INBDE Practice Exam 2026 – Complete Study Guide

Question: 1 / 1180

What causes back-pressure porosity of metal?

Too thin sprue

Too long sprue

Too short sprue prevents venting of gas

Back-pressure porosity of metal occurs when trapped gas within the metal creates interior voids. This is caused by inadequate venting of the gas during the pouring process. A thin sprue (option A) may result in a fast flow of metal, which can cause turbulence and trap gas. A long sprue (option B) may not provide enough pressure to push the gas out of the mold. Incorrect temperature control (option D) can also affect the flow of metal and result in trapped gas. However, the main cause of back-pressure porosity is a short sprue (option C). A short sprue does not allow enough time for the gas to escape during the pouring process, resulting in trapped gas pockets within the metal. Therefore, option C is the correct answer.

Get further explanation with Examzify DeepDiveBeta

Incorrect temperature control

Next Question

Report this question

Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy