Try this,
*suppose line_ids is One2many fields in wizard
*order_line is One2many fields in model_b

def create_line(self):
vals = []
for line in self.line_ids
vals.append(
(0, 0, {'field_1': line.field_1.id, 'field_2': line.field_2})
)
model_b = self.env['model_b'].create({
'order_line': vals
})