X2Cr13 + QT conveyor roller of rolling mill

roller

X2Cr13 + QT conveyor roller of rolling mill:

Products type: X2Cr13 Conveyor roller of rolling mill.

Producing Date:2015-1.

Material: X2Cr13 + QT conveyor roller

Forgings, Martensitic stainless steel.

Country:Germany.

Client:SMSDEMAG.

The  conveyor roller of rolling mill producing process: Forged round  of martensite—- Tempered —- Rough machining—- Finishing —-Inspection— Packaging.

The material is a chrome-alloyed heat treatable steel with medium carbon content which is rust proof. It has a good corrosion resistance because of its chrome content in moderate aggressive, non chloric substances like soap, solvents and organic acid.

This material shows its highest corrosion resistance with fine grinded and polished surface. The machinability of the material is comparable with alloyed heat treatable steels and causes no significant difficulties.

The material can be hardened by holding the temperature between 950°C and 1050° C with a subsequent cooling in air, oil or polymer. The strength of the material depends on the tempering temperature.It is usually divided in two heat treatment conditions, QT700 and QT800. This material is used in mechanical engineering and power engineering.

X2Cr13 roller
X2Cr13 + QT conveyor roller of rolling mill

 

 

 

roller
X2Cr13 conveyor roller of rolling mill

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Hearth rolls structure optimization and cost control (3)

3. Optimization of the structure of hearth rolls:                                 Link above
(1). Diameter of outstretched shaft affect the mechanical properties of the hearth rolls. The results are given in Figure 3 below we can see, with the increase of the diameter, the value of the torsion deformation resultant vector decreases. From 0.664E-3 down Low to 0.512E-3, to improve the Stiffness of hearth rolls. But when diameter of elongate shaft increases from 40mm to 60mm, the maximum stress values did not change significantly, diameter of outstretched shaft d generally selected about 60mm when designing.
(2) Effect of thickness of ring plate to mechanical properties of hearth roll. The results are given in Figure 4 below shows. When changes in the thickness of the ring plate of hearth roll (t = 50mmt = 100mm), Impact strength and stiffness of the hearth rolls more obvious. When the thickness of the ring plate is reduced, the strength and rigidity of it is weakened. Thereby increasing the possibility of damage of the hearth rolls under billet weight motor drive and furnace temperature interaction.

The effect of elongate shaft diameter d on the static performance of the hearth rolls
The effect of elongate shaft diameter d on the static performance of the hearth rolls——-Fig

 

 

 

 

 

 

 

 

to be Continue……

 

 

 

Hearth roller structure optimization and cost control(2)

Link above

Hearth roller structure diagram  show Fig 1

2. Finite element analysis of a hearth roll
1). Establish finite element model of the size of the actual structure of the hearth roller. Using software ANSYS of finite element analysis to analysis. In the modeling process of hearth roller finite element, simplify some the original structure appropriately:

hearth roller
hearth roller structure diagram  Fig 1

(1). Ignored the effects of various friction.
(2). All position welding are considered ideal for welding.
According to the requirements of the calculation accuracy , the finite element model subdivided into a grid chart. The part of thin-walled made of the shell elements,part of collar plate are made of solid elements. Completion of the corresponding element real constants and materials parameters define the operating (Young’s modulus EX = 206, the thermal expansion coefficient of 0.45E-6, Poisson’s ratio of 0.28 and a density of 7800).
2). Determine the constraints condition.

In the analysis process, except angular displacement of the x-direction on surface of the hearth roller ends is free. Other linear displacement and angular displacement are restrictions. Symmetry constraints are imposed on symmetry boundary of finite element model, to ensure that the symmetry of deformation.
3). Solving and result processing, By analyzing the deformation and stress distribution of the hearth roll y-axis direction in the billet pressure, weight, torque, and the furnace temperature (1050 ℃) and other loads.
From the results shown in Figure 2
Hearth roller cone body weld stress maximum and lower weld strength here, this may explain the reason that weld fracture is the main failure mode in a way. Therefore, the need to optimize the design through construction to improve stress distribution, to minimize the stress at the weld cone body as possible.

ANSYS analysis of bottom rollers
ANSYS analysis of bottom rollers  Fig 2

 

 

 

 

 

 

to be Continue……

Hearth roller structure optimization and cost control(1)

INTRODUCTION

Hearth roller is a typical centrifugal casting pipe fittings, is one of the important components in support of metallurgical equipment and transport slabs, widely used in Continuous casting- rolling production line, in the rolling processfirst, the need to heat the steel slab to 1050 ~ 1150 rolling temperature in the furnace continuously and stablyStable support of the slab through the hearth roller, to ensure a smooth and uniform delivery. Since intermediate section of  the Hearth roller mounted on the billet calcining furnace directly , the furnace temperature is about 1150 during the process of productionHearth roller usually was manufactured with ZG45Cr28Ni48W5Si2 and other high-temperature alloys. Meanwhilesince the intermediate section of the hearth roller mounted in furnace directlyThe tapered section and the bearing support section are mounted inside the calcining furnace and outside the furnace respectively. The temperature gradient of hearth rolls is very large at different partsSo hearth roller  welded  together by  the sleeve and cone and shaft generallyIn order to reduce the burning of the inner surface of the cone, the inside of the cone have insulation board to ensure the smooth delivery of high-temperature slab.

Hearth roller
Hearth roller

Requirements hearth roller shaft not deformed, external roller ring heat-resistant, wear-resistant. Research shows that the hearth roller is use of large in the metallurgical industry, high manufacturing costs, long-term high temperature overload working conditionsprone to failure damage

Several major forms of roller hearth failure:

1 Weld fracture.

2 Shaft neck fracture.

3 Connect the fracture.

Which mainly reason include: welding performance of high temperature nickel-base alloy is poor, prone to weld cracking and other defects; welds to withstand pull – push alternating stress loads, prone to fatigue fracture; weld is cold-hot junctional zone, exists of large temperature gradient cause thermal stress, thermal stress will accelerate fracture Despite attempts to improve hearth roller on material and welding workmanship , but The life of a hearth roller has not achieved significant results. So by structural optimization to improve the performance of a hearth roller and increase their use life, may improve the quality of the product, an effective way to enhance the market competitiveness has important research value. Therefore, to improve the performance of  hearth roller and improve its life by structural optimization, it may improve the quality of the product, effective way to enhance the competitiveness of products.

to be continue

Sink roll bush structure improvements(3)

 Link above

c. Considering the material expansion coefficient of Sellite6 alloy and 00Cr17Ni14Mo2 is not the same, the proper clearance retained between part 2 and part 4. And to prevent zinc adhesion between part 2 and part 4 causes applied force to part 2 because sink roll bush returned to normal temperature after bush off lined, the graphite gaskets installed in the gap between part 2 and the part 4.

d. After rollers mounted the gap between the shaft end and the bush inner end is less than the gap between sink roll end and sink roll arm stopper. So in the actual use of the process it could easily lead to shaft end wear at first then the roller head was worn after. Therefore, the improvements will be Sellite6 alloy part (part 2) put to the bush in the middle in order to increase the gap between the inner roll arm and sink roll shaft end.

 

3. Conclusion

Through the four improvements of optimizing the bush structure we resolve the problem of the stall and crack in the production. It greatly extended its working life.

After Improved structure of the liner – Figure 4.
After Improved structure of the liner – Figure 4.

 

 

END

Sink roll bush structure improvements (2)

Link above

The cracks were found on Stellite6 alloy block part after the structure put into use a period. After analysis the cause of cracks is the welded structure of Stellite6 alloy block and sink roll bush body. In the production the line is under high temperature environment of greater than 600 ℃.The state returns to normal temperature after the offline. In this process of expansion and contraction, Since Stellite6 alloy material is different with bush body material 00Cr17Ni14Mo2, the thermal expansion coefficient is different, so that Stellite6 alloy subjected to tension and pressing force, thus cracks even breaks were found at weld position. See figure2.

 Fig2 sink roller bush after use

Figure 2 sink roller bush after use offline

 

 

From whole assembly drawings (Figure 3) The clearance between carbide block and sink roll sleeve end is 13 mm, while the spacing between sink roll head and stopper block is 15mm. That means actually the head did not play the effect of reducing friction area.

2. Improved sleeve

In order to avoid recurrence of the above two cases, the bush re- designed and the assembly form changed. See figure4 Improved bush structure

a. Due to the action in the course of the strip steel, the actual contact surface of the roll sleeve and the bush is in the upper part of the bush. Therefore, the Sellite6 alloy blocks changes to one unit which can still meet the requirements and also reduces the manufacturing cost.

b. As for Sellite6 alloy part (part 2) installation, two stoppers (part 3) welded at two sides and 2 semicircle with material 00Cr17Ni14Mo2 (part 4) welded at the lower half of the body to support. Not to weld Sellite6 alloy directly with 00Cr17Ni14Mo2 body which reduce the difficulty of construction and potentially dangerous.

 

Figure 3  original bush assembly drawing
Figure 3 original bush assembly drawing

Link below

Sink roll bush structure improvements (1)

The CGL unit annual output 250000 ton, produce width of 800 ~ 1 300 mm, thickness of 0. 3 5 ~ 2. 0 mm, product varieties are full of hard grade, commercial-grade, high-strength steel, mainly used for household appliances industry and the construction industry and other fields.

Sink roll is located just above the zinc pan , when unit continuous productstrip steel is imported into zinc pot , the strip steel is immersed in liquid zinc by the sink roll and changed direction, that is, from entering into the zinc pot, dip into zinc pot, galvanized layer solidification & cooling , and to be entering the air knife the strip steel remains stable and flat . With the movement of the strip steel rotatingsink roll bush supported by the bracket of both sides , the bush acts as a sliding bearing.

1. Bush problems in production

CGL unit sink roll and stabilizing roll off the line after use we found Stellite 6 alloy block had cracks on semicircle parts of the bush, even alloy block has been broken which affect the normal use of the bushing and resulting in stall phenomenon of stable roll and correction rollers. After analysis and research of the structure and working condition the structure of bush has been improved to avoid cracks.

  •  The original design structure using a semicircle and a 1 / 4 circle, two Stellite6 alloy blocks are welded with bush body, shown in Figure 1.
sink roll bush

 
Figure1  original design structure diagram
 
 
 Link…..
 

Hearth roll of continuous annealing furnace

Hearth roll is one of the most important part of continuous annealing furnace. Its working condition is the decisive factor if annealing furnace can be normal production.

Work and structural features of a hearth roll

Structures and materialhearth rolls of hearth roll

Working at over 800 in the furnace and rotation under load, meantime mechanical damage by charge , the hearth roll material must have high temperature strength and oxidation resistance. The structure shown that centrifugal casting roll is a hollow cylinder, two alloy roll end welded, then two end shaft welded in the roll end. The thin-walled rollers to give axial thermal resistance, insulation materials inserted from the roll barrel to roll end to reduce the temperature of the bearings.

Furnace hearth roll materials are ZG35Ni20Si or ZGCr25Ni35Nb, due to the high Ni alloy is expensive, domestic production of furnace hearth rollers using cheap ZG3Cr24Ni7SiNRe, this material has high temperature strength, endurance strength higher than ZGCr25Ni20Si2, after long-term use aging embrittlement tendency is small. Due to the addition of rare earth the oxidation resistance of the steel improved.

The hearth roll body
The hearth roll body

The diameter of the furnace hearth roll if possible use of smaller size at high temperature strength permitting to reduce the weight of the weight and save precious metal.

Spiral roller bearings or spherical bearings are used for furnace hearth roll. The bearing temperature is high so high-temperature grease lubrication is needed. The diameter of haft journal is usually smaller than the 0.1-0.25mm of bearing because of radial expansion.

 

Centrifugal casting stainless steel products

Radiant tube
Radiant tube

 

radiant tube installation
radiant tube installation

 

 

Radiant tubes:

U-type, W-Type, 0-Type, P-type, L-Type, S-Type, Straight-type and Electric radiant tubes

Application:

One of centrifugal casting stainless steel products. The radiant tubes are working at high temperature environment on average: 800-1200° C, most of them are used for indirect heating to furnace like CAL (continuous annealing line) CGL (continuous galvanizing line).

Process:

One of centrifugal casting stainless steel products. Centrifugal/spun casting method for tube sections, investment casting or sand casting for the bends, hangers, welding and machining

Material:

High Nickel and high Chrome heat resistant alloys, Cobalt base alloys, like HU, HT, HK, HP, HW, 24/24NbTiZr, 50Cr/50Ni (2.4813), 1.4865, 1.4849, 1.4848, 1.4410, 1.4059, 1.4841, 1.4845, 1.4852, 2.4879 or as per customer’s requirements

Standard:

ANSI, ASTM, ASME, DIN, GB etc.

20101119102810346


 

Stainless steel

roller —Immersion roller, Sink roll, Furnace roller, Bottom roller, Heat resistant roller:

1. Furnace roller

2. Hearth roll

3. immersion roller

4. Heat resistant roller

Application:
One of centrifugal casting stainless steel products. Centrifugal casting stainless steel roll are of good heat, corrosion, wear resistant properties, working at high temperature environment on average: 800 to 1, 200° C, which are used in the steel mills, like continuous annealing line, continuous galvanizing line.

Process of centrifugal casting stainless steel products of roll: Centrifugal casting for barrel/tube, forging for journal/shaft, static /investment or sand casting for cone/turnings, welding and machining and grinding.

Material of centrifugal casting stainless steel products of roll: High nickel and high chrome heat resistant alloys, cobalt base alloys, like HU, HT, HK, HP, HW, 24/24NbTiZr, 50Cr/50Ni (2.4813), 1.4865, 1.4849, 1.4848, 1.4410, 1.4059, 1.4841, 1.4845, 1.4852, 2.4879 or as per customer’s requirements.