Preparation method of ultra-long seamless mooring chain

Abstract

The invention discloses a preparation method of a super-long seamless mooring chain, during preparation, a novel additive manufacturing printer is adopted, the super-long seamless mooring chain is formed by tightly connecting n subareas, each subarea is internally provided with a front scraper, a laser, a powder bed, an ascending cylinder and a descending cylinder, and a rear scraper is arranged behind the joint of every two adjacent front scrapers; the preparation method specifically comprises the following steps: (1) designing a placement mode, making a printing file, and inputting the printing file into a printer; (2) pushing powder, paving the powder on a powder bed, and scraping the powder; (3) laser scanning and printing; and (4) circulation is carried out again until the complete high-grade super-long seamless mooring chain is printed out. According to the method, the extra-long seamless mooring chain is manufactured through additive manufacturing, the method is greatly different from a traditional production mode, and the produced mooring chain product is free of welding seams, high in strength, resistant to corrosion, quite excellent in performance, short in production process and high in manufacturing efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of mooring chain manufacturing, and more specifically, to a preparation method for ultra-long seamless mooring chains. Background Art

[0002] Offshore mooring chains are important devices for maintaining the safety of offshore engineering facilities and are key components of the offshore mooring and positioning systems of offshore engineering equipment. Marine mooring chains are mainly used for mooring in application scenarios such as offshore drilling platforms, deep-sea fishery aquaculture systems, floating deep-sea wind power generation, deep-sea mooring systems, military ships, floating production storage tankers, and other offshore development facilities. Since marine mooring chains are immersed in seawater for a long time and are always in a working state, it is required that the mooring chains not only have a high combination of strength and toughness, but also have properties such as seawater corrosion resistance, fatigue resistance, and wear resistance. According to the Norwegian-German classification society standard "Marine Mooring Chains" 2018 edition, mooring chains can be divided into R3 class, R3S class, R4 class, R4S class, R5 class, and R6 class according to their strength levels.

[0003] Currently, marine mooring chains are mainly divided into two categories: studless mooring chains and studded mooring chains. Studless mooring chains are commonly used for permanent mooring. Without crossbars, they reduce the weight per unit strength and increase the fatigue life of the chain. The disadvantage is that they are not very convenient to operate when hoisted. Studded mooring chains have been used for mooring MODUS and FPSOS in relatively shallow waters. It has been proven to be strong, reliable, and relatively easy to handle. The crossbars provide stable connections between the chain links and the convenience of hoisting.

[0004] Mooring chain steel is generally round steel. The traditional production process flow is: scrap steel, hot-charged hot metal - electric arc furnace smelting - LF (ladle furnace refining) refining - RH (vacuum circulation degassing furnace) degassing - bloom continuous casting - primary rolling blooming - continuous rolling into finished products - steel annealing - surface peeling - ultrasonic flaw detection - inspection, packaging and warehousing. For the production of some large-sized round steel, the ingot casting process is also used for production.

[0005] After producing hot-rolled round steel or forged round steel, mooring chains are manufactured. In a mooring chain processing factory, the round steel is cut into the lengths required for individual chain links, sent to an eddy current heating furnace to be heated up, bent at one end in a red-hot state, then sleeved onto the entire mooring chain, and then the other end is bent. After that, the mooring chain is sent to a welding machine for flash welding and de-burred on a de-burring machine. The crossbar is placed in the middle of the chain link, and using a mechanical clamping device, the crossbar and the red-hot chain link are clamped together and further welded. After the mooring chain passes the flaw detection test, it is sent to a heat treatment furnace for heat treatment. Tensile and breaking tests are carried out on the mooring chain again. The qualified mooring chains are ground and shot blasted, sent to a painting workshop for painting, and the manufactured mooring chains are shipped out after passing the inspection by the classification society.

[0006] However, in the traditional production process, the mooring chain must be welded, and there are weld seams at the connections of the chain links and the rungs. The weld seam of the chain link is the weak link of the entire mooring chain, and its strength, plasticity, toughness, corrosion resistance, etc. are all lower than those of other parts.

[0007] Therefore, how to improve the performance of the chain link weld seam in the traditional production process is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a preparation method for an ultra-long seamless mooring chain to solve the deficiencies in the prior art.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions:

[0010] A preparation method for an ultra-long seamless mooring chain, which uses a new type of additive manufacturing printer during preparation. It is composed of n partitions tightly connected. There is 1 front scraper, 1 laser, 1 powder bed, 1 lifting cylinder and 1 lowering cylinder in each partition. There is 1 rear scraper behind the connection of every two adjacent front scrapers;

[0011] The preparation method specifically includes the following steps:

[0012] (1) According to the type and size of the mooring chain link, design the placement mode of the mooring chain on the powder bed of the printer, make a printing file, and input it into the printer;

[0013] (2) On the printer with the program set, after the mooring chain steel powder in the n lifting cylinders is simultaneously ejected, the n front scrapers push the powder forward to evenly spread the powder on the powder bed, and the n - 1 rear scrapers follow up simultaneously to scrape the powder;

[0014] (3) The front scraper and the rear scraper retreat to the initial position, the laser is started, and the powder bed is scanned according to the set laser parameters to print the first layer of the mooring chain;

[0015] (4) Finally, the n lowering cylinders drive the powder bed to move down one layer, the mooring chain steel powder in the n lifting cylinders is ejected for the second time, and this powder printing process flow is repeated again to print the second layer, the third layer... until a complete high-grade ultra-long seamless mooring chain is printed.

[0016] The present invention uses additive manufacturing for ultra-long seamless mooring chains, which is quite different from the traditional production method. The produced mooring chain products have no weld seams, are high-strength and corrosion-resistant, have very excellent performance, a short production process, and high manufacturing efficiency.

[0017] Furthermore, the above n partitions are n independent but simultaneously printable subsystems. The number of n depends on the required length of the printed mooring chain, and it can print ultra-long, and theoretically can even be infinitely long.

[0018] Furthermore, there are n front scrapers in total as described above, which are the main powder spreading scrapers; there are n - 1 rear scrapers in total, mainly for scraping flat the raised linear powder between the gaps of two front scrapers.

[0019] Furthermore, in the above step (1), the types of mooring chain links include studded links and studless links; the size of the studded links is a nominal diameter of 165 - 240 mm, and the size of the studless links is a nominal diameter of 34 - 240 mm.

[0020] Furthermore, in the above step (1), the placement modes include the snake - bend type and the straight - line type; the snake - bend type is applicable to short links, and the links are bent and coiled to increase the printing length; the straight - line type is applicable to thick links and cannot be bent and coiled.

[0021] Furthermore, in the above step (4), the high levels include R4, R4S, R5, R6, and the new R7 levels; seamless means that each link of the mooring chain is formed in one time and has no weld seam throughout.

[0022] Through the above - mentioned technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. The mooring chain for additive manufacturing is integrally formed, the chain is extremely long, and the links have no weld seams.

[0024] 2. The manufactured mooring chain has a high level, high strength, good toughness, and excellent corrosion resistance.

[0025] 3. The production process is short, the efficiency is high, and the production cycle of the mooring chain is shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of a new - type additive manufacturing printer;

[0027] Among them, 1 - mooring chain, 2 - front scraper, 3 - rear scraper, 4 - laser, 5 - powder bed, 6 - lowering cylinder, 7 - raising cylinder, 8 - the nth partition;

[0028] Figure 2 It is a particle size distribution diagram of steel powder;

[0029] Figure 3 It is the microscopic morphology of steel powder;

[0030] Figure 4 It is the physical diagram of cubic parts, tensile parts, and impact parts;

[0031] Figure 5 It is a schematic diagram of the traditional manufacturing process and the additive manufacturing process of the mooring chain;

[0032] Figure 6 It is the mechanical properties of mooring chain specimens under different laser powers;

[0033] Figure 7 is the impact absorption work of the mooring chain specimens under different laser powers;

[0034] Figure 8 is the impact fracture morphology of the mooring chain specimens under different laser powers. Among them, a is the T2 specimen, b is the T4 specimen, and c is the T6 specimen;

[0035] Figure 9 is a physical picture of the successfully printed three-ring mooring chain sample. Specific implementation mode

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] Embodiment 1

[0038] A preparation method of an ultra-long seamless mooring chain. When preparing, a new type of additive manufacturing printer is used, which is tightly connected by 20 independent but simultaneously printable partitions (sub-systems). Each partition is provided with 1 front scraper 2, 1 laser 4, 1 powder bed 5, 1 lifting cylinder 7 and 1 lowering cylinder 6. 1 rear scraper 3 is arranged behind the connection of every two adjacent front scrapers 2;

[0039] The preparation method specifically includes the following steps:

[0040] (1) According to the type of the mooring chain 1 link being a stud link with a nominal diameter of 230 mm, the placement mode of the mooring chain 1 on the printer powder bed 5 is designed as a straight line type, a printing file is made and input into the printer;

[0041] (2) On the printer with the program set, after the steel powder of the mooring chain 1 in the 20 lifting cylinders 7 is simultaneously ejected, the 20 front scrapers 2 push the powder forward to evenly spread the powder on the powder bed 5, and the 19 rear scrapers 3 follow up simultaneously to scrape the powder and scrape the raised linear powder in the gap between the two front scrapers 2 flat;

[0042] (3) The front scraper 2 and the rear scraper 3 retreat to the initial position, the laser 4 is started, and the powder bed 5 is scanned according to the set laser parameters to print the first layer of the mooring chain 1;

[0043] (4) Finally, the 20 lowering cylinders 6 drive the powder bed 5 to move down one layer, and the mooring chain 1 steel powder in the 20 lifting cylinders 7 is pushed out for the second time. This powder printing process flow is recycled again to print the second layer, the third layer,..., until a complete high-level R4-class ultra-long seamless mooring chain 1 is printed. Each link is formed in one piece and has no weld seam throughout.

[0044] Example 2

[0045] A preparation method of an ultra-long seamless mooring chain. When preparing, a new type of additive manufacturing printer is used, which is tightly connected by 10 independent but simultaneously printable partitions (sub-systems). Each partition is provided with 1 front squeegee 2, 1 laser 4, 1 powder bed 5, 1 lifting cylinder 7 and 1 lowering cylinder 6. 1 rear squeegee 3 is arranged behind the connection of every two adjacent front squeegees 2;

[0046] The preparation method specifically includes the following steps:

[0047] (1) According to the type of the link of the mooring chain 1 being a studless link and the size being a nominal diameter of 50 mm, the placement mode of the mooring chain 1 on the powder bed 5 of the printer is designed as a snake bend type, a printing file is made and input into the printer;

[0048] (2) On the printer with the program set, after the mooring chain 1 steel powder in the 10 lifting cylinders 7 is simultaneously pushed out, the 10 front squeegees 2 push the powder forward to evenly spread the powder on the powder bed 5, and the 9 rear squeegees 3 follow up simultaneously to scrape the powder and scrape flat the raised linear powder in the gap between the two front squeegees 2;

[0049] (3) The front squeegee 2 and the rear squeegee 3 retract to the initial position, the laser 4 is started, and the powder bed 5 is scanned according to the set laser parameters to print the first layer of the mooring chain 1;

[0050] (4) Finally, the 10 lowering cylinders 6 drive the powder bed 5 to move down one layer, and the mooring chain 1 steel powder in the 10 lifting cylinders 7 is pushed out for the second time. This powder printing process flow is recycled again to print the second layer, the third layer,..., until a complete high-level R5-class ultra-long seamless mooring chain 1 is printed. Each link is formed in one piece and has no weld seam throughout.

[0051] Example 3

[0052] A preparation method of an ultra-long seamless mooring chain. When preparing, a new type of additive manufacturing printer is used, which is tightly connected by 25 independent but simultaneously printable partitions (sub-systems). Each partition is provided with 1 front squeegee 2, 1 laser 4, 1 powder bed 5, 1 lifting cylinder 7 and 1 lowering cylinder 6. 1 rear squeegee 3 is arranged behind the connection of every two adjacent front squeegees 2;

[0053] The preparation method specifically includes the following steps:

[0054] (1) According to the type of the link of the mooring chain 1 being a studless link with a nominal diameter of 120 mm, the placement mode of the mooring chain 1 on the printer powder bed 5 is designed to be linear. Make a printing file and input it into the printer;

[0055] (2) On the printer with the program set, after the steel powder of the mooring chain 1 in the 25 lifting cylinders 7 is simultaneously ejected, the 25 front scrapers 2 push the powder forward to evenly spread the powder on the powder bed 5. The 24 rear scrapers 3 follow up simultaneously to scrape the powder and level the raised linear powder in the gap between the two front scrapers 2;

[0056] (3) The front scraper 2 and the rear scraper 3 retract to the initial position, the laser 4 is started, and the powder bed 5 is scanned according to the set laser parameters to print the first layer of the mooring chain 1;

[0057] (4) Finally, the 25 lowering cylinders 6 drive the powder bed 5 to move down one layer. The steel powder of the mooring chain 1 in the 25 lifting cylinders 7 is ejected for the second time, and this powder printing process flow is recycled again to print the second layer, the third layer... until the complete high - level R7 - class extra - long seamless mooring chain 1 is printed. Each link is formed in one piece and has no weld seam throughout.

[0058] Performance Test

[0059] I. Steel Powder Characterization

[0060] 1. Chemical Composition of Steel Powder

[0061] In Example 1, the steel powder prepared by the vacuum induction melting gas atomization method (VIGA) was analyzed for its chemical composition using ICP - OES and a carbon - sulfur analyzer. The results are shown in Table 1.

[0062] Table 1 Chemical Composition of Steel Powder in Example 1 (wt%)

[0063]

[0064] As can be seen from Table 1, the steel powder used in Example 1 belongs to the R4 - class mooring chain steel.

[0065] 2. Particle Size Distribution of Steel Powder

[0066] In Example 1, the particle size of the gas - atomized raw material powder is relatively fine. The particle size distribution of the powder was measured using a Malvern laser particle size analyzer, and the particle size distribution diagram of the powder is as Figure 2 shown.

[0067] As Figure 2It can be seen that the proportion of powder with a particle size of 15 - 53 μm suitable for 3D printing is the highest. The fluidity of the powder measured by a Hall flowmeter is 18.6 s / 50 g, and the apparent density of the powder measured by a Topsizer particle size analyzer is 4.16 g / cm 3 .

[0068] 3. Microscopic Morphology of Steel Powder

[0069] In Example 1, the microscopic morphology of the powder is as Figure 3 shown.

[0070] It can be seen from Figure 3 that the powder has a high sphericity and no obvious agglomeration phenomenon, and is suitable for preparing printed parts by SLM.

[0071] II. Performance Characterization

[0072] 1. Selection of Steel Powder

[0073] The atomized powder is dried in a vacuum drying oven with drying parameters of holding at 80 °C for 6 h. After screening the powder through a special sieve, the powder with a particle size range of 15 - 53 μm and an average particle size of 30.3 μm is selected as the raw material for preparing the ultra-long seamless mooring chain.

[0074] 2. Experimental Scheme and Corresponding SLM Process Parameters

[0075] In the experimental scheme of Example 1, the powder bed selects a layer thickness (h) of 30 μm and a scanning spacing (d) of 110 μm. The laser processing parameters include laser power (P) and scanning speed (v). The laser power is optimized in the range of 175 - 325 W, and three scanning speeds of 800, 1000, and 1200 mm / s are selected for the scanning speed. As shown in Table 2, the parameter combinations studied and the corresponding energy densities are listed. Generally, the laser energy density E (J / mm 3 ) is used as an evaluation index for the printing parameters, and the formula is: E = P / (vhd), where P is the laser power, v is the laser scanning speed, h is the powder layer thickness, and d is the laser scanning spacing.

[0076] Table 2 Experimental Scheme and Corresponding SLM Process Parameters

[0077]

[0078] 3. Forming of Printed Parts

[0079] In the experimental scheme of Example 1, the obtained cube parts, tensile parts, and impact parts are as Figure 4 shown.

[0080] It can be seen from Figure 4 that the forming effect of the experimental printed parts is good, without macroscopic cracks and pore defects, and has a high density.

[0081] 4. Mechanical properties

[0082] The mechanical property data of the mooring chain steel printed with different laser parameters are shown in Table 4.

[0083] Table 4 Mechanical properties of mooring chain steel under different laser parameters

[0084]

[0085]

[0086] As can be seen from Table 4, the tensile strength of the 22MnCrNiMo steel prepared by selective laser melting is much higher than the standard 860 MPa, with an average exceeding 38% or more. At the same time, the changes in the strength and elongation of the T2 and T5 specimens are consistent with the law that the proportion of large-angle grain boundaries and small-angle grain boundaries affects the properties.

[0087] The strength of the T1 specimen under a laser power of 175 W is the highest, with a tensile strength of 1281 MPa, a yield strength of 1121 MPa, and an elongation of 6.7%. The plasticity of the T5 specimen under a laser power of 275 W is the best, with an elongation of 10.2%, a tensile strength of 1175 MPa, and a yield strength of 1010 MPa. The elongation of the specimens shows a trend of first increasing and then decreasing with the increase of the laser power, and the tensile strength and yield strength show a trend opposite to that of the elongation.

[0088] The above experimental results show that the elongation of the SLM-formed steel is slightly lower than the standard. The elongation mainly affects the plasticity of the formed parts and the ductility during reprocessing. Since selective laser melting can directly prepare the required shape, there is no need for reprocessing and shaping a specific shape. Therefore, the influence of elongation in the selective laser melting process is not significant.

[0089] 5. Process comparison

[0090] Comparison of the schematic diagrams of the traditional manufacturing process (TM) and the additive manufacturing process (AM) of Example 1 of the mooring chain Figure 5 is shown as follows.

[0091] As can be seen from Figure 5It can be seen that the traditional manufacturing process of mooring chains requires smelting - casting - rolling - bending - welding, that is, smelting qualified molten steel in an electric furnace of a steel plant, continuously casting it into a round billet ingot through a ladle, hot rolling it into bars of different diameters in a rolling mill, cutting the bars to a fixed length and bending them into rings at an anchor chain factory, and then welding the chain ring interfaces together to finally form a mooring chain. However, the additive manufacturing process of Example 1 only requires smelting - atomization - additive manufacturing, that is, smelting qualified molten steel in an electric furnace of a steel plant, atomizing it into powder through a ladle, and forming chain rings through additive manufacturing to finally form a mooring chain. By comparison, it can be seen that the additive manufacturing process of Example 1 does not require rolling - bending - welding, and the requirement for elongation is no longer so important. The selective laser melting process for manufacturing mooring chains is of great pioneering significance.

[0092] 6. Engineering stress - strain

[0093] The engineering stress - strain curves of steel specimens prepared at three typical laser powers of low, medium, and high (200 W, 250 W, 300 W) are as Figure 6 shown.

[0094] It can be seen from Figure 6 that the elongation of T4 is significantly higher than that of T2 and T6, while the maximum engineering stress of T2 is also significantly higher than that of T4 and T6.

[0095] 7. Impact performance

[0096] The impact toughness requirement for R4 - class mooring chains is greater than 50 J at - 20 °C. The impact performance of mooring chain specimens under different laser powers of the SLM process of the present invention is as Figure 7 shown.

[0097] It can be seen from Figure 7 that under the conditions of laser powers of 175 W and 200 W, the impact absorption energies of the specimens are 121 J and 127 J respectively, exceeding the standard requirements; while from 200 W to 325 W laser power, the impact absorption energy shows a downward trend with the increase of laser power, but the impact absorption energy at 325 W also exceeds the standard requirements. The impact energy under the condition of 200 W laser power is much higher than that at 275 W, which is consistent with the influence law of the area ratio of lower bainite and martensite. Therefore, the impact toughness of the steel prepared by the selective laser melting process meets the requirements of R4 - class mooring chains.

[0098] 8. Impact fracture morphology

[0099] The impact fracture morphologies of mooring chain specimens under different laser powers are as Figure 8 shown.

[0100] It can be seen from Figure 8It can be seen that there are a large number of dimples on the impact fracture surface. Local plastic deformation occurred during the impact of the specimen, which microscopically manifested as the continuous expansion of microcracks inside the material under the action of shear stress, and finally formed small pits. The size and depth of the dimples reflect the plastic deformation ability of the material during the impact process. In the area with deeper and larger dimples, the material experienced greater plastic deformation before fracture and had better impact toughness, such as Figure 8 the area marked with an orange circle in

[0101] 9. Three-ring mooring chain sample

[0102] The physical diagram of the successfully printed three-ring mooring chain sample is as shown in Figure 9 the figure.

[0103] As can be seen from Figure 9 it, the mooring chain is integrally formed without welds.

[0104] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of an ultra-long seamless mooring chain, characterized in that When preparing, a new type of additive manufacturing printer is used, which is composed of n partitions closely connected. One front scraper, one laser, one powder bed, one rising cylinder and one falling cylinder are arranged in each partition. One rear scraper is arranged behind the connection of every two adjacent front scrapers; The preparation method specifically includes the following steps: (1) According to the type and size of the mooring chain links, design the placement mode of the mooring chain on the printer powder bed, make a printing file, and input it into the printer; (2) On the printer with the program set, after the mooring chain steel powder in the n rising cylinders is simultaneously ejected, the n front scrapers push the powder forward to evenly spread the powder on the powder bed, and the n - 1 rear scrapers follow up simultaneously to scrape the powder; (3) The front scraper and the rear scraper retreat to the initial position, the laser is started, and the powder bed is scanned according to the set laser parameters to print the first layer of the mooring chain; (4) Finally, the n falling cylinders drive the powder bed to move down one layer, and the mooring chain steel powder in the n rising cylinders is ejected for the second time, and this powder printing process flow is recycled again to print the second layer, the third layer... until a complete high - level extra - long seamless mooring chain is printed.

2. The preparation method of an ultra-long seamless mooring chain according to claim 1, characterized in that, The n partitions are n independent but simultaneously printable subsystems, and the number of n depends on the required length of the mooring chain to be printed.

3. The preparation method of an ultra-long seamless mooring chain according to claim 1, characterized in that, There are n front scrapers in total, which are the main powder spreading scrapers; there are n - 1 rear scrapers in total, mainly to scrape flat the raised linear powder in the gap between two front scrapers.

4. The preparation method of an ultra-long seamless mooring chain according to claim 1, characterized in that, In step (1), the types of the mooring chain links include studded chain links and studless chain links; the size of the studded chain links is a nominal diameter of 165 - 240 mm, and the size of the studless chain links is a nominal diameter of 34 - 240 mm.

5. The preparation method of an ultra-long seamless mooring chain according to claim 1, characterized in that, In step (1), the placement modes include serpentine and straight; the serpentine is suitable for short chain links, and is bent and coiled to increase the printing length; the straight is suitable for thick chain links and cannot be bent and coiled.

6. The preparation method of an ultra-long seamless mooring chain according to claim 1, characterized in that In step (4), the high - level includes R4, R4S, R5, R6 and the new R7; the seamless means that each link of the mooring chain is formed in one time and there is no weld throughout the body.

Images