Use and purpose have the same meaning in this context.
Purpose may be considered slightly more formal, so you may use this in business situations. Both sentences ask the customer what they will be using the steel for so you can find the appropriate material.
Instead of saying "what is the usage of this steel" you can say "what do you intend to use the for."
Another word of intend is wish.Therefore you want to know what they wish to use the steel for so that you properly help the.
"what is the usage of this steel"と言う代わりに "what do you intend to use the steel for"と言う事が出来ます。
"intend"の他の言い方は"wish"です。ですので、何にこのsteelを使う[つもり](https://eikaiwa.dmm.com/uknow/questions/62335/)なのか知りたいという意味になります。
The purpose of this questioning is to find out how the prospective buyer intends to use the steel once he has acquired it.
Obviously there are different types of steel available: for example, galvanised steel, or non glvanised steel, together with different thicknesses and finishes, so knowing the end purpose for its application is essential at the selling stage.
"I'd like to buy some steel please?"
"Cerrtainly sir. May I ask, what do you need the steel for?"
"It's for roofing an old farm building."
"I see. Well probably you'll need something like our galvanised, corrugated, steel roofing sheets. If you tell me the area of the roof, I'll work you out a price."
この質問の原理としては、買った後にその鉄を何に使うか知りたいからですよね。
もちろん鉄にはいろんな種類があります。
例えば、亜鉛メッキ鋼なのかそうでないのかやその厚さや仕上げ具合などです。
そのため、その後何に使うのかをわかることで、どれを勧めれば良いのか売り手側もわかるわけですね。
"I'd like to buy some steel please?"
いくつか鋼が買いたいのですが？
"Cerrtainly sir. May I ask, what do you need the steel for?"
もちろんです。何に使うものかお教え願いますか？
"It's for roofing an old farm building."
小屋の屋根に使うんです。
"I see. Well probably you'll need something like our galvanised, corrugated, steel roofing sheets. If you tell me the area of the roof, I'll work you out a price."
なるほど、それではシワシワの入ってる屋根用のトタンシートがいいでしょうね。屋根の面積を教えてもらえれば金額出しますよ。
>What function will the steel serve?
*function=the purpose of a thing
*serve=perform duties
..............................
>What idea do you have with the steel?
*idea=the aim or purpose.
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>What function will the steel serve?
鋼の用途は何でしょうか？
*function=用途
*serve=任務を遂行する。
..............................
>What idea do you have with the steel?
その鋼で何をするおつもりですか？
*idea=目的、理由
..................***..............***...................***...........
What is the purpose of the steel you require? Exactly how will it be used?
They say everything has its purpose...and in this case it is essential to know what that purpose is! How will it be used?
Since supplying the wrong grade of steel "could prove disasterous" or "catastrophic"
"What is the purpose of the steel you require? Exactly how will it be used?"
すべてのものに理由（purpose）があるといわれます...ここではその理由が聞かなければなりません。何に使うのか（How will it be used?）。
鉄鋼の等級を間違えれば、大惨事になりかねません。
"What is the purpose of the steel you require? Exactly how will it be used?"
〔訳〕鉄鋼の使い道を教えてください。何にお使いになりますか？
"May I know what are you using the steel for?" in this sentence you are being polite in asking what the customer is using the steel for. This is the recommended way to speak to customers because sometimes if you ask them directly they might feel that you are being nosy.
"How will you be utilizing the steel?" this is a bit more direct approach right to the point. You can use this sentence when you have had a conversation with the customer and you can see that he/she is relaxed.
例文
"May I know what are you using the steel for?"
この鋼材を何に使うか伺ってもよろしいですか？
この文では顧客が何のために鋼材を使うのかを聞く際は丁寧に聞きます。このような表現で聞くことをお勧めします。というのも直接的な聞き方をすると詮索好きだと思われることがあるからです。
例文
"How will you be utilizing the steel?"
この鋼材をどのように使われますか？
こちらはどちらかというと単刀直入な聞き方です。この文を使うことが出来るのは、顧客と話しをしていて相手がリラックスしていると分かる時です。
"What is the steel being used for?", is a question that can asked when you would like to know the specific purpose or use of the steel the client is buying.
"What is the steel being used for?"は顧客が購入しようとしている鋼鉄の特定の目的や用途を聞きたい時に使える疑問文です。
For what are you using the steel?（その鋼鉄はあなたは何に使いますか？）
What is the steel being used for?（その鋼鉄は何に使われますか？）
For what purpose will you be using the steel?（どんな用途でその鋼鉄をあなたは使用しますか？）
We can ask the question using either the, "Why," form of the question or we can use the question indicator, "what." Keep in mind that when we use what, we must include the preposition, "for," at the end of the phrase to be grammatically correct.
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