Button readonly when adding in one2many field on wizard for Odoo 10

Question

I have a wizard in sale order form. On this wizard i added a "button" field in one2many field, but it show no click-able action or it is readonly. and this accidence happen only for button field, other fields are work well. So, Why it is readonly ?

My code Xml code here:

<group>
  <field name="wizard" style="width:600px">
    <tree editable="bottom">
        <field name="index" invisible="1"/>
        <field name="check_box" style="width:50px"/>
        <field name="products_ids"/>
        <field name="services"/>
        <button name="text_test_field1" string="test" type="object"/>
        <field name="prices" widget="monetary"/>
    </tree>
  </field>
</group>