above-mentioned target composition ratio of tapping, use electric furnace or converter for initial refining, and then pour into steel ingot or continuous casting slab after refining outside the furnace or vacuum degassing;

S3. After heating the steel ingot to 1150-1300°C, forging or rolling it into round steel.

Specifically, in step S1, the metal raw material used in the primary smelting process of an electric furnace or a converter is molten iron, One or a mixture of any two or more of pig iron, steel scrap, ferroalloy, sponge iron, metal oxide and ore.

Specifically, in step S2, the ratio of the cross-sectional area of the steel ingot to the cross-sectional area of the finished round steel is ≥7.

Specifically, after step S3, step S4 is also included, after the round steel is straightened and grinded or turned by a grinding wheel, flaw detection, sampling and testing are carried out according to classification society specifications.

The third object of the present invention is a mooring chain, which is prepared by using the round steel made of the mooring chain steel mentioned above.

After the overall heat treatment of the mooring chain, the performance of the matrix at one-third of the radius and the impact energy of the matrix and the weld, the minimum value is,

Among them, ABS, American Bureau of Shipping; DNVGL, Det Norske Veritas; Rm, tensile strength; Rp0.2, conditional yield strength; YR, yield ratio; Aim value, target value; A, elongation; Z, section Shrinkage; CVN, Charpy V-notch impact energy; B, ring back; W, weld. Regarding YR, this patent selects a more demanding ABS target value.

The fourth object of the present invention is to provide a production method of the above-mentioned mooring chain. The mooring chain adopts the above-mentioned mooring chain steel, which is sequentially cut, heated at 950-850°C, and bent at 900-800°C. ℃, temperature measurement, flash butt welding, and finally weaving chains; among them, the braided chains are heat treated in batch or vertical continuous tempering furnaces, and their accessories are heat treated in batch tempering furnaces. The heat treatment steps are: firstly carry out at least one quenching treatment, each time the quenching temperature is >890°C, water cooling, the water temperature is less than 50°C; after the quenching treatment, tempering treatment is carried out, the tempering temperature is 570-650°C, water cooling or air cooling.

Specifically, the braided chain and its accessories are quenched twice in a batch or vertical continuous tempering furnace.

The present invention has the following advantages compared with the prior art:

(1) The first production covers the diameter range required by the market, which improves performance and reduces costs;

(2) The steel of the present invention is applied to flash butt welding workpieces for the first time to obtain stable and tough welds. One of the reasons is that, Compared with C0.22MnCrNiMo steel, increasing Mn and reducing Mo, Cr, and Ni reduces the thermal deformation resistance of link flash butt welding by 6-16%, and it is easy to form a well-bonded tight weld, and the decrease rate of weld toughness is greatly reduced. The second reason is that the final close upsetting temperature range of traditional steel increases the process window, reduces the difficulty of ensuring the stability of the weld joint, and stabilizes the welding quality; the allowable final close upsetting temperature of the R4 steel of the present invention is about 750 ~ 850°C; while the final close upsetting temperature allowed by traditional R4 steel is about 800-850°C;

(3) Realize the simple management of one steel with multiple uses: Due to the adjustment of the composition system, the amount of precious alloy elements is reduced, so the simple management of one steel with multiple uses can be realized. Since steel grades R3S, R4, R4S, R5 (also grade R6) have the same classification society composition and process specifications, it is allowed, for example, to produce grades R4 and R4S steel and chains at the cost of grade R4 round bar products; The cost of round bar products produces R3S and R4 grade steel and chain. And this process can be realized technically as long as the tempering parameters are changed. For example, the standard tensile strength difference of each level, R4S and R4, 960-860 = 100MPa, R4 and R3S difference 860-770 = 90MPa, the problem can be solved by adjusting the tempering parameters within the fluctuation range of the high temperature tempering temperature ± 30°C; Mass production management, reducing manufacturing costs, improving efficiency, and realizing the management revolution of chain steel production and chain ring manufacturing;

(4) Eliminate the third type of cracks on the surface of ingots and billets: the surface cracks of low-carbon alloy steel ingots and billets with Nb and Al microalloying are the main cause of waste products. Due to the increased bainite hardenability, the large cross-section ingot does not undergo ferrite, pearlite and phase transformation. The R3, R4, R4S (R5) steels of the present invention are less likely to reduce thermoplasticity due to the precipitation of ferrite at the grain boundaries, and are less prone to low strain rate strain conditions in the process of continuous casting straightening or ingots and billets being heated into the heating furnace. Cracks caused by cracking stress (external mechanical stress or thermal stress) eliminate the third type of cracks on the surface of low-carbon steel ingots and billets known in the industry, improve the billet rate and production efficiency of products, and reduce costs;

(5) Quenching is relatively uniform in the cross-sectional performance of the present invention in the phase transformation of the bainite region; the present invention has NbCN, AlN, TiN alone or a combination of multiple methods to prevent the growth of austenite grains to choose from, improving the comprehensive performance and reduced EAC sensitivity;

(6) Reduce thermoplastic deformation resistance, which is very beneficial to flash butt welding of large sections;

(7) It has reliable environmental performance.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

The composition of embodiment 1 to embodiment 8 of the present invention and comparative example 1 to comparative example 6 is shown in table 1:

Table 1: Steelmaking composition of the embodiment of the present invention and comparative example, wt%

The production method of the mooring chain steel in embodiment 1～8 is as follows:

S1, the mass percentage of the tapping composition is: C 0.18～0.32, Mn 1.95～2.60, Si 0.15～0.50, Cr0.45～1.20, Mo 0.008～0.250, Ni 0.02～1.20, Cu≤0.40, S≤0.005, Al 0.005～0.250, (V+Ti+Nb)≤0.35, (Sn+As+Sb)≤0.06, N 0.004～0.024, O≤0.002, H≤0.00015, the balance is Fe and unavoidable impurities; electric furnace, primary refining The metal raw materials used in the process are molten iron, pig iron, scrap steel, ferroalloy, ore, etc.

S2, according to the above-mentioned tapping target composition ratio, adopt electric furnace for initial refining, then through refining outside the furnace, pour into steel ingot after vacuum degassing, wherein embodiment 8 does not degas; Area ratio ≥ 7;

S3. After heating the steel ingot to 1150-1300°C, forging it into round steel;

S4. After the round steel is straightened and stripped by grinding wheels, flaw detection, sampling and testing are carried out.

The round steel prepared by the above-mentioned production method for the mooring chains of Examples 1 to 8 is sequentially cut, heated at 950-900°C, bent at 850-800°C, temperature measured, flash-butt welded, chain-braided, and bottomed. Furnace heating and quenching water cooling - tempering water cooling; the chain is heat treated in a batch tempering furnace. The heat treatment steps are: heating to 920°C for water-cooling and quenching, and the water temperature is less than 50°C; reheating to 610°C for tempering, and water cooling.

Embodiment 1～8 and comparative example 1～6 are now carried out the mechanical performance detection under the same conditions, and the detection results are shown in Table 2

Table 2

From this it can be seen that

(1) The amount of Mn in the comparative example exceeds the upper and lower limits of the scope of the invention, respectively. Although the elements Cr and Ni have been added, the mechanical properties (yield strength ratio or tensile strength) still cannot reach the standard stably;

(2) The ingredients of Comparative Examples 3, 4, and 5 have been used consistently for decades. Compared with Examples 1-7, the content of the precious alloy element Ni or/and Mo is increased by about one time respectively, and the cost will increase accordingly;

(3) The amounts of Mn in Comparative Examples 1 and 2 respectively exceed the upper and lower limits of the scope of the invention. Even with the addition of elements Cr and Ni, the strength still cannot stably reach the standard (R4) or the yield ratio often exceeds 0.92; the yield ratio YR of comparative examples 1 and 5 exceeds the ABS target of the American Bureau of Shipping; comparative examples 2, 3, and 4 Is the R4 grade chain, its resistance The tensile strength is lower than the standard; comparative example 6 is an R3 grade chain, and its toughness is unqualified;

(4) Compared with the ring back, the decrease rate of weld toughness=1-(weld seam impact/ring back impact)=23-39%, which is only about half of 42-73% of the comparative example. Stable mechanical properties and improved plasticity and toughness in the examples show that in the production of chain links, especially large-scale link links, the improvement of the ability to remove welding slag is related to the reduction of thermal deformation resistance and the improvement of weld adhesion in the examples;

(5) The ingredients of Comparative Examples 3, 4, and 5 have been used consistently for decades. Compared with the embodiment, the contents of the precious alloy elements Mo and Ni are increased by about one time respectively, and the cost will increase correspondingly. The yield strength ratio YR of Comparative Examples 1 and 5 exceeds the ABS standard of the American Bureau of Shipping. Comparative examples 2, 3, and 4 are R4 chains whose tensile strength is lower than the standard. Comparative example 6 is an R3 grade chain, and its toughness is unqualified. The weld seam toughness reduction rate of the comparative example is 42-73%, and the Mn content of the comparative example exceeds the upper and lower limits of the scope of the invention respectively. Even with the addition of elements Cr and Ni, the mechanical properties (yield ratio or tensile strength or toughness) are still unqualified.

Table 3 is the corrosion rate trend and environmental crack resistance performance table in the seawater of embodiment 5 and 7

It can be seen that the internal hydrogen of the steel and the chain is at a very low level; the corrosion rate tends to decrease with the increase of Al and Cu; the corrosion rate in the deep-sea anoxic environment decreases by an order of magnitude; the data of environmental crack sensitivity is provided.

Table 4 is the hardness (wt %) of r/3 of embodiment and comparative example cross-section and core portion

The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the described embodiments, and those skilled in the art can also make various equivalents without violating the spirit of the present invention. These equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims (12)

1. A kind of mooring chain steel, characterized in that, its component content according to the mass percentage is, C 0.18～0.32, Mn 1.95～2.60, Si 0.15～0.50, Cr 0.45～1.20, Mo 0.008～0.250, Ni 0.02～1.20, Cu≤0.40, S≤0.005, Al 0.005～0.250, (V+Ti+Nb)≤0.35, (Sn+As+Sb)≤0.06, N 0.004～0.024, O≤0.002, H≤0.00015, the balance is Fe and unavoidable impurities.
2. The mooring chain steel according to claim 1, characterized in that its component content is, in terms of mass percentage, C 0.18-0.32, Mn 1.95-2.60, Si 0.15-0.50, Cr 0.45-1.20, Mo 0.008-0.250, Ni 0.02～1.20, Cu≤0.40, S≤0.005, P≤0.015, Al 0.005～0.250, (V+Ti+Nb)≤0.35, (Sn+As+Sb)≤0.06, N 0.004～0.024, O≤0.002 , H≤0.00015, the balance is Fe and unavoidable impurities.
3. A method for producing mooring chain steel according to claim 1, characterized in that it comprises the steps of,

   S1, the mass percentage of the steel target composition is: C 0.18～0.32, Mn 1.95～2.60, Si 0.15～0.50, Cr0.45～1.20, Mo 0.008～0.250, Ni 0.02～1.20, Cu≤0.40, S≤0.005, Al 0.005～0.250, (V+Ti+Nb)≤0.35, (Sn+As+Sb)≤0.06, N 0.004～0.024, O≤0.002, H≤0.00015, the balance is Fe and unavoidable impurities;

   S2. According to the above-mentioned target composition ratio for tapping, use electric furnace or converter for primary refining, then refine outside the furnace, and/or vacuum degas and then cast into steel ingots or continuous casting slabs;

   S3. After heating the steel ingot or continuous casting slab to 1150-1300° C., forging or rolling it into round steel.
4. The production method of mooring chain steel according to claim 3 is characterized in that, in step S1, the metal raw materials used in the primary smelting process of electric furnace or converter are molten iron, pig iron, scrap steel, ferroalloy, sponge iron, metal oxide One or a mixture of any two or more of minerals and ores.
5. The production method of mooring chain steel according to claim 3, characterized in that, in step S2, the ratio of the cross-sectional area of the steel ingot or continuous casting slab to the cross-sectional area of the finished round steel is ≥7.
6. The production method of mooring chain steel according to claim 3, is characterized in that, after step S3, also includes step S4, after said round steel is carried out straightening and grinding wheel grinding stripping or turning, carry out flaw detection, sampling and test.
7. The production method of mooring chain steel according to claim 3, is characterized in that, comprises the following steps,

   S1, the mass percentage of the steel target composition is: C 0.18～0.32, Mn 1.95～2.60, Si 0.15～0.50, Cr0.45～1.20, Mo 0.008～0.250, Ni 0.02～1.20, Cu≤0.40, S≤0.005, P≤0.015, Al 0.005～0.250, (V+Ti+Nb)≤0.35, (Sn+As+Sb)≤0.06, N 0.004～0.024, O≤0.002, H≤0.00015, the balance is Fe and unavoidable impurities ;

   S2. According to the above-mentioned target composition ratio for tapping, use electric furnace or converter for primary refining, then refine outside the furnace, and/or vacuum degas and then cast into steel ingots or continuous casting slabs;

   S3. After heating the steel ingot or continuous casting slab to 1150-1300° C., forging or rolling it into round steel.
8. A mooring chain, characterized in that it is prepared from round steel made of the mooring chain steel according to claim 1.
9. A mooring chain according to claim 8, characterized in that, after the overall heat treatment of the mooring chain, the performance of the matrix at one-third of the radius and the impact energy between the matrix and the weld seam, the minimum value is,
   

   Among them, ABS, American Bureau of Shipping; DNVGL, Det Norske Veritas; Rm, tensile strength; Rp0.2, conditional yield strength; YR, yield ratio; Aim value, target value; A, elongation; Z, section Shrinkage; CVN, Charpy V-notch impact energy; B, ring back; W, weld.
10. A production method for a mooring chain according to claim 8, characterized in that the round steel made of the mooring chain steel according to claim 1 is used for the mooring chain and is sequentially cut and heated at 950-900°C , bending ring, temperature measurement, flash butt welding, chain knitting, heating, quenching, water cooling, tempering, water cooling or air cooling; wherein, the braided chain is heat treated in a batch or vertical continuous tempering furnace; its accessories Heat treatment is carried out in a batch tempering furnace.
11. The production method according to claim 10, characterized in that the temperature of the bent ring is 850-800°C.
12. The production method of mooring chains according to claim 10, characterized in that the heat treatment step is: first perform at least one quenching treatment, each time the quenching temperature is > 890 ° C, water cooling, the water temperature is less than 50 ° C; Fire treatment, tempering temperature is 570 ~ 650 ℃, water cooling or air cooling.