You're using an HTML5 button element. Remember the reason is this button has a default behavior of submit, as stated in the W3 specification ... ... <看更多>

The value of the id attribute on the form with which to associate the element. type = "submit" #: Specifies that its input element is a button for submitting a ... ... <看更多>

Submitting a form. Typically, a form has a submit button. When you click it, the browser sends form data to the server. To create a submit button ... ... <看更多>

There's an example in the Gravity Forms documentation, but it lacks the proper code to show your custom button text, AND removes important attributes like the ... ... <看更多>