Alloys or metallic compositions – Ferrous – Chromium containing – but less than 9 percent
Reexamination Certificate
2000-06-14
2002-04-23
Yee, Deborah (Department: 1742)
Alloys or metallic compositions
Ferrous
Chromium containing, but less than 9 percent
C420S067000, C420S099000, C148S519000, C148S520000, C148S521000, C148S529000, C428S684000, C285S333000
Reexamination Certificate
active
06375895
ABSTRACT:
FIELD OF THE INVENTION
The present invention is in the field of hardfacing alloys having high abrasion resistance for improving the service life of surfaces of industrial products subject to wear such as tool joints, drill collars, and stabilizers used in drilling strings for earth boring for oil and gas as well as other industrial products subjected to high abrasion.
BACKGROUND OF THE INVENTION
There has been a severe problem with the service life of tool joints and stabilizers used in earth boring such as drilling a bore hole in the earth to a formation or formations from which oil or gas are to be produced since approximately 95 percent of the surface of the earth is composed of silicious materials which are very abrasive and which cause considerable wear on the surfaces of tool joints and stabilizers, as well as wear prone surfaces of other industrial products.
There have been numerous attempts to provide hardfacing alloys suitable for welding protective hardfacing (referred to as “hardbanding”) on tool joints. For a description of prior art hardbanding for tool joints, reference is made to U.S. Pat. No. 4,256,518, the composite catalog of oil field equipment and services, 1976/77 edition, at pages 3216-19 and pages 4994-5; U.S. Pat. No. 3,067,593. Also, for the use of hardbanding materials, such as tungsten carbide particles to form a hardened surface at a tool joint to increase wear resistance, reference is made to U.S. Pat. No. 3,989,554 issued Nov. 2, 1976 and the history of oil well drilling by J. E. Brantly published in 1971 by the book division of Gulf Publishing Company, Houston, Tex. Also, reference is made to U.S. Pat. Nos. 2,259,232; 2,262,211; 4,431,902; and 4,942,059 which illustrate various prior art ways to hardband tool joints.
Historically, and in practice, tool joints on drilling strings (pipe) such as used in drilling oil and gas wells have been faced at the bottom of the box end with tungsten carbide to resist the abrasion of the rock earth in the drill hole on the tool joint. This has three disadvantages. Tungsten carbide is expensive, it acts as a cutting tool to cut the well casing in which it runs, and the matrix is a soft steel which erodes away easily to allow the carbide particles to fall away.
Most prior art hardfacing materials harder than silicious earth materials are brittle and crack. These hardfacing materials are alloys which belong to a well-known group of “high Cr-irons” and their high abrasive resistance is derived from the presence in the microstructure of the Cr-carbides of the eutectic and/or hypereutectic type. In the as-welded condition, whatever the precautions taken, these hardfacing overlays always show a more or less dense network of cracks. Preheat of the base material being hardfaced is not a prerequisite. On the contrary, the lower the preheat and interpass temperatures, the denser the network of cracks, which can be considered as a favorable factor from the point of view of the risk of crack propagation into the base material under service conditions.
In the 50 year history of hardbanding tool joints or stabilizers of drilling pipe, no facing which cracked during application has been used in practice prior to the development of the invention in U.S. Pat. No. 5,244,559.
In most industries, however, the metal components which make up the structure and equipment of a given plant must have integrity, which means being free of any kind of cracks since these might be expected to progress through the piece and destroy the part.
When the loss of human life may be involved or when great property damage may result, the requirements for integrity are particularly strict. Examples of such industrial products are pressure vessels in the process industries, structural members in buildings and bridges, and down hole drilling equipment in the oil and gas industry.
Silicious earth particles have a hardness of about 800 Brinell hardness number (BHN). In U.S. Pat. No. 5,244,559 the hardfacing material used is of the group of high Cr-irons that contains primary carbides which have a hardness of about 1700 BHN in a matrix of a hardness of at least 300 BHN to 600 BHN. These primary carbides at this high hardness have little tensile strength and hence pull apart on cooling from molten state at a frequency that depends on the relative quantity of the primary carbides in the mix of metal and carbide. Thus, this type of hardfacing material, which is harder than silicious earth materials, when applied by welding or with bulk welding form shrinkage cracks across the weld bead. This material has been applied extensively and successfully during many years for the hardbanding of tool joints and hardfacing of other industrial products. Although the material has become and still is widely accepted by the trade, some users have expressed a desire for hardbanding tool joints alloy combining the property of including the minimum possible amount of wear in drill casing with the capability of being welded crack free in order to minimize any concerns of mechanical failure risks.
It would be highly desirable and advantageous to provide a hardfacing alloy composition having a microstructure of high abrasive resistance capable of being weld deposited without cracks that does not need to workharden to achieve the hardness properties to withstand the conditions of use, such as abrasion by silicious particles, and which, in addition, has a low coefficient of friction to minimize casing wear by hardbanded tool joints and stabilizers.
SUMMARY OF THE INVENTION
The present invention is directed to such a hardfacing alloy composition and industrial products, such as tool joints and stabilizers hardbanded with the alloy composition and other industrial products hardfaced with the alloy composition, which results in a microstructure in the alloy characterized by a high abrasion resistance to withstand the conditions of use, such as abrasive wear by silicious rock formations and particles and which has a low coefficient of friction that confers an excellent metal to metal wear resistance and which confers minimum casing wear, and the capability of being welded crack free when using appropriate preheat and post cooling conditions, as hereinafter set forth.
The hardfacing alloy of the present invention is particularly suited for welding on wear prone surfaces of tool joints and stabilizers (hardbanding) where it provides great protection from abrasion while remaining in a crack free state. The hardfacing alloy of the present invention has a low coefficient of friction, which provides an excellent metal to metal wear resistance and excellent abrasion resistance, and in the case of hardbanded joints has an optimum balance between the minimizing of induced casing wear and the maximizing of tool joint resistance, for example, about 40 percent less casing wear than the hardfacing alloy of U.S. Pat. No. 5,244,559.
The hardfacing alloy can be welded to a surface using the following products and processes, under various types of gas, such as CO
2
, and Argon based mixtures, self shielded (open arc) tubular wire and submerged-arc tubular wire.
The hardfacing alloy has an all weld metal composition undiluted by base metal by weight of about 0.65 to about 1.1 percent carbon, about 4.5 to about 10.5 percent chromium, about 0.05 to about 1.0 percent molybdenum, about 0.65 to about 1.5 percent manganese, and the remainder iron including impurities as trace elements. The hardfacing alloy in undiluted and as-welded condition has a hardness of from about 48 Rc (455 BHN) to 52 Rc (512 BHN). Its hardness, when welded in a single layer on a typical high carbon tool joint steel, reaches about 55 Rc (560 BHN). It is further characterized by high abrasion resistance against silicious rock formations and particles, a low coefficient of friction resulting in excellent metal to metal use or resistance and very significant reduction in induced casing wear, and a microstructure consisting of Martensite with about 10 to 40 percent Austenite. It is capable of being welded crack-free in single and double la
ATT Technology, Ltd.
Weiler James F.
Yee Deborah
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