They are different grades or designations for classifying different types of steel. See below a brief explanation of each: 1. C235: Not a widely recognized steel grade designation,difficult to determine the specific properties or characteristics ,Without further context. It's possible that it may be a regional or company-specific designation. 2. C245: Similar to C235, "C245" is not a commonly known steel grade. It may have specific meaning within a particular industry or standard, but without additional information, it is challenging to provide a definitive explanation. 3. C195: Similar to C235 and C245, "C195" is not a standard or widely recognized steel grade. It may have specific meaning within a particular industry or context, but without further information, it is difficult to provide a specific explanation. 4. 45#: "45#" refers to a Chinese steel grade, specifically GB 45# steel. It is a medium carbon steel with a carbon content of approximately 0.45%. 45# steel is known for its good strength, toughness, and wear resistance. It is widely used in machinery parts, shafts, gears, bolts, and other applications that require medium strength and hardness. 5. Q235: Q235 is a Chinese steel grade that is widely used in various industries. It is equivalent to ASTM A36 steel in the United States and S235JR steel in Europe. It is a low carbon steel with a carbon content of approximately 0.2%. It has good weldability, machinability, and strength. Q235 is commonly used for general structural purposes, such as buildings, bridges, and machinery. In summary, it's important to note that the meaning and properties associated with steel grades can vary depending on the specific standard or country of origin. Different parts request different nature steel, to fully comply with the relevant technical standard. Right material is the base to producing the suitable products, of course the production cost is also different. Being customer, we are pay attention to the production materials all the time, not only the price of them.