Dual gallery steel piston

A piston comprising:

• a body having an upper portion formed of a single piece of material and a lower portion formed of a single piece of material, the upper portion and the lower portion joined to one another and each including inner surfaces forming a cooling gallery therebetween, said cooling gallery extending circumferentially around a center axis of said body and spaced from said center axis, said lower portion including a partition extending into said cooing gallery and having a distal end engaging one of said inner surfaces of said upper portion, said partition extending circumferentially around said center axis, said partition dividing said cooling gallery into at least a first gallery portion and a second gallery portion, and said partition sealing said first gallery portion and said second gallery portion,
• wherein said body is formed of steel, said upper portion of said body includes an upper combustion wall, said upper combustion wall presents a combustion bowl surrounded by an outer rim, said upper portion includes an upper outer rib depending from said outer rim of said upper combustion wall, said upper outer rib extends circumferentially around said center axis of said body and is spaced from said center axis of said body, said upper portion includes an upper inner rib depending from said upper combustion wall opposite said combustion bowl, said upper inner rib extends circumferentially around said center axis of said body and is located between said center axis of said body and said upper outer rib, said lower portion of said body includes a lower outer rib extending circumferentially around said center axis of said body and spaced from said center axis of said body, said lower outer rib is welded to said upper outer rib at an outer weld joint, said lower portion of said body includes a lower inner rib extending circumferentially around said center axis of said body and located between said center axis of said body and said lower outer rib, said lower inner rib is welded to said upper inner rib at an inner weld joint, said lower portion includes a lower wall located between said lower outer rib and said lower inner rib, said upper combustion wall includes an upper inner surface located between said upper outer rib and said upper inner rib, said lower wall includes a lower inner surface, said inner ribs present a first inner surface, and said outer ribs present a second inner surface, said inner surfaces face and surround said cooling gallery, and said body includes flash located adjacent said weld joints, and
• wherein said partition extends upwardly from said lower wall and curves to said distal end at or adjacent said first inner surface of said upper inner rib such that said first gallery portion is located between said partition and a portion of said inner ribs and a portion of said lower wall, and said second gallery portion has a volume larger than a volume of said first gallery portion, said flash is located along said first weld joint in said first gallery portion and is physically separated from said second gallery portion by said partition, said lower portion of said body includes an oil inlet to said second gallery portion, said second gallery portion contains cooling oil, and said first gallery portion is sealed and contains air.

A piston comprising:

• a body having an upper portion formed of a single piece of material and a lower portion formed of a single piece of material, the upper portion and the lower portion joined to one another and each including inner surfaces forming a cooling gallery therebetween, said cooling gallery extending circumferentially around a center axis of said body and spaced from said center axis, said lower portion including a partition extending into said cooing gallery and having a distal end engaging one of said inner surfaces of said upper portion, said partition extending circumferentially around said center axis, said partition dividing said cooling gallery into at least a first gallery portion and a second gallery portion, and said partition sealing said first gallery portion and said second gallery portion,
• wherein said body is formed of steel, said upper portion of said body includes an upper combustion wall, said upper combustion wall presents a combustion bowl surrounded by an outer rim, said upper portion includes an upper outer rib depending from said outer rim of said upper combustion wall, said upper outer rib extends circumferentially around said center axis of said body and is spaced from said center axis of said body, said upper portion includes an upper inner rib depending from said upper combustion wall opposite said combustion bowl, said upper inner rib extends circumferentially around said center axis of said body and is located between said center axis of said body and said upper outer rib, said lower portion of said body includes a lower outer rib extending circumferentially around said center axis of said body and spaced from said center axis of said body, said lower outer rib is welded to said upper outer rib at an outer weld joint, said lower portion of said body includes a lower inner rib extending circumferentially around said center axis of said body and located between said center axis of said body and said lower outer rib, said lower inner rib is welded to said upper inner rib at an inner weld joint, said lower portion includes a lower wall located between said lower outer rib and said lower inner rib, said upper combustion wall includes an upper inner surface located between said upper outer rib and said upper inner rib, said lower wall includes a lower inner surface, said inner ribs present a first inner surface, and said outer ribs present a second inner surface, said inner surfaces face and surround said cooling gallery, and said body includes flash located adjacent said weld joints, and
• wherein said partition extends horizontally from said lower outer rib to said distal end at or adjacent said first inner surface of said upper inner rib, said first gallery portion is located between said partition and an upper inner surface of said upper combustion wall and said second gallery portion is located between said partition and said lower inner surface of said lower wall, said flash is located along said second weld joint in said first gallery portion and is physically separated from said second gallery portion by said partition, said lower portion of said body includes an oil inlet to said second gallery portion, said second gallery portion contains cooling oil, and said first gallery portion is sealed and contains air.