* End link. 

Type and size of end link. ( unit  mm)

Permissible deviation of the link and its accessories.

1) The manufacturing tolerance of the anchor chain and accessories should be within ±2.5% (and a good fit between the various components of the anchor chain should be guaranteed).

2) The cross-bearing area at the ring crown is at least equal to the theoretically calculated area of the chain link or attachment diameter, i.e. the lower deviation is 0. The area is obtained from the average of the four measured values in the horizontal direction along the circumference of the chain diameter.

3) The tolerance of the diameter at the crown of the chain link.

4) The deviation of the connecting five chain links is +2.5% in the upper and 0 in the lower part.

5) The curved part of the end link, connecting the shackle and the end shackle has a deviation of +2.5% in the inner diameter and 0 in the lower deviation.

6) The upper deviation of the attachment diameter is +5% and the lower deviation is 0.

* Technical requirement.

1,The material of anchor chain and its accessories.

1) The material of anchor chain and its accessories should use marine anchor chain steel which is above CM490 specified in GB/T 18669.

2) The surface quality, dimensional deviation, chemical composition, mechanical properties and process properties of the materials used for anchor chains and accessories shall comply with the relevant provisions of GB/T 18669.

3) The round steel manufacturing anchor chain and accessories shall be checked by the anchor chain manufacturing plant whether its mark is consistent with the items listed in the certificate, and check whether the surface quality, dimensional deviation, chemical composition, mechanical properties and process properties of the round steel comply with the provisions of GB/T18669.

4)  links in the same link should be made of the same grade material.

2, Test load of the anchor chain. Under the load of this table, the links should not be cracked or fractured.

3, The technology of anchor chain and accessories.

1) The link shall not be welded by hand, and the link with a diameter greater than 26mm shall be manufactured by flash butt welding or other welding methods approved by the inspection agency.

2) The joining shackles, end shackles and swivels should be forged.

4, The surface quality.

1) The surface of the link and accessory shall not have cracks, delamination and other defects affecting the quality, and shall not obstruct the fit and relative rotation of the parts, as well as changes in the size of the link.

2) The welding area of the link should be welded thoroughly, and there should be no defects such as porosity, overburning, slag clamping, etc.

3) Small surface defects can be eliminated by sanding, but the diameter of the polished chain link should be within its tolerance, and the polished part should transition smoothly with the surrounding surface, and the grinding depth away from the chain crown part is allowed to be relaxed, but not more than 5% of the chain diameter.

4) Links and accessories are painted in accordance with GB/T 533 after the completion of tests and inspections.

5, Heat treatment.

1) After welding, the entire section of anchor chain and accessories should be normalized or normalized and tempered or quenched and tempered to eliminate internal stress and ensure mechanical properties of heat treatment.

2) The heat treatment of the anchor chain should be carried out before the tensile test and the pull test.

3) All specimens should be heat treated with the same process as the anchor chain they represent.

4) The heat treatment of the accessory should adopt the heat treatment method of the same level of anchor chain.

*Test method.

1, Material test.

1) The test method of material test is carried out in accordance with the relevant provisions of GB/T 18669.

2) When any one of the tensile and bending tests is unqualified, the unqualified items should be doubled for re-testing, and the re-test specimens should be taken from different round steels, and must not be sampled from the original round steel. If the re-examination result is qualified, the batch of materials can be accepted.

3) When the impact test is unqualified, as long as the single value below the specified average value does not exceed two, and at most only one single value is less than 70% of the average value, another set of three impact specimens can be taken in the vicinity of the original sample for additional testing, and the results obtained by the additional test should be added to the original results to obtain a new average, which can be accepted when the value is not lower than the specified average, and among the six single values participating in the average, the single value below the specified average value shall not exceed two. And only allow at most one single value to be less than 70% of the average, otherwise it cannot be accepted.

4) If the results of the re-examination test do not meet the specified requirements, a second heat treatment can be carried out, followed by a re-sampling test, and if the results are good, the batch of materials is considered to be qualified. If the re-test after heat treatment is still unqualified, the batch of materials should be scrapped.

2, Size, quality and technic test.

1) The relevant dimensions are detected with the corresponding measuring instrument.

2) Check the quality by observation.

3) Check welding methods, manufacturing processes and heat treatments by observing and consulting relevant process documents.

3，Anchor chain and accessories test.

1)  Breaking test.

a, The connected chain link specimen should be intercepted from the chain link made by the same production process for a breaking test. Here is the Methods of sampling.

b, Unsected unsubscribed chains, generally take a five-ring specimen in 55m for breaking test.

c, Anchor chains with a single section length less than the specified length can sample sections made of the same batch of materials and the same process. Under normal circumstances, when the chain diameter d is not more than 12mm, the total length is taken every 55m to take a five-ring specimen; When d is greater than 12.5mm, a three-ring specimen is taken for breaking test every 27.5m of total length.

d, Accessories should be sampled for breaking testing. Under the same condition that the chain diameter of the same batch of materials, the same production process and the joining links are the same, the end link, the end shackle, swivel, and the joining shackle are taken from each of the 25. Where attachments that have been pulled off tests have been done, they shall not be used as accessories.

e, After the link is applied to the corresponding load, the accessory specimen is applied to the corresponding load of the chain diameter of the link to which it is connected, and the specimen has no signs of breaking, and the specimen test is considered to be qualified.

f, If the breaking test of the anchor chain is not qualified, another specimen should be taken from the same link for testing, and if the test is qualified, the remaining three links can be considered qualified. If the re-test fails, the link of the specimen should be scrapped. The remaining three links should be sampled section by section for a breaking test, and as long as one of the sampling experiments is unqualified, the three links should be scrapped.

g, If the breaking test of the attachment is not qualified, two additional attachments from the same batch of attachments should be retested. If one of the two annexes fails a specimen test, the annex should be scrapped.

2) Proof test.

a, After the breaking test of the anchor chain and accessories is passed, the proof test of the chain link and accessories can be carried out.

b, Each link should be subjected to a proof test, the same material, the same production process and various accessories with the same chain diameter, which can be connected together individually or several times, or can be carried out with the link for proof testing.

c, Apply a specified load to the test, and the relative position of each chain link should be correct during the test, and there must be no rubbing.

d, After the proof test, the length of the entire section of each link and the length of the five rings connected should be measured, and the overlapping two rings should be measured again after the measurement of the length of the five rings; Measurements should be made while maintaining a tensile load of 10% and should conform to the specified tolerances.

e, Three links are selected from each 27.5m long anchor link for additional dimensional inspection, and if one link does not meet the specified tolerances, five more chain links should be taken from every 27.5m long link for measurement. Five-link measurement If two of the links exceed the tolerance requirements, then all the links of the link should be measured in accordance with the regulations

f, When the link is subjected to proof test, the number of broken rings of the first link shall not exceed the following specified number of rings:

--- chain diameter d is not more than 22mm, it shall not exceed the second ring;

- When the chain diameter d is greater than 22mm, it shall not exceed one ring.

g, The link with serious defects and size exceeding the tolerance requirements after the proof test should be removed and replaced with a qualified  link (the new link should be heat treated with the same heat treatment as the whole link). The newly replaced link should still be subjected to a proof test.

h, If the number of links to be swapped exceeds 5% of the number of links, the link shall be scrapped.

I, When there is a breaking link in the proof test, a new chain link is replaced before a proof test is performed. If there are any more signs of breakage in the experiment, the link should be scrapped.

3) Mechanical properties test of anchor chains and accessories of CM690 grade.

a, The CM690 anchor chain should cut one tensile specimen and two sets (three in each group) of notched impact specimens from each four sections of 27.5m or less than 27.5m long links, but the specimen should not be cut on the link where the proof test was performed.

b, The proof and impact specimens of the anchor chain should be cut on the base metal, and one set of specimens should be placed so that the notch is located at the weld. 

c, One proof specimen and a group of three V-notched impact specimens are taken from the same specification, the same furnace number, and the same heat treatment process attachment.

d, The proof and impact tests of the specimen are respectively stipulated in GB/T228 and GB/T229. The test results should comply with the provisions of GB/T18669-2002.

e, When the proof test of the anchor chain is unqualified, a double specimen should be taken for re-examination, and the re-test sample should be taken from different links of the original link, and when the proof test of the accessory is unqualified, a double specimen should be taken for re-examination.

f, When the impact test fails, as long as the single value below the specified average value does not exceed two, and at most only one single value is less than 70% of the average value, it is carried out according to the requirements.

g, Re-examination failure is not allowed to re-perform a heat treatment, and then do tensile, impact test, if it is not qualified, the link should be scrapped. The remaining sections represented by the link should be sampled section by section for tensile and impact testing.