Identify your needsDetermine the mill rolls type
According to different rolling processes, rollers can be divided into hot rollers and cold rollers.
Hot rollers are mainly used to heat metal billets for rolling. The working environment temperature is high and they need to have good heat resistance and wear resistance. For example, in the production of hot-rolled steel plates, rollers have to withstand repeated rolling of high-temperature steel billets.
Cold rollers are used to roll metal at room temperature. They have higher requirements for the surface accuracy and hardness of the rollers and are often used to produce high-precision cold-rolled thin plates.
According to the shape of the roll, there are flat rolls, grooved rolls and special-shaped rolls.
Flat rolls are used to roll flat materials, and grooved rolls can be used to roll profiles, such as channel steel, angle steel, etc.
Special-shaped rolls are customized according to the shape requirements of specific products. For example, the rolls of the piercing machine for producing seamless steel pipes have special internal structures.
Specifications
In terms of size, the diameter, length and width of the roll body must be determined. The diameter affects the distribution of rolling force, while the length and width are determined according to the size of the rolled material and production efficiency.
For example, the roll length of a large steel section mill is longer to accommodate the rolling of longer steel sections; while the diameter of a small precision cold rolling roll may be smaller, but the dimensional accuracy requirements are extremely high.
The hardness of the roll is also an important specification parameter. Different hardnesses result in different wear and compression resistance of the roll. It is usually measured by Rockwell hardness (HRC) or Brinell hardness (HB). For example, the hardness of cold rolling work rolls is usually higher, HRC can reach 60 – 90, to ensure that the material can be accurately rolled and maintain good surface quality during the cold rolling process.
Quality requirements
Surface quality requirements include roughness, roundness, and straightness.
Roughness affects the surface finish of the rolled material. For rollers for cold-rolled high-precision thin plates, the surface roughness may be required to be between Ra0.2 and 0.8μm.
Excessive deviations in roundness and straightness will lead to uneven thickness of the rolled material. For example, the roundness error of high-precision rollers may be required to be controlled within ±0.005mm.
In terms of internal quality, the rolls should avoid internal defects such as pores, slag inclusions, etc. These defects may cause the rolls to break during the rolling process, affecting production safety and product quality. Internal quality can be detected by non-destructive testing techniques such as ultrasonic testing.
Investigating the roll manufacturing process
Processing accuracy: The processing accuracy of the roller is directly related to the quality of the rolled product. Including the diameter tolerance, cylindricity, surface roughness and other indicators of the roller must strictly meet the requirements.
Only high-precision rollers can roll steel products with precise dimensions and good surface quality. For example, a roller with surface roughness that does not meet the standards may cause scratches, pitting and other defects on the surface of the rolled steel.
Heat treatment process: Appropriate heat treatment process can significantly improve the performance of the roll. Heat treatment processes such as quenching and tempering can change the internal structure of the roll and improve its hardness, toughness and wear resistance.
It is necessary to understand whether the heat treatment process used by the roll manufacturer is scientific and standardized, and whether it can ensure that the roll reaches the expected performance indicators.
Find a supplier
Supplier Research
Roller suppliers can be found through Internet searches, industry exhibitions, peer recommendations, etc. During the research process, learn about the supplier’s company size, production capacity, technical level, etc. For example, some large roll manufacturers such as HANI have advanced casting or forging equipment and are able to produce high-quality, large-sized rolls; while small suppliers may focus on the production of specific types or specifications of rolls and have a certain degree of professionalism.
Supplier Screening
Based on the survey results, select a list of suppliers that meet your needs. You can consider the geographical location of the supplier. Suppliers that are closer may have more advantages in terms of transportation costs and delivery time. For example, for urgent orders, local suppliers can respond and deliver faster. At the same time, compare the prices and payment methods of different suppliers to ensure that the procurement cost is within the budget.
Procurement Process
Request a Quote
Send a quotation to the selected suppliers, which should include detailed information such as roll specifications, quality requirements, quantity, delivery date, etc. The supplier will quote according to the content of the quotation, which generally includes the unit price of the roll, the total price, transportation costs, packaging costs, etc. For example, for a batch of cold-rolled rolls with specific specifications, HANI may reply with a quotation within a week, and the quotation will list in detail the price of each roll, the cost of wooden box packaging, and the transportation cost of delivery to the designated location, etc.
Sample testing (if necessary)
For some key roll procurement, especially when the quality and performance requirements are extremely high, the supplier can be asked to provide samples. The samples are tested, including rolling test, hardness test, surface quality test, etc. For example, when purchasing high-precision cold rolling work rolls, the samples are installed on the test rolling mill for cold rolling thin plate test, and the surface quality, thickness accuracy and other indicators of the thin plate after rolling are observed. At the same time, the surface wear and hardness change of the roll after the test are detected.
Signing a contract
After the supplier and price are determined, a purchase contract is signed. The contract should clearly define the rights and obligations of both parties, including the specifications, quality standards, quantity, delivery date, payment method, liability for breach of contract, etc. For example, the contract stipulates that if the actual hardness of the roll is lower than the contractually agreed value, the supplier shall bear the corresponding quality responsibility, such as return or compensation for losses; at the same time, the purchaser shall pay in a timely manner according to the agreed payment method, such as advance payment, payment after acceptance of the goods upon arrival, etc.
Delivery and Acceptance
The supplier delivers the goods according to the delivery date agreed in the contract, and the purchaser inspects and accepts the rolls after receiving them.
The inspection includes checking whether the specifications and quantity of the rolls are consistent with the contract, and checking whether the surface quality and packaging are intact.
Then the inspection is carried out according to the quality standards, such as hardness test and dimensional accuracy test. For example, a hardness tester is used to check whether the hardness of the roll meets the contract requirements, and a measuring tool is used to measure whether the diameter, length and other dimensions of the roll have deviations. If the inspection is qualified, the purchaser accepts the rolls; if problems are found, they are handled according to the contract agreement, such as requiring the supplier to replenish, replace or rectify.
