Development of Cold Rolled Steel Strip for Kunming Steel Yellow Phosphorus Packaging Bucket

Development of Cold Rolled Steel Strip for Kunming Steel Yellow Phosphorus Packaging Bucket

Zhang Yu 1, Song Shaozhong 2
(1.Technology Center of Kunming Iron and Steel Co., Ltd., WISCO Group, Kunming , China
2. Kunming Tenghe Electromechanical Engineering Co., Ltd., Kunming, Yunnan , China)

1 Introduction

Yellow phosphorus is an important basic industrial raw material with a melting point of 44.1 ° C. It can spontaneously ignite in air at room temperature. Yellow phosphorus is a flammable dangerous product, and its transportation must be transported in a container in a closed package. Yunnan is one of the major producing areas of yellow phosphorus. The yellow phosphorus produced is not only sold throughout the country, but also exported to many countries and regions. The annual demand for cold-rolled strips used in Yunnan for the production of yellow-phosphorous drums is about 50,000 tons. .

Kunming Iron and Steel Group Co., Ltd. is the only enterprise in Yunnan Province that has the equipment and capacity for producing special cold-rolled steel strips for yellow phosphorus packaging drums. Kunming Steel began research and development of special cold-rolled steel strips for yellow phosphorus packaging barrels in 2002, 2003. In the year, the production process of special cold-rolled steel strip for yellow phosphorus packaging drum was formed. After that, the production process was continuously optimized and improved, and the batch production capacity was formed. The product quality was excellent and the performance fully satisfied the yellow phosphorus packaging requirements. In 2008, the project of “Hot-Powder Packing Barrels for Yellow Phosphorus Packaging Barrels” was included in the Yunnan Local Standard System Project. The standards were drafted by Kunming Iron and Steel Group Co., Ltd. and Kunming Tenghe Electromechanical Engineering Co., Ltd., and the standard was completed. After the approval work, the standard approval work was completed on April 1, 2009, and Yunnan Province was promulgated on August 1, 2009. DB53/T286-2009 "Special Cold Rolled Steel Strip for Yellow Phosphorus Packaging Bucket" is a close-to-market of Kunming Steel and Kunming Tenghe Company. It has jointly developed the results of independent intellectual property rights, the promulgation and implementation of standards, and the specification of steel for yellow phosphorus packaging barrels. Ensuring the safety of storage and transportation of yellow phosphorus is of great significance, reflecting the responsibility of state-owned large and medium-sized enterprises to the society, and marking the significant progress made by Kunming Steel's yellow phosphorus packaging barrel steel from the product strategy to the standard strategy.

2. Analysis of yellow phosphorus barrel production and quality characteristics requirements

Yellow phosphorus is an important basic industrial raw material with a melting point of 44.1 ° C. It can spontaneously ignite in air at room temperature. Yellow phosphorus is a flammable, explosive and highly toxic dangerous product. The process of yellow phosphorus production and packaging is carried out under the conditions of water sealing and air isolation. In the long-distance transportation and storage process, safety accidents and environmental pollution may not occur due to the leakage of the quality of the packaging barrel. The yellow phosphorus packaging barrel material must have good deformation performance, surface quality and strength suitable to meet the requirements of the production of yellow phosphorus packaging drum.

2.1 Introduction to the processing technology of yellow phosphorus packaging drum
The manufacturing and processing of yellow phosphorus packaging drums consists of barrel processing, barrel bottom processing, barrel top processing and assembly processes. The assembly process refers to the process of assembling the barrel body with the bottom of the bucket and the top of the bucket by using a seven-layer triple round seam, filling the sealant with the sealant, and processing into a finished bucket. The processing technology is as follows:

(1) Processing process of the barrel:

Cutting → three rolls rolled into a barrel shape → spot welding of the joints → barrel body bonding welding → weld grinding → flange forming → barrel body reinforcement → barrel weld quality inspection → pickling → cleaning → Electroplated zinc → passivation → natural drying

(2) Processing process of the bottom of the barrel (barrel):

Cutting → stamping → flanging forming → (punching injection port and venting port → injection port and vent thread processing →) pickling → cleaning → electro-galvanizing → passivation → natural drying

(3) Assembly and inspection of the barrel:

Seven-layer triple round crimping assembly for barrel body and bucket lid and barrel bottom → Air tightness test → Hydraulic test → Drop test → Bucket spray marking → Acceptance

It can be seen from the manufacturing process that the processing process of welding, flanging, ribbing and punching is included in the production process of yellow phosphorus packaging drum, and it must pass the air tightness test, hydraulic pressure test and drop test after processing into barrels. And the stacking test is carried out using the conditional simulation. After passing the test, it can be shipped as a qualified yellow phosphorus packaging drum. The entire processing and inspection process has certain requirements on the welding performance, strength, stamping deformation performance and surface quality of the material.

3. Material handling requirements of packaging barrel processing and quality characteristics of Kunming Steel products

(1) Standard related requirements

The state has strict requirements on the processing size of yellow phosphorus packaging barrels and the inspection methods of finished barrels. However, there is no specific requirement for the performance of the raw material for the manufacture of yellow phosphorus packaging drums - cold rolled sheet, see Table 2.

Table 2

GB16473-1996 "Yellow Phosphorus Packaging"

HG2035-1991
"Technical Conditions for Yellow Phosphorus Packaging Steel Barrels"

Description

Steel plate thickness

≥1.2mm

1.2mm~1.5mm

material

When the thickness of the barrel body, the top of the barrel and the bottom of the barrel is greater than the thickness, the performance is in accordance with or better than the hot-rolled steel sheet specified in GB/T912; when the thickness is not greater than, the cold-rolled steel sheet with the performance conforming to or better than GB/T11253 is used.

The material of the steel drum should be made of materials with the performance and quality not lower than Q215 as specified in GB/T912, GB/T11253, GB/T2518 and GB/T3276.

A certain strength and plasticity are required. Steel plates must have product standards and quality certificates.

Bucket assembly

A seven-layer triple round bead is used. The barrel body, the top of the bucket and the bottom of the bucket are made of the entire thin steel plate, and the splicing is not allowed.

A triple rounded edge is used. The barrel body, the top of the bucket and the bottom of the bucket are made of the entire thin steel plate, and the splicing is not allowed.

Good plasticity and certain deformation properties are required.

Appearance requirements

The barrel is round and smooth, with no obvious rounding, unevenness, and skew; no burrs and mechanical damage. The outside of the barrel is smooth and smooth, and the structure is fine.

The steel drum should be smooth and round, with no obvious rounding, skew, burrs and mechanical damage. The barrel is completely plated and densely organized.

The steel plate is required to have a good shape and a high surface quality, and no scratches are allowed.

test

Air tightness test, hydraulic test, stacking test and drop test.

Air tightness test, hydrostatic test, stacking test and drop test

Required test pass rate of 100%

(2) Welding performance requirements:
For steel materials, the lower the carbon equivalent, the better the weldability. It is generally believed that the soldering performance can be guaranteed after the carbon equivalent is less than 0.32%. The International Welding Association uses carbon equivalents to calculate and evaluate the weldability of steel. The approximate formula is as follows:

Ceq = C+Mn/6+(Ni+Cu)/15+(Cr+Mo+V)/5
Where: the element symbol represents the weight percentage of the element.
The cold-rolled steel strip for Kunming Steel's yellow phosphorus packaging drum is made of low-carbon, low-silicon and low-manganese cold-rolled sheet. The composition requirements are shown in Table 3. The carbon equivalent is less than 0.20%, and the welding performance can be guaranteed.

table 3

Deoxidation mode

chemical composition

C

Si

Mn

S

P

St12P

Aluminum calm

≤0.12

≤0.07

≤0.50

≤0.030

≤0.030

(3) Stamping formability requirements:

The forming process of the yellow phosphorus packaging barrel is composed of the rib, the flanging, the punching and the curling, and the forming process involves the forming processes such as stamping, drawing and bending. The material is required to have good stamping deformation properties, and deformation and cracking cannot occur during the production process.

In Europe, according to the deep-rolling performance of cold rolling, the deep-drawing performance is generally divided into commercial grade CQ, stamping grade DQ, deep draw grade DDQ and ultra deep draw grade EDDQ. Generally, the deep drawing performance indexes of cold rolled sheets are specified as follows:

・CQ r = 1; ・DQ r = 1.1~1.3;

・DDQ r = 1.5~2.0; ・EDDQ r >2.0;

At present, domestic yellow phosphorus packaging barrels are made of cold-rolled sheets. The main grades are Q195, St12, SPCC, DC01, etc. The performance requirements are shown in Table 4.

Table 4 Mechanical properties

Yield strength ReL (MPa)

Tensile strength Rm (MPa)

Elongation A80mm (Bo=20mm) %

n value

r value

DC01

≤280

270-410

≥28

―

―

St12

≤280

270-410

≥28

≥0.2

1.2 to 1.4

SPCC

≤280

≥270

≥28

≥0.2

1.2 to 1.4

Q195

≥195

315-430

≥24

St12P real thing

≤280

270-380

≥32

≥0.2

1.4 to 1.6

2.3 Surface quality

(1) Surface inclusions:

Refers to the slag inclusion on the surface of the steel and the residual iron oxide scale on the surface. After packaging yellow phosphorus, it is easy to cause holes in the steel barrel under transportation and corrosion conditions, resulting in fire. The airtightness test and hydraulic pressure test of the yellow phosphorus packaging drum are not easy to check the slag inclusions and the surface residual iron oxide scale. The drop test can be found that the surface of the packaging drum has slag inclusions and the surface residual iron oxide scale cannot be repaired, and can only be scrapped.

(2) Scratch:

Scratches are produced during the rolling process, leveling, rewinding, slitting, and user cutting and barreling processes. Light scratches affect the appearance of the barrel, but they do not affect the use. Severe scratching not only affects the appearance of the surface, but also directly affects the strength of the yellow phosphorus packaging barrel, affecting the air tightness test, hydraulic pressure test and drop test results of the yellow phosphorus packaging drum.

(3) Surface residue:

Mainly refers to residual oil (oiling) and other substances adsorbed on the surface of the steel plate, too much is likely to cause virtual welding, affecting the welding quality of the barrel.

3.4 Dimensional requirements

The production of packaging drums uses special equipment. The accuracy of the length and width of the raw materials directly affects the production of the barrel. The small size and large size will cause the raw materials to be inaccurately placed into the mold, resulting in the quality of the barrels not meeting the requirements. Under the condition of ensuring safety, the raw material thickness should be negatively biased as much as possible, which can save raw materials and reduce the weight of the barrel, thereby reducing the cost.

3. Kunming Steel Yellow Phosphorus Packaging Bucket Special Cold Rolled Steel Strip Production Process

3.1 Process

Hot metal pretreatment→50t oxygen top-blown converter smelting (steel water)→LF ladle refining furnace refining (steel water)→Vertical curved slab continuous casting machine continuous casting (steel billet)→Double-stand furnace rolling mill hot rolling (cold rolling raw material) → Pickling → Four-roller reversing mill cold rolling (cold rolling) → heat treatment (annealing) → leveling → rewinding (surface quality inspection, oiling) → physical and chemical properties inspection → vertical winding (surface quality secondary inspection) → judgment →Packaging

2.2 Process characteristics

The smelting of yellow phosphorus barrels in Kunming Steel uses the “step-by-step deoxidation” deoxidation process of low carbon low silicon aluminum killed steel. The hot rolling mill adopts “three highs and one low” (high heating temperature, high rolling temperature, High final rolling temperature, low enough coiling temperature) process principle to produce special raw materials for yellow phosphorus barrels, steel strip pickling in push-pull pickling unit production line adopts “micro-acid pickling process”, reasonably match pickling tank The acid concentration, the acid temperature, and the pickling time in the inside effectively clean the scale of the cold rolled raw material (hot rolled steel strip). Cold rolling adopts a four-roll reversing cold rolling mill to produce cold-rolled sheets, and annealing using full-hydrogen hood annealing is beneficial to the improvement of punching performance.

The cold-rolled steel strip St12P for Kunming Steel's yellow-phosphorous packaging drum is aluminum-killed steel, which strictly controls the C, Si, Mn, S and P contents that affect the stamping performance. The hot-rolling rolling adopts the principle of “three highs and one low”. Cold rolling adopts appropriate reduction ratio and full hydrogen annealing to make AlN uniformly precipitate, forming a {111} texture favorable for stamping deformation, grain size of 6 to 8, and free cementite is granular and dispersed. The deep drawing performance of St12P cold-rolled sheet is improved, so that the strain hardening index n value reaches 0.2 or more, and the plastic strain ratio r value reaches 1.4 or more.

The special cold-rolled steel strip St12P of Kunming Steel Yellow Phosphorus packaging barrel has good strength and good stamping deformation performance. The yellow phosphorus packaging barrel is more qualified than the St12 and SPCC cold-rolled sheets, and it is not easy to deform and crack.

Kunming Steel requires that the surface of the cold-rolled steel strip for yellow phosphorus packaging barrels should be free of defects such as delamination, cracks, air bubbles, crusting, cracking and inclusions. The steel strip allows pitting, small bubbles, small cracks, scratches, roll indentations that do not exceed the thickness tolerance range; localized oxidation colors and acid-washed heterochromatic films are allowed.

Kunming Steel has established strict dimensional control requirements to meet user requirements. The allowable deviation of thickness and width of cold-rolled steel strip for yellow phosphorus packaging drum is shown in Table 5.

Table 5 The allowable deviation of the thickness and width of the steel strip is mm

width(

DB53/T286-2009

GB708-88

DB53/T286-2009

GB708-88

0~-0.06

Class A: ±0.10

0 to +3

0 to +6

4. Management system and process control

(1) Kunming Steel has formulated a standard for yellow phosphorus barrel special plate products

DB53/T286-2009 "Huang Phosphorus Packaging Bucket Special Cold Rolled Steel Strip" standard specifies the size, shape, weight, delivery status, chemical composition, mechanics and process properties, test methods, and specifications of the cold-rolled steel strip for yellow phosphorus packaging drum. The specific requirements for inspection rules, packaging, marking and quality certificates provide a specification document for widespread use.

(2) Strict process control, strengthen process discipline management

1) Level 3 process discipline inspection system

The workshop technicians conduct self-inspection every week, the factory-level technical quality management personnel conduct random inspections, and the company's technical center organizes relevant personnel to form a three-level quality spot check system for quarterly inspection of the company's process discipline to ensure strict implementation of the process discipline of the production process.

2) Unscheduled inspections by competent technicians

The technical staff of the technical center and the quality measurement management center conducts irregular inspections on the production process and product quality. If there is a product that is not produced according to the technical discipline requirements, even if the physical and chemical quality of the product is qualified and the surface quality is qualified, it is judged according to the non-conforming product. The management department shall issue a rectification opinion in accordance with the process discipline, and the parties shall impose economic penalties.

(3) Improve the quality of quality inspectors, improve the business level and operational skills of inspectors, strictly control quality, and ultimately ensure product quality.

1) Understand the use, raise awareness of the importance of inspection, and improve product quality awareness

The packaging and transportation of yellow phosphorus is a dangerous product. Kunming Steel organizes inspection personnel to visit the yellow phosphorus and yellow phosphorus barrel packaging production plant, so that the inspectors can fully understand the requirements for the production and use of yellow phosphorus packaging barrels, and improve the importance of testing the yellow phosphorus packaging board. understanding.

2) Strengthen learning standards and improve the business level and operational skills of employees

Since the surface quality inspection defects of cold-rolled products are numerous, the inspection judgment is carried out in continuous production, and the inspection is difficult, and the judgment is highly subjective. Process technicians and standard setters conduct on-the-job training for inspectors, systematically analyze the causes, hazards and controls of surface defects of cold rolled sheets, and improve the business level and operational skills of inspectors.

3) Formation mechanism, and the uniformity of comparative inspection and coordinated inspection

The organization judges conduct back-to-back inspection and judgment on the same coil, and unifies the judgment scale of the inspectors to ensure the accuracy of the judgment.

4) Product quality supervision system

The quality supervision of yellow phosphorus barrel special board is checked by the quality inspection staff of the workshop, the monthly quality inspection of the factory-level quality management personnel, and the quality inspection system of the company's product quality quarterly quality inspection by the company management department to ensure the product quality is stable and tested. The result is accurate.

5 Conclusion:

For the processing and use characteristics of yellow phosphorus packaging barrels, Kunming Iron and Steel Group Co., Ltd., after years of research and process technology optimization, developed a special cold-rolled steel strip for yellow phosphorus packaging barrels to better meet the requirements of yellow phosphorus packaging and transportation. The DB53/T286-2009 "Hot-Phosten Packaging Barrel Special Cold-Rolled Steel Strip" promulgated and implemented on August 1, 2009 is the result of the joint development of Kunming Steel and Kunming Tenghe Company, and the standard is promulgated and implemented. The use of steel for phosphorus packaging barrels ensures the safety of storage and transportation of yellow phosphorus.
Kunming Iron and Steel Group Co., Ltd. develops a special cold-rolled steel strip for yellow phosphorus packaging barrels, which can be used not only for the manufacture of yellow phosphorus packaging drums, but also for the manufacture of other types of packaging drums.