Why is my table before the section title?

I know that it is not a popular solution on this site but I like it anyway.

• The float package offers an additional placement parameter/option called H. If you use it then the float object (figure or table) is exactly placed where you put it in the code.
• Normally you want floating objects to float and let LaTeX decide where to put it.
• But with approach that I describe here, you have full manual control of the float position if you want to.
• You can still combine this approach with the other solutions mentioned here (flafter package and !htb placement parameter). Just decide from table to table (or figure and figure) what is best.

---

\documentclass{article}
\usepackage{float} % here for H placement parameter

\begin{document}

Text before table.    

\begin{table}[H] % placement parameter H
    \centering % if you want to center the table
    \caption{Table showing \ldots}
    \label{table:ExampleTable}
    % Code for table
\end{table}

Text after table.      

\end{document} 

By the way, normally you want to have a little unbreakable space between the number and the unit: 720\,°C or 720~°C. Where \, is a half space and ~ a full space. See here and here for further information. But this is not related to the question at all.

You need \begin{table}[htp] in order to allow the figure to appear mid-page (h).

Also you might want to add

\usepackage{flafter} 

which prevents figures ever floating backwards up the current page

So with flafter (but not h) the float will appear at the bottom of the current page or top of the next.

With [htpb] then without flafter the order that is tried is h, t on this page, b on this page, p, t on next page. (But it is t on this page that you want to avoid).

With [htpb] then withflafter the order that is tried is h, b on this page, p, t on next page.

Use the [!htbp] option. I also used makecell and siunitx to have a nicer formatting of the table, so you don't have to use \resizebox:

\documentclass[a4paper, french]{report}
\usepackage[utf8]{inputenc}
\usepackage[TS1,T1]{fontenc}
\usepackage{lmodern}
\usepackage{babel}
\usepackage{geometry}
\usepackage{makecell, caption}
\renewcommand\theadfont{\normalsize\bfseries\boldmath}
\usepackage{siunitx}
\sisetup{detect-weight, range-phrase=/, range-units = single}
\usepackage{lipsum}
\renewcommand\thesection{\arabic{section}}
\setcounter{section}{3}

\begin{document}

\subsection{Cinétique d'oxydation des joints de grains avec teneur nominale en chrome}

\lipsum[2]

\begin{table}[!hbt]
  \centering\renewcommand{\arraystretch}{1.2}
  \caption{Données utilisées pour la calibration de la cinétique d'oxydation des joints de grains présentant une teneur nominale en chrome à \SIrange{320}{325}{\celsius}}
  \begin{tabular}{|c|c|c|c|c|}
    \hline
    \thead{Repère} & \thead{Échantillon} & \thead{pox max & & \\ (nm)} & \thead {Température \\ (\si{\celsius})} & \thead{Temps\\ (h)} \\
    \hline
    \hline
    B356 (TT 1\,h $ \times $ \SI{720}{\celsius}) & 1816-22 & 10 & 325 & 0,16 \\
    \hline
    T265 & 1866-20 & 307 & 325 & 100 \\
    \hline
    B356 SA & 1866-187 & 847 & 320 & 1000 \\
    \hline
  \end{tabular}
  \label{tab:calibrecinetique}
\end{table}

\lipsum[3]

\subsection{Cinétique d'oxydation des carbures de chrome}

\lipsum[5]

\end{document}