Abstract: A threaded joint for steel pipes comprising a pin 1 and a box 2 each having a contact surface comprising a threaded portion 3 or 4 and an unthreaded metal contact portion 8 is provided with improved anti-galling propertied by forming a lubricating coating on the contact surface of at least one of the pin and the box, the lubricating coating exhibiting a self-repairing function by liquid lubrication and having a decreased greasiness. The lubricating coating is (1) a coating which comprises a lower lubricant layer which is in liquid form in the temperature range of above 0° C. and below 40° C. and an upper lubricant layer which is in solid form at 40° C., or (2) a coating which is semi-solid or solid at 40° C. and is formed of a mixture comprising a lubricating oil which is in liquid form in the temperature range of above 0° C. and below 40° C. and a wax which is in solid form at 40° C., the mixture preferably having been heated so as to liquefy the wax and dissolve in each other the wax and lubricant oil.

Abstract: By employing a Cr-plated mandrel bar for producing hot seamless tubes according to the present invention wherein centerline average roughness Ra in axial and circumferential directions as well as maximum depth Rv in axial and circumferential directions is specified and further maximum height Rp in axial and circumferential is specified, surface defects such as seizure unlikely generate in an elongation-rolling process by a mandrel mill so that the service life can be dramatically extended, thereby the remarkable reduction of tool cost can be achieved. Moreover, it contributes greatly to improve the inner surface quality of hot seamless tubes to be rolled by a mandrel mill rolling process. Also, the manufacturing method by the present invention makes it possible to efficiently manufacture Cr-plated mandrel bar for producing hot seamless tubes.

Abstract: By employing a Cr-plated mandrel bar for producing hot seamless tubes according to the present invention wherein centerline average roughness Ra in axial and circumferential directions as well as maximum depth Rv in axial and circumferential directions is specified and further maximum height Rp in axial and circumferential is specified, surface defects such as seizure unlikely generate in an elongation-rolling process by a mandrel mill so that the service life can be dramatically extended, thereby the remarkable reduction of tool cost can be achieved. Moreover, it contributes greatly to improve the inner surface quality of hot seamless tubes to be rolled by a mandrel mill rolling process. Also, the manufacturing method by the present invention makes it possible to efficiently manufacture Cr-plated mandrel bar for producing hot seamless tubes.

Abstract: The present invention relates to a making method for a seamless metallic tube with a tilting roll type piercing rolling mill (piercer). According to the making method for a seamless metallic tube of the present invention, the rotary forging effect and the circumferential shearing strain can be significantly suppressed without generating uncompleted engagement of a billet. Accordingly, a product having reduced inside defects and excellent inside quality can be produced in high productivity. Further, by strengthening a plug nose rolling portion, a sharpened plug nose is obtained and an engagement limit can be increased. Additionally, a product further excellent in the inside quality can be efficiently produced. Accordingly, the present invention can be applied to wide fields of the piercing rolling of the seamless metallic tube.

Abstract: The present invention relates to a making method for a seamless metallic tube with a tilting roll type piercing rolling mill (piercer). According to the making method for a seamless metallic tube of the present invention, the rotary forging effect and the circumferential shearing strain can be significantly suppressed without generating uncompleted engagement of a billet. Accordingly, a product having reduced inside defects and excellent inside quality can be produced in high productivity. Further, by strengthening a plug nose rolling portion, a sharpened plug nose is obtained and an engagement limit can be increased. Additionally, a product further excellent in the inside quality can be efficiently produced. Accordingly, the present invention can be applied to wide fields of the piercing rolling of the seamless metallic tube.

Abstract: A threaded joint for steel pipes comprising a pin 1 and a box 2 each having a contact surface comprising a threaded portion 3 or 4 and an unthreaded metal contact portion 8 is provided with improved anti-galling propertied by forming a lubricating coating on the contact surface of at least one of the pin and the box, the lubricating coating exhibiting a self-repairing function by liquid lubrication and having a decreased greasiness. The lubricating coating is (1) a coating which comprises a lower lubricant layer which is in liquid form in the temperature range of above 0° C. and below 40° C. and an upper lubricant layer which is in solid form at 40° C., or (2) a coating which is semi-solid or solid at 40° C. and is formed of a mixture comprising a lubricating oil which is in liquid form in the temperature range of above 0° C. and below 40° C. and a wax which is in solid form at 40° C.

Abstract: A threaded joint for steel pipes which is capable of metal-to-metal sealing and which can be subjected to repeated fastening and unfastening without the application of a liquid lubricant containing a heavy metal powder comprises a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion. The contact surface of at least one of the pin and the box are coated with an undercoating layer and a lubricating coating layer atop it. The undercoating layer is a porous metal coating having a porosity of 5-80% and a thickness of 1-30 &mgr;m and preferably a hardness of 50-250 Hv. The lubricating coating is a solid lubricating coating or a liquid lubricating coating, the latter containing substantially no heavy metal powders. The total thickness of the undercoating layer and the lubricating coating layer is at most 100 &mgr;m.

Abstract: In a threaded joint for steel pipes comprising a pin and a box capable of mating with each other, the pin having an externally threaded portion and an unthreaded metal contact portion as a mating surface, and the box having an internally threaded portion and an unthreaded metal contact portion as a mating surface, the mating surface of at least one of the pin and the box is coated with a lower porous zinc or zinc alloy layer by blast plating and with an upper coating which is either a solid lubricating coating (comprising a lubricating powder in an organic or in organic binder) or a liquid, heavy metal powder-free coating (e.g., a liquid coating based on a highly basic organic acid metal salt such as a highly basic metal sulfonate).

Abstract: This invention relates to a threaded joint for steel pipes which comprises a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion and which guarantees galling resistance and gas tightness in a stable manner without application of a compound grease. A solid lubricating coating comprising a lubricating powder (e.g., molybdenum disulfide) and an organic or inorganic binder is formed on the contact surface of at least one of the pin and the box. The proportion of area of a cross section along the thickness of the solid lubricating coating which is occupied by secondary particles of the lubricating powder having an equivalent circular diameter of 15-60 &mgr;m is from 5-90%. Alternatively, the solid lubricating coating comprises, in addition to the lubricating powder, a fibrous filler (e.g., inorganic whiskers) in such an amount that the mass ratio of the fibrous filler to the binder is 0.01-0.5.

Abstract: This invention relates to a threaded joint for steel pipes which comprises a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion and which guarantees galling resistance and gas tightness in a stable manner without application of a compound grease. A solid lubricating coating comprising a lubricating powder (e.g., molybdenum disulfide) and an organic or inorganic binder is formed on the contact surface of at least one of the pin and the box. The proportion of area of a cross section along the thickness of the solid lubricating coating which is occupied by secondary particles of the lubricating powder having an equivalent circular diameter of 15-60 &mgr;m is from 5-90%. Alternatively, the solid lubricating coating comprises, in addition to the lubricating powder, a fibrous filler (e.g., inorganic whiskers) in such an amount that the mass ratio of the fibrous filler to the binder is 0.01-0.5.

Abstract: In a threaded joint for steel pipes comprising a pin and a box capable of mating with each other, the pin having an externally threaded portion and an unthreaded metal contact portion as a mating surface, and the box having an internally threaded portion and an unthreaded metal contact portion as a mating surface, the mating surface of at least one of the pin and the box is coated with a lower porous zinc or zinc alloy layer by blast plating and with an upper coating which is either a solid lubricating coating (comprising a lubricating powder in an organic or in organic binder) or a liquid, heavy metal powder-free coating (e.g., a liquid coating based on a highly basic organic acid metal salt such as a highly basic metal sulfonate).

Abstract: A heat resistant Ni base alloy comprises, on a mass% basis, 0.1% or less C, 2% or less Si, 2% or less Mn, 0.005% or less S, 10 to 25% Cr, 2.1 to less than 4.5% Al, 0.08% or less N, 0.001 to 1% in total of one or more elements of B: 0.03% or less, Zr: 0.2% or less and Hf: 0.8% or less, and 2.5 to 15% in total of one or more elements of Mo: 0.01 to 15% and W: 0.01 to 9%. The alloy is suitable as a material for a pipe used in ethylene cracking furnace.

Abstract: A martensitic stainless steel product having a chromium content of 9 to 15% by weight and a surface from which mill scales generated during production are removed by a shot blasting. The surface satisfies that, when a color image of the surface taken with 640×480 pixels is analyzed on blue color and a histogram of the pixel numbers and the tones divided into 0 to 255 classes is obtained, a relationship between the maximum frequency Yp and the tone value Xp at which Yp is counted satisfies an inequality, 800Xp−Yp−27000>0. This steel product is superior in weatherability under atmospheric environments, and also superior in sulfide stress cracking resistance under environments containing hydro-sulfide.

Abstract: The martensitic stainless steel product comprises a base steel and a dual oxide scale layer on a surface of the steel, wherein the dual scale layer includes an inner scale layer containing FeCr2O4 and Fe3O4 as main components and an outer scale layer containing Fe3O4 as a main component and having an outermost Fe2O3 layer; or includes an inner scale layer containing FeCr2O4 and FeO as main components and an outer scale layer containing FeO and Fe3O4 as main components and having an outermost Fe2O3 layer. If the product is a steel pipe, it exhibits excellent corrosion resistance when used for an oil country tubular goods or line pipe.

Abstract: A high-temperature austenitic stainless steel having improved weldability is disclosed. The steel consists essentially, by weight, of:C: 0.05%-0.15%, Si: less than 1.0%, Mn: 2.0% or less,P: 0.04% or less, S: 0.01% or less, Cr: 20%-30%,Ni: 10%-15%, N: 0.10%-0.30%,B: 0.0010%-0.01%,one or two of La and Ce: 0.01%-0.10% in total,Al: 0.01%-0.20%, anda balance of Fe and incidental impurities, wherein the contents of N and Al satisfy the following inequality:% N+2.times.% Al.ltoreq.0.500%and the value for Ni balance (Ni bal.) of the steel calculated by the following formula is in the range of from -1.0% to +3.0%:Ni bal. (%)=% Ni+0.5.times.% Mn+30.times.(% C+% N)-1.1.times.(% Cr+1.5.times.% Si)+8.2.

Abstract: A low corrosion resistant pipe 1 is jointed with a high corrosion resistant pipe 2 directly or via a coupling 3. An insulating ceramic film having a thickness of 0.4 .mu.m and a resistivity of 10.sup.8 .OMEGA. cm or more is formed on the outer and inner surfaces of the pipes 1 and 2 at a length L of 60 mm or more from the end of the pipe and on the surface which forms a space when the pipes 1 and 2 are jointed at a coverage ratio of 90% or more to less than 100%.