"are joined into" is correct and can be used in written English.
Example: The two pieces of wood are joined into a larger block.
The helmet's outer shell and shock absorbing inner shell are joined into an inseparable component that is lightweight but solid.
German has a fine architecture, in which appositive phrases are joined into compounds, leading to long and goofy-sounding words that express often complicated factual and emotional information.
Other works at Wave Hill include Matthew Conradt's large, vaguely nightmarish collages picturing faceless figures in Cubist-Surrealist compositions, and wooden sculptures by Romy Scheroder, in which parts scavenged from found pieces of furniture are joined into oddly dysfunctional constructions.
Called the Connexion system, it has 1,000 small antenna modules, each shaped more like a jumbo pizza box than an antenna dish, are joined into a single grid.
The representatives are joined into "superclusters" of loosely related term, visualized with different color.
The modules of crRNA and tracrRNA are joined into a single RNA molecule, and termed as guide RNA (Mali et al. 2013).
Later these were joined into collections known as romanceros.
South America, Africa, India, Australia, and Antarctica were joined into the Southern Hemisphere continent of Gondwana.
After World War II, the two were joined into a single structure.
This time around, disparate initiatives will be joined into a single package.
Now 16 East 84th is a condominium, and 18 and 20 have been joined into a single co-op.
