DE102013217251A1 - Method of sand casting aluminum-based piston for light-duty and medium-duty diesel engine, involves forming piston mold around pattern, introducing molten aluminum-based metal into piston mold and contacting piston mold with solvent - Google Patents

Abstract

A pattern including a dome and a reentrant bowl is formed. A piston mold is formed around the pattern. The mold comprises an aggregate material and a binder. The pattern is removed from the piston mold. A molten aluminum-based metal is introduced into piston mold. The piston mold is contacted with a solvent, and the binder and aggregate are removed. The molten aluminum-based metal is cooled by solidifying at 400[deg] C or less and operating pressure of 200 bar or less. Thus, the sand casting of aluminum-based piston (1) is carried out.

Description

BACKGROUND OF THE INVENTION

The present invention relates generally to apparatus and methods for casting engine components, and more particularly to a sophisticated aluminum-based diesel piston having complex features and a method of casting the same.

Pistons used in internal combustion engines are typically made up of a head (also referred to as a dome or a crown), a stem, one or more annular grooves, and a land between the grooves. Increasingly stringent emissions and efficiency requirements dictate that in future, pistons will have to work closer to stoichiometric conditions, higher cylinder pressures, and tighter packaging specifications, which in turn will require higher component load and operating temperature conditions. This is especially true for pistons used in diesel engines, which are increasingly being used to operate passenger vehicles, in addition to being the predominant engine shape for larger commercial vehicles. Likewise, sophisticated dome designs are being developed to achieve a more thorough, efficient combustion process that further increases the temperatures in the combustion chamber. These advanced dome designs with their three-dimensional (3D) profiles require more complex shapes, which increases the difficulty in casting the pistons or necessitates the use of excessive machining to achieve the desired dome geometry.

Higher operating temperatures require the use of materials capable of operating under these conditions. Cooling programs have also been used as a way to improve the life of the pistons and similar high temperature components. One way to accomplish cooling is to pass an engine lubricant through passages (also referred to as galleries) formed in the piston. The cooling of the dome is very advantageous because it is directly exposed to the combustion process. However, the addition of cooling channels further increases the difficulty in casting the piston.

Traditional consumption-free forms of casting such. Durable casting, for example, are not well suited for forming complex shapes. In particular, the permanent nature of the mold, associated with the re-entrant areas, which in some designs such as, for For example, if the 3D dome design forms discussed above are present, the ability to retract the part once the casting has solidified. As a result, excessive machining is necessary to produce the complex shapes. This additional machining adds to the complexity and cost of permanent casting approaches. The quality of parts can also suffer from permanent casting. The presence of enhancers can affect the microstructure of the casting and the extent of grain refinement that can be achieved. For example, the relatively large thermal mass of the large risers tends to slow the solidification of the cast component while providing faster cooling and the concomitant improved mechanical properties, such as the presence of a smaller secondary dendrite arm spacing (SADS) poor spacing ") are often desirable. There may be a difference of up to 20% in the mechanical properties at the inlet compared to the riser sides.

In order to overcome the design constraints of permanent mold casting, other approaches may be used which incorporate various forms of lost mold casting, such as die casting. B. investment casting (or lost wax casting), sand casting and the like. Investment casting typically involves the use of a lost mold or pattern and the use of a ceramic molding material to solidify the part in the mold so that only a minimum of mechanical post-molding is required. One variant of the sand casting approach, known as salt core casting, uses techniques that are generally similar to sand casting, except that a water-soluble salt is used instead of a fresh or dry sand for internal molding geometries. Once the part is made, the salt form can be washed away with water without exposing the part to additional thermal stresses. Sand casting involves storage and handling problems that reduce its appeal.

Another approach that has been used to create a dome in the cast state is semi-mold casting. This approach still requires that the combustion bowl be machined. As with the die castings discussed above, a considerable amount of funnel removal from the dome is required. Furthermore, higher performance (high performance) pistons may also require remelting of the bowl rim. These additional operations contribute significantly to the cost of the piston. This applies in particular to the costs of remelting and machine trough processing and still more for pistons designed to operate under high temperature and high pressure conditions (also known as high stress applications, as explained in more detail below), such as those described in more detail below. B. powerful diesel pistons. Such pistons can operate at cylinder pressures above 200 bar (even up to 230 bar) and reach temperatures above 400 ° C; therefore, they require the use of steel forgings with an even greater cost impact.

Strong fluctuations in operating conditions such. As the above-mentioned temperature and pressure conditions make corresponding design differences between high-pressure diesel pistons (the buses, tractors, long-distance trucks, construction equipment or the like) and those with light-duty applications (which may include passenger cars, light trucks or the like) or medium stresses necessary, whereby diesel-powered vehicles (and their demands) are legally defined in the USA, in Europe and elsewhere. For example, in the US For example, the maximum gross vehicle weight (GVWR) rating distinguishes between high, medium and light duty motors, with high duty motors being those exceeding more than a certain amount (eg more than 33,000 pounds according to Federal and California Directives), while medium duty vehicles (eg, between 19500 and 33000 pounds according to federal guidelines and 14000 and 33000 according to the California guidelines) and light duty (eg between 8400 and 19500 pounds according to federal guidelines and 8500 and 14000 according to the California guidelines) lower weights. Other measurement systems can also be used, with z. B. is a medium-pressure diesel engine with a displacement of between about 4 liters and about 7 liters, while its high-pressure counterpart can have a displacement between about 10 liters and 15 liters. Furthermore, in the context of diesel engines, the load cycle may be defined by drag requests (which in turn determine cylinder pressure). In particular, high stress applications rely on steel-based pistons to withstand the harsh conditions to which they are exposed by the above-mentioned temperatures and pressures.

SUMMARY OF THE INVENTION

One aspect of the invention is a method of manufacturing a diesel piston. In one embodiment, the method includes providing a pattern for the piston, the pattern including a dome and a recessed well; a piston mold is formed around the pattern, the mold comprising a aggregate material and a binder; the pattern is removed from the piston mold; a molten metal is introduced into the piston mold; the flask mold is contacted with a solvent for the binder and the binder and aggregate are removed; the molten metal is cooled; and solidifying the molten metal to form the piston with the dome and the re-entrant bowl with minimal need for further reflow processing. In the present context, refill processing includes (but is not limited to) machining the well, certain finishing operations, or other procedures. Significant dimensions of such a refining process are those activities that involve substantial additional cost or time to prepare the part as cast for its final shape. In contrast to substantial post-molding mechanical machining or the like, routine or occasional cleaning or similar finishing steps would not constitute a significant post-molding mechanical processing. Likewise, a piston made in accordance with the present invention would essentially not require such additional steps in the as-cast condition to accommodate complex shapes such as e.g. For example, to define the basic reentrant shape of the trough inside the dome. Furthermore, the aggregate and the binder typically make the shape. As such, sand casting according to the present invention will not require repeated generation of foam or wax patterns or the removal of such patterns from a ceramic mold prior to casting. Moreover, it is to be expected that the ablation-casting cycle times (ie, the time required from making the mold to producing a casting) are shorter because it is not necessary to completely solidify the casting before it is removed from the mold becomes.

The use of this approach of the present invention is particularly advantageous for aluminum-based cast pistons for diesel engine applications (especially light duty engines and medium-duty engines where the cylinder pressures are maintained at about 200 bar or below) compared to their iron-based counterparts. One reason why aluminum is the metal of choice is that it has about one-third the density of a steel-based component (resulting in weight reduction and concomitant simplification of bearings and similar support structures that are particularly advantageous in components, which rotate at a high speed or translate). Another reason is that aluminum based materials are very are readily pourable and have the ability to be formed at lower processing temperatures; this in turn advantageously affects tooling design, durability and cost. Further, because the thermal conductivity of aluminum is twice that of steel, aluminum-based parts reduce the need for cooling oil to be circulated through the galleries in the piston during engine operation, which in turn can simplify the engine oil pump construction. This higher thermal conductivity (and the concomitant ability to remove excess heat) reduces the likelihood that the temperature regime around the crown and other components adjacent to the combustion will produce an undesirable effect on emissions and efficiency. In addition, casting processes, as used in the present invention, allow the inclusion of details such as e.g. As a hardened upper annular groove and the aforementioned oil galleries to form as a natural part of the casting process, whereas steel forgings would require subsequent heat treatment, machining or assembly activities.

In addition, the casting tooling is more accessible to changes that may be required as a result of validation test results or other design modifications. Moreover, a cast diesel piston may be optimized in terms of mass in the as-cast state as compared to the forged piston even in cases where the casting is such that considerable post-molding mechanical work may be required.

As discussed above, while casting in general (and casting of aluminum-based metals in particular) is beneficial, there are limits associated with certain types of casting operations. For example, half mold and permanent mold casting processes are used to form complex shapes such as, for example, As used in newer, more powerful diesel pistons, reentrant combustion bowl not well suited. The ablative approach in connection with the present invention eliminates the need for extensive or substantial machining of the combustion bowl or other portions of the plunging piston, while still minimizing the inclusion of details, such as, e.g. B. the core for the oil gallery or an iron-containing upper Ringnuteinsatzes allowed. The ablation casting used in the present invention has significant differences from the investment casting approach discussed above. For example, patterns in ablation casting are not consumable in the manner of an investment casting pattern. While investment casting techniques employ the use of slurry-based and ceramic-based molds which are subsequently impacted or otherwise broken away from the casting, ablation casting uses quartz sand, zircon sand, chromite sand or the like which does not require repeated coating, stuccoing and curing of the mold; Significantly, the sand used in ablation casting is reusable. Thus, while the sand-based materials used to form the supplement of the present invention may exhibit certain ceramic-like properties (including relative fire resistance), they are considered separate from ceramics in that they are (eg, by coating , Stuccoing and curing) can not be converted into another type of structure. Also, the solidification of the metal in an ablation casting in the mold begins after the completion of the filling and is completed during the water ablation of the mold. The ablation casting may still require some mechanical post-molding processing.

The ablative casting approach of the present invention, when used to form an aluminum-based diesel piston, also results in a fine and uniform as-cast microstructure. This (at least in part) due to the non-existent need for large risers which would slow down the solidification times and affect the extent of grain refinement achievable. By the present invention, grain structures within different parts of the piston can be tailored for the property which is to be optimized. Thus, thicker sections that require more aggressive ablation and cooling could be cooled at rates other than thinner sections as a way to achieve particularly desirable grain refinement or patterning. Other procedures such. B. Counterbalancing and similar slow filling techniques are costly to set up. The faster mold filling times made possible by the sand molds of the present invention, combined with the solidification by ablation of the mold, can be advantageously used to avoid the difficulties of casting an aluminum based piston with such slow filling techniques.

Modern complex components were traditionally inaccessible to final, one-piece or similar near-net shape approaches. Especially with respect to pistons, casting complexity is typically reduced separately by casting individual components. For example, the crown and ring band area can be cast, then joined together to form a second component consisting of the jackets, piston pin or the like. As well Components with reentrant features (such as combustion chamber domes) tend to diverge from one-piece, endform castings. Castings produced in accordance with the present invention do not require two-part constructions to achieve ultimate properties for an aluminum based cast piston with undercut, recessed troughs and similar complex features. As such, they may use a monobloc structure, with many (or all) of the features of the piston (such as the dome, the annular grooves, the oil gallery, the shrouds, and the bolt holes) being formed as a solid part. Monobloc designs differ z. B. from a hinged piston, in which the shaft moves independently of the bolt or the pin hole. Monoblock designs may be cast as one piece or they may be two separate pieces that are rigidly connected together (eg, by welding). The pistons disclosed herein would be considered as a cast monobloc aluminum construction. Further, such casting techniques may use rapid cooling and part removal to ensure excellent grain structures and high throughput of fabricated parts. In the present context, the present inventors have found that the use of aluminum pistons and a monobloc assembly are well suited for high duty diesel engine applications where operating pressures of not more than 200 bar are present. Furthermore, the present approach achieves the complexities of the undercut trough, oil gallery, cast-in ring-groove insert and other features right out of the mold with little (or no) need for refilling operations.

According to another aspect of the present invention, there is disclosed a one-piece cast aluminum-based piston having at least one reentrant feature (particularly a trough formed in the dome of the piston). The piston is configured such that after placement in a diesel engine and operating in the same, the piston can withstand an operating pressure of up to about 200 bar cylinder pressure and a temperature of up to about 400 degrees Celsius. These properties allow it to operate over the normal life of the aforementioned diesel engine applications under light or medium load conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments is best understood when read in conjunction with the following drawings, wherein like structures are designated by like reference numerals and in which:

1 Figure 5 is a cut-away, perspective, partial view of a diesel piston highlighting undercut, reentrant, and similar features that may be produced by sand casting the present invention;

2 Fig. 11 is a cutaway plan view of a diesel piston in a casting condition; and

3 a cutaway top view of the diesel piston of 2 is after the completion of the machining.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to the drawings, there are shown the features associated with an aluminum-based diesel piston which may be poured in a manner as taught herein. In particular, a piston comprises 1 a crown section (also called a crown) 10 a shank portion (also referred to as a shank) 20 and a piston pin bore 30 , The crown 10 defines a generally flat top surface 12 , which is a generally dome-shaped combustion bowl 14 forms in it. The wall 16 the hollow 14 is contoured and terminates at the upper portion thereof with a lip, so that the overhang created thereby rebounds features of the trough 14 Are defined. The outer radial surface of the crown 10 includes various longitudinally spaced circumferentially extending grooves 18 into which piston rings (not shown) may be employed to assist with combustion seal and oil skimming functions. Nuteinsätze 19 can in one or more of the grooves 18 be arranged. The shaft 20 may include longitudinally extending sidewalls in which ribs, flanges, and similar reinforcing structures (not shown) may be included. The shaft 20 helps with the alignment of the piston 1 during its reciprocation within an engine cylinder (not shown). Likewise, the piston pin holes 30 integral in the side walls 40 formed in (especially in 1 shown) which is part of the shaft 20 to define a generally radial passage in which a bolt is used to tighten the piston 1 rotatably on a connecting rod, which traverses the cylinder in response to the rotation of a crankshaft (none of which is shown). Numerous openings that form oil channels that make up the oil gallery are over the entire crown 10 formed to facilitate the passage of oil or similar refrigerant, which is introduced into the cylinder.

An ablation casting lug may be used to create a piston with a dome having a re-entrant valley in the casting condition and an optional internal cooling channel. Ablation casting uses inorganic (ie, water soluble) nuclei, and water is sprayed onto the mold (preferably from many directions), which slowly flushes away (hence the term "ablation") and rapidly cools the casting. The fast cooling leads to improved material properties. In the present context, rapid cooling is one that is significantly faster than traditional (eg, investment casting) cooling approaches. While an investment casting approach may require between half an hour and one hour for a corresponding cool down, an aluminum based diesel piston made in accordance with the present ablation casting may be cooled to room temperature in only three to five minutes. Furthermore, the use of water allows one to control component solidification and cooling separately (eg, by applying water to specific areas of the casting before others or by applying different amounts of water to different areas). Thus, ablation casting allows to create complex parts with a consistently fine solidification microstructure, if desired. By providing the high solidification rates and refined microstructure often necessary to achieve better mechanical properties (such as tensile or fatigue properties at room temperature and elevated temperatures) across the segment, ablation casting allows for parts to be removed Both thin and thick sections combine, as well as those with complex inner cores to form. The properties over the section are superior to those produced by trough edge melting, which provides the desirable fine microstructure only to a depth just below the surface (e.g., a few mm).

The ablation casting method is in the U.S. Patent No. 7,121,318 generally described, which is incorporated herein by reference. A pattern is formed of a material and a shape is formed around at least a portion of the pattern. The mold is formed from a aggregate material and a binder. The pattern is removed from the mold, and then a molten metal is introduced into the mold. The mold is contacted with a solvent and the molten metal is cooled so that it at least partially solidifies to form a casting. The cooling step includes contacting a shell of solidified metal around the molten metal with the solvent.

Ablation casting was generally not used for casting diesel pistons and special diesel pistons with a re-entrant trough, and more particularly aluminum-based diesel pistons with recessed troughs or similar undercut features.

The U.S. Patent No. 7,164,963 . 7 618 823 and 7 225 049 describe analytical methods for full mold casting (a type of ablation casting) and are each incorporated herein by reference.

The use of ablation casting provides the ability to cast the piston with a near net shape dome without the substantial reflow processing and / or machining required for other processes. Thus, the dome and the combustion bowl can be poured simultaneously. In a special form would be the invading trough 14 and inner channels may be created using a disposable knock-over mold that could be created using conventional core technology with retractable tooling in the mold. In the present context, the aggregate form of the forming media includes, but is not limited to, silica sand, zircon sand, chromite sand, ceramic microspheres, or the like.

The advantages associated with the present invention include, but are not limited to, one or more of the following: reduced machining costs, a refined as-cast microstructure for improved mechanical properties, the benefits of a sand (or similar) molding process tailoring a reentrant dome area, reducing cast weight, and eliminating the need for an inner salt core. The traditional salt core could be replaced by an aggregate core of the same material as the flask shape.

In one form, sand casting can be used to make the piston 1 of the present invention. This process would reduce the massive risers typically used in permanent mold casting, resulting in improved material yield. Furthermore, the high cooling rate inherent in ablation casting makes it easier to tailor the process to achieve a refined microstructure with improved material properties. These improved material properties should make a stronger piston 1 Overall, as well as the required strength of the edge of the piston recess 14 Provide (without having to remelt this area) to persist in the stringent head gasket assessment tests.

In a special form, the mold may be made of a sand that is capable of ablation casting so that complex dome shapes, including those with undercut and internal cooling channel features, can be made easily and inexpensively. As such, the sand mold can be used as part of the ablation process.

Improved material yield can be realized by eliminating the large risers that are often used as part of a permanent mold casting operation. In particular, by using an ablation casting attachment, the natural high cooling rate may allow the formed piston 1 has a homogeneous microstructure and similar structural properties.

In addition to the refined microstructure and improved plunger properties, the use of the ablation process allows much finer details, including complicated cooling channels, to be poured into the part. The process reduces or eliminates the need for re-molding in the area around the dome or crown 10 especially as it has the reentrant features of the combustion bowl 14 , the piston pin hole 30 and the cooling channel regions. Because ablation casting is ready for production, transfer to making large quantities of pistons or similar components is relatively easy. A disposable supplement could be used to allow the combustion bowl to be used 14 the piston dome and a lubricating and cooling oil gallery (not shown) are formed as part of the casting.

The use of ablation casting for diesel pistons helps to achieve significant microstructural refinement by reducing or eliminating the need for costly secondary refining processing, e.g. As a machining or remelting to achieve. In cases where a refined microstructure is desired, such as the trough edge or other complex 3D regions of the piston 1 , Tungsten inert gas (TIG), or laser remelting locally (eg, in the reentrant region of the combustion bowl 14 ) be performed. A subsequent machining, z. B. to provide an exact shape of the trough edge, can be equally reduced or eliminated.

This invention utilizes the ablation casting process to eliminate the need for large risers on the piston dome or crown 10 to eliminate. The ability to dome or crown 10 Cooling faster and more uniformly should improve the mechanical properties. Thus, as soon as the mold is filled, the cast metal begins to form a skin. Before the solidification is completed, the mold undergoes a curtain of water formed by one or more spray water jets (not shown) used to dissolve the mold, and in the process the water effectively cools the casting. In particular, the disposable supplement form should allow the combustion bowl 14 to form in the casting state. Further, the disposable supplement form can also be used to the oil gallery 15 behind the upper ring groove 18 to form, eliminating the need for a salt core. This also allows rapid prototyping of pistons, which can improve general development testing. Although not shown in the present sectional views of the figure, it will be appreciated that one or more passages are integral with the piston 1 can be poured so that these passage (s) from a lower surface of the oil gallery 15 Can extend upward to / from the oil flow in and out of the oil gallery 15 to facilitate. Similarly, other features -. As a passage to facilitate the drop of oil to a rod or a pin - in the lower surface of the piston 1 be formed into it.

Unlike steel pistons, where mouths and similar openings to and from the oil galleries are often oversized to ensure proper core removal, the ablation casting attachment for use on aluminum-based diesel pistons of the present invention can remain small because water-based solvents are capable of to penetrate such openings of reduced size. Since the pistons move very quickly translationally back and forth, as explained above, have any such simplifications such. For example, reducing the oil access line size may provide additional multiplier-like advantages in terms of bearing and support structure construction because a designer may reduce the weight, complexity, or similar robustness of such a structure. In a non-limiting embodiment of a piston assembly made in accordance with the present invention, those for the oil inlet and outlet ports of the oil gallery 15 holes used have a diameter of up to about 8 mm and more particularly in the range of about 4 mm to 7 mm. Likewise, equally a drip lubrication hole can be formed.

It should be understood that terms such as "preferred," "typical," and "typically" are not used herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the invention claimed invention. Rather, these terms are intended merely to highlight alternative or additional features that may or may not be used in a particular embodiment of the present invention.

It should be understood that in order to describe and define the present invention, the term "device" is used herein to represent a combination of components and individual components regardless of whether the components are combined with other components. A "device" according to the present invention may e.g. Example, an electrochemical conversion assembly or fuel cell, a vehicle in which an electrochemical conversion assembly according to the present invention is incorporated, etc. include.

It should be understood that in order to describe and define the present invention, the term "substantially" is used herein to represent the natural level of uncertainty associated with any quantitative comparison, value, measurement or other representation can be. The term "substantially" is also used herein to represent the degree to which a quantitative representation may differ from a given reference without causing a change in the basic function of the subject under consideration.

While certain representative embodiments and details have been shown to illustrate the invention, it will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention, which is defined in the following appended claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7121318 [0021]
• US 7164963 [0023]
• US 7618823 [0023]
• US 7225049 [0023]

Claims (10)

A method of sand casting an aluminum based piston for a light or medium duty diesel engine, the method comprising: a pattern is provided for the piston, the pattern comprising a dome and a re-entrant trough; a piston mold is formed around the pattern, the mold comprising a aggregate material and a binder; the pattern is removed from the piston mold; an aluminum-based molten metal is introduced into the piston mold; the flask mold is contacted with a solvent for the binder and the binder and aggregate are removed; and the molten aluminum-based molten metal is cooled so that after solidification of the pistons substantially defines the dome and the recessed trough which can withstand operating pressures up to about 200 bar cylinder pressure and a temperature up to about 400 degrees Celsius. The method of claim 1, further comprising cooling the molten metal rapidly, wherein the rapid cooling takes place in about 5 minutes or less. The method of claim 1, wherein the piston comprises a crown portion and a shank portion which are molded together as a single part to define a one-piece casting. The method of claim 1, wherein the binder is water-soluble and wherein the solvent is water. The method of claim 1, wherein the cooling of the molten metal and the solidification of the molten metal are controlled separately so that tailored grain structures are formed within different portions of the piston. The method of claim 1, wherein cooling the molten metal comprises contacting a shell of solidified metal around the molten metal with the solvent. The method of claim 1, further comprising: a mold for an inner cooling channel is provided, wherein the mold for the inner cooling channel comprises a second aggregate material and a second binder; the mold for the inner cooling passage is arranged in the piston mold before the molten metal is introduced into the piston mold; and the mold for the inner cooling channel is brought into contact with a solvent for the second binder and the second binder and the second aggregate are removed. A method of manufacturing an aluminum-based diesel piston for light or medium duty engine assemblies, the method comprising: a pattern is provided for the piston, the pattern comprising a dome and a re-entrant trough; a piston mold is formed around the pattern, the mold comprising a aggregate material and a water-soluble binder; the pattern is removed from the piston mold; an aluminum-based molten metal is introduced into the piston mold; the flask mold is contacted with water and the binder and aggregate are removed; the molten metal is cooled; and solidifying the molten metal to substantially form the piston with the dome and the re-entrant trough without refilling the piston such that upon solidification, the piston becomes an operating pressure of up to about 200 bar cylinder pressure and a temperature of up to about 400 degrees Celsius can withstand. The method of claim 8, wherein the cooling of the molten metal and the solidification of the molten metal are separately controlled by applying water to one area of the piston in front of other areas or by applying different amounts of water to different areas of the piston. A one-piece cast piston comprising an aluminum based material having a recessed well formed in the dome thereof, the piston configured to operate after being placed in a diesel engine and operating at the same operating pressure up to about 200 bar cylinder pressure and a temperature can withstand up to about 400 degrees Celsius.

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