U.S. patent number 3,880,436 [Application Number 05/376,562] was granted by the patent office on 1975-04-29 for ram block.
This patent grant is currently assigned to The Rucker Company. Invention is credited to Jose Roberto Canal.
United States Patent |
3,880,436 |
Canal |
April 29, 1975 |
Ram block
Abstract
A ram block for a blowout preventer which can be used
successfully in a hydrogen embrittlement environment. The body of
the ram block is made of an alloy having an upper hardness level of
Rockwell 22 on the C scale (Rc 22), and is provided with an inner
supporting edge of a soft, relatively stress-free, workhardenable
alloy having an upper hardness level of about Rc22 which is capable
of rapidly hardening on slight deformation at least about Rc 35 and
upon engagement with and deformation by a tool joint and the load
of the drill or other string of pipe forms a cutting and supporting
edge of a hardness level sufficient to bite into the tool joint and
support the heavy weight of the drill or other string of pipe. The
relatively soft, work-hardenable alloy, may be deposited in place
by welding and is soft enough to be readily machined to the desired
shape. A number of embodiments and examples of the invention is
disclosed.
Inventors: |
Canal; Jose Roberto (Beaumont,
TX) |
Assignee: |
The Rucker Company (Houston,
TX)
|
Family
ID: |
23485506 |
Appl.
No.: |
05/376,562 |
Filed: |
July 5, 1973 |
Current U.S.
Class: |
277/325; 428/680;
428/679; 428/684; 277/940 |
Current CPC
Class: |
E21B
33/062 (20130101); Y10T 428/12944 (20150115); Y10S
277/94 (20130101); Y10T 428/12972 (20150115); Y10T
428/12937 (20150115) |
Current International
Class: |
E21B
33/06 (20060101); E21B 33/03 (20060101); F16j
015/00 () |
Field of
Search: |
;277/126,127,185,236
;148/34 ;29/196.6,196 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rothberg; Samuel B.
Attorney, Agent or Firm: Weiler; James F. Giller; Jefferson
D. Dobie, Jr.; Dudley R.
Claims
What is claimed is:
1. A ram block comprising,
a body portion formed of an alloy having an upper hardness level of
about Rc22 and having an arcuate opening at its inner portion for
engaging pipe and tool joints in a string of pipe, and
a supporting inner edge portion at its arcuate opening formed of a
work hardenable alloy of an upper hardness level of about Rc22 when
relatively stressfree and capable of work-hardening to a hardness
level of at least about Rc35 upon deformation, engagement with and
deformation by one of the tool joints by the load of the string of
pipe work hardening the alloy sufficiently to indent itself into
the tool joint.
2. The ram block of claim 1 where,
the body portion includes at least one guide member extending from
its inner portion and at least one recessed portion for receiving a
guide member or members of a mating ram block.
3. The ram block of claim 2 including,
sealing means disposed on the ram block for sealingly engaging the
string of pipe.
4. The ram block of claim 1 where,
the work-hardenable alloy is welded to the upper surface of the
arcuate opening, and is machined to shape.
5. In a blowout preventor for sealing off and engaging pipe and
tool joints in a string of pipe,
a generally cylindrical body portion arranged to be connected to
casing through which the string of pipe passes,
a pair of mating ram blocks arranged on opposite sides of the body
portion so that when in open position the passageway through the
body is open sufficiently to permit passage of the pipe and tool
joints in the string of pipe and when in closed position engage one
another to close the passageway through the body,
ram means operable to open and close said ram blocks,
each of said ram blocks comprising a body portion formed of an
alloy having an upper hardness level of about Rc22 and provided
with an inner arcuate opening, and
a supporting inner edge of the arcuate portion formed of a
work-hardenable alloy of an upper hardness level of about Rc22 when
relatively stress-free and capable of hardening to a hardness level
of at least about Rc35 upon deformation, engagement with and
deformation by one of the tool joints caused by the load of the
string of pipe work hardening the alloy sufficiently to indent
itself into the tool joint.
6. The invention of claim 5 where,
each of the pair of mating ram blocks has at least one guide member
and a mating recess or recesses for receiving the guide member or
members of the other arranged so that upon closing the ram blocks
the guide member or members or each ram block is received in the
recess or recesses of the other of the mating pair of ram blocks
thereby guiding the pair of ram blocks into engagement about the
tool joint and the string of pipe.
7. The invention of claim 6 including,
seal means on each of the ram blocks arranged to seal the space
between engaging faces of the ram blocks and about the string of
pipe and between the ram blocks and the body.
8. The invention of claim 5 where,
the work-hardenable alloy is welded to the body portion to provide
the upper surface, and
is machined to shape.
9. The ram block of claim 1 where,
the work-hardenable alloy comprises, by weight,
from about 0 to about 0.10 percent carbon,
from about 8 to about 20 percent chromium,
from about 10 to about 20 percent molybdenum,
from about 2 to about 6 percent tungsten,
from about 0 to about 10 percent iron,
up to about 1.2 percent silicon,
up to about 1.5 percent manganese,
from about 41 to about 78 percent nickel.
10. The invention of claim 8 where the work-hardenable alloy
comprises, by weight,
from about 0 to about 0.10 percent carbon,
from about 8 to about 20 percent chromium,
from about 10 to about 20 percent molybdenum,
from about 2 to about 6 percent tungsten,
from about 0 to about 10 percent iron,
up to about 1.2 percent silicon,
up to about 1.5 percent manganese,
from about 41 to about 78 percent nickel.
Description
BACKGROUND OF THE INVENTION
Occasionally, in the drilling of oil and gas wells it is necessary,
as an emergency procedure, to rely on the rams of a blowout
preventer to support a string of drill pipe. Common practice is to
close the pipe rams immediately below a tool joint and suspend the
dill pipe load on the upper face of the ram blocks upon which the
tool joint's shoulder is resting.
Deep drilling on land and especially offshore has resulted in very
high load-carrying requirements for the ram blocks: for example, up
to and in excess of 600,000 pounds of load. In drilling many wells,
a hydrogen sulfide environment is encountered which causes hydrogen
embrittlement and hence failure of ram blocks having a strength and
hardness level sufficient to support these heavy drill string loads
in a non-hydrogen embrittlement environment.
For example, when hydrogen sulfide contacts ram blocks made from a
steel alloy having a strength and hardness level exceeding that of
the tool joint, say Rc35-40, the hydrogen sulfide decomposes to
form a metal sulfide and to liberate atomic hydrogen which diffuses
into the metal lattice. The metal is then said to be hydrogen
embrittled. If a metal is subjected to high stress, brittle failure
occurs at stress levels many times lower than the stress required
for failure in the absence of hydrogen.
It has been found that alloy steels not exceeding a hardness level
of Rc22 may be used successfully in hydrogen sulfide environments
since these alloys are tough and resist crack propagation and do
not become hydrogen embrittled under stresses. Alloys of such a
hardness level, however, have a strength and hardness level less
than that of the tool joints in the drill string and, accordingly,
upon engagement with a tool joint, these alloys are deformed by the
tool joints and do not support the heavy drill string load. In
order to support the drill string load, it is necessary that the
hardness of the supporting edge and tool-engaging part of the ram
block exceed the hardness of the tool joints in order to prevent
deformation of the supporting portion of the ram blocks and to
support the drill string load.
Ram blocks made of alloys of Rc45 have a strength and hardness
which exceeds the hardness of the tool joints and thus are not
deformed by and support the drill string load when engaged by a
tool joint; however, such alloys are subject to hydrogen
embrittlement when used in a hydrogen sulfide environment, and thus
crack and fail under heavy drill string loads.
One solution to the problem is to make the ram blocks from exotic
metals not subject to hydrogen embrittlement which do have a
sufficient level of hardness to bite into the lower tapered
shoulder of a tool joint and support the drill string without
deformation of the load-supporting upper face of the ram block; for
example, A-286, Waspalloy, Inconel, and Rene 41. However, these
metals are extremely expensive.
What might appear to be a solution to the problem is to provide on
a relatively soft ductile matrix, that is, one having an upper
hardness level of about Rc22, a hard edge which is harder than the
tool joint so that it will bite into the tapered lower end of the
tool joint without losing its cutting edge or cutting ability. It
would appear that such a hard supporting edge could be mechanically
fastened to the ram block or friction welded in place. Hard facing
material of sufficient hardness to bite into the tool joint and
support the drill string load could be welded on the relatively
soft ram block. Such a hard supporting edge or hard facing,
however, is subject to hydrogen embrittlement and fail when used in
a hydrogen sulfide environment. In addition, hardfacing by welding
is difficult to machine and cracks as it is being welded.
The foregoing problems and disadvantages are solved and overcome by
the provision of, and the present invention is directed to, a ram
block having a body of a relatively soft ductile material, that is,
having an upper hardness level of Rc22, provided with a supporting
inner portion of a relatively soft, work-hardenable alloy, which
when relatively stress-free has an upper hardness level of about
Rc22 and hence not subject to failure because of hydrogen
embrittlement, is easily machined into the desired shape, and upon
energizing the ram blocks to bring them into engagement with the
tool joint, rapidly work-hardens sufficiently to indent itself into
the tool joint and support the drill string load without
substantial deformation. Thus, the supporting edge portion of the
ram blocks is made of a work- or strain-hardenable alloy low enough
in hardness in the welded condition to allow the metal to be easily
machined and which upon slight deformation is capable of rapidly
work hardening to stength levels of Rc35-40. At this hardless level
the ram block supporting edge can "bite" into a normal tool joint
and support the drill string load. The work-hardenable alloys
almost immediately harden to a leval sufficient to bite into the
tool joint upon very slight deformation by engagement with the tool
joints so that there is only slight deformation of the
work-hardenable supporting edges and, after work-hardening, the
edges can bite into the tool joint and support considerable load:
such as 600,000 pounds and more.
The inventor is not aware of any prior publications or uses of a
ram block provided with a rather soft, stress-free deposit which is
part of the supporting edge of a ram block and remains soft until
the ram blocks are energized and upon engagement of the supporting
edge with the tool joint, the surface of the supporting edge is
deformed slightly and immediately becomes work-hardened sufficient
to indent itself into the tool joint and support the drill string
load. There are, however, publications which discuss work,
precipitation or strain hardening of alloys and the structure of
such alloys. For example, see Dislocations and Plastic Flow of
Crystals by A. H. Cottrell, International Series of Monographs on
Physics, published at Oxford, England, by the Clarendon Press and
particularly Sections 12 and 14; and Structure of Metals by
Barrett, Metallurgy and Metallurgic Engineering Series, 2d Edition,
published by McGraw-Hill Book Company, Inc., New York, beginning at
pages 221, 351 and 414.
SUMMARY
The present invention relates to ram blocks used in blowout
preventers which may be used universally, that is, under all
conditions, including conditions causing hydrogen embrittlement
such as use in hydrogen sulfide environments, but yet when it is
necessary to rely on the rams of the blowout preventer to support
the drill pipe string, the ram blocks will bite into a tool joint
of the drill string and support the drill string load without
excessive deformation. More particularly, the present invention
relates to such ram blocks which have a metal body having an upper
hardness level of about Rc22, and hence not subject to failure by
hydrogen embrittlement, provided with a relatively soft as
deposited hardness which very easily meets the upper hardness level
of about Rc22, is easily machinable, yet upon deformation is
capable of work- or strain-hardening to a at least about Rc35, and
upon engagement with and deformation by a tool joint and the load
of the drill pipe string, work-hardens to level sufficient to bite
into the tool joint without any further deformation and support the
drill string load.
It is therefore an object of the present invention to provide ram
blocks for use in blowout prevents capable of supporting
substantial drill pipe weight, have the necessary hardness to bite
into and support a drill pipe string by its tool joint and which
can be used in a hydrogen sulfide environment.
A still further object of the present invention is the provision of
ram blocks, the body of which is formed of an alloy having an upper
a hardness level of about Rc22 and which has a relatively soft
supporting edge which rapidly work- and strain-hardens upon slight
deformation to a hardness level sufficient to bite into a tool
joint and support an extremely heavy drill string load.
A still further object of the present invention is the provision of
ram blocks for use in blowout preventers which are formed of an
alloy having an upper hardness level of about Rc22 and which have
supporting inner edges with a stress-free metal which stays in situ
until the strength is needed and, by energizing the ram blocks to
engage a tool joint, work harden upon slight deformation and indent
themselves in the tool joint and have sufficient strength to
support the drill string load.
Yet a further object of the present invention is the provision of
such ram blocks in which a work-hardenable surface is deposited
about the edge of the ram block to provide a work-hardenable
supporting surface for the conditions of use and yet is soft enough
when deposited to be readily machined without substantial
cracking.
A still further object of the present invention is the provision of
ram blocks for use in blowout preventers which may be used under
all well conditions and which may be manufactured readily, easily
and economically.
A further object of the present invention is the provision of ram
blocks for use in blowout preventers, the body of which is formed
of an alloy having an upper hardness level of about Rc22 and which
has a weld deposit of work-hardenable material having an upper
hardness level of about Rc22 and capable upon deformation of work
hardening to a hardness level of at least about Rc35, machined to a
desirable cutting edge on its inner surface and which upon
deformation by engagement with a tool joint and the load of the
drill string hardens to a level sufficient to bite into the tool
joint of the drill string and to carry the heavy load of the drill
string should it become necessary in the course of operation.
A still further object of the present invention is the provision of
a ram block for use in blowout preventers which will support a
heavy drill string load, should it become necessary in the course
of operation, and which is not subject to hydrogen embrittlement
when used in a hydrogen sulfide environment.
Other and further objects, features and advantages of the present
invention are apparent from the abstract of the disclosure, the
background of the invention, this summary, a brief description of
the several views of the drawings, the description of the preferred
embodiments, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary, side view, partly in section, illustrating
a blowout preventer having ram blocks according to the present
invention shown supporting a drill string by engagement with a tool
joint,
FIG. 2 is a plan view of one of the ram blocks, sealing rubber and
ram holder illustrated in FIG. 1,
FIG. 3 is a fragmentary, cross-sectional view taken along the line
3--3 of FIG. 2 and illustrates the work-hardenable supporting
surface and edge of the ram block,
FIG. 4 is a perspective view of one of the ram blocks in FIG.
1,
FIG. 5 is a vertical, sectional view of the work-hardenable
supporting edge of the ram block of FIG. 4,
FIG. 6 is a perspective view of another form of ram block having a
work-hardenable supporting surface according to the invention,
FIG. 7 is a fragmentary, vertical sectional view illustrating a ram
block having a modified form of work-hardenable supporting
surface,
FIG. 8 is a view similar to that of FIG. 7 illustrating a still
further modification of the work-hardenable supporting surface,
FIG. 9 is a view similar to that of FIGS. 7 and 8 illustrating a
still further modification of a work-hardenable supporting
surface,
FIG. 10 is a view similar to that of FIGS. 7-9 illustrating a still
further embodiment of a work-hardenable supporting surface, and
FIG. 11 is a view similar to that of FIGS. 7-10 illustrating a
still further embodiment of a work-hardenable supporting surface on
a ram block
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, and particularly to FIG. 1, a
conventional blowout preventer, generally indicated by the
reference numeral 10, is illustrated, which may be any conventional
type blowout preventer, such as a Rucker-Shaffer LWS hydraulic
blowout preventer. The blowout preventer 10 includes a central
generally cylindrical body 12 having an enlarged passage 14 which
is secured to conductor pipe or casing, not shown, used in drilling
an oil or gas well. A drill string, generally indicated by the
reference numeral 16, and including the sections of drill pipe 18
connected by the tool joints 20 pass through the central opening or
passage 14 in the body 12 of the blowout preventer 10 during normal
operations. It is noted that the tool joints, or connections, 20
are of a larger diameter than the sections of drill string 18 and
normally have tapered, outwardly-extending circumferential
shoulders 22 and 24 at their lower and upper ends,
respectively.
The blowout preventer 10 includes a pair of ram blocks or ram block
assemblies 26 which are actuated to a closed and opened position by
ram means, such as the ram shafts 28 movable within the ram bodies
30, normally by a piston, not shown, in the ram piston chamber 32.
During normal operations, the ram blocks are in open position
providing a generally unobstructed passage 14, but upon actuation
of the ram means the rams close the mating ram blocks 26 about the
drill string, as shown in FIG. 1.
No more description is given or deemed necessary of the blowout
preventer and the manner of actuating the rams for opening and
closing the ram blocks or ram block assemblies 26 as the ram blocks
or ram block assemblies of the present invention may be used with
any type of blowout preventer and may be actuated in any desired
manner, many of which are well known to and used in the commercial
drilling of oil and gas wells.
Referring now to FIG. 2, a ram block assembly 26 is illustrated
which is here illustrated as composed of three principal parts, a
ram block holder 34, the ram block 36, provided with a generally
arcuate opening 38, and sealing member 39 fitted between the ram
holder 34 and the ram block 36.
In the ram blocks illustrated in FIGS. 2 and 4, the upper surface
40 of the ram block 36 has an extending upper guide member 42 and a
diametrically opposed upper recessed portion 44 for reception of
the guide member on a mating ram block, not shown, making up a pair
of ram blocks. Similarly, the lower face 46 is provided with a
similar lower guide member 48 diametrically spaced from the upper
guide member 42 and a lower space 50 diametrically spaced from the
lower guide member 48 which receives an interfitting guide member,
not shown, on the mating ram block of the pair of ram blocks.
The sealing member 39 provided on the circumference and the recess
portion of the ram block 36 seals the cavity and around the drill
pipe 18. This effective seal is provided on actuating of the ram
shafts 28 to close the ram blocks 26 together and about the drill
pipe 18, as illustrated in FIG. 1. The ram blocks illustrated in
FIGS. 2 and 4, when without a work- or strain-hardenable inner
supporting edge, are commercial ram blocks of Rucker-Shaffer.
The ram block may be made up of a series of parts in the form of an
assembly or may be one integral piece and may take any desired
shape. For example, and as illustrated in FIG. 6, to which
reference is now made, a ram block 26a is illustrated, which is a
commercial ram block available on the market and sold by Cameron
Iron Works of Houston, Texas. In this figure, the reference letter
"a" has been added to numerals corresponding to like parts in
Figures 1, 2 and 4. As illustrated, the ram block 26a is an
integral member and is provided with the recessed portions 44a and
50a to receive a seal member, not shown.
No more description of ram block assemblies or ram blocks is given
or deemed necessary as the present invention is applicable to all
ram blocks and ram block assemblies which are provided with a
generally circular opening, when in closed position, to provide an
effective seal about the string of drill or other pipe in the well
casing and which, when in open position, permit normal movement and
operation of the drill string 16 and tool joints 20.
For ram blocks to be used in a hydrogen embrittlement atmosphere,
for example, in a hydrogen sulfide atmosphere, it is necessary that
the steel alloy not exceed or have an upper hardness level of about
Rc22. A tool joint, such as the tool joint 20 on the string of
drill pipe 16, as illustrated in FIG. 1, has a hardness level well
in excess of Rc22 and, accordingly, if it were necessary to support
the heavy load of the drill string, such as weights up to and in
excess of 600,00 pounds, by the ram blocks having an upper hardness
level of about Rc22, the tool joint 20 would cut into and deform
the inner surfaces 38 of the ram blocks 26 and thus would not
support the heavy load of the drill string 16. It is not feasible
to form the ram blocks out of a steel alloy having a hardness level
exceeding that of the tool joint, for example, Rc35-40, for use in
hydrogen sulfide atmospheres because the hydrogen sulfide
decomposes when it comes in contact with metal; for example, to
form a metal sulfide and to liberate atomic hydrogen which diffuses
into the metal lattice. The metal is said to be "hydrogen
embrittled" when steels absorb hydrogen. When the metal is under a
high tensile stress, such as when supporting a heavy load of a
string of drill pipe, brittle failure does occur at stress many
times lower than the stress required for failure in the absence of
hydrogen. At normal temperatures, the hydrogen atom diffuses
through the grain, tending to gather at the inclusion or other
lattice defects. The metal fails in a transgranular mode (across
the grain) under the influence of a stress. At higher temperatures,
the absorbed hydrogen tends to gather in the grain boundaries and
stress-induced cracking is then intergranular (between the grain).
In either event, the ram blocks become brittle in the hydrogen
sulfide environment and fail when under stress many times lower
than the stress required for failure in the absence of
hydrogen.
The use of a hard edge insert on the ram body at a hardness level
above that of the tool joints becomes hydrogen embrittled when used
in a hydrogen sulfide atmosphere and fails under heavy loads.
Hardfacing the inner surface of the ram blocks provides too brittle
a deposit and cracks during welding.
The present invention is based upon the surprising discovery that
the base metal or matrix of the ram block can be made of an alloy
having hardness level an upper or one not exceeding about Rc22 in
surface hardness, to avoid stresses higher than the threshold for
brittle failure, and be provided with a work-hardenable alloy
deposit on its inner surface which, when in a relatively
free-stress condition has hardness level an upper or one not
exceeding about Rc22, but upon slight deformation due to stress the
material will rapidly work harden to strength and hardness levels
above that of the normal tool joint on a string of drill pipe, for
example, to strength and hardness levels of Rc35-40. At these
strength and hardness levels, the ram block edge surface can bite
into a normal tool joint and support heavy drill string loads.
Preferably, the ram block is made of a low alloy steel with a
controlled hardness preferably in the range of BHN 207-235 provided
with a relatively soft, inner work-hardenable supporting edge
surface.
For a discussion of alloy hardening, work hardening, precipitation
hardening, the type of solid solutions important for the work-and
strain-hardening concept, and the structure of cold worked metal,
reference is made to the publications set forth in the section
entitled "Background of the Invention." In general, however, any
alloy which will harden on slight deformation and which can be
deposited in a rather soft-stressfree deposit, that is, under an
upper hardness level of about Rc22, is satisfactory in that when
put into service in a hydrogen sulfide environment stays in situ
until the increase in hardness and strength is needed and
consequently does not fail because of hydrogen embrittlement. Upon
energizing the ram blocks into engagement with the tool joints, the
chemistry of the deposited alloy is such that the alloy immediately
hardens to indent itself into the tool joint and by this action
only becomes hard enough to repeatedly cut into a tool joint and to
support the drill string load.
Terms such as "alloy hardening", "work hardening", "strain
hardening", "precipitation hardening", "work hardenable", "strain
hardenable" are used herein to describe the ability of an alloy to
harden substantially upon deformation and are so used herein.
The following examples of work or strain-hardenable compositions
satisfactory for use in the present invention are illustrated, in
which all percentages are by weight.
EXAMPLE 1
Work-hardenable compositions satisfactory for use in the present
invention are set forth in the following Table I.
TABLE I ______________________________________ Welding rod
composition for the work-hardenable feature Carbon 0 - .10% Chrome
8 - 20% Molybdenum 10 - 20% Tungsten 2 - 6% Fe (Iron) 0 - 10%
residual Silicon 1.2% max. Manganese 1.5% max. Nickel balance 41 -
78% usually nickel should be 45% or greater to insure an austenitic
structure ______________________________________
The compositions listed in Table I may be welded to the inner edge
of the ram blocks in a relatively free-stress condition and may be
readily machined to the desired shape. Upon slight deformation,
these compositions almost immediately work harden or strain harden
to a strength and hardness level of Rc35 and with very slight
additional deformation have a strength and work hardness of about
Rc45. These compositions may readily be in the form of a welding
rod or wire for easy welding to the inner surface of the ram
blocks.
EXAMPLE 2
In this example the work-hardenable alloy edge had a composition as
set forth in the following Table II.
TABLE II
C=.05%, cr=15%, Mo=15%, W=4.5%, Fe=5%, Si=1.00 max.
Mm=1.0 max., balance nickel
Residual P=.010 max. S=.005 max.
the as-deposited or welded hardness in relatively stress-free
condition of the alloy in Table II was Rb90 (Rockwell B Scale). An
average displacement of 0.015 inch increased the hardness to Rc35
and further work hardening increased the hardness to Rc45 with very
little metal displacement.
EXAMPLE III
In this example the work-hardenable alloy edge had a composition as
set forth in the following Table III.
TABLE III
C=.02%, Cr=17.75%, Mo=15.8%,
W=3.80%, Fe=6.80%, Si=.80%,
Mn=.90%, balance nickel.
Residual P=.03% S=.025%
The as-deposited or welded hardness in relatively stress-free
condition of the alloy of Table III was Rb97. An average
displacement of 0.020 inch increased the hardness to Rc34.2 and
further work hardening increased the hardness to Rc39 with very
little metal displacement.
EXAMPLE IV
In this example the work-hardenable alloy edge had a composition as
set forth in the following Table IV.
TABLE IV
C=.01%, Cr=15.6%, Mo=16.20%,
W=4.50%, Fe=5.00%, Si=1.05%,
Mn=1.02%, balance nickel.
Residual P=.035% S=.030%
The as-deposited or welded hardness in relatively stress-free
condition of the alloy of Table IV was Rb92. An average
displacement of 0.030 inch increased the hardness to Rc34 and
further work hardening increased the hardness to Rc41 with very
little metal displacement.
From the foregoing examples and tables, a variety of alloys may be
used, as desired, which work harden to the desired strength and
hardness level upon engagement with and deformation by the drill
string load.
The shape of the work-hardenable material may take a variety of
forms, a number of which are illustrated in the drawings. For
example, and with reference to FIG. 3, the work-hardenable deposit
52 is illustrated in cross-section as having a curved base portion
54 with an upper or supporting surface 56 slightly below the upper
surface 40 of the ram block 26.
FIGS. 5, 7-11 illustrate a variety of shapes for the work- or
strain-hardenable alloy forming the inner edge supporting surface,
in which the reference characters "a", "b", "c", "d", "e" and "f"
have been added to corresponding reference numerals for convenience
of reference.
In FIG. 5, the work-hardenable edge supporting surface 52a is not
recessed and has its upper surface 56a flush with the surface 40a
of the ram block and is supported by a gently curved base portion
54.
In FIG. 7 a still different form of work-hardenable insert 52b is
illustrated which is provided with an upper surface slightly lower
or recessed with respect to the upper surface 50b of the ram block
36b, but provided with a generally rectangular, viewed in
cross-section, lower surface 54b.
A still further variation in shape or form of the work-hardenable
insert 52c is illustrated in FIG. 8 which has a downwardly and
inwardly sloping upper surface 56c terminating in the generally
horizontal surface 57c, a vertical surface 59c extending downwardly
and provided with a lower inner surface having a vertical and
upwardly extending legs 54c.
A still further variation in form or shape of the work-hardenable
insert 52d is illustrated in FIG. 9 which has the downwardly and
inwardly sloping upper surface 56d terminating in a generally flat
horizontal surface 57d and, when viewed in cross-section, has a
generally straight lower surface 54d and upwardly and inclined
surface 61d.
With reference to FIG. 10, a still further variation in shape or
form of the work-hardenable inner edge insert 52e is illustrated
which is generally of a triangular configuration, when viewed in
vertical section, provided with the generally flat upper surface
56e level with and forming a continuation of the upper surface 40e
of the ram block 26e and having a generally vertical flat side 59e
and an angularly disposed lower inner surface 54e which forms what
in effect is a base of a triangle when viewed in vertical
section.
FIG. 11 illustrates a still further modification in the shape or
form of the work-hardenable inner supporting insert 52f for the ram
block 26f which is here illustrated as having a upper flat surface
56f level with and forming a continuation of the upper surface 49f
of the ram block 26f and a vertical surface 59f, provided with a
generally semi-eliptical inner surface 54f.
No more examples of the various forms or shapes the inner edge
portion may take are illustrated as any desired shape or form may
be utilized.
Preferably the work-hardenable inner edge is welded to a
machined-out portion of the ram block and then is itself machined
to the desired shape. The weld deposit may be one or many passes of
weld deposit of the work-hardenable or strain-hardenable material
until the desired thickness has been achieved. The proper cutting
edge is then machined to the desired shape. The soft work- or
strain-hardenable material may then be used in a hydrogen
embrittlement atmosphere, such as in the presence of hydrogen
sulfide, and will not fail due to hydrogen embrittlement. Yet, when
it is necessary to support the drill pipe, the rams 28 are actuated
to bring the ram blocks 26 into engagement with the drill string 18
and its tool joints 20, which upon slight deformation almost
instantly and readily work hardens the material to a hardness level
sufficient to bite into the shoulder 22 of the tool joint and
support the drill string load.
The present invention therefore is well suited and adapted to
attain the objects and ends and has the advantages and features
mentioned as well as others inherent therein.
While a number of presently-preferred embodiments have been
described and illustrated in the drawings for the purpose of
disclosure, numerous changes in details and arrangements of parts
may be made which are within the spirit of the invention as defined
by the scope of the appended claims .
* * * * *