SOMETIMES those type of blade are made of 4140, but that's the problem with "recycled" stuff for Bladesmithing/Knifemaking..... you just never know. What makes it even more maddening for a Bladesmith/Knifemaker is that the same item/part number, from the same company, is very often made of a different steel type from run to run. This is called "Spec Manufacturing"...... where as at one point in time, the exact steel type an item was to be made from, was the first annotation on an order, that's no longer the case. It all has to do with profit.... even saving a few pennies on the production of an item adds up to more profit for a company when you consider thousands and thousands of the item are produced. These days, with "spec manufacturing", the functional requirements, for a given amount of time, or repetitions of use are the driving factor(s), and an annotation of "use the least expensive material that will meet the requirements at the time of production" are how the decision is made as to what steel type is utilized. This means that all the old literature that many Bladesmiths/Blacksmiths still refer to concerning certain items being made of specific steel types is totally useless.
If you stick with Bladesmithing/Knifemaking long enough, you will find yourself wondering about all those blades you made from "recycled" items, and waiting for one to come back and bite you.