# Making tcolorbox titles section headings

I want to set up a customised tcolorbox where the title of the box is automatically formatted as a section heading. Here's a MWE with my current set up:

\documentclass[a0]{a0poster}
\usepackage{lipsum}
\usepackage[margin=4cm]{geometry}
\usepackage{multicol}
\columnsep=3cm
\columnseprule=0pt
\usepackage{xcolor}
\definecolor{grey}{RGB}{240,240,240}
\usepackage{tcolorbox}
\newtcolorbox{info}[1]{boxrule=1.5mm,sharp corners,colback=grey,colframe=black,title=#1,fontupper=\color{black},fonttitle={\color{white}\bf\section{#1}}}
\begin{document}
\begin{multicols}{3}
\begin{info}{Introduction}
\lipsum[1]
\end{info}
\lipsum[2-30]
\end{multicols}
\end{document}


The problem is that this creates this:

Rather than, as desired, this:

A solution would be welcome.

• Well, you're typesetting the title twice, effectively. \bf is deprecated – user31729 Apr 24 '17 at 13:33

The \section should go into title=..., not again in fonttitle=, which is meant for font settings, not for structure levels.

(Well, 'again' is the wrong term: fonttitle settings are done first, so \section will come first then as well, which is clearly visible in the O.P.'s screenshot)

\documentclass[a0]{a0poster}
\usepackage{lipsum}
\usepackage[margin=4cm]{geometry}
\usepackage{multicol}
\columnsep=3cm
\columnseprule=0pt
\usepackage{xcolor}
\definecolor{grey}{RGB}{240,240,240}
\usepackage{tcolorbox}
\newtcolorbox{info}[1]{boxrule=1.5mm,sharp corners,colback=grey,colframe=black,title=\protect\section{#1},fontupper=\color{black},fonttitle={\color{white}}}
\begin{document}
\begin{multicols}{3}
\begin{info}{Introduction}
\lipsum[1]
\end{info}
\lipsum[2-30]
\end{multicols}
\end{document}