How to choose mill rolls?
The performance and quality of the rolls generally depend on their chemical composition and manufacturing and can be assessed by their metallographic tissue, physical and mechanical properties, and residual stress type present in the mill roll.
The use effect of mill rolls in the mill is not only dependent on the material of the roll and its metallurgical quality, and it is also related to the conditions, roll design, and operation maintenance.
There is a big difference in the use conditions of rolls of different types of mills, resulting in differences:
- Rolling mill conditions. Such as rolling mills, rolling mills, and mill rolls design, hole design, water-cooled conditions, etc.
- Rolling conditions such as rolling products, specifications, and deformation resistance, depression systems, and temperature systems, yield requirements, and operations.
- Requirements for product quality and surface quality.
Common mill rolls material and use table
|Mill rolls category||Mill rolls body hardness(HS)||Mill rolls neck Strength (MPA)||Applications|
|Cast steel mill rolls||Cast steel|
Tool steel (high carbon
|Large, medium-sized steel, roughing mill housing, slate rolling mill Roughing Mill Housing, BUR.|
Big, medium, small steel middle, and finishing mill housing, slate steel WR.
Big, medium, and small steel roughing mill housing.
With steel coarse rolled horn, finished rolling front, cold-rolled strip work roller (WR).
Hot rolled steel finishing mill housing, small or wire Finishing mill housing.
|Cast iron mill rolls||Cold cast iron|
Unbounded (limited) cold and hard cast iron
High chromium cast iron
Special cast iron
|Plate, wire, profile, pipe Finishing mill housing.|
Plate, wire, profile, tube, rolled, finishing mill housing, slate steel finishing mill housing.
Profile, wire, pipe, medium rolling housing.
Small steel, wire rolling mill finishing mill housing, steel pre-finishing mill housing.
Small, wire, pipe pre-finishing mill, finishing mill.
|Powder metallurgy mill rolls||Tungsten carbide|
|–||Small, wire finishing mill housing, cold-rolled small steel.|
Small, wire finishing mill housing, strip steel finishing mill housing.
|Forged steel mill rolls||Hot roll|
Forging semi-steel and white mouth iron
|Blooming mill, large thick rolling rack, steel Roughing mill housing|
Cold rolled steel work roller, profile, welded pipe forming roller
Cold, hot plate strip rolling mill
Big, medium, small, medium, finishing mill housing
Note: The composite roller neck material is selected according to the strength requirements.
Therefore, different types of rolling mills and rolling mills are used in the same type, which requires no thunder, such as bullet and slab initial rolling rolls to have good twists and bend strength, toughness, bitterness, Anti-thermal cracking and thermal impact and wear resistance; and the tropical finishing rack requires high hardness, resistance, wear-resistant, anti-flakes and heat-resistant cracks such as roll surface.
To clarify the use conditions of the roll and the failure of the rolls used in the same type of rolling mill to understand the performance and manufacturing process of the current various rolls, in order to correctly formulate the technical conditions of the rolling mill and the selected suitable and economical roll material.
The most common method of evaluating the performance of the roll in the mill is:
- Rolling the rolling weight (kg) (referred to as the roll consumption) consumed by the 1t rolling material, expressed by kg/t;
- Reduce the weight of the rolled material per unit roll, expressed with t/mm.
With the modernization of the rolling mill, the in-depth study of the fading of the rolls and the improvement of roll materials and manufacturing processes, the average roll consumption of industrially developed countries has decreased below 1kg/t.
What are the performance requirements of the mill rolls?
- Anti-thermal crack: Typically, the coarse roll is mainly required, and the thermal crack is mainly required; the working roll of the small 20 rolling mills is only 100 grams, while the weight of the support roller of the wide plate roller has exceeded 200 tons. When the roll is used, the safety-loaded body material (various levels of cast iron, cast steel or forged steel, or the like) is selected according to the basic strength of the roll.
- Hardness: The finishing roller speed is high, and the final product of rolling should have a certain surface quality, which is mainly required to hardness, wear resistance, etc. The wear resistance should then be considered when the roll is used. Since the wear mechanism of the roll is complicated, including mechanical stress, the thermal action, cooling effect, the chemical effect of cooling effect, lubrication medium, and other effects, no comprehensive evaluation of the anti-wear resistance of the roll resistance. Since the hardness is easy to measure, and the wear resistance can be reflected under certain conditions, the wear-resistant indicator of the roll is generally expressed in the radial hardness curve.
- Impact Resistance: In addition, there are some special requirements for the roll, such as the amount of pressure, which requires a strong bit bite ability, more impact.
- Degree of finish: When the thin size product is rolled, the rigidity, tissue performance uniformity, processing accuracy, and surface finish of the roll are strictly required.
- Cutting performance: When rolling the complex section, the cutting performance of the roller working layer is considered.
When the roll is selected, some of the performance requirements of the roll often are opposite each other. The roll purchase fees and maintenance costs are very expensive, so we should fully weigh the techniques and economical pros and cons decided to cast or forged, alloys or non-alloys, Single material or composite.
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