Intermediate drill stem

Claim 2

An intermediate drill stem comprising an elongated, tubular, steel Body the main portion of which has a substantially uniform outer diameter, said body having a wall thickness of at least about five-eighths inch in the main portion thereof. a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connected to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, said intermediate stem being distinguished by the length of the maximum diameter portion of the pin connector being in the range of nearly twice to about seven times the outer diameter of the connector, the combined length of the maximum diameter portions of the pin and box connectors being in the range of four to ten times the outer diameter of said maximum diameter portions, the body of the stem being made of alloy steel having a yield strength of at least about 120,000 psi, the outer surface of said body being a machined surface, said body having ends of larger outer diameter than that of said main portion of the body but of somewhat smaller outer diameter than that of the maximum diameter portion of the connectors, each connector being rod welded to one of said ends with the weld metal overlapping the end to build up the maximum outer diameter of the end to equal that of the connector, and a tapered elevator shoulder at each end of the body extending into said build up of weld metal.

Claim 3

Subject matter of claim 1 further distinguished by: the inner diameters of said connectors being equal to each other and slightly smaller than that of the main portion of said body, the inner diameter of said body being uniform througout except at the ends where the body is built up with weld metal on the inside to make the ends have the same inner diameter as the connectors adjacent the welds.

Claim 4

Subject matter of claim 2 further distinguished by: said body having a transition portion between each end and the main body portion, said transition portions each having an outer diameter smaller than that of said ends and larger than that of said main portion of the body.

Claim 5

Subject matter of claim 3 further distinguished by: said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter being formed integral with said main portion of the body and providing a protector against wear on the main portion of the body.

Claim 6

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having a wall thickness of at least about five-eighths inch in the main portion thereof, a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connected to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the Rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, said intermediate stem being distinguished by the length of the maximum diameter portion of the pin connector being in the range of nearly twice to about seven times the outer diameter of the connector, the combined length of the maximum diameter portions of the pin and box connectors being in the range of four to ten times the outer diameter of said maximum diameter portions, the body of the stem being made of alloy steel having a yield strength of at least about 120,000 psi, the outer surface of said body being a machined surface, said body having ends of larger outer diameter than that of said main portion of the body but of somewhat smaller outer diameter than that of the maximum diameter portion of the connectors, each connector being rod welded to one of said ends with the weld metal overlapping the end to build up the maximum outer diameter of the end to equal that of the connector, a tapered elevator shoulder at each end of the body extending into said build up of weld metal, the inner diameters of said connectors being equal to each other and slightly smaller than that of the main portion of said body, the inner diameter of said body being uniform throughout except at the ends where the body is built up with weld metal of the inside to make the ends have the same inner diameter as the connectors adjacent the welds, said body having a plurality of protectors located between and spaced from the ends of the body each of which protectors has a larger outer diameter than said main portion of the body, said protectors being formed integral with said main portion of the body and providing protection against wear on the main portion of the body, said protectors each having an outer diameter at least one-half inch larger than the outer diameter of the main portion of the body of the stem, the ends of said protectors being tapered where they join the main portion of the body, the length of each protector being at least twice the outer diameter of the connectors.

Claim 7

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having a wall thickness of at least about five-eighths inch in the main portion thereof, a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connected to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the Rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, said intermediate stem being distinguished by the length of the maximum diameter portion of the pin connector being in the range of nearly twice to about seven times the outer diameter of the connector, the combined length of the maximum diameter portions of the pin and box connectors being in the range of four to ten times the outer diameter of said maximum diameter portions, the body of the stem being made of alloy steel having a yield strength of at least about 120,000 psi, the outer surface of said body being a machined surface, said body having ends of larger outer diameter than that of said main portion of the body but of somewhat smaller outer diameter than that of the maximum diameter portion of the connectors, each connector being rod welded to one of said ends with the weld metal overlapping the end to build up the maximum outer diameter of the end to equal that of the connector, a tapered elevator shoulder at each end of the body extending into said build up of weld metal, the inner diameters of said connectors being equal to each other and slightly smaller than that of the main portion of said body, the inner diameter of said body being uniform throughout except at the ends where the body is built up with weld metal of the inside to make the ends have the same inner diameter as the connectors adjacent the welds, said body having a plurality of protectors located between and spaced from the ends of the body each of which protectors has a larger outer diameter than said main portion of the body, said protectors being formed integral with said main portion of the body and providing protection against wear on the main portion of the body, said protectors each having an outer diameter at least one-half inch larger than the outer diameter of the main portion of the body of the stem, the ends of said protectors being tapered where they join the main portion of the body, the length of each protector being at least twice the outer diameter of the connectors.

Claim 8

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter being formed integral with said main portion of the body and providing a protector against wear on the main portion of the body, the ends of said protector being tapered where they join the main portion of the body, said body having a wall thickness of at least five-eighths inch in the main portion thereof. said body having ends of larger outer diameter than the main portion of the body, the outer diameter of said ends being substantially as large as that of said protector, a tubular steel connector rod-welded to each end of said body, said connectors each having a larger outer diameter than the end of the body to which it is welded, the weld metal overlapping the end to build up its outer diameter to that of the connector.

Claim 9

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter being formed integral with said main portion of the body and providing a protector against wear on the main portion of the body, the ends of said protector being tapered where they join the main portion of the body, said body having a wall thickness of at least five-eighths inch in the main portion thereof. said body having ends of larger outer diameter than the main portion of the body, the outer diameter of said ends being substantially as large as that of said protector, a tubular steel connector rod-welded to each end of said body, said connectors each having a larger outer diameter than the end of the body to which it is welded, the weld metal overlapping the end to build up its outer diameter to that of the connector.

Claim 10

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having a wall thickness of at least five-eighths inch in the main portion thereof, said body having at least one protector located between and spaced from the ends of the body, said protector having a larger outer diameter than said main portion of the body, said protector being formed integral with said main portion of the body, said body having ends of larger outer diameter than the main portion of the body, the outer diameter of said ends being substantially as large as that of said protector, a tubular steel connector rod welded to each end of said body, said connectors each having a larger outer diameter than the end of the body to which it is welded, the weld metal overlapping the end to build up its outer diameter to that of the connector, a tapered elevator shoulder at each end of the body extending into said build up of weld metal thereon.

Claim 11

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having a wall thickness of at least five-eighths inch in the main portion thereof, said body having at least one protector located between and spaced from the ends of the body, said protector having a larger outer diameter than said main portion of the body, said protector being formed integral with said main portion of the body, said body having ends of larger outer diameter than the main portion of the body, the outer diameter of said ends being substantially as large as that of said protector, a tubular steel connector rod welded to each end of said body, said connectors each having a larger outer diameter than the end of the body to which it is welded, the weld metal overlapping the end to build up its outer diameter to that of the connector, a tapered elevator shoulder at each end of the body extending into said build up of weld metal thereon.

Claim 12

Subject matter of claim 7 further distinguished by: the inner diameters of said connectors being equal to each other and slightly smaller than that of the main portion of said body, the inner diameter of said body being uniform throughout except at the ends where the body is built up with weld metal on the inside to make the ends have the same inner diameter as the connectors adjacent the welds.

Claim 13

Subject matter of claim 7 further distinguished by: the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors may be twice that of the main portion of the body of the stem, said body having a transition portion between each end and the main body portion, said transition portions each having an outer diameter smaller than that of said ends and larger than that of said main portion of the body.

Claim 14

Subject matter of claim 7 further distinguished by: the length of the box connector being at least of the order of twice the outer diameter of the connector, the length of the maximum diameter portion of the pin connector being in the range of nearly twice to aboue seven times the outer diameter of the connector.

Claim 15

An intermediate drill stem comprising an elongated, tubular, alloy steel body the main portion of which has a substantially uniform outer diameter, the exterior surface of said main portion being a machined surface, said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter being formed integral with said main portion of the body and providing a protector against wear on the main portion of the body, the ends of said protector being tapered where they join the main portion of the body, said body having a wall thickness of at least five-eighths inch in the main portion thereof, said body having ends of larger outer diameter than the main portion of the body, the outer diameter of said ends being substantially as large as that of said protector, said body having a transition portion between each end and the main body portion, said transition portions each having an outer diameter smaller than that of said ends and larger than that of said main portion of the body, a tubular alloy steel connector rod welded to each end of said body, said connectors each having a larger outer diameter than the end of the body to which it is welded, the weld metal overlapping the end to build up its outer diameter to that of the connector, a tapered elevator shoulder at each end of the body extending into said build up of weld metal thereon, the inner diameters of said connectors being equal to each other and slightly smaller than that of the main portion of said body, the inner diameter of said body being uniform throughout except at the ends where the body is built up with weld metal on the inside to make the ends have the same inner diameter as the connectors adjacent the welds, one of said connectors being interiorly threaded at its end opposite from its welded end to provide a box at one extemity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its welded end, said portion of reduced outer diameter being threaded to provide a pin at the other extemity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors cay be twice that of the main portion of the body of the stem, the length of the maximum diameter portion of the pin connector being in the range of nearly twice to about seven times the outer diameter of the connector. the combined length of the maximum diameter portions of the pin and box connectors being in the range of four to ten times the outer diameter of said maximum diameter portions, the length of each protector being at least of the same order of magnitude as the outer diameter of the protector, each said protector having a diameter at least one-half inch larger than that of said main portion of the body, said connectors and each protector body providing centralizers for said intermediate stem, the longitudinal spacing between said centralizers being a maximum of 15 feet.

Claim 16

An intermediate drill stem comprising an elongated, tubular, alloy steel body the main portion of which has a substantially uniform outer diameter, the exterior surface of said main portion being a machined surface, said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter being formed integral with said main portion of the body and providing a protector against wear on the main portion of the body, the ends of said protector being tapered where they join the main portion of the body, said body having a wall thickness of at least five-eighths inch in the main portion thereof, said body having ends of larger outer diameter than the main portion of the body, the outer diameter of said ends being substantially as large as that of said protector, said body having a transition portion between each end and the main body portion, said transition portions each having an outer diameter smaller than that of said ends and larger than that of said main portion of the body, a tubular alloy steel connector rod welded to each end of said body, said connectors each having a larger outer diameter than the end of the body to which it is welded, the weld metal overlapping the end to build up its outer diameter to that of the connector, a tapered elevator shoulder at each end of the body extending into said build up of weld metal thereon, the inner diameters of said connectors being equal to each other and slightly smaller than that of the main portion of said body, the inner diameter of said body being uniform throughout except at the ends where the body is built up with weld metal on the inside to make the ends have the same inner diameter as the connectors adjacent the welds, one of said connectors being interiorly threaded at its end opposite from its welded end to provide a box at one extemity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its welded end, said portion of reduced outer diameter being threaded to provide a pin at the other extemity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors cay be twice that of the main portion of the body of the stem, the length of the maximum diameter portion of the pin connector being in the range of nearly twice to about seven times the outer diameter of the connector. the combined length of the maximum diameter portions of the pin and box connectors being in the range of four to ten times the outer diameter of said maximum diameter portions, the length of each protector being at least of the same order of magnitude as the outer diameter of the protector, each said protector having a diameter at least one-half inch larger than that of said main portion of the body, said connectors and each protector body providing centralizers for said intermediate stem, the longitudinal spacing between said centralizers being a maximum of 15 feet.

Claim 17

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having a wall thickness of at least about five-eighths inch in the main portion thereof, a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connected to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, said connectors being long axially compared to the diameter thereof, the combined length of the maximum diameter portions of the pin and box connectors being at least four times the outer diameter of said maximum diameter portions, the outer surface of said main portion of said body being a turned machined surface, said body having ends of larger outer diameter than that of said main portion of the body, each connector being welded to one of said ends, said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter providing a protector against wear on the main portion of the body, each said protector being homogeneously integral with said main portion of the body, said protector and main portion being one and the same single piece of metal, each said protector having an outer diameter at least one-half inch larger than the outer diameter of the main portion of the body of the stem, the length of each protector being at least twice the outer diameter of the connectors, said long connectors and each said protector being spaced apart along the length of the stem and serving as centralizers for said intermediate stem.

Claim 18

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having a wall thickness of at least about five-eighths inch in the main portion thereof, a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connected to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, said connectors being long axially compared to the diameter thereof, the combined length of the maximum diameter portions of the pin and box connectors being at least four times the outer diameter of said maximum diameter portions, the outer surface of said main portion of said body being a turned machined surface, said body having ends of larger outer diameter than that of said main portion of the body, each connector being welded to one of said ends, said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter providing a protector against wear on the main portion of the body, each said protector being homogeneously integral with said main portion of the body, said protector and main portion being one and the same single piece of metal, each said protector having an outer diameter at least one-half inch larger than the outer diameter of the main portion of the body of the stem, the length of each protector being at least twice the outer diameter of the connectors, said long connectors and each said protector being spaced apart along the length of the stem and serving as centralizers for said intermediate stem.

Claim 19

Subject matter of claim 12, further distinguished by: said body having a transition portion between each end and the main body portion, said transition portions each having an outer diameter smaller than that of said ends and larger than that of said main portion of the body.

Claim 20

Subject matter of claim 12 further distinguished by: the outer diameter of said ends of the body being substantially as large as that of said protector, said connectors each having a larger outer diameter than the end of the body to which it is welded, the weld metal overlapping the end to build up its outer diameter to that of the connector.

Claim 21

Subject matter of claim 14 further distinguished by: said body having a transition portion beTween each end and the main body portion, said transition portions each having an outer diameter smaller than that of said ends and larger than that of said main portion of the body.

Claim 22

Subject matter of claim 14 further distringuished by: said stem having an elevator shoulder at each end of the body at the juncture of said end and the weld, each shoulder including a portion of the metal of the weld and a portion of the metal of the end of the body.

Claim 23

Subject matter of claim 16 further distinguished by: said body having a transition portion between each end and the main body portion, said transition portions each having an outer diameter smaller than that of said ends and larger than that of said main portion of the body.

Claim 24

Subject matter of claim 12 further distinguished by: the ends of said protector being tapered where they join the main portion of the body, the longitudinal distance between the adjacent extremities of adjacent ones of said centralizers being not in excess of 15 feet.

Claim 25

Subject matter of claim 12, said connectors being free of hard facing thereabout, said protector being of smaller outer diameter than that of the maximum outer diameter portion of said connectors, said protector having a band of hard facing material set in an annular groove around said protector.

Claim 26

Subject matter of claim 12 wherein said intermediate stem has an inner diameter characteristic of a drill collar and an outer diameter characteristic of drill pipe.

Claim 27

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having ends of larger outer diameter than that of the main portion thereof, a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connected to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, each of said connectors being connected to one of said ends of the body by added weld metal joining the connector to the end, each connector having a maximum outer diameter larger than the end of the body to which it is welded, the weld metal overlapping the end to such an extent as to build up its outer diameter to that of said maximum diameter of the connector.

Claim 28

An intermediate drill stem comprising an elongated, tubular, steel body the main portion of which has a substantially uniform outer diameter, said body having ends of larger outer diameter than that of the main portion thereof, a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connected to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, each of said connectors being connected to one of said ends of the body by added weld metal joining the connector to the end, each connector having a maximum outer diameter larger than the end of the body to which it is welded, the weld metal overlapping the end to such an extent as to build up its outer diameter to that of said maximum diameter of the connector.

Claim 29

Subject matter of claim 21 said stem having an elevator shoulder at each end of the body at the juncture of said end and the weld, each shoulder including a portion of the metal of the weld and a portion of the metal of the end of the body.

Claim 30

Combination of claim 1 including the hereinbefore set forth invention.

Claim 31

An intermediate drill stem comprising an elongated, tubular, alloy steel body the main portion of which has a substantially uniform outer diameter, said body having ends of larger outer diameter than that of the main portion thereof, said main portion having a wall thickness of at least about five-eighths inch, a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connecteD to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, said connectors being long axially compared to the diameter thereof, the combined length of the maximum diameter portions of the pin and box connectors being at least four times the outer diameter of said maximum diameter portions, the outer surface of said main portion of said body being a turned machined surface, said body having ends of larger outer diameter than that of said main portion of the body, each connector being homogeneously integral with one of said ends of the body, each said connector and body being made of one and the same piece of metal, said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter providing a protector against wear on the main portion of the body, each said protector being homogeneously integral with said main portion of the body, said protector and main portion being one and the same single piece of metal, each said protector each having an outer diameter at least one-half inch larger than the outer diameter of the main portion of the body of the stem, the length of each protector being at least twice the outer diameter of the connectors, said long connectors and each said protector being spaced apart along the length of the stem and serving as centralizers for said intermediate stem.

Claim 32

An intermediate drill stem comprising an elongated, tubular, alloy steel body the main portion of which has a substantially uniform outer diameter, said body having ends of larger outer diameter than that of the main portion thereof, said main portion having a wall thickness of at least about five-eighths inch, a tubular alloy steel connector connected to each end of said body, one of said connectors being interiorly threaded at its end opposite from its end that is connected to said body, said interiorly threaded end providing a box at one extremity of the stem, the other of said connectors having a portion of reduced outer diameter at its end opposite from its end that is connecteD to said body, said portion of reduced outer diameter being threaded to provide a pin at the other extremity of the stem, the maximum outer diameter portion of each of said connectors being at least 1.2 times that of said main portion of the body whereby the rigidity of a connection comprising such pin and box connectors can be twice that of the main portion of the body of the stem, said connectors being long axially compared to the diameter thereof, the combined length of the maximum diameter portions of the pin and box connectors being at least four times the outer diameter of said maximum diameter portions, the outer surface of said main portion of said body being a turned machined surface, said body having ends of larger outer diameter than that of said main portion of the body, each connector being homogeneously integral with one of said ends of the body, each said connector and body being made of one and the same piece of metal, said body having at least one portion located between and spaced from the ends of the body which one portion has a larger outer diameter than said main portion of the body, said portion of larger outer diameter providing a protector against wear on the main portion of the body, each said protector being homogeneously integral with said main portion of the body, said protector and main portion being one and the same single piece of metal, each said protector each having an outer diameter at least one-half inch larger than the outer diameter of the main portion of the body of the stem, the length of each protector being at least twice the outer diameter of the connectors, said long connectors and each said protector being spaced apart along the length of the stem and serving as centralizers for said intermediate stem.

Claim 33

Subject matter of claim 12, said body being made of steel in the A.I.S.I. 1100 to 1,200 series.