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What are the primary tasks of steelmaking, and by what means are they accomplished?

A: The fundamental tasks of steelmaking include decarburization, dephosphorization, desulfurization, deoxidation, removal of harmful gases and non-metallic inclusions, temperature elevation, and adjustment of molten steel composition. These tasks are achieved through oxygen supply, slag formation, stirring, and alloying.

How do I track the project progress in real time? What emergency measures will be taken in case of construction delays?

A: There are the following real-time progress tracking method:
1. Digital tools
Use Gantt charts or project management software (such as Jira) to visualize task status and update progress deviations in real time.
• Combine BIM and iot devices to monitor construction data, such as equipment installation efficiency, and automatically generate progress reports.
2. Control of key nodes
• Set milestones (such as arrival of equipment, acceptance of civil construction), regularly check the actual completion, and trigger the pre-warning mechanism.
3. Dynamic communication mechanism
• Make progress synchronously through daily meetings and weekly reports, and use corporate wechat and other tools to keep team and customer information transparent.

What preparations should be made before steel rolling?

A: For the production of each product, preparations should be made from the beginning of the roll change. In order to ensure the normal rolling production, the roll position, main and auxiliary parts of the mill and related equipment must be inspected before rolling. The structure of the rolling mill is different, and the items that need to be checked are different. Generally, the matters that must be checked are:
1) Roll, consider the roll position after the roll jump;
2) Rolling mill parts, Check various rolling mill parts according to technical regulations;
3) Mill accessories, check mill accessories according to technical specifications and practical experience;
4) Auxiliary equipment, Ensure that the auxiliary equipment is properly correct.

What are the connecting devices of the rolling mill?

A: The connecting shaft is a device that transfers power from the gear base to the roll, or from the roll of one mill to the roll of another mill, or directly from the main motor to the roll. The common connecting shafts are universal shaft and plum-flower shaft.
All roll diameters have a range of variations. From the loading of the new roll to the scrap of the roll, the axis position of the roll changes up and down, while the axis of the herringbone gear in the gear holder is unchanged. The cardan shaft allows the roll axis to have a large inclination Angle to the axis of the herringbone gear, which can drive the torsional moment smoothly. The allowed inclination Angle of the plum-flower coupling is only 1-2 degrees, which is only suitable for rolling mills with little change in the distance between the central lines of the working rolls. It is easy to disassemble and change rolls.
The plum-flower coupling and the plum-flower sleeve should be adapted to the size of the roll neck, so as to disassemble the roll, bear greater impact load and extend the service life. The shaft sleeve is generally made of cast iron, and is made of cast steel under great stress. Roll diameter greater than 500mm of the profile mill has larger shaft and sleeve weight, in order to make the weight of plum-flower shaft and the cardan shaft not act on the hinge of the plum-flower sleeve or cardan shaft, usually in the middle of the shaft is equipped with a coupling bracket, in order to balance the weight of the shaft, so that the shaft rotates smoothly.
Due to the advantages and disadvantages of the plum-flower shaft and the cardan shaft, a joint shaft has recently appeared, that is, the cardan shaft is connected at one end of the shaft and the gear holder, and the other end of the shaft and the roll is connected by the plum-flower shaft. In addition, there are curved gear shaft.

What are the common frame types?

A: Open, closed and semi-closed.
The open frame is composed of a frame base and an upper beam. It has the advantages of simple manufacturing, convenient loading and unloading and roller changing. Its disadvantage is that the strength and stiffness are low, and the roll gap play is large.
Due to the variety and specifications of the section steel, the section mill, especially the small and medium-sized mill, most select the open mill.
The closed frame is made of integral casting part, and its advantages are that the strength and stiffness are larger. If the rolling pressure is larger or the size requirements of the rolling piece are stricter, closed frames are adopted such as the blooming mill, the plate mill, the cold mill, etc.
The semi-closed frame and the frame cover are connected diagonally. It has the advantages of both open type and closed type, convenient loading and unloading, roller change, easy manufacturing, and greater rigidity. Generally, large and medium-sized steel mills use this form of frame.
In addition to the above types, there are also housingless rolling mill, which has the advantages of light weight, good rigidity, high rolling precision, convenient adjustment operation and so on.

What is a short stress path mill? What is a housingless rolling mill?

A: The profit return line of the internal force caused by the rolling force distributed along the bearing parts of the frame in the rolling process of the rolling mill is referred to as the stress path. In order to improve the rigidity of the rolling mill, the rolling mill which adopts various technical measures to shorten the stress path is called short stress path rolling mill. Short stress path mill is a kind of high stiffness mill.
The short stress path rolling mill cancels the frame of the load parts with large length in the ordinary rolling mill, and two tension bolts on each side of the roll fix the two bearing seats with great rigidity, which greatly shortens the stress return path length of the rolling mill and makes the rolling mill have greater rigidity.

What is rolling time, clearance time, cycle time and rolling rhythm?

A: The working chart of the rolling mill represents and reflects the relationship between rolling passes and time. The rolling time, clearance time, rolling rhythm and rolling period indicated in the rolling chart are called the characteristic time of the rolling chart. The form of the rolling chart is different, that is, the four characteristic time changes that reflect the rolling process are different.

The rolling time, that is, the pure rolling time of the steel, can be measured in practice or calculated by the formula: Trolling =L/v

Formula: L- length of rolled piece after rolling, unit: m;

v- Rolling speed, m.

Clearance time refers to the time interval between adjacent passes, which varies with the specific situation of rolling.

Rolling cycle refers to the total time used to roll one piece of steel (including each pass rolling time and gap time) and the gap time between two adjacent pieces of steel.

Rolling rhythm refers to the time required for each piece of steel rolled by the mill unit (that is, the time interval between rolling the first piece of steel and the second piece of steel), which is the main factor determining the output of the mill.

What are the specific stages of a turnkey project from design to delivery? How to plan the time cycle of each stage?

A: The core stage of a turnkey project in the iron & steel industry from design to delivery can be summarized into six key links:

1.Feasibility study and preliminary design (account for 15%-20% of the cycle), focusing on the completion of process demonstration, environmental assessment and site selection, which should combine the green standards such as carbon emission to optimize the scheme;

2.Detailed design and technical procurement, reduce design conflicts through 3D modeling;

3.Equipment procurement and supply chain integration, adopting on-site supervision, modular logistics strategy to reduce the risk of delays;

4.Construction and equipment installation (account for the largest proportion, which is 40%-50%), using modular construction and digital tools (such as BIM) to improve efficiency;

5.System debugging and performance assessment, through the single unit test run, heat load test and other cross-verification to ensure the process standards;

6.Handover and training, complete document archiving, operation training and environmental acceptance.

Time planning should follow the principle of dynamic adjustment, reduce the total construction period by 10%-20% through parallel engineering (such as overlapping design and procurement), and reserve 10%-15% buffer period to cope with supply chain or technical risks.

What are the guide and guard devices of the rolling mill?

A: The guide device is an indispensable part of the section steel mill. In order to make the rolled piece enter and exit the pass accurately according to the specified position, direction and required state, avoid the rolling piece entanglement, the rolling piece is scraped and squeezed, and ensure the safety of workers and equipment, the guide device should be installed in front of and behind the roll. The guide and guard device includes a guide plate, a guide box, a fixed beam, a guide pipe, a torsion guide plate, a torsion roller and a positive and negative repeater.

The guide plate is used to guide the rolled parts in and out of the pass correctly, so that the rolled parts will not skew and distort in the horizontal direction. The guide plate at the loading entrance is called the entrance guide plate, and the one installed at the exit is called the exit guide plate. Sometimes the guide is loaded in the guide box.

The guard plate is installed on the exit side to prevent roller wrap accidents. The lower guard plate is mounted on the guide plate cross beam. The upper guard plate is difficult to fix, and it does not work as reliably as the lower guard plate, and its top may leave the roll due to frame vibration, or it may cause an accident because the rolled piece hits the tip of the guard plate. It is an effective measure to avoid this kind of trouble to use the upper pressure in the pass design.

The three-high rolling mill needs lifting platform or tilting guide plate and various special tilting machine, transfer machine, twist repeater, straight repeater, vertical repeater and other devices.

The function of the twist repeater is to guide the flat oval, diamond, and rectangular rolled pieces to the next frame, and turn the 90 degree Angle so that the rolled pieces are upright into the square hole or the vertical rolled hole. Rolled pieces in the groove of the repeater cannot naturally complete the above-mentioned turning action, and must be assisted by twist conduit.
The role of the straight repeater is to guide the upright square from one mill to the other mill, and to turn the rolled piece naturally at a 45 degree Angle into the oval pass.

The function of the vertical repeater is to guide the rolled parts of the upper rolling line to the lower rolling line on the same frame, and to twist the rolled parts at a 45 degree Angle.

What quality tests (e.g. tensile strength/chemical composition analysis) are carried out before the steel product leaves the factory? What certification documents are provided?

A: Core quality testing items

Chemical composition analysis:

Test the content of carbon (C), manganese (Mn), sulfur (S), phosphorus (P) and other elements in steel to ensure compliance with international standards (such as ASTM, GB).

Use spectral analyzer or chemical titration method to accurately control the alloy ratio.

Mechanical properties test:

Tensile strength and yield strength: The limit value of the tensile force of the material is tested by the universal testing machine.

Impact test (Charpy V notch test) : Assessing the toughness of steel at low temperatures.

Hardness test: Brinell hardness (HB) or Rockwell hardness (HRC) test, reflecting the wear resistance of the material.

Size and appearance check:

Use calipers, laser rangefinders and other tools to verify that the thickness, diameter, length and other tolerances meet the requirements.

Surface defect detection (e.g. cracks, scarring, oxide) is done by visual or magnetic particle inspection (MT).

Non-destructive testing:

Ultrasonic inspection (UT) : detection of internal porosity, slag inclusion and other defects.

Eddy current testing: suitable for surface and near-surface defect screening.

Process performance test:

Bending test: Verify whether the steel is cracked after bending 180°.

Flaring test (for pipe) : Test the deformation ability of the end after flaring.

What aspects should be considered when evaluating the quality of iron ore?

A: The evaluation of iron ore quality should focus on the following aspects:

Iron content: The most critical criterion for assessing iron ore quality.
Gangue composition: The chemical composition of non-metallic impurities in the ore.
Harmful impurities: Concentrations of detrimental elements such as S, P, Pb, Zn, As, Cu, K, Na, and F.
Reducibility: The ore’s ability to release oxygen during reduction processes.
Softening characteristics: Its behavior under high-temperature conditions.
Particle size distribution: The granularity and uniformity of the ore.
Mechanical strength: Resistance to degradation during handling and processing.
Compositional stability: Consistency of chemical composition across batches.

Why is deoxidation necessary for molten steel?

A: If the molten steel is not deoxidized, the continuous casting billet can not get the correct solidification structure. The high oxygen content in steel will also produce defects such as subsurface blowholes and porosity, and aggravate the harmful effect of sulfur. The generated oxide inclusions remain in the steel, which will reduce the mechanical properties of the steel such as ductility and impact toughness, so the excess oxygen in the steel must be removed.

Why is argon gas preferred over nitrogen for gas stirring in steelmaking?

A: The choice of argon over nitrogen for gas stirring is driven by the following technical considerations:
Chemical Inertness of Argon:
Argon is an ideal inert gas that neither dissolves in molten steel nor reacts with any elements, ensuring zero contamination during stirring.
Drawbacks of Nitrogen:
Nitrogen Dissolution: At high temperatures (>1575℃), nitrogen dissolves into molten steel, increasing nitrogen content by ~0.003% per unit time. This compromises steel quality (e.g., embrittlement).
Limited Applicability: Nitrogen is restricted to specific nitrogen-alloyed steel grades (e.g., austenitic stainless steels), but even here, nitrogen pickup remains inconsistent and hard to control.
Cost vs. Performance Trade-off:
While nitrogen is cheaper, argon’s stability and predictability outweigh cost savings in most steelmaking processes.

Why is slag formation essential in steelmaking?

A: Slag formation is fundamental to steelmaking because slag governs nearly all critical processes. The primary objectives are:
1. Removal of harmful elements:
◦ Eliminate phosphorus (P) and sulfur (S) through oxidation and slag-metal reactions.
2. Molten Slag Protective Functions:
◦ Surface Coverage: Shields molten steel from:
■ Excessive oxidation
■ Absorption of harmful gases (e.g., H₂, N₂)
■ Heat loss (thermal insulation)
■ Loss of beneficial elements (e.g., Mn, Si via oxidation).
◦ Inclusion Absorption: Captures floating non-metallic inclusions (e.g., Al2O3, SiO2) and reaction byproducts.
3. Process Optimization:
◦ Facilitates the carbon-oxygen reaction (decarburization) by controlling oxygen activity.
◦ Reduces refractory lining erosion (slag acts as a protective barrier between molten steel and furnace walls).

What are the quality requirements for coke in blast furnace ironmaking?

A: Coke quality in blast furnace operations must meet the following critical criteria:
1. High Fixed Carbon & Low Ash Content:
◦ Ensures efficient heat generation and reduces slag volume.
2. Minimal Harmful Impurities:
◦ Low levels of sulfur (S) and phosphorus (P) to prevent steel embrittlement.
3. Superior Strength Properties:
◦ Mechanical Strength: Resists crushing during charging and descent in the furnace.
◦ High-Temperature Strength (Thermal Stability): Maintains structural integrity under extreme heat (≥1500℃).
4. Uniform Particle Size Distribution:
◦ Optimal granularity (typically 40-80 mm) with minimal fines (<5%) to ensure gas permeability.
5. Controlled Moisture Content:
◦ Stable moisture levels (≤5%) to avoid erratic furnace temperature and energy waste.

What are the causes of refractory lining failure in furnaces?

A: Refractory lining degradation in furnaces arises from the following mechanisms:

1. Mechanical Impact and Abrasion:

◦ Scrap steel and molten iron striking the lining during charging.

◦ Continuous abrasive wear from raw material movement.

2. Dynamic Erosion:

◦ Agitation by molten steel and slag, causing surface erosion.

◦ Gas scouring (e.g., CO, O₂) accelerating material loss.

3. Chemical Corrosion:

◦ Slag (rich in CaO, SiO₂, Al₂O₃) reacting with lining materials (e.g., MgO-C bricks), forming low-melting compounds.

4. Thermal Stress and Spalling:

◦ Thermal shock from rapid temperature fluctuations (e.g., tapping → relining).

◦ Microstructural degradation (e.g., crack propagation due to phase changes).

5. Initial Operational Damage:

◦ Mechanical spalling during the preheating phase due to uneven expansion.

6. Internal Oxidation:

◦ Carbon oxidation in carbon-containing linings (e.g., MgO-C bricks), weakening structural integrity.

Is installment payment supported?

A: Turnkey projects in the iron & steel industry usually support installment payments, specific arrangements need to be combined with the contract terms and project milestones:

Advance payment (10%-20%) : After the contract is signed, payment is made and this part is used to start the feasibility study, preliminary design and initial purchasing.

Progress payments (40%-50%) : Payments are made at key points, such as design confirmation (15%), equipment delivery (20%), and half construction (15%).

Acceptance payment (20%-30%) : payment is made after the project is handed over, subject to performance assessment and environmental acceptance.

Quality guarantee (5%-10%) : to be paid within 1-2 years after the performance of the contract to cover potential quality risks.

What are the precautions for test rolling?

A:1) According to the main motor start-up operation management system and rolling mill operation technical operation rules, notify all relevant posts to achieve safe starting and safe operation.

2) Give cooling water before operation, after a period of idle operation, check whether the rolling mill is running normally, check whether the temperature rise of various bearings is normal, and see whether there is abnormal overheating and deformation.

3) Prepare test rolling materials in advance, slow steel production, and do not roll rolled parts below the specified temperature, so as not to cause the main motor trip or safety device damage.

4) During the test rolling process, the size of each red billet should be measured, and the adjustment icon should be used to check whether the size is correct and the surface quality is good. After the test rolling is qualified, normal production can be carried out.