U.S. patent application number 09/773586 was filed with the patent office on 2001-09-27 for steel composition and chain formed thereof.
Invention is credited to Leppanen, Rainer.
Application Number | 20010024621 09/773586 |
Document ID | / |
Family ID | 20278436 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010024621 |
Kind Code |
A1 |
Leppanen, Rainer |
September 27, 2001 |
Steel composition and chain formed thereof
Abstract
A chain type steel, suitable for the production of bars with a
diameter of up to about 160 mm, e.g. to be used for the manufacture
of heavy anchor chains, including, in weight-%: 1 C 0.15-0.23 Si
0.10-0.40 Mn 1.00-1.50 P max. 0.025 S max. 0.025 Cr 1.50-2.20 Ni
0.80-1.50 Mo 0.30-0.60 Cu max. 0.30 Al <0.2 V <0.2 Nb <0.2
Ti <0.2 the balance being Fe.
Inventors: |
Leppanen, Rainer;
(Hallefors, SE) |
Correspondence
Address: |
Ronald L. Grudziecki
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
20278436 |
Appl. No.: |
09/773586 |
Filed: |
February 2, 2001 |
Current U.S.
Class: |
420/8 ;
148/320 |
Current CPC
Class: |
C21D 1/18 20130101; C21D
1/25 20130101; C22C 38/42 20130101; C22C 38/46 20130101; C22C 38/04
20130101; C22C 38/44 20130101 |
Class at
Publication: |
420/8 ;
148/320 |
International
Class: |
C22C 038/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2000 |
SE |
0000458-0 |
Claims
1. A steel suitable for the production of bars with a diameter of
up to about 160 mm comprising, in weight-%:
10 C 0.15-0.23 Si 0.10-0.40 Mn 1.00-1.50 P max. 0.025 S max. 0.025
Cr 1.50-2.20 Ni 0.80-1.50 Mo 0.30-0.60 Cu max. 0.30 Al <0.2 V
<0.2 Nb <0.2 Ti <0.2
the balance being Fe.
2. The steel according to claim 1, comprising, in weight-%:
11 C 0.19-0.21 Si 0.20-0.30 Mn 1.15-1.25 P max. 0.015 S max. 0.020
Cr 1.65-1.75 Ni 1.15-1.25 Mo 0.42-0.48 Cu max. 0.25 Al <0.2 V
<0.2 Nb <0.2 Ti <0.2
the balance being Fe.
3. The steel according to claim 1, comprising, in weight-%:
12 C 0.18-0.20 Si 0.20-0.30 Mn 1.15-1.25 P max. 0.015 S max. 0.020
Cr 1.65-1.75 Ni 1.15-1.25 Mo 0.30-0.36 Cu max. 0.25 V 0.10-0.14 Al
<0.2 V <0.2 Nb <0.2 Ti <0.2
the balance being Fe.
4. The steel according to claim 2, being hardened at 850.degree. C.
and tempered at 615.degree. C.
5. The steel according to claim 3, hardened at 890.degree. C. and
tempered at above 630.degree. C.
6. The steel according to claim 6, tempered at 645.degree. C.
7. A chain formed from the steel according to claim 1.
8. A chain formed from the steel according to claim 2.
9. A chain formed from the steel according to claim 3.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a steel, and more
specifically a chain type steel, suitable for the production of
bars with a diameter of up to about 160 mm, e.g. to be used for the
manufacture of heavy anchor chains.
[0002] In the discussion of the state of the art that follows,
reference is made to certain structures and/or methods. However,
the following references should not be construed as an admission
that these structures and/or methods constitute prior art.
Applicant expressly reserves the right to demonstrate that such
structures and/or methods do not qualify as prior art against the
present invention.
[0003] For many years the applicant has produced bars for the
manufacture of heavy anchor chains primarily used for anchoring of
oil riggs. Bar dimensions up to 155 mm diameter have been produced.
For these coarse dimensions a very low carbon steel type has been
used which causes a number of difficulties in the steel plant, this
steel being very aggressive towards the melting equipment. The
steel types used for smaller diameter anchor chains, being low
alloyed steels, give unsatisfactory mechanical properties for
bigger diameter anchor chains, that is for bar diameters above
about 130 mm.
[0004] Thus, there is a need for an improved steel for making heavy
anchor chains, which behaves better in the steel plant.
[0005] In e.g. GB 2 110 239 A, a steel for producing anchor chains
is disclosed having the following composition, in wt. %: C
0.03-0.07; Si 0.10-1; Mn 1.2-2.5; Cr 1.8-3; Ni 1.5-3;
Mo.ltoreq.0.5; Nb, V, Ti total 0-0.10. This steel is claimed to
have a yield point of at least 600 Mpa, a rupture limit of at least
900 Mpa at room temperature and an impact toughness of at least 40
Joule at -20.degree. C. The restrictions of anchor steels for oil
riggs in the ocean are becoming even stricter, and there is a
demand for a steel with improved characteristics.
[0006] Through JP-61276956 is previously known a low alloy chain
link steel including chromium and nickel being processed to obtain
a tempered martensitic structure. This steel comprises, in wt. %: C
0.20-0.30; Si 0.10-0.30; Mn 0.70-1.70; Cr 0.40-0.70; Ni 0.75-2.00;
Al 0.01-0.05; P.ltoreq.0.03; S.ltoreq.0.030. This steel is tempered
after being quenched or case-hardened by means of carburising so
that the microstructure is tempered martensite. At the upper region
of the carbon content range, the weldability will deteriorate as
well as the toughness, and there is a risk for hardening cracks.
The absence of Mo means there is a risk for temper embrittlement.
Ni is obviously used to compensate for a low Cr content, which
makes this steel quite expensive.
[0007] Through JP-52006847B is previously known a high stregnth low
alloy steel chain manufactured from steel bars containing, in wt.
%: C 0.1-0.2; Si 0.1-0.5; Mn 1.0-1.6; Cu 0.1-0.5; Ni 0.5-1.5; Cr
0.3-1.0; Mo 0.2-0.8, P<0.02; S>0.015, and acid.sol Al
0.02-0.1. The starting steel bars have a high tensile strength,
improved weldability and good workability, and the steel chain
produced is tempered at 550-680.degree. C. The low Cr, and the low
C content both affect the hardenability, which is deleterious for
large diameter anchor chains.
SUMMARY OF THE INVENTION
[0008] An object of the invention is to provide a steel with
improved properties and an improved behavior in the steel
plant.
[0009] According to one aspect, these and other aspects are
obtained with a steel according to the invention, comprising in
weight-%:
2 C 0.15-0.23 Si 0.10-0.40 Mn 1.00-1.50 P max. 0.025 S max. 0.025
Cr 1.50-2.20 Ni 0.80-1.50 Mo 0.30-0.60 Cu max. 0.30 Al < 0.2 V
< 0.2 Nb < 0.2 Ti < 0.2
[0010] the balance being Fe.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a graph showing the hardness as a function of the
tempering temperature for laboratory melt sample materials.
[0012] FIG. 2 is a graph showing the hardness as a function of the
depth underneath the surface, for hardened and not tempered samples
of said laboratory melt sample materials.
[0013] FIG. 3 is a graph showing the hardness as a function of the
depth underneath the surface, for hardened and tempered samples of
said laboratory melt sample materials.
[0014] FIG. 4 is a graph showing the jominy hardenability for said
laboratory melt sample materials.
[0015] FIG. 5 is a graph showing the jominy hardenability for a
full scale melt material.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The steel grade according to the invention is well-suited
for manufacture of so called K4 chain with a diameter up to about
160 mm, and is not aggressive towards the melting equipment, and
which steels result in very high qualities of the the finished
chain.
[0017] For the investigation, sample material was manufactured as
laboratory melts with ingot dimensions of 225.times.225 mm. The
respective ingots were forged into bars with a diameter of 140 mm.
This gives a reduction rate of about 3, which is insufficient in
normal production. This means that the results from normal
production will be significantly better than the test results
discussed in the following description.
[0018] Test samples were produced having two different analyses,
MnCrNiMo variant, and MnCrNiMoV, respectively.
[0019] The steel according to the invention, after through
hardening, gives a very small difference between surface hardness
and hardness at the center.
[0020] In Table I, the analyses are given for two different steel
samples.
3TABLE I Variant C Si Mn P S Cr Ni Mo Cu V Al MnCrNiMo 0.20 0.30
1.26 0.008 0.004 1.80 1.25 0.45 0.19 0.022 No. 129 MnCrNiMoV 0.19
0.24 1.10 0.007 0.003 1.78 1.20 0.33 0.18 0.10 0.024 No. 131
[0021] These two sample steels were analyzed according to the
following.
[0022] 1. Tempering:
[0023] FIG. 1 shows the hardness as a function of the tempering
temperature, tempering time 1 hour. Hardening temperatures for the
respective melts are 850.degree. C. for melt No. 129, and
890.degree. C. for melt No. 131. Sample size 25.times.25.times.25
mm.
[0024] As can be seen in FIG. 1 melt No. 129 exhibits a flat curve
without breaking points, which makes it less sensitive to
variations in tempering temperature fluctuations. For the melt 131
the vanadium gives a strong tempering resistance up to 630.degree.
C., but at higher temperatures a steep curve is obtained with an
increased sensitivity for temperature variations.
[0025] 2. Through hardening:
[0026] FIG. 2 shows the hardness as a function of the depth
underneath the surface of a hardened not tempered sample with a
diameter of 140 mm, and
[0027] FIG. 3 shows the hardness after tempering at 615.degree. C.
for the melt No. 129 and at 645.degree. C. for melt No. 131.
[0028] The hardening temperature for the melt No. 129 was
850.degree. C. and for the melt No. 131, 890.degree. C., all being
quenched in water.
[0029] As is evident from the diagramms the melt No. 129 exhibits
the best result of the through hardening both for the untempered
and the tempered sample. The difference in hardness between surface
and center is very small.
[0030] 3. Jominy:
[0031] FIG. 4 shows the result of the jominy test. The
austenitization temperature has been the same as with the through
hardening test according to item 2 above.
[0032] The jominy test result corresponds well with the through
hardening result according to item 2. Melt No. 129 has the best
hardenability.
[0033] 4. Mechanical properties
[0034] Table II below shows the mechanical properties of hardened
and tempered bar samples with a diameter of 140 mm. Heat treatment
and taking of samples were made according to normal practice for
testing of chain material. The melt No. 129 showing the best
results in the hardenability testing and tempering tests has been
examined at three different tempering temperatures.
4TABLE II Mechanical properties Harden. Tempering ReI Rm A5 Z KV, J
Melt temp .degree. C. temp .degree. C. Mpa Mpa % % -40.degree. C.
-20.degree. C. .+-.0.degree. C. 129 850 615 822 917 17 63 83 134
138 590 857 937 16 72 89 101 142 570 923 992 15 67 108 102 123 131
890 645 896 963 17 64 99 122 126 Demand acc. to DNV 580 860 12 50
50 70
[0035] The two melt samples show rather similar results. The lowest
allowed tempering temperature for chain K4 is 570.degree. C.
according to DNV (Det Norske Veritas). As is evident from Table II
this demand would not cause any problems, but at the same time does
not allow for any substantial reductions of alloy elements.
[0036] The impact toughness at -20.degree. C. is close to the
demand according to DNV, but only an area reduction rate of 3 is
made with the melt sample, while castings in the production will
have an area reduction rate of about 12, so this feature will be
substantially improved in full scale manufacture.
[0037] 5. Testing according to DNV approval rules of a full scale
production melt.
[0038] Charge analysis for the production of 160 mm.o slashed.
bar:
5 C Si Mn P S Cr Ni Mo Cu 0.19 0.26 1.19 0.008 0.009 1.75 1.18 0.44
0.14 Al Sn Sb (ppm) As B (ppm) O (ppm) N (ppm) 0.015 0.007 2 0.008
1 9.8 72
[0039] Heat treatment sensitivity analysis
[0040] Varied austenitization temperature
[0041] Austenitisation 30 min, cooling in water at hardening
[0042] Tempering 610.degree. C., 60 min, cooling in water after
tempering
6 Sample Austenitisation Rel Rm A5 Z KV - 20.degree. C. No.
temperature .degree. C. Mpa Mpa % % J 1 840 890 958 18 70 over 147*
2 870 879 957 17 71 over 147* 3 910 879 957 18 72 over 147* *Max.
force in testing equipment.
[0043] Heat treatment sensitivity analysis
[0044] Varied tempering temperature
[0045] Austenitisation 870.degree. C., 30 min, cooling in water at
hardening
[0046] Tempering 60 min, cooling in water after tempering
7 Sample Tempering Rel Rm A5 Z KV - 20.degree. C. No. temperature
.degree. C. Mpa Mpa % % J 6 570 991 1057 16 67 over 147* 7 590 925
999 17 69 over 147* 2 610 879 957 17 71 over 147* 8 630 838 914 20
72 over 147* 9 650 782 858 21 73 over 147* *Max. force in testing
equipment.
[0047] Heat treatment sensitivity analysis
[0048] Varied tempering time
[0049] Austenitisation 870.degree. C., 30 min, cooling in water at
hardening
[0050] Tempering 610.degree. C., cooling in water after
tempering
8 Sample Tempering Rel Rm A5 Z KV - 20.degree. C. No. time, min Mpa
Mpa % % J 4 30 890 958 18 70 over 147* 2 60 879 957 17 71 over 147*
5 90 869 941 18 74 over 147* *Max. force in testing equipment.
[0051] Testing for temper embrittelment
[0052] Varied cooling velocity after tempering
[0053] Austenitizing 870.degree. C., 30 min, cooling in water at
hardening
[0054] Tempering 610.degree. C., 60 min
9 Sample Tempering KV - 0.degree. C. KV - 20.degree. C. KV -
40.degree. C. No. temperature .degree. C. J J J 2 water 147* 147*
147* 2L >40 min to 147* 147* 147* 300.degree. C. *Max. force in
testing equipment.
[0055] The degree of reduction is about 12 times, which fact
explains the big differences in performance compared to the
laboratory test materials, having a degree of reduction of only
about 3 times, but still being improved compared to the prior
art.
[0056] While the present invention has been described by reference
to the above-mentioned embodiments, certain modifications and
variations will be evident to those of ordinary skill in the art.
Therefore the present invention is to be limited only by the scope
and spirit of the appended claims.
* * * * *