CA1191077A - Interrupted quench process - Google Patents
Interrupted quench processInfo
- Publication number
- CA1191077A CA1191077A CA000398334A CA398334A CA1191077A CA 1191077 A CA1191077 A CA 1191077A CA 000398334 A CA000398334 A CA 000398334A CA 398334 A CA398334 A CA 398334A CA 1191077 A CA1191077 A CA 1191077A
- Authority
- CA
- Canada
- Prior art keywords
- pipe
- cooling medium
- temperature
- flow
- hardening
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
- C21D9/085—Cooling or quenching
Abstract
ABSTRACT
An improved method of hardening elongated steel pipe, to reduce or eliminate quench cracking, and to produce higher strength product from a given base material, comprises the steps of: quenching the pipe from an initial elevated temperature higher than the austenite transformation temperature, by immersion in a liquid cooling medium;
controlling the flow of liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipes; and interrupting the quenching process and withdrawing the pipe from the liquid cooling medium, not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature. Following interruption of the quench process, the pipe may be promptly conveyed to a tempering furnace, without significant cooling, and tempered at a temperature higher than the martensite start temperature. Alternatively, following interruption of the quenching process, the pipe may be further cooled at a sufficiently slow and uniform rate to avoid quench cracking, and may subsequently be tempered in conventional fashion, if desired.
An improved method of hardening elongated steel pipe, to reduce or eliminate quench cracking, and to produce higher strength product from a given base material, comprises the steps of: quenching the pipe from an initial elevated temperature higher than the austenite transformation temperature, by immersion in a liquid cooling medium;
controlling the flow of liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipes; and interrupting the quenching process and withdrawing the pipe from the liquid cooling medium, not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature. Following interruption of the quench process, the pipe may be promptly conveyed to a tempering furnace, without significant cooling, and tempered at a temperature higher than the martensite start temperature. Alternatively, following interruption of the quenching process, the pipe may be further cooled at a sufficiently slow and uniform rate to avoid quench cracking, and may subsequently be tempered in conventional fashion, if desired.
Description
~191077 FIELD OF THE INVENTION
The present invention relates to the hardening of long steel pipes, such as are used in oilfields, by quenching, and in particular, to improvements in the technique of quenching in a liquid cooling medium, to reduce or eliminate quench cracking and to produce higher strength product from a given base material.
BACKGROUND OF THE INVENTION
It is known to quench the type of pipe contemplated by the present invention, by immersing it in a bath of liquid cooling medium, such as water, and causing the liquid coo~ing medium to flow both through the interior of the pipe and around the exterior of the pipe in controlled proportions, hereinafter referred to as "inside-outside" quenching.
This inside-outside quenching technique, and apparatus for practising same, are the subject of Vnited States Patents Nos. 3,997,375 and 3,877,685, and corresponding Canadian Patent No. 1,016,148, granted to the assignee herein.
Briefly summarized, the method comprises supporting the hot pipe in a elongated container in a predetermined position and passing the liquid cooling medium from an inlet means directly through the inside of the pipe with provision for passing a proportion of the cooling medium directly from the inlet means over the outside of the pipe. The relative proportion of the flow of cooling medium from the inlet means directly through the pipe and over the outside of the pipe is varied to achieve a desired hardening effect. Typically, the desired effect is substantial uniformity of hardness as between the inside and outside surfaces of the pipe, as is required by some oil industry specifications. Suitable apparatus may comprise an q~`
3L~L910~77 elongated container dimensioned to receive the hot pipe to be hardened, means for supporting the hot pipe in a predetermined position in the container~ a cooling medium nozzle having a tip, for introducing cooling medium into the pipe, means for moving the nozzle between a retracted position in which the tip is spaced from an end of the pipe to allow removal of the pipe from the container and an extended position in w~ich the tip lies within the end of the pipe, inlet means for introducing cooling medium into the container so as to pass into the pipe through the tip of the nozzle located in the end of the pipe and also to pass around the outside of the pipe and isolator means, in fluid communication with the nozzle, the isolator means being movable to vary the proportion of liquid cooling medium entering through said inlet means and passing into and through the pipe through the nozzle relative to the proportion of cooling medium passing over the outside of the pipe to control the rate of cooling of the inside surface relative to the outside surface of the pipe.
The inside-outside quenching method and apparatus are described in detail in the above-mentioned patents, Persons knowledgeable in the field will be aware that certain industry specifications, particularly in the oil industry, require steel pipe with both a specified hardness, and uniformity of hardness between the inside and outside pipe surfaces, within fairly narrow specified tolerances. Pipe satisfying these requirements is conventionally made from alloy steels. Plain carbon steels, or carbon-manganese steels .~0 1191(:~77 of suitable carbon content, can be hardened to the necessary degree by suitable heat treatment, such as the inside-outside quenching process mentioned above, but if the process is so controlled as to produce the necessary uniformity of hardness between the inside and outside surfaces, such steels are susceptible to quench cracking. With the inside-outside quenching apparatus presently in use by the assignee herein, it has been found that cracXing will occur if the carbon content exceeds about .32 - .34~. Conversely, if the process is so controlled as to avoid quench cracking, as described for example in U.S. Patent No. 3,997,375, the necessary uniformity of hardness between the inside and outside surfaces will not normally be attained.
It will be understood that the hardness which can be attained in the final product will generally be increased if the carbon content of the steel is increased. Accordingly, a method of inside-outside quenching of steel pipe of higher carbon content, would both extend the available hardness range of the final product, and permit substantial cost reduction in the production of existing grades, by permitting plain carbon or carbon-manganese steels to be substituted for the alloy steels currently used.
In the past, a time-quenching technique has been applied to prevent cracking in the hardening of some high-strength alloys, for example in the tool and die industry. In accordance with this known method, a workpiece may be rapidly quenched down to a black heat (say, 900~) in a liquid medium, typically water, and may then be withdrawn, while still hot, from the liquid quenching medium, and cooled ~} _ 7~7 to room temperature in a less drastic quenching medium, e.g.
room temperature air.
It has now been discovered that a somewhat similar approach may ~e successfully used to avoid quench cracking in the hardening of steel pipe.
SUMMARY OF THE INVENTION
A method of hardening an elongated steel pipe, in accordance with the present invention, comprises the steps of (a) Quenching the pipe from an initial elevated temperature higher than the austenite transformation temperature, by immersion in a liquid cooling medium;
(b) Controlling the flow of the liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe; and (c) interrupting the quenching process and withdrawing the pipe from the liquid cooling medium not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature. The method may comprise the additional step of tempering the pipe at a temperature higher than the martensite start temperature. Tempering may be initiated without significant cooling of the pipe between the interruption of the quenching process and the commencement of the tempering process.
DETAILED DESCRIPTION
In accordance with an embodiment of the present invention, steel pipe is first quenched in a liquid quenching medium, preferably an an aqueous medium, such as water, under carefully controlled conditions, to ensure cooling which is as uniform as possible throughout the workpiece, and sufficiently rapid to avoid unwanted transformations. When the workpiece reaches approximately the martensite start temperature (i.e.
the temperature at which the transformation to martensite begins to occur) the quenching is interrupted and the workpiece is withdrawn from the liquid quenching medium.
The parameters of the quenching process will, of course, depend on the characteristics of the workpiece. The initial temperature of the workpiece before quenching, must be sufficiently high to produce the austenitic structure: the exact value depends on the composition of the steel, but will typically be above about 1400F. The martensite start temperature also depends on the steel composition: typically it is a few hundred degrees Fahrenheit, say in the range of 350F - 650~F.
The quenching process may be conveniently carried out by means of inside-outside quenching apparatus, as described in the assignee's Canadian and United States patents - mentioned above.
The necessary initial temperature (before quenching) and the desired final temperature, (i.e. the martensite start temperature,) for a given composition of steel~ may be ascertained, or estimated with sufficient accuracy, from the available literature, if not alreaay known to the practitioner of the invention from past experience. With these values in hand, the approximate duration of qu nch required to produce the desired temperature reduction may be calculated on the basis of the known properties of the pipe and known characteristics of the quenching apparatus.
Heat treatment of steel pipe, as contemplated herein, is still to some extent an experimental science, and ~i~9~ 7~
the performance of a process can often be improved by empirical adjustments of the parameters based on analysis of preliminary test runs, before production runs are attempted.
If the workpiece is one which will require tempering to produce the finished product (as is typically the case with the types of steel pipe contemplated herein), after being removed from the liquid quenching medium the pipe is conveyed to a tempering furnace.
In one embodiment of the invention, the pipe is conveyed promptly into the tempering furnace, without undergoing any significant cooling. This prompt transfer to the tempering furnace not only avoids the risk of cracking which might otherwise occur if the pipe were permitted to air-cool significantly below the martensite start temperture, but also reduces the energy consumption of the tempering process, since the pipe is at an elevated temperature when it enters the tempering furnace.
In respect of this embodiment, it will be understood that, while the temperature at which the quench is interrupted, must be low enough to avoid undesired transformations, depending on the desired end product it may not be necessary to quench down to the vicinity of the martensite start temperature; i.e. it may be possible to interrupt the quench at a temperature substantially higher than the martensite start temperature. This may be advantageous if further treatment by tempering is being used, since it will facilitate commencement of tempering before the pipe cools to an undesirably low temperature. That is, if the temperature at which the quench is interrupted is higher (within the available range), there will be a longer period of time available for transferring the pipe to a tempering furnace without cooling to an undesirably low temperature.
1~91077 In an alternative embodiment of the invention, the workpiece may be further cooled after the interrupted quench, at a sufficiently slow and uniform rate of cooling to avoid cracking. The necessary parameters for such cooling will of course depend on the dimensions and composition of the workpiece. If simple exposure to air at ambient temperature would cause cooling which is too rapid or insufficiently uniform, the workpiece may be cooled by forced circulation of air (or other suitable quenching medium) at a controlled (i.e.
elevated) temperature, which is reduced at an appropriate rate.
For example, the workpiece may be further cooled down to below the martensite finish temperature (i.e. the temperature at which the transformation to martensite is complete), or down to ambient temperature. (The martensite finish temperature of course depends on the composition of the steel; it is usually, but not always, higher than ambient temperature, assuming the latter to be about 70JF.) Following such further cooling, the workpiece may be tempered in the usual manner, if tempering is required or desirable.
It is commonly accepted that quench cracking occurs as a result of the volumetric expansion of the steel associated with the transformation to the martensitic form.
As noted above, the martensite transformation occurs at relatively low temperatures, i.e. a few hundred degrees Fahrenheit, at which temperatures the steel has lost its high-temperature plasticity. In a worXpiece of large section, subjected to rapid cooling, the transformation and associated expansion will not occur uniformly, but will occur first in 0~7 the portions of the workpiece adjacent the surfaces, producing stresses which can lead to catastrophic failure, i.e.
cracking.
EXAMPLE QF ~XPERIMENTAL ~ESULTS
Five pieces of 7" O.D. x .317" Wall steel pipe were inside-outside quenched. The time to quench the inside surface of the pipe was varied from 2 to 8 seconds. The pipe lay in the bath for approximately 12 seconds, after which it was taken out and transported as normally to the tempering furnace. The I~Do quench time was measured from the moment the first water spray was noticed at the back end of the pipe during quenching.
Quench Temperature: 1540F
Temper Temperature: 1200F
Water Temperature : 60F
Chemical Analysis % C %Mn ~ P ~ S % Si .46 .95 .011 .022 .26 Test Results Each of the 5 pieces. was tested for tensile strength, hardness across wall and impact strength, the results of which are shown in Table 1.
Ultrasonic testing was performed. No quench cracks were found to be present. (One pipe had a longitudinal O.D.
seam which was attributed to non-metallic inclusions.) A cooling rate was obtained which produced the required transformation products. Although the temperature of the pipe when taken out of the tank was not measured, it is believed that the temperature of the pipe was at least 350 -~191~)77 Except for pipe No. 5, impact values of the others were slightly lower than obtained by existing methods. This would mean that to maintain the quality a complete inside-outside quench is necessary viz. approximately 12 seconds in tank with at least 8 seconds internal quench. (See Table 1, column 2.) The foregoing example is, of course, presented only for illustrative purposes, and is not intended to limit the scope of the present invention, which is defined in the appended claims.
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The present invention relates to the hardening of long steel pipes, such as are used in oilfields, by quenching, and in particular, to improvements in the technique of quenching in a liquid cooling medium, to reduce or eliminate quench cracking and to produce higher strength product from a given base material.
BACKGROUND OF THE INVENTION
It is known to quench the type of pipe contemplated by the present invention, by immersing it in a bath of liquid cooling medium, such as water, and causing the liquid coo~ing medium to flow both through the interior of the pipe and around the exterior of the pipe in controlled proportions, hereinafter referred to as "inside-outside" quenching.
This inside-outside quenching technique, and apparatus for practising same, are the subject of Vnited States Patents Nos. 3,997,375 and 3,877,685, and corresponding Canadian Patent No. 1,016,148, granted to the assignee herein.
Briefly summarized, the method comprises supporting the hot pipe in a elongated container in a predetermined position and passing the liquid cooling medium from an inlet means directly through the inside of the pipe with provision for passing a proportion of the cooling medium directly from the inlet means over the outside of the pipe. The relative proportion of the flow of cooling medium from the inlet means directly through the pipe and over the outside of the pipe is varied to achieve a desired hardening effect. Typically, the desired effect is substantial uniformity of hardness as between the inside and outside surfaces of the pipe, as is required by some oil industry specifications. Suitable apparatus may comprise an q~`
3L~L910~77 elongated container dimensioned to receive the hot pipe to be hardened, means for supporting the hot pipe in a predetermined position in the container~ a cooling medium nozzle having a tip, for introducing cooling medium into the pipe, means for moving the nozzle between a retracted position in which the tip is spaced from an end of the pipe to allow removal of the pipe from the container and an extended position in w~ich the tip lies within the end of the pipe, inlet means for introducing cooling medium into the container so as to pass into the pipe through the tip of the nozzle located in the end of the pipe and also to pass around the outside of the pipe and isolator means, in fluid communication with the nozzle, the isolator means being movable to vary the proportion of liquid cooling medium entering through said inlet means and passing into and through the pipe through the nozzle relative to the proportion of cooling medium passing over the outside of the pipe to control the rate of cooling of the inside surface relative to the outside surface of the pipe.
The inside-outside quenching method and apparatus are described in detail in the above-mentioned patents, Persons knowledgeable in the field will be aware that certain industry specifications, particularly in the oil industry, require steel pipe with both a specified hardness, and uniformity of hardness between the inside and outside pipe surfaces, within fairly narrow specified tolerances. Pipe satisfying these requirements is conventionally made from alloy steels. Plain carbon steels, or carbon-manganese steels .~0 1191(:~77 of suitable carbon content, can be hardened to the necessary degree by suitable heat treatment, such as the inside-outside quenching process mentioned above, but if the process is so controlled as to produce the necessary uniformity of hardness between the inside and outside surfaces, such steels are susceptible to quench cracking. With the inside-outside quenching apparatus presently in use by the assignee herein, it has been found that cracXing will occur if the carbon content exceeds about .32 - .34~. Conversely, if the process is so controlled as to avoid quench cracking, as described for example in U.S. Patent No. 3,997,375, the necessary uniformity of hardness between the inside and outside surfaces will not normally be attained.
It will be understood that the hardness which can be attained in the final product will generally be increased if the carbon content of the steel is increased. Accordingly, a method of inside-outside quenching of steel pipe of higher carbon content, would both extend the available hardness range of the final product, and permit substantial cost reduction in the production of existing grades, by permitting plain carbon or carbon-manganese steels to be substituted for the alloy steels currently used.
In the past, a time-quenching technique has been applied to prevent cracking in the hardening of some high-strength alloys, for example in the tool and die industry. In accordance with this known method, a workpiece may be rapidly quenched down to a black heat (say, 900~) in a liquid medium, typically water, and may then be withdrawn, while still hot, from the liquid quenching medium, and cooled ~} _ 7~7 to room temperature in a less drastic quenching medium, e.g.
room temperature air.
It has now been discovered that a somewhat similar approach may ~e successfully used to avoid quench cracking in the hardening of steel pipe.
SUMMARY OF THE INVENTION
A method of hardening an elongated steel pipe, in accordance with the present invention, comprises the steps of (a) Quenching the pipe from an initial elevated temperature higher than the austenite transformation temperature, by immersion in a liquid cooling medium;
(b) Controlling the flow of the liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe; and (c) interrupting the quenching process and withdrawing the pipe from the liquid cooling medium not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature. The method may comprise the additional step of tempering the pipe at a temperature higher than the martensite start temperature. Tempering may be initiated without significant cooling of the pipe between the interruption of the quenching process and the commencement of the tempering process.
DETAILED DESCRIPTION
In accordance with an embodiment of the present invention, steel pipe is first quenched in a liquid quenching medium, preferably an an aqueous medium, such as water, under carefully controlled conditions, to ensure cooling which is as uniform as possible throughout the workpiece, and sufficiently rapid to avoid unwanted transformations. When the workpiece reaches approximately the martensite start temperature (i.e.
the temperature at which the transformation to martensite begins to occur) the quenching is interrupted and the workpiece is withdrawn from the liquid quenching medium.
The parameters of the quenching process will, of course, depend on the characteristics of the workpiece. The initial temperature of the workpiece before quenching, must be sufficiently high to produce the austenitic structure: the exact value depends on the composition of the steel, but will typically be above about 1400F. The martensite start temperature also depends on the steel composition: typically it is a few hundred degrees Fahrenheit, say in the range of 350F - 650~F.
The quenching process may be conveniently carried out by means of inside-outside quenching apparatus, as described in the assignee's Canadian and United States patents - mentioned above.
The necessary initial temperature (before quenching) and the desired final temperature, (i.e. the martensite start temperature,) for a given composition of steel~ may be ascertained, or estimated with sufficient accuracy, from the available literature, if not alreaay known to the practitioner of the invention from past experience. With these values in hand, the approximate duration of qu nch required to produce the desired temperature reduction may be calculated on the basis of the known properties of the pipe and known characteristics of the quenching apparatus.
Heat treatment of steel pipe, as contemplated herein, is still to some extent an experimental science, and ~i~9~ 7~
the performance of a process can often be improved by empirical adjustments of the parameters based on analysis of preliminary test runs, before production runs are attempted.
If the workpiece is one which will require tempering to produce the finished product (as is typically the case with the types of steel pipe contemplated herein), after being removed from the liquid quenching medium the pipe is conveyed to a tempering furnace.
In one embodiment of the invention, the pipe is conveyed promptly into the tempering furnace, without undergoing any significant cooling. This prompt transfer to the tempering furnace not only avoids the risk of cracking which might otherwise occur if the pipe were permitted to air-cool significantly below the martensite start temperture, but also reduces the energy consumption of the tempering process, since the pipe is at an elevated temperature when it enters the tempering furnace.
In respect of this embodiment, it will be understood that, while the temperature at which the quench is interrupted, must be low enough to avoid undesired transformations, depending on the desired end product it may not be necessary to quench down to the vicinity of the martensite start temperature; i.e. it may be possible to interrupt the quench at a temperature substantially higher than the martensite start temperature. This may be advantageous if further treatment by tempering is being used, since it will facilitate commencement of tempering before the pipe cools to an undesirably low temperature. That is, if the temperature at which the quench is interrupted is higher (within the available range), there will be a longer period of time available for transferring the pipe to a tempering furnace without cooling to an undesirably low temperature.
1~91077 In an alternative embodiment of the invention, the workpiece may be further cooled after the interrupted quench, at a sufficiently slow and uniform rate of cooling to avoid cracking. The necessary parameters for such cooling will of course depend on the dimensions and composition of the workpiece. If simple exposure to air at ambient temperature would cause cooling which is too rapid or insufficiently uniform, the workpiece may be cooled by forced circulation of air (or other suitable quenching medium) at a controlled (i.e.
elevated) temperature, which is reduced at an appropriate rate.
For example, the workpiece may be further cooled down to below the martensite finish temperature (i.e. the temperature at which the transformation to martensite is complete), or down to ambient temperature. (The martensite finish temperature of course depends on the composition of the steel; it is usually, but not always, higher than ambient temperature, assuming the latter to be about 70JF.) Following such further cooling, the workpiece may be tempered in the usual manner, if tempering is required or desirable.
It is commonly accepted that quench cracking occurs as a result of the volumetric expansion of the steel associated with the transformation to the martensitic form.
As noted above, the martensite transformation occurs at relatively low temperatures, i.e. a few hundred degrees Fahrenheit, at which temperatures the steel has lost its high-temperature plasticity. In a worXpiece of large section, subjected to rapid cooling, the transformation and associated expansion will not occur uniformly, but will occur first in 0~7 the portions of the workpiece adjacent the surfaces, producing stresses which can lead to catastrophic failure, i.e.
cracking.
EXAMPLE QF ~XPERIMENTAL ~ESULTS
Five pieces of 7" O.D. x .317" Wall steel pipe were inside-outside quenched. The time to quench the inside surface of the pipe was varied from 2 to 8 seconds. The pipe lay in the bath for approximately 12 seconds, after which it was taken out and transported as normally to the tempering furnace. The I~Do quench time was measured from the moment the first water spray was noticed at the back end of the pipe during quenching.
Quench Temperature: 1540F
Temper Temperature: 1200F
Water Temperature : 60F
Chemical Analysis % C %Mn ~ P ~ S % Si .46 .95 .011 .022 .26 Test Results Each of the 5 pieces. was tested for tensile strength, hardness across wall and impact strength, the results of which are shown in Table 1.
Ultrasonic testing was performed. No quench cracks were found to be present. (One pipe had a longitudinal O.D.
seam which was attributed to non-metallic inclusions.) A cooling rate was obtained which produced the required transformation products. Although the temperature of the pipe when taken out of the tank was not measured, it is believed that the temperature of the pipe was at least 350 -~191~)77 Except for pipe No. 5, impact values of the others were slightly lower than obtained by existing methods. This would mean that to maintain the quality a complete inside-outside quench is necessary viz. approximately 12 seconds in tank with at least 8 seconds internal quench. (See Table 1, column 2.) The foregoing example is, of course, presented only for illustrative purposes, and is not intended to limit the scope of the present invention, which is defined in the appended claims.
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Claims (13)
1. A method of hardening an elongated steel pipe, comprising the steps of (a) Quenching the pipe from an initial elevated temperature higher than the austenite transformation temperature, by immersion in a liquid cooling medium;
(b) Controlling the flow of the liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe; and (c) interrupting the quenching process and withdrawing the pipe from the liquid cooling medium not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature.
(b) Controlling the flow of the liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe; and (c) interrupting the quenching process and withdrawing the pipe from the liquid cooling medium not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature.
2. A method of hardening an elongated steel pipe, as defined in claim 1, wherein the pipe is quenched by supporting the pipe in a container in predetermined relationship to an inlet means, and flowing liquid cooling medium directly from the inlet means through the inside Of the pipe while at the same time passing a flow of the cooling medium over the outside of the pipe, and wherein the flow of the cooling medium is controlled to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe, by controlling the rate of flow of the cooling medium passing through the inside of the pipe, relative to the rate of flow of cooling medium over the outside of the pipe.
3. A method of hardening an elongated steel pipe, as defined in claim 2, wherein the flow of cooling medium through the inside of the pipe, and the flow of cooling medium over the outside of the pipe, are in substantially the same direction.
4. A method of hardening an elongated steel pipe as defined in claim 1, additionally comprising the step of tempering the pipe at a temperature higher than the martensite start temperature, following interruption of the quenching process.
5. A method of hardening an elongated steel pipe as defined in claim 4, wherein the tempering is commenced without significant cooling of the pipe between the interruption of the quenching process and the commencement of the tempering process.
6. A method of hardening an elongated steel pipe as defined in claim 1, 2 or 3, wherein the pipe is formed from a plain carbon steel.
7. A method of hardening an elongated steel pipe as defined in claim 1, 2 or 3, wherein the pipe is formed from a carbon-manganese steel.
8. A method of hardening an elongated pipe formed from a steel selected from the group consisting of plain carbon steels and carbon-manganese steels, comprising the steps of (a) Quenching the pipe from an initial elevated temperature higher than the austenite transformation temperature, by supporting the pipe in a container in predetermined relationship to an inlet means, and flowing liquid cooling medium directly from the inlet means through the inside of the pipe while at the same time passing a flow of the cooling medium over the outside of the pipe;
(b) Controlling the flow of the liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe, by controlling the rate of flow of the cooling medium passing through the inside of the pipe, relative to the rate of flow of cooling medium over the outside of the pipe;
(c) Interrupting the quenching process and withdrawing the pipe from the liquid cooling medium not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature; and (d) Tempering the pipe at a temperature higher than the martensite start temperature, following interruption of the quenching process.
(b) Controlling the flow of the liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe, by controlling the rate of flow of the cooling medium passing through the inside of the pipe, relative to the rate of flow of cooling medium over the outside of the pipe;
(c) Interrupting the quenching process and withdrawing the pipe from the liquid cooling medium not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature; and (d) Tempering the pipe at a temperature higher than the martensite start temperature, following interruption of the quenching process.
9. A method of hardening an elongated pipe, as defined in claim 8, wherein the tempering is commenced without significant cooling of the pipe between the interruption of the quenching process and the commencement of the tempering process.
10. A method of hardening an elongated pipe, as defined in claim 8, wherein the tempering is commenced promptly after the interruption of the quenching process, whereby there is no significant cooling of the pipe between the interruption of the quenching process and the commencement of the tempering process.
11. A method of hardening an elongated steel pipe, as defined in claim 1, 2 or 3, additionally comprising the step of subjecting the pipe to further cooling, at a sufficiently slow and uniform rate to avoid quench cracking, following interruption of the quenching process.
12. A method of hardening an elongated steel pipe, as defined in claim 1, 2 or 3, additionally comprising the step of cooling the pipe to below the martensite finish temperature, at a sufficiently slow and uniform rate of cooling to avoid quench cracking, following interruption of the quenching process.
13. A method of hardening an elongated pipe formed from a steel selected from the group consisting of plain carbon steels and carbon-manganese steels, comprising the steps of (a) Quenching the pipe from an initial elevated temperature higher than the austenite trànsformation temperature, by supporting the pipe in a container in predetermined relationship to an inlet means, and flowing liquid cooling medium directly from the inlet means through the inside of the pipe while at the same time passing a flow of the cooling medium over the outside of the pipe;
(b) Controlling the flow of the liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe, by controlling the rate of flow of the cooling medium passing through the inside of the pipe, relative to the rate of flow of cooling medium over the outside of the pipe;
(c) Interrupting the quenching process and withdrawing the pipe from the liquid cooling medium not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature;
(d) Cooling the pipe to below the martensite finish temperature, at a sufficiently slow and uniform rate of cooling to avoid quench cracking, following interruption of the quenching process; and (e) Tempering the pipe at a temperature higher than the martensite start temperature, following completion of said cooling process.
(b) Controlling the flow of the liquid cooling medium to produce a substantially uniform rate of cooling as between the inside and outside surfaces of the pipe, by controlling the rate of flow of the cooling medium passing through the inside of the pipe, relative to the rate of flow of cooling medium over the outside of the pipe;
(c) Interrupting the quenching process and withdrawing the pipe from the liquid cooling medium not later than when the pipe has reached a temperature in the vicinity of the martensite start temperature;
(d) Cooling the pipe to below the martensite finish temperature, at a sufficiently slow and uniform rate of cooling to avoid quench cracking, following interruption of the quenching process; and (e) Tempering the pipe at a temperature higher than the martensite start temperature, following completion of said cooling process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000398334A CA1191077A (en) | 1982-03-15 | 1982-03-15 | Interrupted quench process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000398334A CA1191077A (en) | 1982-03-15 | 1982-03-15 | Interrupted quench process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1191077A true CA1191077A (en) | 1985-07-30 |
Family
ID=4122297
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000398334A Expired CA1191077A (en) | 1982-03-15 | 1982-03-15 | Interrupted quench process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1191077A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002036842A3 (en) * | 2000-11-03 | 2003-01-30 | Brush Wellman | Improved rapid quench of large section precipitation hardenable alloys |
| EP1528109A1 (en) * | 2003-10-28 | 2005-05-04 | Mannesmannröhren-Werke AG | Porcess for the heat treatment of medium carbon steels |
| CN113631730A (en) * | 2019-03-29 | 2021-11-09 | 株式会社爱信 | Quenching method |
-
1982
- 1982-03-15 CA CA000398334A patent/CA1191077A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002036842A3 (en) * | 2000-11-03 | 2003-01-30 | Brush Wellman | Improved rapid quench of large section precipitation hardenable alloys |
| EP1528109A1 (en) * | 2003-10-28 | 2005-05-04 | Mannesmannröhren-Werke AG | Porcess for the heat treatment of medium carbon steels |
| CN113631730A (en) * | 2019-03-29 | 2021-11-09 | 株式会社爱信 | Quenching method |
| CN113631730B (en) * | 2019-03-29 | 2023-09-22 | 株式会社爱信 | Quenching method |
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