1045 carbon steel is commonly used in the production of swords, including katana blades. It is a medium-carbon steel with approximately 0.45% carbon content, making it suitable for blades that require a balance between hardness and flexibility. Here are some factors to consider regarding 1045 carbon steel for katana blades:

1. Hardness and Edge Retention: 1045 carbon steel can achieve a good level of hardness through proper heat treatment. This allows the blade to hold a sharp edge and maintain it during cutting tasks.
2. Toughness and Flexibility: Katana blades need to have a certain level of flexibility to withstand impacts and avoid breaking. 1045 carbon steel provides a reasonable balance of hardness and toughness, offering the necessary resilience and bending capabilities.
3. Affordability: 1045 carbon steel is relatively affordable compared to higher-grade steels and traditional materials like Tamahagane. This makes it a popular choice for entry-level or mid-range katana blades.
4. Prone to Rust: 1045 carbon steel is not stainless and is susceptible to corrosion if not properly cared for. Regular maintenance and proper storage are necessary to prevent rusting and maintain the blade's condition.

It's important to note that the overall quality and performance of a katana blade go beyond the type of steel used. Factors such as the blade's heat treatment, forging techniques, craftsmanship, and the expertise of the swordsmith greatly influence its final characteristics. A well-made and properly heat-treated 1045 carbon steel katana blade can offer satisfactory performance for practitioners and enthusiasts, particularly at an affordable price point.

If you're considering purchasing a katana, it's advisable to consult with reputable swordsmiths, collectors, or experts who can provide specific information about the blade's construction, heat treatment, and quality to ensure you make an informed decision.