First off, I want you to realize that it isn't a job where you deal with a lot of knifemakers. You will be handling very large sales to a variety of industries in a variety of countries. You could get a big head start by learning some foreign languages in High School - Japanese or Mandarin would be a big plus. I am not familiar where the American producers operate worldwide, but if you could identify the market with the most potential and learn the language, after college you could increase your potential earnings by working overseas. You need to learn about EXACTLY what the job you're looking at does - you might not ever see a knife working for one of those companies, and that is serious. Even if you do, it will be a very small part of your overall job duties.
You might try e-mailing jamey.duncan AT crucible.com , and ask what he majored in. The truth is, the sales agents ALWAYS have bachelor degrees, and one in materials science definitely wouldn't hurt - the different positions mean that you could have a marketing degree and fit one better, or have an engineering degree and fit another, or have a mechanical engineering or production management degree for another. There is a lot of production planning associated with getting orders out, and there is usually a sales agent associated with each product family at a large company like Crucible or Carpenter. Most companies will segregate market development and account management, and you'll need to excel at market development to be considered for a position as an account manager.
To get any of the jobs mentioned, you WILL NEED EXPERIENCE, and that's hard to get experience when most companies aren't going to hire you. Most of Crucible's sales and marketing team has been there 20+ years. Your best bet is to get in a Co-Op or College recruitment program. Here are links to Carpenter's programs - be sure you meet all the requirements. I would say if you don't qualify for a program like that, and don't get the proper training, or don't end up with the experience, you will have a very hard time getting into the specialty metals industry.
Carpenter Co-Op Program
Carpenter College Recruitment Program
Here is a cheat sheet from Carpenter for a Market Development Position. Account Management will require even more experience, between 5-10 years of experience.
Market Development Job
A Bachelor’s degree in Materials Science or Metallurgy combined with a minimum of three or more years of sales (or other commercial exposure) and product development experience; three or more years in specialty alloys industry supervision is required. The candidate selected will also have:
The ability to apply management expertise to set direction, resolve problems and provide guidance to employees in own area of responsibility or department.
The breadth and depth of technical or functional expertise in own area of responsibility or department; may be acquiring knowledge of other related areas of departments.
The ability to adapt area/departmental plans and priorities to address business and operational challenges.
The ability to influences or provide input to forecasting and planning resources; may manage allocated budget.
Practical understanding of industrial/manufacturing principles, standards, methods and practices.
Good luck. I would try and get a job in the medical field, or be a lawyer if I were you.