"claimed himself" is correct and usable in written English.
You can use it when someone is asserting or declaring something about themselves, or when someone is taking responsibility for an action. For example, "The suspect claimed himself guilty of all charges thrown at him."
President-elect Donald Trump has stacked his proposed Cabinet with fossil fuel executives and climate science deniers, and has claimed himself or through surrogates that global warming is "a hoax" and "a bunch of bunk".
I obeyed without question until I listened -- along with a nation -- to a Black boy's cry for help as a homegrown terrorist masquerading as neighborhood watch murdered Trayvon Martin then claimed himself as the victim.
He claimed himself to be the defender of the real Church – a pure Church that didn't submit to poncey new ideas about allowing congregations to celebrate mass using their own languages, rather than Latin.
Mistry may therefore claim himself to be the first British male to win a Wimbledon title since Fred Perry in 1936.
He cites no particular influences on his own style, but he does not seem much interested in claiming himself as an original, either.
Guaidó, head of the opposition-controlled National Assembly, invoked the Venezuelan constitution in claiming himself the nation's true president last month.
Hill cannot claim himself capable of replacing Kershaw.
Suarez is perfectly right to claim himself as a hero by sacrificing himself with an immoral act.
As a film-maker, he claims himself as belonging to the realistic way of story-telling devised by Satyajit Ray and Vittorio De Sica.
Ubermann wants to use Indiana as a test subject, but Kerner steps onto the platform first, claiming himself to be most suitable for godhood.
